Method: RBPDF#Gradient

Defined in:

lib/rbpdf.rb

#Gradient(type, coords, stops, background = [], antialias = false) ⇒ Object Also known as: gradient

Output gradient.

@param int :type

type of gradient (1 Function-based shading; 2 Axial shading; 3 Radial shading; 4 Free-form Gouraud-shaded triangle mesh; 5 Lattice-form Gouraud-shaded triangle mesh; 6 Coons patch mesh; 7 Tensor-product patch mesh). (Not all types are currently supported)

@param array :coords

array of coordinates.

@param array :stops

array gradient color components: color = array of GRAY, RGB or CMYK color components; offset = (0 to 1) represents a location along the gradient vector; exponent = exponent of the exponential interpolation function (default = 1).

@param array :background

An array of colour components appropriate to the colour space, specifying a single background colour value.

@param boolean :antialias

A flag indicating whether to filter the shading function to prevent aliasing artifacts.

@since 3.1.000 (2008-06-09)

@access public

# File 'lib/rbpdf.rb', line 11914

def Gradient(type, coords, stops, background=[], antialias=false)
  n = @gradients.size + 1
  @gradients[n] = {}
  @gradients[n]['type'] = type
  @gradients[n]['coords'] = coords
  @gradients[n]['antialias'] = antialias
  @gradients[n]['colors'] = []
  @gradients[n]['transparency'] = false
  # color space
  numcolspace = stops[0]['color'].size
  bcolor = background
  case numcolspace
  when 4 # CMYK
    @gradients[n]['colspace'] = 'DeviceCMYK'
    unless background.empty?
      @gradients[n]['background'] = sprintf('%.3f %.3f %.3f %.3f', bcolor[0]/100.0, bcolor[1]/100.0, bcolor[2]/100.0, bcolor[3]/100.0)
    end
  when 3 # RGB
    @gradients[n]['colspace'] = 'DeviceRGB'
    unless background.empty?
      @gradients[n]['background'] = sprintf('%.3f %.3f %.3f', bcolor[0]/255.0, bcolor[1]/255.0, bcolor[2]/255.0)
    end
  when 1 # Gray scale
    @gradients[n]['colspace'] = 'DeviceGray'
    unless background.empty?
      @gradients[n]['background'] = sprintf('%.3f', bcolor[0]/255.0)
    end
  end
  num_stops = stops.size
  last_stop_id = num_stops - 1
  stops.each_with_index do |stop, key|
    @gradients[n]['colors'][key] = {}
    # offset represents a location along the gradient vector
    if stop['offset']
      @gradients[n]['colors'][key]['offset'] = stop['offset']
    else
      if key == 0
        @gradients[n]['colors'][key]['offset'] = 0
      elsif key == last_stop_id
        @gradients[n]['colors'][key]['offset'] = 1
      else
        offsetstep = (1 - @gradients[n]['colors'][key - 1]['offset']) / (num_stops - key)
        @gradients[n]['colors'][key]['offset'] = @gradients[n]['colors'][key - 1]['offset'] + offsetstep
      end
    end
    if stop['opacity']
      @gradients[n]['colors'][key]['opacity'] = stop['opacity']
      if stop['opacity'] < 1
        @gradients[n]['transparency'] = true
      end
    else
      @gradients[n]['colors'][key]['opacity'] = 1
    end
    # exponent for the exponential interpolation function
    if stop['exponent']
      @gradients[n]['colors'][key]['exponent'] = stop['exponent']
    else
      @gradients[n]['colors'][key]['exponent'] = 1
    end
    # set colors
    color = stop['color']
    case numcolspace
    when 4 # CMYK
      @gradients[n]['colors'][key]['color'] = sprintf('%.3f %.3f %.3f %.3f', color[0]/100.0, color[1]/100.0, color[2]/100.0, color[3]/100.0)
    when 3 # RGB
      @gradients[n]['colors'][key]['color'] = sprintf('%.3f %.3f %.3f', color[0]/255.0, color[1]/255.0, color[2]/255.0)
    when 1 # Gray scale
      @gradients[n]['colors'][key]['color'] = sprintf('%.3f', color[0]/255.0)
    end
  end
  if @gradients[n]['transparency']
    # paint luminosity gradient
    out("/TGS#{n} gs")
  end
  # paint the gradient
  out("/Sh#{n} sh")
  # restore previous Graphic State
  out('Q')
end