Module: ChunkyPNG::Color
Overview
The Color module defines methods for handling colors. Within the ChunkyPNG library, the concepts of pixels and colors are both used, and they are both represented by a Integer.
Pixels/colors are represented in RGBA componetns. Each of the four components is stored with a depth of 8 bits (maximum value = 255 = MAX). Together, these components are stored in a 4-byte Integer.
A color will always be represented using these 4 components in memory. When the image is encoded, a more suitable representation can be used (e.g. rgb, grayscale, palette-based), for which several conversion methods are provided in this module.
Constant Summary collapse
- MAX =
Returns The maximum value of each color component.
0xff
- PREDEFINED_COLORS =
Returns All the prefined color names in HTML.
{ :aliceblue => 0xf0f8ff00, :antiquewhite => 0xfaebd700, :aqua => 0x00ffff00, :aquamarine => 0x7fffd400, :azure => 0xf0ffff00, :beige => 0xf5f5dc00, :bisque => 0xffe4c400, :black => 0x00000000, :blanchedalmond => 0xffebcd00, :blue => 0x0000ff00, :blueviolet => 0x8a2be200, :brown => 0xa52a2a00, :burlywood => 0xdeb88700, :cadetblue => 0x5f9ea000, :chartreuse => 0x7fff0000, :chocolate => 0xd2691e00, :coral => 0xff7f5000, :cornflowerblue => 0x6495ed00, :cornsilk => 0xfff8dc00, :crimson => 0xdc143c00, :cyan => 0x00ffff00, :darkblue => 0x00008b00, :darkcyan => 0x008b8b00, :darkgoldenrod => 0xb8860b00, :darkgray => 0xa9a9a900, :darkgrey => 0xa9a9a900, :darkgreen => 0x00640000, :darkkhaki => 0xbdb76b00, :darkmagenta => 0x8b008b00, :darkolivegreen => 0x556b2f00, :darkorange => 0xff8c0000, :darkorchid => 0x9932cc00, :darkred => 0x8b000000, :darksalmon => 0xe9967a00, :darkseagreen => 0x8fbc8f00, :darkslateblue => 0x483d8b00, :darkslategray => 0x2f4f4f00, :darkslategrey => 0x2f4f4f00, :darkturquoise => 0x00ced100, :darkviolet => 0x9400d300, :deeppink => 0xff149300, :deepskyblue => 0x00bfff00, :dimgray => 0x69696900, :dimgrey => 0x69696900, :dodgerblue => 0x1e90ff00, :firebrick => 0xb2222200, :floralwhite => 0xfffaf000, :forestgreen => 0x228b2200, :fuchsia => 0xff00ff00, :gainsboro => 0xdcdcdc00, :ghostwhite => 0xf8f8ff00, :gold => 0xffd70000, :goldenrod => 0xdaa52000, :gray => 0x80808000, :grey => 0x80808000, :green => 0x00800000, :greenyellow => 0xadff2f00, :honeydew => 0xf0fff000, :hotpink => 0xff69b400, :indianred => 0xcd5c5c00, :indigo => 0x4b008200, :ivory => 0xfffff000, :khaki => 0xf0e68c00, :lavender => 0xe6e6fa00, :lavenderblush => 0xfff0f500, :lawngreen => 0x7cfc0000, :lemonchiffon => 0xfffacd00, :lightblue => 0xadd8e600, :lightcoral => 0xf0808000, :lightcyan => 0xe0ffff00, :lightgoldenrodyellow => 0xfafad200, :lightgray => 0xd3d3d300, :lightgrey => 0xd3d3d300, :lightgreen => 0x90ee9000, :lightpink => 0xffb6c100, :lightsalmon => 0xffa07a00, :lightseagreen => 0x20b2aa00, :lightskyblue => 0x87cefa00, :lightslategray => 0x77889900, :lightslategrey => 0x77889900, :lightsteelblue => 0xb0c4de00, :lightyellow => 0xffffe000, :lime => 0x00ff0000, :limegreen => 0x32cd3200, :linen => 0xfaf0e600, :magenta => 0xff00ff00, :maroon => 0x80000000, :mediumaquamarine => 0x66cdaa00, :mediumblue => 0x0000cd00, :mediumorchid => 0xba55d300, :mediumpurple => 0x9370d800, :mediumseagreen => 0x3cb37100, :mediumslateblue => 0x7b68ee00, :mediumspringgreen => 0x00fa9a00, :mediumturquoise => 0x48d1cc00, :mediumvioletred => 0xc7158500, :midnightblue => 0x19197000, :mintcream => 0xf5fffa00, :mistyrose => 0xffe4e100, :moccasin => 0xffe4b500, :navajowhite => 0xffdead00, :navy => 0x00008000, :oldlace => 0xfdf5e600, :olive => 0x80800000, :olivedrab => 0x6b8e2300, :orange => 0xffa50000, :orangered => 0xff450000, :orchid => 0xda70d600, :palegoldenrod => 0xeee8aa00, :palegreen => 0x98fb9800, :paleturquoise => 0xafeeee00, :palevioletred => 0xd8709300, :papayawhip => 0xffefd500, :peachpuff => 0xffdab900, :peru => 0xcd853f00, :pink => 0xffc0cb00, :plum => 0xdda0dd00, :powderblue => 0xb0e0e600, :purple => 0x80008000, :red => 0xff000000, :rosybrown => 0xbc8f8f00, :royalblue => 0x4169e100, :saddlebrown => 0x8b451300, :salmon => 0xfa807200, :sandybrown => 0xf4a46000, :seagreen => 0x2e8b5700, :seashell => 0xfff5ee00, :sienna => 0xa0522d00, :silver => 0xc0c0c000, :skyblue => 0x87ceeb00, :slateblue => 0x6a5acd00, :slategray => 0x70809000, :slategrey => 0x70809000, :snow => 0xfffafa00, :springgreen => 0x00ff7f00, :steelblue => 0x4682b400, :tan => 0xd2b48c00, :teal => 0x00808000, :thistle => 0xd8bfd800, :tomato => 0xff634700, :turquoise => 0x40e0d000, :violet => 0xee82ee00, :wheat => 0xf5deb300, :white => 0xffffff00, :whitesmoke => 0xf5f5f500, :yellow => 0xffff0000, :yellowgreen => 0x9acd3200 }
- BLACK =
Returns Black pixel/color.
rgb( 0, 0, 0)
- WHITE =
Returns White pixel/color.
rgb(255, 255, 255)
- TRANSPARENT =
Returns Fully transparent pixel/color.
rgba(0, 0, 0, 0)
Instance Method Summary collapse
-
#a(value) ⇒ Integer
Returns the alpha channel value for the color value.
-
#alpha_decomposable?(color, mask, bg, tolerance = 1) ⇒ Boolean
Checks whether an alpha channel value can successfully be composed given the resulting color, the mask color and a background color, all of which should be opaque.
-
#b(value) ⇒ Integer
Returns the blue-component from the color value.
-
#blend(fg, bg) ⇒ Integer
Blends the foreground and background color by taking the average of the components.
-
#compose_precise(fg, bg) ⇒ Integer
Composes two colors with an alpha channel using floating point math.
-
#compose_quick(fg, bg) ⇒ Integer
(also: #compose)
Composes two colors with an alpha channel using integer math.
-
#decompose_alpha(color, mask, bg) ⇒ Integer
Decomposes the alpha channel value given the resulting color, the mask color and a background color, all of which should be opaque.
-
#decompose_alpha_component(channel, color, mask, bg) ⇒ Integer
Decomposes an alpha channel for either the r, g or b color channel.
-
#decompose_alpha_components(color, mask, bg) ⇒ Array<Integer>
Decomposes the alpha channels for the r, g and b color channel.
-
#decompose_color(color, mask, bg, tolerance = 1) ⇒ Integer
Decomposes a color, given a color, a mask color and a background color.
-
#fade(color, factor) ⇒ Integer
Lowers the intensity of a color, by lowering its alpha by a given factor.
-
#from_hex(hex_value, opacity = nil) ⇒ Integer
Creates a color by converting it from a string in hex notation.
-
#from_rgb_stream(stream, pos = 0) ⇒ Integer
Creates a color by unpacking an rgb triple from a string.
-
#from_rgba_stream(stream, pos = 0) ⇒ Integer
Creates a color by unpacking an rgba triple from a string.
-
#fully_transparent?(value) ⇒ true, false
Returns true if this color is fully transparent.
-
#g(value) ⇒ Integer
Returns the green-component from the color value.
-
#grayscale(teint) ⇒ Integer
Creates a new color using a grayscale teint.
-
#grayscale?(value) ⇒ true, false
Returns true if this color is fully transparent.
-
#grayscale_alpha(teint, a) ⇒ Integer
Creates a new color using a grayscale teint and alpha value.
-
#html_color(color_name, opacity = nil) ⇒ Integer
Gets a color value based on a HTML color name.
-
#int8_mult(a, b) ⇒ Integer
Multiplies two fractions using integer math, where the fractions are stored using an integer between 0 and 255.
-
#opaque!(value) ⇒ Integer
Returns the opaque value of this color by removing the alpha channel.
-
#opaque?(value) ⇒ true, false
Returns true if this color is fully opaque.
-
#pass_bytesize(color_mode, depth, width, height) ⇒ Integer
Returns the number of bytes used for an image pass.
-
#pixel_bitsize(color_mode, depth = 8) ⇒ Integer
Returns the size in bits of a pixel when it is stored using a given color mode.
-
#pixel_bytesize(color_mode, depth = 8) ⇒ Integer
Returns the size in bytes of a pixel when it is stored using a given color mode.
-
#r(value) ⇒ Integer
Returns the red-component from the color value.
-
#rgb(r, g, b) ⇒ Integer
Creates a new color using an r, g, b triple.
-
#rgba(r, g, b, a) ⇒ Integer
Creates a new color using an r, g, b triple and an alpha value.
-
#samples_per_pixel(color_mode) ⇒ Integer
Returns the number of sample values per pixel.
-
#scanline_bytesize(color_mode, depth, width) ⇒ Integer
Returns the number of bytes used per scanline.
-
#to_grayscale_alpha_bytes(color) ⇒ Array<Integer>
Returns an array with the grayscale teint and alpha channel values for this color.
-
#to_grayscale_bytes(color) ⇒ Array<Integer>
Returns an array with the grayscale teint value for this color.
-
#to_hex(color, include_alpha = true) ⇒ String
Returns a string representing this color using hex notation (i.e. #rrggbbaa).
-
#to_truecolor_alpha_bytes(color) ⇒ Array<Integer>
Returns an array with the separate RGBA values for this color.
-
#to_truecolor_bytes(color) ⇒ Array<Integer>
Returns an array with the separate RGB values for this color.
Instance Method Details
#a(value) ⇒ Integer
Returns the alpha channel value for the color value.
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# File 'lib/chunky_png/color.rb', line 186 def a(value) value & 0x000000ff end |
#alpha_decomposable?(color, mask, bg, tolerance = 1) ⇒ Boolean
Checks whether an alpha channel value can successfully be composed given the resulting color, the mask color and a background color, all of which should be opaque.
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# File 'lib/chunky_png/color.rb', line 338 def alpha_decomposable?(color, mask, bg, tolerance = 1) components = decompose_alpha_components(color, mask, bg) sum = components.inject(0) { |a,b| a + b } max = components.max * 3 return components.max <= 255 && components.min >= 0 && (sum + tolerance * 3) >= max end |
#b(value) ⇒ Integer
Returns the blue-component from the color value.
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# File 'lib/chunky_png/color.rb', line 178 def b(value) (value & 0x0000ff00) >> 8 end |
#blend(fg, bg) ⇒ Integer
Blends the foreground and background color by taking the average of the components.
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# File 'lib/chunky_png/color.rb', line 293 def blend(fg, bg) (fg + bg) >> 1 end |
#compose_precise(fg, bg) ⇒ Integer
Composes two colors with an alpha channel using floating point math.
This method uses more precise floating point math, but this precision is lost when the result is converted back to an integer. Because it is slower than the version based on integer math, that version is preferred.
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# File 'lib/chunky_png/color.rb', line 270 def compose_precise(fg, bg) return fg if opaque?(fg) || fully_transparent?(bg) return bg if fully_transparent?(fg) fg_a = a(fg).to_f / MAX bg_a = a(bg).to_f / MAX a_com = (1.0 - fg_a) * bg_a new_r = (fg_a * r(fg) + a_com * r(bg)).round new_g = (fg_a * g(fg) + a_com * g(bg)).round new_b = (fg_a * b(fg) + a_com * b(bg)).round new_a = ((fg_a + a_com) * MAX).round rgba(new_r, new_g, new_b, new_a) end |
#compose_quick(fg, bg) ⇒ Integer Also known as: compose
Composes two colors with an alpha channel using integer math.
This version is faster than the version based on floating point math, so this compositing function is used by default.
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# File 'lib/chunky_png/color.rb', line 248 def compose_quick(fg, bg) return fg if opaque?(fg) || fully_transparent?(bg) return bg if fully_transparent?(fg) a_com = int8_mult(0xff - a(fg), a(bg)) new_r = int8_mult(a(fg), r(fg)) + int8_mult(a_com, r(bg)) new_g = int8_mult(a(fg), g(fg)) + int8_mult(a_com, g(bg)) new_b = int8_mult(a(fg), b(fg)) + int8_mult(a_com, b(bg)) new_a = a(fg) + a_com rgba(new_r, new_g, new_b, new_a) end |
#decompose_alpha(color, mask, bg) ⇒ Integer
Decomposes the alpha channel value given the resulting color, the mask color and a background color, all of which should be opaque.
Make sure to call #alpha_decomposable? first to see if the alpha channel value can successfully decomposed with a given tolerance, otherwise the return value of this method is undefined.
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# File 'lib/chunky_png/color.rb', line 357 def decompose_alpha(color, mask, bg) components = decompose_alpha_components(color, mask, bg) (components.inject(0) { |a,b| a + b } / 3.0).round end |
#decompose_alpha_component(channel, color, mask, bg) ⇒ Integer
Decomposes an alpha channel for either the r, g or b color channel.
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# File 'lib/chunky_png/color.rb', line 368 def decompose_alpha_component(channel, color, mask, bg) ((send(channel, bg) - send(channel, color)).to_f / (send(channel, bg) - send(channel, mask)).to_f * MAX).round end |
#decompose_alpha_components(color, mask, bg) ⇒ Array<Integer>
Decomposes the alpha channels for the r, g and b color channel.
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# File 'lib/chunky_png/color.rb', line 378 def decompose_alpha_components(color, mask, bg) [ decompose_alpha_component(:r, color, mask, bg), decompose_alpha_component(:g, color, mask, bg), decompose_alpha_component(:b, color, mask, bg) ] end |
#decompose_color(color, mask, bg, tolerance = 1) ⇒ Integer
Decomposes a color, given a color, a mask color and a background color. The returned color will be a variant of the mask color, with the alpha channel set to the best fitting value. This basically is the reverse operation if alpha composition.
If the color cannot be decomposed, this method will return the fully transparentvariant of the mask color.
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# File 'lib/chunky_png/color.rb', line 320 def decompose_color(color, mask, bg, tolerance = 1) if alpha_decomposable?(color, mask, bg, tolerance) mask & 0xffffff00 | decompose_alpha(color, mask, bg) else mask & 0xffffff00 end end |
#fade(color, factor) ⇒ Integer
Lowers the intensity of a color, by lowering its alpha by a given factor.
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# File 'lib/chunky_png/color.rb', line 301 def fade(color, factor) new_alpha = int8_mult(a(color), factor) (color & 0xffffff00) | new_alpha end |
#from_hex(hex_value, opacity = nil) ⇒ Integer
Creates a color by converting it from a string in hex notation.
It supports colors with (#rrggbbaa) or without (#rrggbb) alpha channel. Color strings may include the prefix “0x” or “#”.
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# File 'lib/chunky_png/color.rb', line 144 def from_hex(hex_value, opacity = nil) if HEX_COLOR_REGEXP =~ hex_value base_color = $1.hex << 8 opacity ||= $2 ? $2.hex : 0xff base_color | opacity else raise ArgumentError, "Not a valid hex color notation: #{hex_value.inspect}!" end end |
#from_rgb_stream(stream, pos = 0) ⇒ Integer
Creates a color by unpacking an rgb triple from a string.
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# File 'lib/chunky_png/color.rb', line 119 def from_rgb_stream(stream, pos = 0) rgb(*stream.unpack("@#{pos}C3")) end |
#from_rgba_stream(stream, pos = 0) ⇒ Integer
Creates a color by unpacking an rgba triple from a string
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# File 'lib/chunky_png/color.rb', line 129 def from_rgba_stream(stream, pos = 0) rgba(*stream.unpack("@#{pos}C4")) end |
#fully_transparent?(value) ⇒ true, false
Returns true if this color is fully transparent.
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# File 'lib/chunky_png/color.rb', line 217 def fully_transparent?(value) a(value) == 0x00000000 end |
#g(value) ⇒ Integer
Returns the green-component from the color value.
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# File 'lib/chunky_png/color.rb', line 170 def g(value) (value & 0x00ff0000) >> 16 end |
#grayscale(teint) ⇒ Integer
Creates a new color using a grayscale teint.
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# File 'lib/chunky_png/color.rb', line 97 def grayscale(teint) teint << 24 | teint << 16 | teint << 8 | 0xff end |
#grayscale?(value) ⇒ true, false
Returns true if this color is fully transparent.
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# File 'lib/chunky_png/color.rb', line 209 def grayscale?(value) r(value) == b(value) && b(value) == g(value) end |
#grayscale_alpha(teint, a) ⇒ Integer
Creates a new color using a grayscale teint and alpha value.
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# File 'lib/chunky_png/color.rb', line 105 def grayscale_alpha(teint, a) teint << 24 | teint << 16 | teint << 8 | a end |
#html_color(color_name, opacity = nil) ⇒ Integer
Gets a color value based on a HTML color name.
The color name is flexible. E.g. 'yellowgreen'
, 'Yellow green'
, 'YellowGreen'
, 'YELLOW_GREEN'
and :yellow_green
will all return the same color value.
You can include a opacity level in the color name (e.g. 'red @ 0.5'
) or give an explit opacity value as second argument. If no opacity value is given, the color will be fully opaque.
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# File 'lib/chunky_png/color.rb', line 608 def html_color(color_name, opacity = nil) if color_name.to_s =~ HTML_COLOR_REGEXP opacity ||= $2 ? ($2.to_f * 255.0).round : 0xff base_color_name = $1.gsub(/[^a-z]+/i, '').downcase.to_sym return PREDEFINED_COLORS[base_color_name] | opacity if PREDEFINED_COLORS.has_key?(base_color_name) end raise ChunkyPNG::Exception, "Unknown color name #{color_name}!" end |
#int8_mult(a, b) ⇒ Integer
Multiplies two fractions using integer math, where the fractions are stored using an integer between 0 and 255. This method is used as a helper method for compositing colors using integer math.
This is a quicker implementation of ((a * b) / 255.0).round.
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# File 'lib/chunky_png/color.rb', line 234 def int8_mult(a, b) t = a * b + 0x80 ((t >> 8) + t) >> 8 end |
#opaque!(value) ⇒ Integer
Returns the opaque value of this color by removing the alpha channel.
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# File 'lib/chunky_png/color.rb', line 201 def opaque!(value) value | 0x000000ff end |
#opaque?(value) ⇒ true, false
Returns true if this color is fully opaque.
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# File 'lib/chunky_png/color.rb', line 194 def opaque?(value) a(value) == 0x000000ff end |
#pass_bytesize(color_mode, depth, width, height) ⇒ Integer
Returns the number of bytes used for an image pass
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# File 'lib/chunky_png/color.rb', line 675 def pass_bytesize(color_mode, depth, width, height) return 0 if width == 0 || height == 0 (scanline_bytesize(color_mode, depth, width) + 1) * height end |
#pixel_bitsize(color_mode, depth = 8) ⇒ Integer
Returns the size in bits of a pixel when it is stored using a given color mode.
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# File 'lib/chunky_png/color.rb', line 656 def pixel_bitsize(color_mode, depth = 8) samples_per_pixel(color_mode) * depth end |
#pixel_bytesize(color_mode, depth = 8) ⇒ Integer
Returns the size in bytes of a pixel when it is stored using a given color mode.
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# File 'lib/chunky_png/color.rb', line 647 def pixel_bytesize(color_mode, depth = 8) return 1 if depth < 8 (pixel_bitsize(color_mode, depth) + 7) >> 3 end |
#r(value) ⇒ Integer
Returns the red-component from the color value.
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# File 'lib/chunky_png/color.rb', line 162 def r(value) (value & 0xff000000) >> 24 end |
#rgb(r, g, b) ⇒ Integer
Creates a new color using an r, g, b triple.
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# File 'lib/chunky_png/color.rb', line 90 def rgb(r, g, b) r << 24 | g << 16 | b << 8 | 0xff end |
#rgba(r, g, b, a) ⇒ Integer
Creates a new color using an r, g, b triple and an alpha value.
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# File 'lib/chunky_png/color.rb', line 81 def rgba(r, g, b, a) r << 24 | g << 16 | b << 8 | a end |
#samples_per_pixel(color_mode) ⇒ Integer
Returns the number of sample values per pixel.
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# File 'lib/chunky_png/color.rb', line 633 def samples_per_pixel(color_mode) case color_mode when ChunkyPNG::COLOR_INDEXED; 1 when ChunkyPNG::COLOR_TRUECOLOR; 3 when ChunkyPNG::COLOR_TRUECOLOR_ALPHA; 4 when ChunkyPNG::COLOR_GRAYSCALE; 1 when ChunkyPNG::COLOR_GRAYSCALE_ALPHA; 2 else raise ChunkyPNG::NotSupported, "Don't know the numer of samples for this colormode: #{color_mode}!" end end |
#scanline_bytesize(color_mode, depth, width) ⇒ Integer
Returns the number of bytes used per scanline.
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# File 'lib/chunky_png/color.rb', line 665 def scanline_bytesize(color_mode, depth, width) ((pixel_bitsize(color_mode, depth) * width) + 7) >> 3 end |
#to_grayscale_alpha_bytes(color) ⇒ Array<Integer>
Returns an array with the grayscale teint and alpha channel values for this color.
This method expects the r,g and b value to be equal.
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# File 'lib/chunky_png/color.rb', line 433 def to_grayscale_alpha_bytes(color) [b(color), a(color)] # assumption r == g == b end |
#to_grayscale_bytes(color) ⇒ Array<Integer>
Returns an array with the grayscale teint value for this color.
This method expects the r,g and b value to be equal, and the alpha channel will be discarded.
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# File 'lib/chunky_png/color.rb', line 422 def to_grayscale_bytes(color) [b(color)] # assumption r == g == b end |
#to_hex(color, include_alpha = true) ⇒ String
Returns a string representing this color using hex notation (i.e. #rrggbbaa).
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# File 'lib/chunky_png/color.rb', line 394 def to_hex(color, include_alpha = true) include_alpha ? ('#%08x' % color) : ('#%06x' % [color >> 8]) end |
#to_truecolor_alpha_bytes(color) ⇒ Array<Integer>
Returns an array with the separate RGBA values for this color.
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# File 'lib/chunky_png/color.rb', line 402 def to_truecolor_alpha_bytes(color) [r(color), g(color), b(color), a(color)] end |
#to_truecolor_bytes(color) ⇒ Array<Integer>
Returns an array with the separate RGB values for this color. The alpha channel will be discarded.
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# File 'lib/chunky_png/color.rb', line 411 def to_truecolor_bytes(color) [r(color), g(color), b(color)] end |