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[css-color] Add CMYKColor class.
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‎css-color/Overview.bs‎

Lines changed: 163 additions & 45 deletions
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@@ -1671,14 +1671,7 @@ CMYK Colors: the ''device-cmyk()'' function</h2>
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The sixth argument specifies the fallback color,
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used when the user agent doesn't know how to accurately transform the CMYK color to RGB.
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If omitted, it defaults to an RGBA color calculated as follows:
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<ul>
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<li><code>red = 1.0 - min(1.0, cyan + black)</code>
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<li><code>green = 1.0 - min(1.0, magenta + black)</code>
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<li><code>blue = 1.0 - min(1.0, yellow + black)</code>
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<li>Alpha remains as specified.
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</ul>
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If omitted, it defaults to the CMYK color <a>naively converted to RGBA</a>.
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Typically, print-based applications will actually store the used colors as CMYK,
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and send them to the printer in that form.
@@ -1710,6 +1703,52 @@ CMYK Colors: the ''device-cmyk()'' function</h2>
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to avoid any color-matching difficulties.
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</div>
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<h3 id='cmyk-rgb'>
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Converting Between CMYK and RGB-Based Colors</h3>
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While most colors defined in this specification are directly compatible with RGBA,
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and thus can be mechanically and consistently converted back and forth with it,
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CMYK colors are not necessarily directly compatible;
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a given CMYK color
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might map to various RGBA colors
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depending on the physical characteristics of the output device.
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Ideally, the user agent will be aware of the output device's color profiles for RGBA and CMYK.
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If this is true,
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then the user agent must convert between CMYK and RGBA colors (and vice versa)
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by first converting the color into an appropriate device-independent color space,
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such as CIELab,
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and then converting into the output color space,
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using the appropriate color profiles for each operation.
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This is not always possible, however.
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In that case, the user agent must use the following naive conversion algorithms.
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To <dfn title="naively convert from CMYK to RGBA | naively converted to RGBA">naively convert from CMYK to RGBA</dfn>:
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If a fallback color was specified,
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return that color
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(converting it to RGB as well, if necessary).
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Otherwise:
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<ul>
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<li><code>red = 1.0 - min(1.0, cyan + black)</code>
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<li><code>green = 1.0 - min(1.0, magenta + black)</code>
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<li><code>blue = 1.0 - min(1.0, yellow + black)</code>
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<li>Alpha is same as for input color.
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</ul>
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To <dfn title="naively convert from RGBA to CMYK | naively converted to CMYK">naively convert from RGBA to CMYK</dfn>:
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<ul>
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<li>k = 1 - max(r, g, b)
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<li>c = (1 - r - k) / (1 - k), or 0 if k is 1
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<li>m = (1 - g - k) / (1 - k), or 0 if k is 1
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<li>y = (1 - b - k) / (1 - k), or 0 if k is 1
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<li>alpha is the same as the input color
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<li>fallback color must be set to the input color
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</ul>
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<h2 id='modifying-colors'>
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Modifying Colors: the ''color()'' function</h2>
@@ -2487,21 +2526,21 @@ The RGBColor Object</h3>
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</pre>
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<dl dfn-for="RGBColor">
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<dt><dfn constructor title="RGBColor(r, g, b, a)">RGBColor</dfn>(double r, double g, double b, optional double a=1)
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<dd>
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Constructs an instance of the <a idl>RGBColor</a> class,
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initializing the <a idl for=RGBColor>r</a>, <a idl for=RGBColor>g</a>, <a idl for=RGBColor>b</a>, and <a idl for=RGBColor>a</a> attributes of the instance to the passed arguments of the same name.
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<dt><dfn constructor title="RGBColor(r, g, b, a) | RGBColor(r, g, b)">RGBColor</dfn>(double r, double g, double b, optional double a=1)
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<dd link-for="RGBColor">
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Constructs an instance of the <a idl for>RGBColor</a> class,
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initializing the <a idl>r</a>, <a idl>g</a>, <a idl>b</a>, and <a idl>a</a> attributes of the instance to the passed arguments of the same name.
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Note: The <a idl>RGBColor</a> class's attributes have a normal range of 0 to 1,
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Note: The <a idl for>RGBColor</a> class's attributes have a normal range of 0 to 1,
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not 0 to 255.
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See the <a idl>HexColor</a> class if you prefer working in the 0-255 range.
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See the <a idl for>HexColor</a> class if you prefer working in the 0-255 range.
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<dt><dfn constructor title="RGBColor(color) | RGBColor()">RGBColor</dfn>(optional RGBColorInit color)
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<dd>
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Constructs an instance of the <a idl>RGBColor</a> class,
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initializing the <a idl for=RGBColor>r</a>, <a idl for=RGBColor>g</a>, <a idl for=RGBColor>b</a>, and <a idl for=RGBColor>a</a> attributes of the instance to the passed dictionary attributes of the same name (or their defaulted values).
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<dd link-for="RGBColor">
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Constructs an instance of the <a idl for>RGBColor</a> class,
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initializing the <a idl>r</a>, <a idl>g</a>, <a idl>b</a>, and <a idl>a</a> attributes of the instance to the passed dictionary attributes of the same name (or their defaulted values).
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<dt><dfn constructor title="RGBColor(string)">RGBColor</dfn>(DOMString css)
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<dt><dfn constructor title="RGBColor(css)">RGBColor</dfn>(DOMString css)
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<dd>
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<a>Parse a component value</a> from the passed string.
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If this operation succeeds and the result is a valid CSS color,
@@ -2594,16 +2633,8 @@ The RGBColor Object</h3>
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the 8-digit syntax must be used.
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When serializing in the ''device-cmyk()'' syntax,
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the various components must be set as follows:
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<ul>
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<li>k = 1 - max(r, g, b)
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<li>c = (1 - r - k) / (1 - k), or 0 if k is 1
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<li>m = (1 - g - k) / (1 - k), or 0 if k is 1
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<li>y = (1 - b - k) / (1 - k), or 0 if k is 1
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<li>alpha is the same as the input color
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<li>fallback color must be set to the input color, serialized in the ''rgba()'' syntax
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</ul>
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the color must be <a>naively converted to CMYK</a>,
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and the fallback color must be serialized in the ''rgba()'' syntax.
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<dt><dfn attribute>defaultStringifier</dfn> <span attribute-info for="RGBColor/defaultStringifier"></span>
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<dd>
@@ -2638,17 +2669,17 @@ The HSLColor Class</h3>
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</pre>
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<dl dfn-for="HSLColor">
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<dt><dfn constructor title="HSLColor(h, s, l, a)">HSLColor</dfn>(double h, double s, double l, optional double a=1)
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<dd>
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Constructs an instance of the <a idl>HSLColor</a> class,
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initializing the <a idl for=HSLColor>h</a>, <a idl for=HSLColor>s</a>, <a idl for=HSLColor>l</a>, and <a idl for=HSLColor>a</a> attributes of the instance to the passed arguments of the same name.
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<dt><dfn constructor title="HSLColor(h, s, l, a) | HSLColor(h, s, l)">HSLColor</dfn>(double h, double s, double l, optional double a=1)
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<dd link-for="HSLColor">
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Constructs an instance of the <a idl for>HSLColor</a> class,
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initializing the <a idl>h</a>, <a idl>s</a>, <a idl>l</a>, and <a idl>a</a> attributes of the instance to the passed arguments of the same name.
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<dt><dfn constructor title="HSLColor(color) | HSLColor()">HSLColor</dfn>(optional HSLColorInit color)
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<dd>
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Constructs an instance of the <a idl>HSLColor</a> class,
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initializing the <a idl for=HSLColor>h</a>, <a idl for=HSLColor>s</a>, <a idl for=HSLColor>l</a>, and <a idl for=HSLColor>a</a> attributes of the instance to the passed dictionary attributes of the same name (or their defaulted values).
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<dd link-for="HSLColor">
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Constructs an instance of the <a idl for>HSLColor</a> class,
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initializing the <a idl>h</a>, <a idl>s</a>, <a idl>l</a>, and <a idl>a</a> attributes of the instance to the passed dictionary attributes of the same name (or their defaulted values).
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<dt><dfn constructor title="HSLColor(string)">HSLColor</dfn>(DOMString css)
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<dt><dfn constructor title="HSLColor(css)">HSLColor</dfn>(DOMString css)
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<dd>
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<a>Parse a component value</a> from the passed string.
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If this operation succeeds and the result is a valid CSS color,
@@ -2732,17 +2763,17 @@ The HexColor Class</h3>
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</pre>
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<dl dfn-for="HexColor">
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<dt><dfn constructor title="HexColor(r, g, b, a)">HexColor</dfn>([Clamp] octet r, [Clamp] octet g, [Clamp] octet b, optional [Clamp] octet a=255)
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<dd>
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Constructs an instance of the <a idl>HexColor</a> class,
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initializing the <a idl for=HexColor>r</a>, <a idl for=HexColor>g</a>, <a idl for=HexColor>b</a>, and <a idl for=HexColor>a</a> attributes of the instance to the passed arguments of the same name.
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<dt><dfn constructor title="HexColor(r, g, b, a) | HexColor(r, g, b)">HexColor</dfn>([Clamp] octet r, [Clamp] octet g, [Clamp] octet b, optional [Clamp] octet a=255)
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<dd link-for="HexColor">
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Constructs an instance of the <a idl for>HexColor</a> class,
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initializing the <a idl>r</a>, <a idl>g</a>, <a idl>b</a>, and <a idl>a</a> attributes of the instance to the passed arguments of the same name.
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<dt><dfn constructor title="HexColor(color) | HexColor()">HSLColor</dfn>(optional HexColorInit color)
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<dd>
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Constructs an instance of the <a idl>HexColor</a> class,
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initializing the <a idl for=HexColor>r</a>, <a idl for=HexColor>g</a>, <a idl for=HexColor>b</a>, and <a idl for=HexColor>a</a> attributes of the instance to the passed dictionary attributes of the same name (or their defaulted values).
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<dd link-for="HexColor">
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Constructs an instance of the <a idl for>HexColor</a> class,
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initializing the <a idl>r</a>, <a idl>g</a>, <a idl>b</a>, and <a idl>a</a> attributes of the instance to the passed dictionary attributes of the same name (or their defaulted values).
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<dt><dfn constructor title="HexColor(string)">HexColor</dfn>(DOMString css)
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<dt><dfn constructor title="HexColor(css)">HexColor</dfn>(DOMString css)
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<dd>
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<a>Parse a component value</a> from the passed string.
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If this operation succeeds and the result is a valid CSS color,
@@ -2786,7 +2817,94 @@ The HexColor Class</h3>
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<h3 id='api-CMYKColor'>
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The CMYKColor Class</h3>
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Issue: Fill this in.
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<pre class='idl'>
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[Constructor(double c, double m, double y, double k, optional double a=1, optional fallback RGBColor?=null),
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Constructor(optional CMYKColorInit color),
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Constructor(DOMString css)]
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interface CMYKColor : CSSColor {
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attribute double c;
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attribute double m;
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attribute double y;
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attribute double k;
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attribute double a;
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attribute RGBColor? fallback;
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RGBColor toRGB();
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static attribute ColorStringifiers stringifiers;
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attribute ColorStringifierType defaultStringifier;
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};
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dictionary CMYKColorInit {
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double c = 0;
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double m = 0;
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double y = 0;
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double k = 0;
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double a = 1;
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RGBColor? fallback = null;
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};
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</pre>
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<dl dfn-for="CMYKColor">
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<dt><dfn constructor title="CMYKColor(c, m, y, k, a, fallback) | CMYKColor(c, m, y, k, a) | CMYKColor(c, m, y, k)">CMYKColor</dfn>(double c, double m, double y, double k, optional double a=1, optional RGBColor? fallback=null)
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<dd link-for="CMYKColor">
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Constructs an instance of the <a idl for>CMYKColor</a> class,
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initializing the <a idl>c</a>, <a idl>m</a>, <a idl>y</a>, <a idl>k</a>, <a idl>a</a>, and <a idl>fallback</a> attributes of the instance to the passed arguments of the same name.
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<dt><dfn constructor title="CMYKColor(color) | CMYKColor()">CMYKColor</dfn>(optional HexColorInit color)
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<dd link-for="CMYKColor">
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Constructs an instance of the <a idl for>CMYKColor</a> class,
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initializing the <a idl>c</a>, <a idl>m</a>, <a idl>y</a>, <a idl>k</a>, <a idl>a</a>, and <a idl>fallback</a> attributes of the instance to the passed dictionary attributes of the same name (or their defaulted values).
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<dt><dfn constructor title="CMYKColor(css)">CMYKColor</dfn>(DOMString css)
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<dd>
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<a>Parse a component value</a> from the passed string.
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If this operation succeeds and the result is a valid ''device-cmyk()'' function,
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construct an instance of the <a idl>CMYKColor</a> class
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with attributes initialized to represent that color.
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Otherwise, if the operation succeeds and the result is any other type of valid CSS color,
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construct an instance of the <a idl>CMYKColor</a> class
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with attributes initialized to represent that color
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using the
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Otherwise, throw an XXXError.
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<dt><dfn method>toRGB()</dfn>
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<dd>
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Defined as follows in ECMAScript:
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<pre>
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function() {
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const r = 1 - Math.min(1, this.c + this.k);
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const g = 1 - Math.min(1, this.m + this.k);
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const b = 1 - Math.min(1, this.y + this.k);
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return new RGBColor(r, g, b, this.a);
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}
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</pre>
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<dt><dfn attribute>c</dfn> <span attribute-info for="CMYKColor/c"></span>
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<dt><dfn attribute>m</dfn> <span attribute-info for="CMYKColor/m"></span>
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<dt><dfn attribute>y</dfn> <span attribute-info for="CMYKColor/y"></span>
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<dt><dfn attribute>k</dfn> <span attribute-info for="CMYKColor/k"></span>
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<dt><dfn attribute>a</dfn> <span attribute-info for="CMYKColor/a"></span>
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<dt><dfn attribute>fallback</dfn> <span attribute-info for="CMYKColor/fallback"></span>
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<dd link-for="CMYKColor">
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The <a idl>c</a>, <a idl>m</a>, <a idl>y</a>, <a idl>k</a>, <a idl>a</a>, and <a idl>fallback</a> attributes
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represent the red, blue, green, and alpha channels of the CMYK color
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that the <a idl for>CMYKColor</a> instance represents.
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Note: The <a idl for>CMYKColor</a> class's c, m, y, k, and a attributes have a normal range of 0 to 1.
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Its fallback attribute is always an RGBColor, or null (indicating it should convert itself to an RGBColor per <a section href="#cmyk-rgb"></a>).
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<dt><dfn attribute>stringifiers</dfn> <span attribute-info for="CMYKColor/stringifiers"></span>
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<dd>
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Initialized to an empty object.
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<dt><dfn attribute>defaultStringifier</dfn> <span attribute-info for="CMYKColor/defaultStringifier"></span>
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<dd>
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The <a idl for=HexColor>defaultStringifier</a> attribute must be initially set to "cmyk".
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</dl>
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