Class: HexaPDF::Content::Canvas

Inherits:
Object
  • Object
show all
Includes:
Utils::GraphicsHelpers, Utils::MathHelpers
Defined in:
lib/hexapdf/content/canvas.rb

Overview

This class provides the basic drawing operations supported by PDF.

General Information

A canvas object is used for modifying content streams on a level higher than text. It would be possible to write a content stream by hand since PDF uses a simplified reversed polish notation for specifying operators: First come the operands, then comes the operator and no operator returns any result. However, it is easy to make mistakes this way and one has to know all operators and their operands.

This is rather tedious and therefore this class exists. It allows one to modify a content stream by invoking methods that should be familiar to anyone that has ever used a graphic API. There are methods for moving the current point, drawing lines and curves, setting the color, line width and so on.

The PDF operators themselves are implemented as classes, see Operator. The canvas class uses the Operator::BaseOperator#invoke and Operator::BaseOperator#serialize methods for applying changes and serialization, with one exception: color setters don’t invoke the corresponding operator implementation but directly work on the graphics state.

PDF Graphics

Graphics Operators and Objects

There are about 60 PDF content stream operators. Some are used for changing the graphics state, some for drawing paths and others for showing text. This is all abstracted through the Canvas class.

PDF knows about five different graphics objects: path objects, text objects, external objects, inline image objects and shading objects. If none of the five graphics objects is current, the content stream is at the so called page description level (in between graphics objects).

Additionally the PDF operators are divided into several groups, like path painting or text showing operators, and such groups of operators are allowed to be used only in certain graphics objects or the page description level.

Have a look at the PDF specification (PDF1.7 s8.2) for more details.

HexaPDF tries to ensure the proper use of the operators and graphics objects and if it cannot do it, an error is raised. So if you don’t modify a content stream directly but via the Canvas methods, you generally don’t have to worry about the low-level inner workings.

Graphics State

Some operators modify the so called graphics state (see Content::GraphicsState). The graphics state is a collection of settings that is used during processing or creating a content stream. For example, the path painting operators don’t have operands to specify the line width or the stroke color but take this information from the graphics state.

One important thing about the graphics state is that it is only possible to restore a prior state using the save and restore methods. It is not possible to reset the graphics state while creating the content stream!

Paths

A PDF path object consists of one or more subpaths. Each subpath can be a rectangle or can consist of lines and cubic bezier curves. No other types of subpaths are known to PDF. However, the Canvas class contains additional methods that use the basic path construction methods for drawing other paths like circles.

When a subpath is started, the current graphics object is changed to :path. After all path constructions are finished, a path painting method needs to be invoked to change back to the page description level. Optionally, the path painting method may be preceeded by a clipping path method to change the current clipping path (see #clip_path).

There are four kinds of path painting methods:

  • Those that stroke the path,

  • those that fill the path,

  • those that stroke and fill the path and

  • one to neither stroke or fill the path (used, for example, to just set the clipping path).

In addition filling may be done using either the nonzero winding number rule or the even-odd rule.

Special Graphics State Methods

These methods are only allowed when the current graphics object is :none, i.e. operations are done on the page description level.

  • #save_graphics_state

  • #restore_graphics_state

  • #transform, #rotate, #scale, #translate, #skew

See: PDF1.7 s8, s9

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Utils::GraphicsHelpers

calculate_dimensions, point_on_line

Methods included from Utils::MathHelpers

deg_to_rad, rad_to_deg

Constructor Details

#initialize(context) ⇒ Canvas

Creates a new Canvas object for the given context object (either a Page or a Form).



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# File 'lib/hexapdf/content/canvas.rb', line 192

def initialize(context)
  @context = context
  @operators = Operator::DEFAULT_OPERATORS.dup
  @graphics_state = GraphicsState.new
  @graphics_object = :none
  @font = nil
  @serializer = HexaPDF::Serializer.new
  @current_point = [0, 0]
  @start_point = [0, 0]
  @contents = ''.b
  @stream_data = HexaPDF::StreamData.new do
    case graphics_object
    when :path, :clipping_path then end_path
    when :text then end_text
    end
    restore_graphics_state while graphics_state.saved_states?
    @contents
  end
end

Instance Attribute Details

#contents ⇒ Object (readonly)

The serialized contents produced by the various canvas operations up to this point.

Note that the returned string may not be a completely valid PDF content stream since a graphic object may be open or the graphics state not completely restored.

See: #stream_data



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# File 'lib/hexapdf/content/canvas.rb', line 148

def contents
  @contents
end

#context ⇒ Object (readonly)

The context for which the canvas was created (a HexaPDF::Type::Page or HexaPDF::Type::Form object).



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# File 'lib/hexapdf/content/canvas.rb', line 140

def context
  @context
end

#current_point ⇒ Object (readonly)

The current point [x, y] of the path.

This attribute holds the current point which is only valid if the current graphics objects is :path.

When the current point changes, the array is modified in place instead of creating a new array!



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# File 'lib/hexapdf/content/canvas.rb', line 186

def current_point
  @current_point
end

#graphics_object ⇒ Object

The current graphics object.

The graphics object should not be changed directly. It is automatically updated according to the invoked methods.

This attribute can have the following values:

:none

No current graphics object, i.e. the page description level.

:path

The current graphics object is a path.

:clipping_path

The current graphics object is a clipping path.

:text

The current graphics object is a text object.

See: PDF1.7 s8.2



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# File 'lib/hexapdf/content/canvas.rb', line 177

def graphics_object
  @graphics_object
end

#graphics_state ⇒ Object (readonly)

The Content::GraphicsState object containing the current graphics state.

The graphics state must not be changed directly, only by using the provided methods. If it is changed directly, the output will not be correct.



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# File 'lib/hexapdf/content/canvas.rb', line 162

def graphics_state
  @graphics_state
end

#operators ⇒ Object (readonly)

The operator name/implementation map used when invoking or serializing an operator.



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# File 'lib/hexapdf/content/canvas.rb', line 189

def operators
  @operators
end

#stream_data ⇒ Object (readonly)

A StreamData object representing the serialized contents produced by the various canvas operations.

In contrast to #contents, it is ensured that an open graphics object is closed and all saved graphics states are restored when the contents of the stream data object is read. Note that this means that reading the stream data object may change the state of the canvas.



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# File 'lib/hexapdf/content/canvas.rb', line 156

def stream_data
  @stream_data
end

Instance Method Details

#arc(cx, cy, a:, b: a, start_angle: 0, end_angle: 360, clockwise: false, inclination: 0) ⇒ Object

:call-seq:

canvas.arc(cx, cy, a:, b: a, start_angle: 0, end_angle: 360, clockwise: false, inclination: 0)   => canvas

Appends an elliptical arc to the path. The endpoint of the arc becomes the new current point.

cx

x-coordinate of the center point of the arc

cy

y-coordinate of the center point of the arc

a

Length of semi-major axis

b

Length of semi-minor axis (default: a)

start_angle

Angle in degrees at which to start the arc (default: 0)

end_angle

Angle in degrees at which to end the arc (default: 360)

clockwise

If true the arc is drawn in clockwise direction, otherwise in counterclockwise direction.

inclination

Angle in degrees between the x-axis and the semi-major axis (default: 0)

If a and b are equal, a circular arc is drawn. If the difference of the start angle and end angle is equal to 360, a full ellipse (or circle) is drawn.

If there is no current path when the method is invoked, a new path is automatically begun.

Since PDF doesn’t have operators for drawing elliptical or circular arcs, they have to be approximated using Bezier curves (see #curve_to). The accuracy of the approximation can be controlled using the configuration option ‘graphic_object.arc.max_curves’.

Examples:

canvas.arc(0, 0, a: 10)                         # Circle at (0, 0) with radius 10
canvas.arc(0, 0, a: 10, b: 5)                   # Ellipse at (0, 0) with radii 10 and 5
canvas.arc(0, 0, a: 10, b: 5, inclination: 45)  # The above ellipse inclined 45 degrees

# Circular and elliptical arcs from 45 degrees to 135 degrees
canvas.arc(0, 0, a: 10, start_angle: 45, end_angle: 135)
canvas.arc(0, 0, a: 10, b: 5, start_angle: 45, end_angle: 135)

# Arcs from 135 degrees to 15 degrees, the first in counterclockwise direction (i.e. the
# big arc), the other in clockwise direction (i.e. the small arc)
canvas.arc(0, 0, a: 10, start_angle: 135, end_angle: 15)
canvas.arc(0, 0, a: 10, start_angle: 135, end_angle: 15, clockwise: true)

See: Content::GraphicObject::Arc



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# File 'lib/hexapdf/content/canvas.rb', line 1067

def arc(cx, cy, a:, b: a, start_angle: 0, end_angle: 360, clockwise: false, inclination: 0)
  arc = GraphicObject::Arc.configure(cx: cx, cy: cy, a: a, b: b,
                                     start_angle: start_angle, end_angle: end_angle,
                                     clockwise: clockwise, inclination: inclination)
  arc.draw(self)
  self
end

#begin_text(force_new: false) ⇒ Object

:call-seq:

canvas.begin_text(force_new: false)      -> canvas

Begins a new text object.

If force is true and the current graphics object is already a text object, it is ended and a new text object is begun.

See: PDF1.7 s9.4.1



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# File 'lib/hexapdf/content/canvas.rb', line 1499

def begin_text(force_new: false)
  raise_unless_at_page_description_level_or_in_text
  end_text if force_new
  invoke0(:BT) if graphics_object == :none
  self
end

#character_spacing(amount = nil, &bk) ⇒ Object Also known as: character_spacing=

:call-seq:

canvas.character_spacing                       => current_character_spacing
canvas.character_spacing(amount)               => canvas
canvas.character_spacing(amount) { block }     => canvas

The character spacing determines how much additional space is added between two consecutive characters. For horizontal writing positive values increase the distance between two characters, whereas for vertical writing negative values increase the distance.

Returns the current character spacing value (see Content::GraphicsState#character_spacing) when no argument is given. Otherwise sets the character spacing using the amount argument and returns self. The setter version can also be called in the character_spacing= form.

If the amount and a block are provided, the changed character spacing is only active during the block by saving and restoring the graphics state.

Examples:

canvas.character_spacing(0.25)
canvas.character_spacing                      # => 0.25
canvas.character_spacing = 0.5                # => 0.5

canvas.character_spacing(0.10) do
  canvas.character_spacing                    # => 0.10
end
canvas.character_spacing                      # => 0.5

See: PDF1.7 s9.3.2



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# File 'lib/hexapdf/content/canvas.rb', line 1315

def character_spacing(amount = nil, &bk)
  gs_getter_setter(:character_spacing, :Tc, amount, &bk)
end

#circle(cx, cy, radius) ⇒ Object

:call-seq:

canvas.circle(cx, cy, radius)      => canvas

Appends a circle with center (cx, cy) and the given radius (in degrees) to the path as a complete subpath (drawn in counterclockwise direction). The point (center_x + radius, center_y) becomes the new current point.

If there is no current path when the method is invoked, a new path is automatically begun.

Examples:

canvas.circle(100, 100, 10)

See: #arc (for approximation accuracy)



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# File 'lib/hexapdf/content/canvas.rb', line 983

def circle(cx, cy, radius)
  arc(cx, cy, a: radius)
  close_subpath
end

#clip_path(rule = :nonzero) ⇒ Object

:call-seq:

canvas.clip_path(rule = :nonzero)     => canvas

Modifies the clipping path by intersecting it with the current path.

The argument rule may either be :nonzero to use the nonzero winding number rule or :even_odd to use the even-odd rule for determining which regions lie inside the clipping path.

Note that the current path cannot be modified after invoking this method! This means that one of the path painting methods or #end_path must be called immediately afterwards.

See: PDF1.7 s8.5.4



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# File 'lib/hexapdf/content/canvas.rb', line 1212

def clip_path(rule = :nonzero)
  raise_unless_in_path
  invoke0(rule == :nonzero ? :W : :'W*')
  self
end

#close_fill_stroke(rule = :nonzero) ⇒ Object

:call-seq:

canvas.close_fill_stroke(rule = :nonzero)    => canvas

Closes the last subpath and then fills and strokes the path using the given rule.

The argument rule may either be :nonzero to use the nonzero winding number rule or :even_odd to use the even-odd rule for determining which regions to fill in.

See: PDF1.7 s8.5.3



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# File 'lib/hexapdf/content/canvas.rb', line 1178

def close_fill_stroke(rule = :nonzero)
  raise_unless_in_path_or_clipping_path
  invoke0(rule == :nonzero ? :b : :'b*')
  self
end

#close_stroke ⇒ Object

:call-seq:

canvas.close_stroke    => canvas

Closes the last subpath and then strokes the path.

See: PDF1.7 s8.5.3.1, s8.5.3.2



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# File 'lib/hexapdf/content/canvas.rb', line 1131

def close_stroke
  raise_unless_in_path_or_clipping_path
  invoke0(:s)
  self
end

#close_subpath ⇒ Object

:call-seq:

canvas.close_subpath      => canvas

Closes the current subpath by appending a straight line from the current point to the start point of the subpath which also becomes the new current point.



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# File 'lib/hexapdf/content/canvas.rb', line 900

def close_subpath
  raise_unless_in_path
  invoke0(:h)
  @current_point = @start_point
  self
end

#curve_to(x, y, p1: nil, p2: nil) ⇒ Object

:call-seq:

canvas.curve_to(x, y, p1:, p2:)       => canvas
canvas.curve_to(x, y, p1:)            => canvas
canvas.curve_to(x, y, p2:)            => canvas

Appends a cubic Bezier curve to the current subpath starting from the current point. The end point becomes the new current point.

A Bezier curve consists of the start point, the end point and the two control points p1 and p2. The start point is always the current point and the end point is specified as x and y arguments.

Additionally, either the first control point p1 or the second control p2 or both control points have to be specified (as arrays containing two numbers). If the first control point is not specified, the current point is used as first control point. If the second control point is not specified, the end point is used as the second control point.

Examples:

canvas.curve_to(100, 100, p1: [100, 50], p2: [50, 100])
canvas.curve_to(100, 100, p1: [100, 50])
canvas.curve_to(100, 100, p2: [50, 100])



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# File 'lib/hexapdf/content/canvas.rb', line 849

def curve_to(x, y, p1: nil, p2: nil)
  raise_unless_in_path
  if p1 && p2
    invoke(:c, *p1, *p2, x, y)
  elsif p1
    invoke(:y, *p1, x, y)
  elsif p2
    invoke(:v, *p2, x, y)
  else
    raise ArgumentError, "At least one control point must be specified for Bézier curves"
  end
  @current_point[0] = x
  @current_point[1] = y
  self
end

#draw(name, **options) ⇒ Object

:call-seq:

canvas.draw(obj, **options)      => canvas
canvas.draw(name, **options)     => canvas

Draws the given graphic object on the canvas.

See #graphic_object for information on the arguments.

Examples:

canvas.draw(:arc, cx: 10, cy: 10)



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# File 'lib/hexapdf/content/canvas.rb', line 1108

def draw(name, **options)
  graphic_object(name, **options).draw(self)
  self
end

#ellipse(cx, cy, a:, b:, inclination: 0) ⇒ Object

:call-seq:

canvas.ellipse(cx, cy, a:, b:, inclination: 0)      => canvas

Appends an ellipse with center (cx, cy), semi-major axis a, semi-minor axis b and an inclination from the x-axis of inclination degrees to the path as a complete subpath. The outer-most point on the semi-major axis becomes the new current point.

If there is no current path when the method is invoked, a new path is automatically begun.

Examples:

# Ellipse aligned to x-axis and y-axis
canvas.ellipse(100, 100, a: 10, b: 5)

# Inclined ellipse
canvas.ellipse(100, 100, a: 10, b: 5, inclination: 45)

See: #arc (for approximation accuracy)



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# File 'lib/hexapdf/content/canvas.rb', line 1006

def ellipse(cx, cy, a:, b:, inclination: 0)
  arc(cx, cy, a: a, b: b, inclination: inclination)
  close_subpath
end

#end_marked_content_sequence ⇒ Object

:call-seq:

canvas.end_marked_content_sequence       -> canvas

Ends a marked-content sequence.

See #marked_content_sequence for details.

See: PDF1.7 s14.6, #marked_content_sequence



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# File 'lib/hexapdf/content/canvas.rb', line 1847

def end_marked_content_sequence
  raise_unless_at_page_description_level
  invoke0(:EMC)
  self
end

#end_path ⇒ Object

:call-seq:

canvas.end_path     => canvas

Ends the path without stroking or filling it.

This method is normally used in conjunction with the clipping path methods to define the clipping.

See: PDF1.7 s8.5.3.1 #clip



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# File 'lib/hexapdf/content/canvas.rb', line 1193

def end_path
  raise_unless_in_path_or_clipping_path
  invoke0(:n)
  self
end

#end_text ⇒ Object

:call-seq:

canvas.end_text       -> canvas

Ends the current text object.

See: PDF1.7 s9.4.1



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# File 'lib/hexapdf/content/canvas.rb', line 1512

def end_text
  raise_unless_at_page_description_level_or_in_text
  invoke0(:ET) if graphics_object == :text
  self
end

#fill(rule = :nonzero) ⇒ Object

:call-seq:

canvas.fill(rule = :nonzero)    => canvas

Fills the path using the given rule.

The argument rule may either be :nonzero to use the nonzero winding number rule or :even_odd to use the even-odd rule for determining which regions to fill in.

Any open subpaths are implicitly closed before being filled.

See: PDF1.7 s8.5.3.1, s8.5.3.3



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# File 'lib/hexapdf/content/canvas.rb', line 1148

def fill(rule = :nonzero)
  raise_unless_in_path_or_clipping_path
  invoke0(rule == :nonzero ? :f : :'f*')
  self
end

#fill_color(*color, &block) ⇒ Object Also known as: fill_color=

The fill color defines the color used for non-stroking operations, i.e. for filling paths.

Works exactly the same #stroke_color but for the fill color. See #stroke_color for details on invocation and use.



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# File 'lib/hexapdf/content/canvas.rb', line 732

def fill_color(*color, &block)
  color_getter_setter(:fill_color, color, :rg, :g, :k, :cs, :scn, &block)
end

#fill_stroke(rule = :nonzero) ⇒ Object

:call-seq:

canvas.fill_stroke(rule = :nonzero)    => canvas

Fills and then strokes the path using the given rule.

The argument rule may either be :nonzero to use the nonzero winding number rule or :even_odd to use the even-odd rule for determining which regions to fill in.

See: PDF1.7 s8.5.3



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# File 'lib/hexapdf/content/canvas.rb', line 1163

def fill_stroke(rule = :nonzero)
  raise_unless_in_path_or_clipping_path
  invoke0(rule == :nonzero ? :B : :'B*')
  self
end

#font(name = nil, size: nil, **options) ⇒ Object Also known as: font=

:call-seq:

canvas.font                              => current_font
canvas.font(name, size: nil, **options)  => canvas

Specifies the font that should be used when showing text.

A valid font size need to be provided on the first invocation, otherwise an error is raised.

Note that this method returns the font object itself, not the PDF dictionary representing the font!

If size is specified, the #font_size method is invoked with it as argument. All other options are passed on to the font loaders (see HexaPDF::FontLoader) that are used for loading the specified font.

Returns the current font object when no argument is given.

Examples:

canvas.font("Times", variant: :bold, size: 12)
canvas.font                                          # => font object
canvas.font = "Times"

See: PDF1.7 s9.2.2



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# File 'lib/hexapdf/content/canvas.rb', line 1613

def font(name = nil, size: nil, **options)
  if name
    @font = (name.respond_to?(:dict) ? name : context.document.fonts.load(name, options))
    if size
      font_size(size)
    else
      size = font_size
      raise HexaPDF::Error, "No valid font size set" if size <= 0
      invoke_font_operator(@font.dict, size)
    end
    self
  else
    @font
  end
end

#font_size(size = nil, leading: size && size * 1.2) ⇒ Object Also known as: font_size=

:call-seq:

canvas.font_size                                  => font_size
canvas.font_size(size, leading: size * 1.2)       => canvas

Specifies the font size.

Note that an error is raised if no font has been set before!

The leading can be additionally set and defaults to the font size times 1.2. If the leading should not be changed, nil has to be passed for leading.

Returns the current font size when no argument is given.

Examples:

canvas.font_size(12)
canvas.font_size                       # => 12
canvas.font_size(12, leading: 20)
canvas.font_size = 12

See: PDF1.7 s9.2.2



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# File 'lib/hexapdf/content/canvas.rb', line 1651

def font_size(size = nil, leading: size && size * 1.2)
  if size
    unless @font
      raise HexaPDF::Error, "A font needs to be set before the font size can be set"
    end
    invoke_font_operator(@font.dict, size)
    self.leading(leading) if leading
    self
  else
    graphics_state.font_size
  end
end

#graphic_object(obj, **options) ⇒ Object

:call-seq:

canvas.graphic_object(obj, **options)      => obj
canvas.graphic_object(name, **options)     => graphic_object

Returns the named graphic object, configured with the given options.

If an object responding to :configure is given, it is used. Otherwise the graphic object is looked up via the given name in the configuration option ‘graphic_object.map’. Then the graphic object is configured with the given options if at least one is given.

Examples:

obj = canvas.graphic_object(:arc, cx: 10, cy: 10)
canvas.draw(obj)



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# File 'lib/hexapdf/content/canvas.rb', line 1089

def graphic_object(obj, **options)
  unless obj.respond_to?(:configure)
    obj = context.document.config.constantize('graphic_object.map', obj)
  end
  obj = obj.configure(options) if options.size > 0 || !obj.respond_to?(:draw)
  obj
end

#horizontal_scaling(amount = nil, &bk) ⇒ Object Also known as: horizontal_scaling=

:call-seq:

canvas.horizontal_scaling                        => current_horizontal_scaling
canvas.horizontal_scaling(percent)               => canvas
canvas.horizontal_scaling(percent) { block }     => canvas

The horizontal scaling adjusts the width of text character glyphs by stretching or compressing them in the horizontal direction. The value is specified as percent of the normal width.

Returns the current horizontal scaling value (see Content::GraphicsState#horizontal_scaling) when no argument is given. Otherwise sets the horizontal scaling using the percent argument and returns self. The setter version can also be called in the horizontal_scaling= form.

If the percent and a block are provided, the changed horizontal scaling is only active during the block by saving and restoring the graphics state.

Examples:

canvas.horizontal_scaling(50)                  # each glyph has only 50% width
canvas.horizontal_scaling                      # => 50
canvas.horizontal_scaling = 125                # => 125

canvas.horizontal_scaling(75) do
  canvas.horizontal_scaling                    # => 75
end
canvas.horizontal_scaling                      # => 125

See: PDF1.7 s9.3.4



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# File 'lib/hexapdf/content/canvas.rb', line 1386

def horizontal_scaling(amount = nil, &bk)
  gs_getter_setter(:horizontal_scaling, :Tz, amount, &bk)
end

#leading(amount = nil, &bk) ⇒ Object Also known as: leading=

:call-seq:

canvas.leading                       => current_leading
canvas.leading(amount)               => canvas
canvas.leading(amount) { block }     => canvas

The leading specifies the vertical distance between the baselines of adjacent text lines.

Returns the current leading value (see Content::GraphicsState#leading) when no argument is given. Otherwise sets the leading using the amount argument and returns self. The setter version can also be called in the leading= form.

If the amount and a block are provided, the changed leading is only active during the block by saving and restoring the graphics state.

Examples:

canvas.leading(14.5)
canvas.leading                      # => 14.5
canvas.leading = 10                 # => 10

canvas.leading(25) do
  canvas.leading                    # => 25
end
canvas.leading                      # => 10

See: PDF1.7 s9.3.5



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# File 'lib/hexapdf/content/canvas.rb', line 1417

def leading(amount = nil, &bk)
  gs_getter_setter(:leading, :TL, amount, &bk)
end

#line(x0, y0, x1, y1) ⇒ Object

:call-seq:

canvas.line(x0, y0, x1, y1)        => canvas

Moves the current point to (x0, y0) and appends a line to (x1, y1) to the current path.

This method is equal to “canvas.move_to(x0, y0).line_to(x1, y1)”.

Examples:

canvas.line(10, 10, 100, 100)



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# File 'lib/hexapdf/content/canvas.rb', line 917

def line(x0, y0, x1, y1)
  move_to(x0, y0)
  line_to(x1, y1)
end

#line_cap_style(style = nil, &block) ⇒ Object Also known as: line_cap_style=

:call-seq:

canvas.line_cap_style                    => current_line_cap_style
canvas.line_cap_style(style)             => canvas
canvas.line_cap_style(style) { block }   => canvas

The line cap style specifies how the ends of stroked open paths should look like. The style parameter can either be a valid integer or one of the symbols :butt, :round or :projecting_square (see Content::LineCapStyle.normalize for details). Note that the return value is always a normalized line cap style.

Returns the current line cap style (see Content::GraphicsState#line_cap_style) when no argument is given. Otherwise sets the line cap style to the given style and returns self. The setter version can also be called in the line_cap_style= form.

If the style and a block are provided, the changed line cap style is only active during the block by saving and restoring the graphics state.

Examples:

canvas.line_cap_style(:butt)
canvas.line_cap_style               # => #<NamedValue @name=:butt, @value=0>
canvas.line_cap_style = :round      # => #<NamedValue @name=:round, @value=1>

canvas.line_cap_style(:butt) do
  canvas.line_cap_style             # => #<NamedValue @name=:butt, @value=0>
end
canvas.line_cap_style               # => #<NamedValue @name=:round, @value=1>

See: PDF1.7 s8.4.3.3



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# File 'lib/hexapdf/content/canvas.rb', line 494

def line_cap_style(style = nil, &block)
  gs_getter_setter(:line_cap_style, :J, style && LineCapStyle.normalize(style), &block)
end

#line_dash_pattern(value = nil, phase = 0, &block) ⇒ Object Also known as: line_dash_pattern=

:call-seq:

canvas.line_dash_pattern                                  => current_line_dash_pattern
canvas.line_dash_pattern(line_dash_pattern)               => canvas
canvas.line_dash_pattern(length, phase = 0)               => canvas
canvas.line_dash_pattern(array, phase = 0)                => canvas
canvas.line_dash_pattern(value, phase = 0) { block }      => canvas

The line dash pattern defines the appearance of a stroked path (line or curve), ie. if it is solid or if it contains dashes and gaps.

There are multiple ways to set the line dash pattern:

  • By providing a Content::LineDashPattern object

  • By providing a single Integer/Float that is used for both dashes and gaps

  • By providing an array of Integers/Floats that specify the alternating dashes and gaps

The phase (i.e. the distance into the dashes/gaps at which to start) can additionally be set in the last two cases.

A solid line can be achieved by using 0 for the length or by using an empty array.

Returns the current line dash pattern (see Content::GraphicsState#line_dash_pattern) when no argument is given. Otherwise sets the line dash pattern using the given arguments and returns self. The setter version can also be called in the line_dash_pattern= form (but only without the second argument!).

If arguments and a block are provided, the changed line dash pattern is only active during the block by saving and restoring the graphics state.

Examples:

canvas.line_dash_pattern(10)
canvas.line_dash_pattern                # => LineDashPattern.new([10], 0)
canvas.line_dash_pattern(10, 2)
canvas.line_dash_pattern([5, 3, 1], 2)
canvas.line_dash_pattern = LineDashPattern.new([5, 3, 1], 1)

canvas.line_dash_pattern(10) do
  canvas.line_dash_pattern              # => LineDashPattern.new([10], 0)
end
canvas.line_dash_pattern                # => LineDashPattern.new([5, 3, 1], 1)

See: PDF1.7 s8.4.3.5, LineDashPattern



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# File 'lib/hexapdf/content/canvas.rb', line 609

def line_dash_pattern(value = nil, phase = 0, &block)
  case value
  when nil, LineDashPattern
  when Array
    value = LineDashPattern.new(value, phase)
  when 0
    value = LineDashPattern.new([], 0)
  else
    value = LineDashPattern.new([value], phase)
  end
  gs_getter_setter(:line_dash_pattern, :d, value, &block)
end

#line_join_style(style = nil, &block) ⇒ Object Also known as: line_join_style=

:call-seq:

canvas.line_join_style                    => current_line_join_style
canvas.line_join_style(style)             => canvas
canvas.line_join_style(style) { block }   => canvas

The line join style specifies the shape that is used at the corners of stroked paths. The style parameter can either be a valid integer or one of the symbols :miter, :round or :bevel (see Content::LineJoinStyle.normalize for details). Note that the return value is always a normalized line join style.

Returns the current line join style (see Content::GraphicsState#line_join_style) when no argument is given. Otherwise sets the line join style to the given style and returns self. The setter version can also be called in the line_join_style= form.

If the style and a block are provided, the changed line join style is only active during the block by saving and restoring the graphics state.

Examples:

canvas.line_join_style(:miter)
canvas.line_join_style               # => #<NamedValue @name=:miter, @value=0>
canvas.line_join_style = :round      # => #<NamedValue @name=:round, @value=1>

canvas.line_join_style(:bevel) do
  canvas.line_join_style             # => #<NamedValue @name=:bevel, @value=2>
end
canvas.line_join_style               # => #<NamedValue @name=:round, @value=1>

See: PDF1.7 s8.4.3.4



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# File 'lib/hexapdf/content/canvas.rb', line 528

def line_join_style(style = nil, &block)
  gs_getter_setter(:line_join_style, :j, style && LineJoinStyle.normalize(style), &block)
end

#line_to(x, y) ⇒ Object

:call-seq:

canvas.line_to(x, y)       => canvas

Appends a straight line segment from the current point to the given point (which becomes the new current point) to the current subpath.

Examples:

canvas.line_to(100, 100)



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# File 'lib/hexapdf/content/canvas.rb', line 819

def line_to(x, y)
  raise_unless_in_path
  invoke2(:l, x, y)
  @current_point[0] = x
  @current_point[1] = y
  self
end

#line_width(width = nil, &block) ⇒ Object Also known as: line_width=

:call-seq:

canvas.line_width                    => current_line_width
canvas.line_width(width)             => canvas
canvas.line_width(width) { block }   => canvas

The line width determines the thickness of a stroked path.

Returns the current line width (see Content::GraphicsState#line_width) when no argument is given. Otherwise sets the line width to the given width and returns self. The setter version can also be called in the line_width= form.

If the width and a block are provided, the changed line width is only active during the block by saving and restoring the graphics state.

Examples:

canvas.line_width(10)
canvas.line_width          # => 10
canvas.line_width = 5      # => 5

canvas.line_width(10) do
  canvas.line_width        # => 10
end
canvas.line_width          # => 5

See: PDF1.7 s8.4.3.2



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# File 'lib/hexapdf/content/canvas.rb', line 460

def line_width(width = nil, &block)
  gs_getter_setter(:line_width, :w, width, &block)
end

#marked_content_point(tag, property_list: nil) ⇒ Object

:call-seq:

canvas.marked_content_point(tag, property_list: nil)     -> canvas

Inserts a marked-content point, optionally associated with a property list.

A marked-content point is used to identify a position in the content stream for later use by other applications. The symbol tag is used to uniquely identify the role of the marked-content point and should be registered with ISO to avoid conflicts.

The optional property_list argument can either be a valid PDF dictionary or a symbol referencing an already used property list in the resource dictionary’s /Properties dictionary.

Examples:

canvas.marked_content_point(:Divider)
canvas.marked_content_point(:Divider, property_list: {Key: 'value'})

See: PDF1.7 s14.6



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# File 'lib/hexapdf/content/canvas.rb', line 1781

def marked_content_point(tag, property_list: nil)
  raise_unless_at_page_description_level_or_in_text
  if property_list
    property_list = resources.property_list(property_list) if property_list.kind_of?(Symbol)
    invoke2(:DP, tag, resources.add_property_list(property_list))
  else
    invoke1(:MP, tag)
  end
  self
end

#marked_content_sequence(tag, property_list: nil) ⇒ Object

:call-seq:

canvas.marked_content_sequence(tag, property_list: nil)               -> canvas
canvas.marked_content_sequence(tag, property_list: nil) { block }     -> canvas

Inserts a marked-content sequence, optionally associated with a property list.

A marked-content sequence is used to identify a sequence of complete graphics objects in the content stream for later use by other applications. The symbol tag is used to uniquely identify the role of the marked-content sequence and should be registered with ISO to avoid conflicts.

The optional property_list argument can either be a valid PDF dictionary or a symbol referencing an already used property list in the resource dictionary’s /Properties dictionary.

If invoked without a block, a corresponding call to #end_marked_content_sequence must be done. Otherwise the marked-content sequence automatically ends when the block is finished.

Although the PDF specification would allow using marked-content sequences inside text objects, this is prohibited.

Examples:

canvas.marked_content_sequence(:Divider)
# Other instructions
canvas.end_marked_content_sequence

canvas.marked_content_sequence(:Divider, property_list: {Key: 'value'}) do
  # Other instructions
end

See: PDF1.7 s14.6, #end_marked_content_sequence



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# File 'lib/hexapdf/content/canvas.rb', line 1824

def marked_content_sequence(tag, property_list: nil)
  raise_unless_at_page_description_level
  if property_list
    property_list = resources.property_list(property_list) if property_list.kind_of?(Symbol)
    invoke2(:BDC, tag, resources.add_property_list(property_list))
  else
    invoke1(:BMC, tag)
  end
  if block_given?
    yield
    end_marked_content_sequence
  end
  self
end

#miter_limit(limit = nil, &block) ⇒ Object Also known as: miter_limit=

:call-seq:

canvas.miter_limit                    => current_miter_limit
canvas.miter_limit(limit)             => canvas
canvas.miter_limit(limit) { block }   => canvas

The miter limit specifies the maximum ratio of the miter length to the line width for mitered line joins (see #line_join_style). When the limit is exceeded, a bevel join is used instead of a miter join.

Returns the current miter limit (see Content::GraphicsState#miter_limit) when no argument is given. Otherwise sets the miter limit to the given limit and returns self. The setter version can also be called in the miter_limit= form.

If the limit and a block are provided, the changed miter limit is only active during the block by saving and restoring the graphics state.

Examples:

canvas.miter_limit(10)
canvas.miter_limit          # => 10
canvas.miter_limit = 5      # => 5

canvas.miter_limit(10) do
  canvas.miter_limit        # => 10
end
canvas.miter_limit          # => 5

See: PDF1.7 s8.4.3.5



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# File 'lib/hexapdf/content/canvas.rb', line 561

def miter_limit(limit = nil, &block)
  gs_getter_setter(:miter_limit, :M, limit, &block)
end

#move_text_cursor(offset: nil, absolute: true) ⇒ Object

:call-seq:

canvas.move_text_cursor(offset: nil, absolute: true)     -> canvas

Moves the text cursor by modifying the text and text line matrices.

If offset is not specified, the text cursor is moved to the start of the next text line using #leading as vertical offset.

Otherwise, the arguments offset, which has to be an array of the form [x, y], and absolute work together:

  • If absolute is true, then the text and text line matrices are set to [1, 0, 0, 1, x, y], placing the origin of text space, and therefore the text cursor, at [x, y].

    Note that absolute has to be understood in terms of the text matrix since for the actual rendering the current transformation matrix is multiplied with the text matrix.

  • If absolute is false, then the text cursor is moved to the start of the next line, offset from the start of the current line (the origin of the text line matrix) by offset.

See: #show_glyphs



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# File 'lib/hexapdf/content/canvas.rb', line 1563

def move_text_cursor(offset: nil, absolute: true)
  begin_text
  if offset
    if absolute
      text_matrix(1, 0, 0, 1, offset[0], offset[1])
    else
      invoke2(:Td, offset[0], offset[1])
    end
  else
    invoke0(:"T*")
  end
  self
end

#move_to(x, y) ⇒ Object

:call-seq:

canvas.move_to(x, y)       => canvas

Begins a new subpath (and possibly a new path) by moving the current point to the given point.

Examples:

canvas.move_to(100, 50)



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# File 'lib/hexapdf/content/canvas.rb', line 802

def move_to(x, y)
  raise_unless_at_page_description_level_or_in_path
  invoke2(:m, x, y)
  @current_point[0] = @start_point[0] = x
  @current_point[1] = @start_point[1] = y
  self
end

#opacity(fill_alpha: nil, stroke_alpha: nil) ⇒ Object

:call-seq:

canvas.opacity                                           => current_values
canvas.opacity(fill_alpha:)                              => canvas
canvas.opacity(stroke_alpha:)                            => canvas
canvas.opacity(fill_alpha:, stroke_alpha:)               => canvas
canvas.opacity(fill_alpha:, stroke_alpha:) { block }     => canvas

The fill and stroke alpha values determine how opaque drawn elements will be. Note that the fill alpha value applies not just to fill values but to all non-stroking operations (e.g. images, …).

Returns the current fill alpha (see Content::GraphicsState#fill_alpha) and stroke alpha (see Content::GraphicsState#stroke_alpha) values using a hash with the keys :fill_alpha and :stroke_alpha when no argument is given. Otherwise sets the fill and stroke alpha values and returns self. The setter version can also be called in the #opacity= form.

If the values are set and a block is provided, the changed alpha values are only active during the block by saving and restoring the graphics state.

Examples:

canvas.opacity(fill_alpha: 0.5)
canvas.opacity                               # => {fill_alpha: 0.5, stroke_alpha: 1.0}
canvas.opacity(fill_alpha: 0.4, stroke_alpha: 0.9)
canvas.opacity                               # => {fill_alpha: 0.4, stroke_alpha: 0.9}

canvas.opacity(stroke_alpha: 0.7) do
  canvas.opacity                             # => {fill_alpha: 0.4, stroke_alpha: 0.7}
end
canvas.opacity                               # => {fill_alpha: 0.4, stroke_alpha: 0.9}

See: PDF1.7 s11.6.4.4



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# File 'lib/hexapdf/content/canvas.rb', line 769

def opacity(fill_alpha: nil, stroke_alpha: nil)
  if !fill_alpha.nil? || !stroke_alpha.nil?
    raise_unless_at_page_description_level_or_in_text
    save_graphics_state if block_given?
    if (!fill_alpha.nil? && graphics_state.fill_alpha != fill_alpha) ||
        (!stroke_alpha.nil? && graphics_state.stroke_alpha != stroke_alpha)
      dict = {Type: :ExtGState}
      dict[:CA] = stroke_alpha unless stroke_alpha.nil?
      dict[:ca] = fill_alpha unless fill_alpha.nil?
      dict[:AIS] = false if graphics_state.alpha_source
      invoke1(:gs, resources.add_ext_gstate(dict))
    end
    if block_given?
      yield
      restore_graphics_state
    end
    self
  elsif block_given?
    raise ArgumentError, "Block only allowed with an argument"
  else
    {fill_alpha: graphics_state.fill_alpha, stroke_alpha: graphics_state.stroke_alpha}
  end
end

#polygon(*points, radius: 0) ⇒ Object

:call-seq:

canvas.polygon(x0, y0, x1, y1, x2, y2, ..., radius: 0)          => canvas

Appends a polygon consisting of the given points to the path as a complete subpath. The point (x0, y0 + radius) becomes the new current point.

If radius is greater than 0, the corners are rounded with the given radius.

If there is no current path when the method is invoked, a new path is automatically begun.

Examples:

canvas.polygon(0, 0, 100, 0, 100, 100, 0, 100)
canvas.polygon(0, 0, 100, 0, 100, 100, 0, 100, radius: 10)



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# File 'lib/hexapdf/content/canvas.rb', line 957

def polygon(*points, radius: 0)
  if radius == 0
    polyline(*points)
  else
    check_poly_points(points)
    move_to(*point_on_line(points[0], points[1], points[2], points[3], distance: radius))
    points.concat(points[0, 4])
    0.step(points.length - 6, 2) {|i| line_with_rounded_corner(*points[i, 6], radius)}
  end
  close_subpath
end

#polyline(*points) ⇒ Object

:call-seq:

canvas.polyline(x0, y0, x1, y1, x2, y2, ...)          => canvas

Moves the current point to (x0, y0) and appends line segments between all given consecutive points, i.e. between (x0, y0) and (x1, y1), between (x1, y1) and (x2, y2) and so on. The last point becomes the new current point.

Examples:

canvas.polyline(0, 0, 100, 0, 100, 100, 0, 100, 0, 0)



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# File 'lib/hexapdf/content/canvas.rb', line 932

def polyline(*points)
  check_poly_points(points)
  move_to(points[0], points[1])
  i = 2
  while i < points.length
    line_to(points[i], points[i + 1])
    i += 2
  end
  self
end

#rectangle(x, y, width, height, radius: 0) ⇒ Object

:call-seq:

canvas.rectangle(x, y, width, height, radius: 0)       => canvas

Appends a rectangle to the current path as a complete subpath (drawn in counterclockwise direction), with the lower-left corner specified by x and y and the given width and height.

If radius is greater than 0, the corners are rounded with the given radius.

If there is no current path when the method is invoked, a new path is automatically begun.

The current point is set to the lower-left corner if radius is zero, otherwise it is set to (x, y + radius).

Examples:

canvas.rectangle(100, 100, 100, 50)
canvas.rectangle(100, 100, 100, 50, radius: 10)



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# File 'lib/hexapdf/content/canvas.rb', line 883

def rectangle(x, y, width, height, radius: 0)
  raise_unless_at_page_description_level_or_in_path
  if radius == 0
    invoke(:re, x, y, width, height)
    @current_point[0] = @start_point[0] = x
    @current_point[1] = @start_point[1] = y
    self
  else
    polygon(x, y, x + width, y, x + width, y + height, x, y + height, radius: radius)
  end
end

#rendering_intent(intent = nil, &bk) ⇒ Object Also known as: rendering_intent=

:call-seq:

canvas.rendering_intent                       => current_rendering_intent
canvas.rendering_intent(intent)               => canvas
canvas.rendering_intent(intent) { block }     => canvas

The rendering intent is used to specify the intent on how colors should be rendered since sometimes compromises have to be made when the capabilities of an output device are not sufficient. The intent parameter can be one of the following symbols:

  • :AbsoluteColorimetric

  • :RelativeColorimetric

  • :Saturation

  • :Perceptual

Returns the current rendering intent (see Content::GraphicsState#rendering_intent) when no argument is given. Otherwise sets the rendering intent using the intent argument and returns self. The setter version can also be called in the rendering_intent= form.

If the intent and a block are provided, the changed rendering intent is only active during the block by saving and restoring the graphics state.

Examples:

canvas.rendering_intent(:Perceptual)
canvas.rendering_intent                      # => :Perceptual
canvas.rendering_intent = :Saturation        # => :Saturation

canvas.rendering_intent(:Perceptual) do
  canvas.rendering_intent                    # => :Perceptual
end
canvas.rendering_intent                      # => :Saturation

See: PDF1.7 s8.6.5.8, RenderingIntent



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# File 'lib/hexapdf/content/canvas.rb', line 656

def rendering_intent(intent = nil, &bk)
  gs_getter_setter(:rendering_intent, :ri, intent && RenderingIntent.normalize(intent), &bk)
end

#resources ⇒ Object

Returns the resource dictionary of the context object.



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# File 'lib/hexapdf/content/canvas.rb', line 213

def resources
  @context.resources
end

#restore_graphics_state ⇒ Object

:call-seq:

canvas.restore_graphics_state      => canvas

Restores the current graphics state and returns self.

Must not be invoked more times than #save_graphics_state.

See: PDF1.7 s8.4.2, #save_graphics_state



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# File 'lib/hexapdf/content/canvas.rb', line 259

def restore_graphics_state
  raise_unless_at_page_description_level
  invoke0(:Q)
  self
end

#rotate(angle, origin: nil, &block) ⇒ Object

:call-seq:

canvas.rotate(angle, origin: nil)               => canvas
canvas.rotate(angle, origin: nil) { block }     => canvas

Rotates the user space angle degrees around the coordinate system origin or around the given point and returns self.

If invoked with a block, the rotation of the user space is only active during the block by saving and restoring the graphics state.

Note that the origin of the coordinate system itself doesn’t change!

origin

The point around which the user space should be rotated.

Examples:

canvas.rotate(90) do                 # Positive x-axis is now pointing upwards
  canvas.line(0, 0, 100, 0)          # Actually from (0, 0) to (0, 100)
end
canvas.line(0, 0, 100, 0)            # Again from (0, 0) to (100, 0)

canvas.rotate(90, origin: [100, 100]) do
  canvas.line(100, 100, 200, 0)      # Actually from (100, 100) to (100, 200)
end

See: #transform



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# File 'lib/hexapdf/content/canvas.rb', line 327

def rotate(angle, origin: nil, &block)
  cos = Math.cos(deg_to_rad(angle))
  sin = Math.sin(deg_to_rad(angle))

  # Rotation is performed around the coordinate system origin but points are translated so
  # that the rotated rotation origin coincides with the unrotated one.
  tx = (origin ? origin[0] - (origin[0] * cos - origin[1] * sin) : 0)
  ty = (origin ? origin[1] - (origin[0] * sin + origin[1] * cos) : 0)
  transform(cos, sin, -sin, cos, tx, ty, &block)
end

#save_graphics_state ⇒ Object

:call-seq:

canvas.save_graphics_state              => canvas
canvas.save_graphics_state { block }    => canvas

Saves the current graphics state and returns self.

If invoked without a block a corresponding call to #restore_graphics_state must be done. Otherwise the graphics state is automatically restored when the block is finished.

Examples:

# With a block
canvas.save_graphics_state do
  canvas.line_width(10)
  canvas.line(100, 100, 200, 200)
end

# Same without a block
canvas.save_graphics_state
canvas.line_width(10)
canvas.line(100, 100, 200, 200)
canvas.restore_graphics_state

See: PDF1.7 s8.4.2, #restore_graphics_state



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# File 'lib/hexapdf/content/canvas.rb', line 241

def save_graphics_state
  raise_unless_at_page_description_level
  invoke0(:q)
  if block_given?
    yield
    restore_graphics_state
  end
  self
end

#scale(sx, sy = sx, origin: nil, &block) ⇒ Object

:call-seq:

canvas.scale(sx, sy = sx, origin: nil)              => canvas
canvas.scale(sx, sy = sx, origin: nil) { block }    => canvas

Scales the user space sx units in the horizontal and sy units in the vertical direction and returns self. If the optional origin is specified, scaling is done from that point.

If invoked with a block, the scaling is only active during the block by saving and restoring the graphics state.

Note that the origin of the coordinate system itself doesn’t change!

origin

The point from which the user space should be scaled.

Examples:

canvas.scale(2, 3) do                # Point (1, 1) is now actually (2, 3)
  canvas.line(50, 50, 100, 100)      # Actually from (100, 150) to (200, 300)
end
canvas.line(0, 0, 100, 0)            # Again from (0, 0) to (100, 0)

canvas.scale(2, 3, origin: [50, 50]) do
  canvas.line(50, 50, 100, 100)      # Actually from (50, 50) to (200, 300)
end

See: #transform



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# File 'lib/hexapdf/content/canvas.rb', line 366

def scale(sx, sy = sx, origin: nil, &block)
  # As with rotation, scaling is performed around the coordinate system origin but points
  # are translated so that the scaled scaling origin coincides with the unscaled one.
  tx = (origin ? origin[0] - origin[0] * sx : 0)
  ty = (origin ? origin[1] - origin[1] * sy : 0)
  transform(sx, 0, 0, sy, tx, ty, &block)
end

#show_glyphs(glyphs) ⇒ Object

:call-seq:

canvas.show_glyphs(glyphs)      -> canvas

Low-level method for actually showing text on the canvas.

The argument glyphs needs to be a an array of glyph objects valid for the current font, optionally interspersed with numbers for kerning.

Text is always shown at the current position of the text cursor, i.e. the origin of the text matrix. To move the text cursor to somewhere else use #move_text_cursor before calling this method.

The text matrix is updated to correctly represent the graphics state after the invocation.

This method is usually not invoked directly but by higher level methods like #text.



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# File 'lib/hexapdf/content/canvas.rb', line 1711

def show_glyphs(glyphs)
  begin_text

  result = [''.b]
  offset = 0
  glyphs.each do |item|
    if item.kind_of?(Numeric)
      result << item << ''.b
      offset -= item * graphics_state.scaled_font_size
    else
      encoded = @font.encode(item)
      result[-1] << encoded

      offset += item.width * graphics_state.scaled_font_size +
        graphics_state.scaled_character_spacing
      offset += graphics_state.scaled_word_spacing if encoded == " ".freeze
    end
  end

  invoke1(:TJ, result)
  graphics_state.tm.translate(offset, 0)
  self
end

#show_glyphs_only(glyphs) ⇒ Object

:call-seq:

canvas.show_glyphs_only(glyphs)      -> canvas

Same operation as with #show_glyphs but without updating the text matrix.

This method should only be used by advanced text layouting algorithms which perform the necessary calculations themselves!

Warning: Since this method doesn’t update the text matrix, all following results from #text_cursor and other methods using the current text matrix are invalid until the next call to #text_matrix or #end_text.



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# File 'lib/hexapdf/content/canvas.rb', line 1746

def show_glyphs_only(glyphs)
  begin_text

  result = [''.b]
  glyphs.each do |item|
    if item.kind_of?(Numeric)
      result << item << ''.b
    else
      result[-1] << @font.encode(item)
    end
  end

  serialize1(:TJ, result)
  self
end

#skew(a, b, origin: nil, &block) ⇒ Object

:call-seq:

canvas.skew(a, b, origin: nil)               => canvas
canvas.skew(a, b, origin: nil) { block }     => canvas

Skews the the x-axis by a degrees and the y-axis by b degress and returns self. If the optional origin is specified, skewing is done from that point.

If invoked with a block, the skewing is only active during the block by saving and restoring the graphics state.

Note that the origin of the coordinate system itself doesn’t change!

origin

The point from which the axes are skewed.

Examples:

canvas.skew(0, 45) do                 # Point (1, 1) is now actually (2, 1)
  canvas.line(50, 50, 100, 100)       # Actually from (100, 50) to (200, 100)
end
canvas.line(0, 0, 100, 0)             # Again from (0, 0) to (100, 0)

canvas.skew(0, origin: [50, 50]) do
  canvas.line(50, 50, 100, 100)       # Actually from (50, 50) to (200, 300)
end

See: #transform



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# File 'lib/hexapdf/content/canvas.rb', line 423

def skew(a, b, origin: nil, &block)
  tan_a = Math.tan(deg_to_rad(a))
  tan_b = Math.sin(deg_to_rad(b))

  # As with rotation, skewing is performed around the coordinate system origin but points
  # are translated so that the skewed skewing origin coincides with the unskewed one.
  tx = (origin ? -origin[1] * tan_b : 0)
  ty = (origin ? -origin[0] * tan_a : 0)
  transform(1, tan_a, tan_b, 1, tx, ty, &block)
end

#stroke ⇒ Object

:call-seq:

canvas.stroke    => canvas

Strokes the path.

See: PDF1.7 s8.5.3.1, s8.5.3.2



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# File 'lib/hexapdf/content/canvas.rb', line 1119

def stroke
  raise_unless_in_path_or_clipping_path
  invoke0(:S)
  self
end

#stroke_color(*color, &block) ⇒ Object Also known as: stroke_color=

:call-seq:

canvas.stroke_color                             => current_stroke_color
canvas.stroke_color(gray)                       => canvas
canvas.stroke_color(r, g, b)                    => canvas
canvas.stroke_color(c, m, y, k)                 => canvas
canvas.stroke_color(string)                     => canvas
canvas.stroke_color(color_object)               => canvas
canvas.stroke_color(array)                      => canvas
canvas.stroke_color(color_spec) { block }       => canvas

The stroke color defines the color used for stroking operations, i.e. for painting paths.

There are several ways to define the color that should be used:

  • A single numeric argument specifies a gray color (see Content::ColorSpace::DeviceGray::Color).

  • Three numeric arguments specify an RGB color (see Content::ColorSpace::DeviceRGB::Color).

  • A string in the format “RRGGBB” where “RR” is the hexadecimal number for the red, “GG” for the green and “BB” for the blue color value also specifies an RGB color.

  • Four numeric arguments specify a CMYK color (see Content::ColorSpace::DeviceCMYK::Color).

  • A color object is used directly (normally used for color spaces other than DeviceRGB, DeviceCMYK and DeviceGray).

  • An array is treated as if its items were specified separately as arguments.

Returns the current stroke color (see Content::GraphicsState#stroke_color) when no argument is given. Otherwise sets the stroke color using the given arguments and returns self. The setter version can also be called in the stroke_color= form.

If the arguments and a block are provided, the changed stroke color is only active during the block by saving and restoring the graphics state.

Examples:

# With no arguments just returns the current color
canvas.stroke_color                        # => DeviceGray.color(0.0)

# Same gray color because integer values are normalized to the range of 0.0 to 1.0
canvas.stroke_color(102)
canvas.stroke_color(0.4)

# Specifying RGB colors
canvas.stroke_color(255, 255, 0)
canvas.stroke_color("FFFF00")

# Specifying CMYK colors
canvas.stroke_color(255, 255, 0, 128)

# Can use a color object directly
color = HexaPDF::Content::ColorSpace::DeviceRGB.color(255, 255, 0)
canvas.stroke_color(color)

# An array argument is destructured - these calls are all equal
cnavas.stroke_color(255, 255, 0)
canvas.stroke_color([255, 255, 0])
canvas.stroke_color = [255, 255, 0]

# As usual, can be invoked with a block to limit the effects
canvas.stroke_color(102) do
  canvas.stroke_color                      # => ColorSpace::DeviceGray.color(0.4)
end

See: PDF1.7 s8.6, ColorSpace



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# File 'lib/hexapdf/content/canvas.rb', line 723

def stroke_color(*color, &block)
  color_getter_setter(:stroke_color, color, :RG, :G, :K, :CS, :SCN, &block)
end

#text(text, at: nil) ⇒ Object

:call-seq:

canvas.text(text)                  -> canvas
canvas.text(text, at: [x, y])      -> canvas

Shows the given text string.

If no position is provided, the text is positioned at the current position of the text cursor (the origin in case of a new text object or otherwise after the last shown text).

The text string may contain any valid Unicode newline separator and if so, multiple lines are shown, using #leading for offsetting the lines.

Note that there are no provisions to make sure that all text is visible! So if the text string is too long, it will just flow off the page and be cut off.

Examples:

canvas.font('Times', size: 12)
canvas.text("This is a \n multiline text", at: [100, 100])

See: www.unicode.org/reports/tr18/#Line_Boundaries



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# File 'lib/hexapdf/content/canvas.rb', line 1686

def text(text, at: nil)
  move_text_cursor(offset: at) if at
  lines = text.split(/\u{D A}|(?!\u{D A})[\u{A}-\u{D}\u{85}\u{2028}\u{2029}]/, -1)
  lines.each_with_index do |str, index|
    show_glyphs(@font.decode_utf8(str))
    move_text_cursor unless index == lines.length - 1
  end
  self
end

#text_cursor ⇒ Object

:call-seq:

canvas.text_cursor     -> [x, y]

Returns the position of the text cursor, i.e. the origin of the current text matrix.

Note that this method can only be called while the current graphic object is a text object since the text matrix is otherwise undefined.



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# File 'lib/hexapdf/content/canvas.rb', line 1584

def text_cursor
  raise_unless_in_text
  graphics_state.tm.evaluate(0, 0)
end

#text_matrix(a, b, c, d, e, f) ⇒ Object

:call-seq:

canvas.text_matrix(a, b, c, d, e, f)     => canvas

Sets the text matrix (and the text line matrix) to the given matrix and returns self.

The given values are interpreted as a matrix in the following way:

a b 0
c d 0
e f 1

Examples:

canvas.begin_text
canvas.text_matrix(1, 0, 0, 1, 100, 100)

See: PDF1.7 s9.4.2



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# File 'lib/hexapdf/content/canvas.rb', line 1535

def text_matrix(a, b, c, d, e, f)
  begin_text
  invoke(:Tm, a, b, c, d, e, f)
  self
end

#text_rendering_mode(m = nil, &bk) ⇒ Object Also known as: text_rendering_mode=

:call-seq:

canvas.text_rendering_mode                     => current_text_rendering_mode
canvas.text_rendering_mode(mode)               => canvas
canvas.text_rendering_mode(mode) { block }     => canvas

The text rendering mode determines if and how glyphs are rendered. The mode parameter can either be a valid integer or one of the symbols :fill, :stroke, :fill_stroke, :invisible, :fill_clip, :stroke_clip, :fill_stroke_clip or :clip (see TextRenderingMode.normalize for details). Note that the return value is always a normalized text rendering mode value.

Returns the current text rendering mode value (see Content::GraphicsState#text_rendering_mode) when no argument is given. Otherwise sets the text rendering mode using the mode argument and returns self. The setter version can also be called in the text_rendering_mode= form.

If the mode and a block are provided, the changed text rendering mode is only active during the block by saving and restoring the graphics state.

Examples:

canvas.text_rendering_mode(:fill)
canvas.text_rendering_mode               # => #<NamedValue @name=:fill, @value = 0>
canvas.text_rendering_mode = :stroke     # => #<NamedValue @name=:stroke, @value = 1>

canvas.text_rendering_mode(3) do
  canvas.text_rendering_mode             # => #<NamedValue @name=:invisible, @value = 3>
end
canvas.text_rendering_mode               # => #<NamedValue @name=:stroke, @value = 1>

See: PDF1.7 s9.3.6



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# File 'lib/hexapdf/content/canvas.rb', line 1453

def text_rendering_mode(m = nil, &bk)
  gs_getter_setter(:text_rendering_mode, :Tr, m && TextRenderingMode.normalize(m), &bk)
end

#text_rise(amount = nil, &bk) ⇒ Object Also known as: text_rise=

:call-seq:

canvas.text_rise                       => current_text_rise
canvas.text_rise(amount)               => canvas
canvas.text_rise(amount) { block }     => canvas

The text rise specifies the vertical distance to move the baseline up or down from its default location. Positive values move the baseline up, negative values down.

Returns the current text rise value (see Content::GraphicsState#text_rise) when no argument is given. Otherwise sets the text rise using the amount argument and returns self. The setter version can also be called in the text_rise= form.

If the amount and a block are provided, the changed text rise is only active during the block by saving and restoring the graphics state.

Examples:

canvas.text_rise(5)
canvas.text_rise                      # => 5
canvas.text_rise = 10                 # => 10

canvas.text_rise(15) do
  canvas.text_rise                    # => 15
end
canvas.text_rise                      # => 10

See: PDF1.7 s9.3.7



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# File 'lib/hexapdf/content/canvas.rb', line 1485

def text_rise(amount = nil, &bk)
  gs_getter_setter(:text_rise, :Ts, amount, &bk)
end

#transform(a, b, c, d, e, f) ⇒ Object

:call-seq:

canvas.transform(a, b, c, d, e, f)              => canvas
canvas.transform(a, b, c, d, e, f) { block }    => canvas

Transforms the user space by applying the given matrix to the current transformation matrix and returns self.

If invoked with a block, the transformation is only active during the block by saving and restoring the graphics state.

The given values are interpreted as a matrix in the following way:

a b 0
c d 0
e f 1

Examples:

canvas.transform(1, 0, 0, 1, 100, 100) do  # Translate origin to (100, 100)
  canvas.line(0, 0, 100, 100)              # Actually from (100, 100) to (200, 200)
end
canvas.line(0, 0, 100, 100)                # Again from (0, 0) to (100, 100)

See: PDF1.7 s8.3, s8.4.4



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# File 'lib/hexapdf/content/canvas.rb', line 289

def transform(a, b, c, d, e, f)
  raise_unless_at_page_description_level
  save_graphics_state if block_given?
  invoke(:cm, a, b, c, d, e, f)
  if block_given?
    yield
    restore_graphics_state
  end
  self
end

#translate(x, y, &block) ⇒ Object

:call-seq:

canvas.translate(x, y)               => canvas
canvas.translate(x, y) { block }     => canvas

Translates the user space coordinate system origin to the given x and y coordinates and returns self.

If invoked with a block, the translation of the user space is only active during the block by saving and restoring the graphics state.

Examples:

canvas.translate(100, 100) do        # Origin is now at (100, 100)
  canvas.line(0, 0, 100, 0)          # Actually from (100, 100) to (200, 100)
end
canvas.line(0, 0, 100, 0)            # Again from (0, 0) to (100, 0)

See: #transform



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# File 'lib/hexapdf/content/canvas.rb', line 392

def translate(x, y, &block)
  transform(1, 0, 0, 1, x, y, &block)
end

#word_spacing(amount = nil, &bk) ⇒ Object Also known as: word_spacing=

:call-seq:

canvas.word_spacing                       => current_word_spacing
canvas.word_spacing(amount)               => canvas
canvas.word_spacing(amount) { block }     => canvas

If the font’s PDF encoding supports this, the word spacing determines how much additional space is added when the ASCII space character is encountered in a text. For horizontal writing positive values increase the distance between two words, whereas for vertical writing negative values increase the distance.

Note that in HexaPDF only the standard 14 PDF Type1 fonts support this property! When using any other font, for example a TrueType font, this property has no effect.

Returns the current word spacing value (see Content::GraphicsState#word_spacing) when no argument is given. Otherwise sets the word spacing using the amount argument and returns self. The setter version can also be called in the word_spacing= form.

If the amount and a block are provided, the changed word spacing is only active during the block by saving and restoring the graphics state.

Examples:

canvas.word_spacing(0.25)
canvas.word_spacing                      # => 0.25
canvas.word_spacing = 0.5                # => 0.5

canvas.word_spacing(0.10) do
  canvas.word_spacing                    # => 0.10
end
canvas.word_spacing                      # => 0.5

See: PDF1.7 s9.3.3



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# File 'lib/hexapdf/content/canvas.rb', line 1352

def word_spacing(amount = nil, &bk)
  gs_getter_setter(:word_spacing, :Tw, amount, &bk)
end

#xobject(obj, at:, width: nil, height: nil) ⇒ Object Also known as: image

:call-seq:

canvas.xobject(filename, at:, width: nil, height: nil)       => xobject
canvas.xobject(io, at:, width: nil, height: nil)             => xobject
canvas.xobject(image_object, at:, width: nil, height: nil)   => image_object
canvas.xobject(form_object, at:, width: nil, height: nil)    => form_object

Draws the given XObject (either an image XObject or a form XObject) at the specified position and returns the XObject.

Any image format for which a HexaPDF::ImageLoader object is available and registered with the configuration option ‘image_loader’ can be used. PNG and JPEG images are supported out of the box.

If the filename or the IO specifies a PDF file, the first page of this file is used to create a form XObject which is then drawn.

The at argument has to be an array containing two numbers specifying the lower-left corner at which to draw the XObject.

If width and height are specified, the drawn XObject will have exactly these dimensions. If only one of them is specified, the other dimension is automatically calculated so that the aspect ratio is retained. If neither is specified, the width and height of the XObject are used (for images, 1 pixel being represented by 1 PDF point, i.e. 72 DPI).

Note: If a form XObject is drawn, all currently set graphics state parameters influence the rendering of the form XObject. This means, for example, that when the line width is set to 20, all lines of the form XObject are drawn with that line width unless the line width is changed in the form XObject itself.

Examples:

canvas.xobject('test.png', at: [100, 100])
canvas.xobject('test.pdf', at: [100, 100])

File.new('test.jpg', 'rb') do |io|
  canvas.xobject(io, at: [100, 200], width: 300)
end

image = document.object(5)    # Object with oid=5 is an image XObject in this example
canvas.xobject(image, at: [100, 200], width: 200, heigth: 300)

See: PDF1.7 s8.8, s.8.10.1



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# File 'lib/hexapdf/content/canvas.rb', line 1261

def xobject(obj, at:, width: nil, height: nil)
  unless obj.kind_of?(HexaPDF::Stream)
    obj = context.document.images.add(obj)
  end

  if obj[:Subtype] == :Image
    width, height = calculate_dimensions(obj[:Width], obj[:Height],
                                         rwidth: width, rheight: height)
  else
    width, height = calculate_dimensions(obj.box.width, obj.box.height,
                                         rwidth: width, rheight: height)
    width /= obj.box.width.to_f
    height /= obj.box.height.to_f
    at[0] -= obj.box.left
    at[1] -= obj.box.bottom
  end

  transform(width, 0, 0, height, at[0], at[1]) do
    invoke1(:Do, resources.add_xobject(obj))
  end

  obj
end