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<pre><a name="line-1"></a><span class='hs-comment'>{-
<a name="line-2"></a>Copyright (c) 2008, 2009
<a name="line-3"></a>Russell O'Connor
<a name="line-4"></a>
<a name="line-5"></a>Permission is hereby granted, free of charge, to any person obtaining a copy
<a name="line-6"></a>of this software and associated documentation files (the "Software"), to deal
<a name="line-7"></a>in the Software without restriction, including without limitation the rights
<a name="line-8"></a>to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
<a name="line-9"></a>copies of the Software, and to permit persons to whom the Software is
<a name="line-10"></a>furnished to do so, subject to the following conditions:
<a name="line-11"></a>
<a name="line-12"></a>The above copyright notice and this permission notice shall be included in
<a name="line-13"></a>all copies or substantial portions of the Software.
<a name="line-14"></a>
<a name="line-15"></a>THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
<a name="line-16"></a>IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
<a name="line-17"></a>FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
<a name="line-18"></a>AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
<a name="line-19"></a>LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
<a name="line-20"></a>OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
<a name="line-21"></a>THE SOFTWARE.
<a name="line-22"></a>-}</span>
<a name="line-23"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Colour</span><span class='hs-varop'>.</span><span class='hs-conid'>Internal</span> <span class='hs-keyword'>where</span>
<a name="line-24"></a>
<a name="line-25"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>List</span>
<a name="line-26"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Colour</span><span class='hs-varop'>.</span><span class='hs-conid'>Chan</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Chan</span>
<a name="line-27"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Colour</span><span class='hs-varop'>.</span><span class='hs-conid'>Chan</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-28"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Monoid</span>
<a name="line-29"></a>
<a name="line-30"></a><a name="Red"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Red</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Red</span>
<a name="line-31"></a><a name="Green"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Green</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Green</span>
<a name="line-32"></a><a name="Blue"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Blue</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Blue</span>
<a name="line-33"></a>
<a name="line-34"></a><span class='hs-comment'>-- |This type represents the human preception of colour.</span>
<a name="line-35"></a><span class='hs-comment'>-- The @a@ parameter is a numeric type used internally for the</span>
<a name="line-36"></a><span class='hs-comment'>-- representation.</span>
<a name="line-37"></a><span class='hs-comment'>--</span>
<a name="line-38"></a><span class='hs-comment'>-- The 'Monoid' instance allows one to add colours, but beware that adding</span>
<a name="line-39"></a><span class='hs-comment'>-- colours can take you out of gamut. Consider using 'blend' whenever</span>
<a name="line-40"></a><span class='hs-comment'>-- possible.</span>
<a name="line-41"></a>
<a name="line-42"></a><a name="Colour"></a><span class='hs-comment'>-- Internally we store the colour in linear ITU-R BT.709 RGB colour space. </span>
<a name="line-43"></a><a name="Colour"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Colour</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RGB</span> <span class='hs-varop'>!</span><span class='hs-layout'>(</span><span class='hs-conid'>Chan</span> <span class='hs-conid'>Red</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-varop'>!</span><span class='hs-layout'>(</span><span class='hs-conid'>Chan</span> <span class='hs-conid'>Green</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-varop'>!</span><span class='hs-layout'>(</span><span class='hs-conid'>Chan</span> <span class='hs-conid'>Blue</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-44"></a> <span class='hs-keyword'>deriving</span> <span class='hs-layout'>(</span><span class='hs-conid'>Eq</span><span class='hs-layout'>)</span>
<a name="line-45"></a>
<a name="line-46"></a><a name="colourConvert"></a><span class='hs-comment'>-- |Change the type used to represent the colour coordinates.</span>
<a name="line-47"></a><span class='hs-definition'>colourConvert</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Fractional</span> <span class='hs-varid'>b</span><span class='hs-layout'>,</span> <span class='hs-conid'>Real</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Colour</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Colour</span> <span class='hs-varid'>b</span>
<a name="line-48"></a><span class='hs-definition'>colourConvert</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGB</span> <span class='hs-varid'>r</span> <span class='hs-varid'>g</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-49"></a> <span class='hs-conid'>RGB</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>convert</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>convert</span> <span class='hs-varid'>g</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>convert</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-50"></a>
<a name="line-51"></a><a name="black"></a><span class='hs-comment'>-- 'black' is the colourless colour. It is the identity colour in</span>
<a name="line-52"></a><span class='hs-comment'>-- additive colour spaces.</span>
<a name="line-53"></a><span class='hs-definition'>black</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Num</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Colour</span> <span class='hs-varid'>a</span>
<a name="line-54"></a><span class='hs-definition'>black</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RGB</span> <span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>empty</span> <span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>empty</span> <span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>empty</span>
<a name="line-55"></a>
<a name="line-56"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>Num</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Monoid</span> <span class='hs-layout'>(</span><span class='hs-conid'>Colour</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-57"></a> <span class='hs-varid'>mempty</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>black</span>
<a name="line-58"></a> <span class='hs-layout'>(</span><span class='hs-conid'>RGB</span> <span class='hs-varid'>r1</span> <span class='hs-varid'>g1</span> <span class='hs-varid'>b1</span><span class='hs-layout'>)</span> <span class='hs-varop'>`mappend`</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGB</span> <span class='hs-varid'>r2</span> <span class='hs-varid'>g2</span> <span class='hs-varid'>b2</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-59"></a> <span class='hs-conid'>RGB</span> <span class='hs-layout'>(</span><span class='hs-varid'>r1</span> <span class='hs-varop'>`</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>add</span><span class='hs-varop'>`</span> <span class='hs-varid'>r2</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>g1</span> <span class='hs-varop'>`</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>add</span><span class='hs-varop'>`</span> <span class='hs-varid'>g2</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>b1</span> <span class='hs-varop'>`</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>add</span><span class='hs-varop'>`</span> <span class='hs-varid'>b2</span><span class='hs-layout'>)</span>
<a name="line-60"></a> <span class='hs-varid'>mconcat</span> <span class='hs-varid'>l</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RGB</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>sum</span> <span class='hs-varid'>lr</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>sum</span> <span class='hs-varid'>lg</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>sum</span> <span class='hs-varid'>lb</span><span class='hs-layout'>)</span>
<a name="line-61"></a> <span class='hs-keyword'>where</span>
<a name="line-62"></a> <span class='hs-layout'>(</span><span class='hs-varid'>lr</span><span class='hs-layout'>,</span><span class='hs-varid'>lg</span><span class='hs-layout'>,</span><span class='hs-varid'>lb</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unzip3</span> <span class='hs-layout'>(</span><span class='hs-varid'>map</span> <span class='hs-varid'>toRGB</span> <span class='hs-varid'>l</span><span class='hs-layout'>)</span>
<a name="line-63"></a> <span class='hs-varid'>toRGB</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGB</span> <span class='hs-varid'>r</span> <span class='hs-varid'>g</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varid'>r</span><span class='hs-layout'>,</span><span class='hs-varid'>g</span><span class='hs-layout'>,</span><span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-64"></a>
<a name="line-65"></a><a name="Alpha"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Alpha</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Alpha</span>
<a name="line-66"></a>
<a name="line-67"></a><span class='hs-comment'>-- |This type represents a 'Colour' that may be semi-transparent.</span>
<a name="line-68"></a><span class='hs-comment'>--</span>
<a name="line-69"></a><span class='hs-comment'>-- The 'Monoid' instance allows you to composite colours.</span>
<a name="line-70"></a><span class='hs-comment'>--</span>
<a name="line-71"></a><span class='hs-comment'>-- >x `mappend` y == x `over` y</span>
<a name="line-72"></a><span class='hs-comment'>--</span>
<a name="line-73"></a><span class='hs-comment'>-- To get the (pre-multiplied) colour channel of an 'AlphaColour' @c@,</span>
<a name="line-74"></a><span class='hs-comment'>-- simply composite @c@ over black.</span>
<a name="line-75"></a><span class='hs-comment'>--</span>
<a name="line-76"></a><span class='hs-comment'>-- >c `over` (mempty :: Colour a)</span>
<a name="line-77"></a>
<a name="line-78"></a><a name="AlphaColour"></a><span class='hs-comment'>-- Internally we use a premultiplied-alpha representation.</span>
<a name="line-79"></a><a name="AlphaColour"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RGBA</span> <span class='hs-varop'>!</span><span class='hs-layout'>(</span><span class='hs-conid'>Colour</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-varop'>!</span><span class='hs-layout'>(</span><span class='hs-conid'>Chan</span> <span class='hs-conid'>Alpha</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>deriving</span> <span class='hs-layout'>(</span><span class='hs-conid'>Eq</span><span class='hs-layout'>)</span>
<a name="line-80"></a>
<a name="line-81"></a><a name="transparent"></a><span class='hs-comment'>-- |This 'AlphaColour' is entirely transparent and has no associated</span>
<a name="line-82"></a><span class='hs-comment'>-- colour channel.</span>
<a name="line-83"></a><span class='hs-definition'>transparent</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Num</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span>
<a name="line-84"></a><span class='hs-definition'>transparent</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RGBA</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGB</span> <span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>empty</span> <span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>empty</span> <span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>empty</span><span class='hs-layout'>)</span> <span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>empty</span>
<a name="line-85"></a>
<a name="line-86"></a><a name="alphaColourConvert"></a><span class='hs-comment'>-- |Change the type used to represent the colour coordinates.</span>
<a name="line-87"></a><span class='hs-definition'>alphaColourConvert</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Fractional</span> <span class='hs-varid'>b</span><span class='hs-layout'>,</span> <span class='hs-conid'>Real</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span>
<a name="line-88"></a> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>b</span>
<a name="line-89"></a><span class='hs-definition'>alphaColourConvert</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGBA</span> <span class='hs-varid'>c</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RGBA</span> <span class='hs-layout'>(</span><span class='hs-varid'>colourConvert</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>convert</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-90"></a>
<a name="line-91"></a><a name="opaque"></a><span class='hs-comment'>-- |Creates an opaque 'AlphaColour' from a 'Colour'.</span>
<a name="line-92"></a><span class='hs-definition'>opaque</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Num</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Colour</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span>
<a name="line-93"></a><span class='hs-definition'>opaque</span> <span class='hs-varid'>c</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RGBA</span> <span class='hs-varid'>c</span> <span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>full</span>
<a name="line-94"></a>
<a name="line-95"></a><a name="dissolve"></a><span class='hs-comment'>-- |Returns an 'AlphaColour' more transparent by a factor of @o@.</span>
<a name="line-96"></a><span class='hs-definition'>dissolve</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Num</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span>
<a name="line-97"></a><span class='hs-definition'>dissolve</span> <span class='hs-varid'>o</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGBA</span> <span class='hs-varid'>c</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RGBA</span> <span class='hs-layout'>(</span><span class='hs-varid'>darken</span> <span class='hs-varid'>o</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>scale</span> <span class='hs-varid'>o</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-98"></a>
<a name="line-99"></a><a name="withOpacity"></a><span class='hs-comment'>-- |Creates an 'AlphaColour' from a 'Colour' with a given opacity.</span>
<a name="line-100"></a><span class='hs-comment'>--</span>
<a name="line-101"></a><span class='hs-comment'>-- >c `withOpacity` o == dissolve o (opaque c) </span>
<a name="line-102"></a><span class='hs-definition'>withOpacity</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Num</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Colour</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span>
<a name="line-103"></a><a name="withOpacity"></a><span class='hs-definition'>c</span> <span class='hs-varop'>`withOpacity`</span> <span class='hs-varid'>o</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RGBA</span> <span class='hs-layout'>(</span><span class='hs-varid'>darken</span> <span class='hs-varid'>o</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span> <span class='hs-varid'>o</span><span class='hs-layout'>)</span>
<a name="line-104"></a>
<a name="line-105"></a><span class='hs-comment'>--------------------------------------------------------------------------</span>
<a name="line-106"></a><span class='hs-comment'>-- Blending</span>
<a name="line-107"></a><span class='hs-comment'>--------------------------------------------------------------------------</span>
<a name="line-108"></a>
<a name="line-109"></a><span class='hs-keyword'>class</span> <span class='hs-conid'>AffineSpace</span> <span class='hs-varid'>f</span> <span class='hs-keyword'>where</span>
<a name="line-110"></a> <span class='hs-comment'>-- |Compute a affine Combination (weighted-average) of points.</span>
<a name="line-111"></a> <span class='hs-comment'>-- The last parameter will get the remaining weight.</span>
<a name="line-112"></a> <span class='hs-comment'>-- e.g.</span>
<a name="line-113"></a> <span class='hs-comment'>--</span>
<a name="line-114"></a> <span class='hs-comment'>-- >affineCombo [(0.2,a), (0.3,b)] c == 0.2*a + 0.3*b + 0.4*c</span>
<a name="line-115"></a> <span class='hs-comment'>--</span>
<a name="line-116"></a> <span class='hs-comment'>-- Weights can be negative, or greater than 1.0; however, be aware</span>
<a name="line-117"></a> <span class='hs-comment'>-- that non-convex combinations may lead to out of gamut colours.</span>
<a name="line-118"></a> <span class='hs-varid'>affineCombo</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Num</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-keyglyph'>[</span><span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span><span class='hs-varid'>f</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>f</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>f</span> <span class='hs-varid'>a</span>
<a name="line-119"></a>
<a name="line-120"></a><a name="blend"></a><span class='hs-comment'>-- |Compute the weighted average of two points.</span>
<a name="line-121"></a><span class='hs-comment'>-- e.g.</span>
<a name="line-122"></a><span class='hs-comment'>--</span>
<a name="line-123"></a><span class='hs-comment'>-- >blend 0.4 a b = 0.4*a + 0.6*b</span>
<a name="line-124"></a><span class='hs-comment'>--</span>
<a name="line-125"></a><span class='hs-comment'>-- The weight can be negative, or greater than 1.0; however, be aware</span>
<a name="line-126"></a><span class='hs-comment'>-- that non-convex combinations may lead to out of gamut colours.</span>
<a name="line-127"></a><span class='hs-definition'>blend</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Num</span> <span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>AffineSpace</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>f</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>f</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>f</span> <span class='hs-varid'>a</span>
<a name="line-128"></a><span class='hs-definition'>blend</span> <span class='hs-varid'>weight</span> <span class='hs-varid'>c1</span> <span class='hs-varid'>c2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>affineCombo</span> <span class='hs-keyglyph'>[</span><span class='hs-layout'>(</span><span class='hs-varid'>weight</span><span class='hs-layout'>,</span><span class='hs-varid'>c1</span><span class='hs-layout'>)</span><span class='hs-keyglyph'>]</span> <span class='hs-varid'>c2</span>
<a name="line-129"></a>
<a name="line-130"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>AffineSpace</span> <span class='hs-conid'>Colour</span> <span class='hs-keyword'>where</span>
<a name="line-131"></a> <span class='hs-varid'>affineCombo</span> <span class='hs-varid'>l</span> <span class='hs-varid'>z</span> <span class='hs-keyglyph'>=</span>
<a name="line-132"></a> <span class='hs-varid'>foldl1'</span> <span class='hs-varid'>mappend</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>darken</span> <span class='hs-varid'>w</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>|</span> <span class='hs-layout'>(</span><span class='hs-varid'>w</span><span class='hs-layout'>,</span><span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-layout'>(</span><span class='hs-num'>1</span><span class='hs-comment'>-</span><span class='hs-varid'>total</span><span class='hs-layout'>,</span><span class='hs-varid'>z</span><span class='hs-layout'>)</span><span class='hs-conop'>:</span><span class='hs-varid'>l</span><span class='hs-keyglyph'>]</span>
<a name="line-133"></a> <span class='hs-keyword'>where</span>
<a name="line-134"></a> <span class='hs-varid'>total</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>sum</span> <span class='hs-varop'>$</span> <span class='hs-varid'>map</span> <span class='hs-varid'>fst</span> <span class='hs-varid'>l</span>
<a name="line-135"></a>
<a name="line-136"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>AffineSpace</span> <span class='hs-conid'>AlphaColour</span> <span class='hs-keyword'>where</span>
<a name="line-137"></a> <span class='hs-varid'>affineCombo</span> <span class='hs-varid'>l</span> <span class='hs-varid'>z</span> <span class='hs-keyglyph'>=</span>
<a name="line-138"></a> <span class='hs-varid'>foldl1'</span> <span class='hs-varid'>rgbaAdd</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>dissolve</span> <span class='hs-varid'>w</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>|</span> <span class='hs-layout'>(</span><span class='hs-varid'>w</span><span class='hs-layout'>,</span><span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-layout'>(</span><span class='hs-num'>1</span><span class='hs-comment'>-</span><span class='hs-varid'>total</span><span class='hs-layout'>,</span><span class='hs-varid'>z</span><span class='hs-layout'>)</span><span class='hs-conop'>:</span><span class='hs-varid'>l</span><span class='hs-keyglyph'>]</span>
<a name="line-139"></a> <span class='hs-keyword'>where</span>
<a name="line-140"></a> <span class='hs-varid'>total</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>sum</span> <span class='hs-varop'>$</span> <span class='hs-varid'>map</span> <span class='hs-varid'>fst</span> <span class='hs-varid'>l</span>
<a name="line-141"></a>
<a name="line-142"></a><span class='hs-comment'>--------------------------------------------------------------------------</span>
<a name="line-143"></a><span class='hs-comment'>-- composite</span>
<a name="line-144"></a><span class='hs-comment'>--------------------------------------------------------------------------</span>
<a name="line-145"></a>
<a name="line-146"></a><a name="AlphaColour"></a><span class='hs-keyword'>class</span> <span class='hs-conid'>ColourOps</span> <span class='hs-varid'>f</span> <span class='hs-keyword'>where</span>
<a name="line-147"></a> <span class='hs-comment'>-- |@c1 \`over\` c2@ returns the 'Colour' created by compositing the</span>
<a name="line-148"></a> <span class='hs-comment'>-- 'AlphaColour' @c1@ over @c2@, which may be either a 'Colour' or</span>
<a name="line-149"></a> <span class='hs-comment'>-- 'AlphaColour'.</span>
<a name="line-150"></a> <span class='hs-varid'>over</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Num</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>f</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>f</span> <span class='hs-varid'>a</span>
<a name="line-151"></a> <span class='hs-comment'>-- |@darken s c@ blends a colour with black without changing it's opacity.</span>
<a name="line-152"></a> <span class='hs-comment'>--</span>
<a name="line-153"></a> <span class='hs-comment'>-- For 'Colour', @darken s c = blend s c mempty@</span>
<a name="line-154"></a> <span class='hs-varid'>darken</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Num</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>f</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>f</span> <span class='hs-varid'>a</span>
<a name="line-155"></a>
<a name="line-156"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ColourOps</span> <span class='hs-conid'>Colour</span> <span class='hs-keyword'>where</span>
<a name="line-157"></a> <span class='hs-layout'>(</span><span class='hs-conid'>RGBA</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGB</span> <span class='hs-varid'>r0</span> <span class='hs-varid'>g0</span> <span class='hs-varid'>b0</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span> <span class='hs-varid'>a0</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varop'>`over`</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGB</span> <span class='hs-varid'>r1</span> <span class='hs-varid'>g1</span> <span class='hs-varid'>b1</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-158"></a> <span class='hs-conid'>RGB</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>over</span> <span class='hs-varid'>r0</span> <span class='hs-varid'>a0</span> <span class='hs-varid'>r1</span><span class='hs-layout'>)</span>
<a name="line-159"></a> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>over</span> <span class='hs-varid'>g0</span> <span class='hs-varid'>a0</span> <span class='hs-varid'>g1</span><span class='hs-layout'>)</span>
<a name="line-160"></a> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>over</span> <span class='hs-varid'>b0</span> <span class='hs-varid'>a0</span> <span class='hs-varid'>b1</span><span class='hs-layout'>)</span>
<a name="line-161"></a> <span class='hs-varid'>darken</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGB</span> <span class='hs-varid'>r</span> <span class='hs-varid'>g</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RGB</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>scale</span> <span class='hs-varid'>s</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span>
<a name="line-162"></a> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>scale</span> <span class='hs-varid'>s</span> <span class='hs-varid'>g</span><span class='hs-layout'>)</span>
<a name="line-163"></a> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>scale</span> <span class='hs-varid'>s</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-164"></a>
<a name="line-165"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ColourOps</span> <span class='hs-conid'>AlphaColour</span> <span class='hs-keyword'>where</span>
<a name="line-166"></a> <span class='hs-varid'>c0</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>RGBA</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>a0</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>Chan</span> <span class='hs-varid'>a0'</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varop'>`over`</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGBA</span> <span class='hs-varid'>c1</span> <span class='hs-varid'>a1</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-167"></a> <span class='hs-conid'>RGBA</span> <span class='hs-layout'>(</span><span class='hs-varid'>c0</span> <span class='hs-varop'>`over`</span> <span class='hs-varid'>c1</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>over</span> <span class='hs-varid'>a0</span> <span class='hs-varid'>a0'</span> <span class='hs-varid'>a1</span><span class='hs-layout'>)</span>
<a name="line-168"></a> <span class='hs-varid'>darken</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGBA</span> <span class='hs-varid'>c</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RGBA</span> <span class='hs-layout'>(</span><span class='hs-varid'>darken</span> <span class='hs-varid'>s</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span>
<a name="line-169"></a>
<a name="line-170"></a><span class='hs-comment'>-- | 'AlphaColour' forms a monoid with 'over' and 'transparent'.</span>
<a name="line-171"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>Num</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Monoid</span> <span class='hs-layout'>(</span><span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-172"></a> <span class='hs-varid'>mempty</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>transparent</span>
<a name="line-173"></a> <span class='hs-varid'>mappend</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>over</span>
<a name="line-174"></a>
<a name="line-175"></a><a name="atop"></a><span class='hs-comment'>-- | @c1 \`atop\` c2@ returns the 'AlphaColour' produced by covering</span>
<a name="line-176"></a><span class='hs-comment'>-- the portion of @c2@ visible by @c1@.</span>
<a name="line-177"></a><span class='hs-comment'>-- The resulting alpha channel is always the same as the alpha channel</span>
<a name="line-178"></a><span class='hs-comment'>-- of @c2@.</span>
<a name="line-179"></a><span class='hs-comment'>--</span>
<a name="line-180"></a><span class='hs-comment'>-- >c1 `atop` (opaque c2) == c1 `over` (opaque c2)</span>
<a name="line-181"></a><span class='hs-comment'>-- >AlphaChannel (c1 `atop` c2) == AlphaChannel c2</span>
<a name="line-182"></a><span class='hs-definition'>atop</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Fractional</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span>
<a name="line-183"></a><span class='hs-definition'>atop</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGBA</span> <span class='hs-varid'>c0</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span> <span class='hs-varid'>a0</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGBA</span> <span class='hs-varid'>c1</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span> <span class='hs-varid'>a1</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-184"></a> <span class='hs-conid'>RGBA</span> <span class='hs-layout'>(</span><span class='hs-varid'>darken</span> <span class='hs-varid'>a1</span> <span class='hs-varid'>c0</span> <span class='hs-varop'>`mappend`</span> <span class='hs-varid'>darken</span> <span class='hs-layout'>(</span><span class='hs-num'>1</span><span class='hs-comment'>-</span><span class='hs-varid'>a0</span><span class='hs-layout'>)</span> <span class='hs-varid'>c1</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span> <span class='hs-varid'>a1</span><span class='hs-layout'>)</span>
<a name="line-185"></a>
<a name="line-186"></a><a name="quantize"></a><span class='hs-comment'>-- |'round's and then clamps @x@ between 0 and 'maxBound'.</span>
<a name="line-187"></a><span class='hs-definition'>quantize</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>RealFrac</span> <span class='hs-varid'>a1</span><span class='hs-layout'>,</span> <span class='hs-conid'>Integral</span> <span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>Bounded</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>a1</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-188"></a><span class='hs-definition'>quantize</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>x</span> <span class='hs-varop'><=</span> <span class='hs-varid'>fromIntegral</span> <span class='hs-varid'>l</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>l</span>
<a name="line-189"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>fromIntegral</span> <span class='hs-varid'>h</span> <span class='hs-varop'><=</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>h</span>
<a name="line-190"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>otherwise</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>round</span> <span class='hs-varid'>x</span>
<a name="line-191"></a> <span class='hs-keyword'>where</span>
<a name="line-192"></a> <span class='hs-varid'>l</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>minBound</span>
<a name="line-193"></a> <span class='hs-varid'>h</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>maxBound</span>
<a name="line-194"></a>
<a name="line-195"></a><a name="alphaChannel"></a><span class='hs-comment'>{- Avoid using -}</span>
<a name="line-196"></a><span class='hs-comment'>-- |Returns the opacity of an 'AlphaColour'.</span>
<a name="line-197"></a><span class='hs-definition'>alphaChannel</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-198"></a><span class='hs-definition'>alphaChannel</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGBA</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>a</span>
<a name="line-199"></a>
<a name="line-200"></a><a name="colourChannel"></a><span class='hs-comment'>-- |Returns the colour of an 'AlphaColour'.</span>
<a name="line-201"></a><span class='hs-comment'>-- @colourChannel transparent@ is undefined and may result in @nan@ or an</span>
<a name="line-202"></a><span class='hs-comment'>-- error.</span>
<a name="line-203"></a><span class='hs-comment'>-- Its use is discouraged.</span>
<a name="line-204"></a><span class='hs-comment'>-- If you are desperate, use</span>
<a name="line-205"></a><span class='hs-comment'>--</span>
<a name="line-206"></a><span class='hs-comment'>-- >darken (recip (alphaChannel c)) (c `over` black)</span>
<a name="line-207"></a><span class='hs-definition'>colourChannel</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Fractional</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>AlphaColour</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Colour</span> <span class='hs-varid'>a</span>
<a name="line-208"></a><span class='hs-definition'>colourChannel</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGBA</span> <span class='hs-varid'>c</span> <span class='hs-layout'>(</span><span class='hs-conid'>Chan</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>darken</span> <span class='hs-layout'>(</span><span class='hs-varid'>recip</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-varid'>c</span>
<a name="line-209"></a>
<a name="line-210"></a><span class='hs-comment'>--------------------------------------------------------------------------</span>
<a name="line-211"></a><span class='hs-comment'>-- not for export</span>
<a name="line-212"></a><span class='hs-comment'>--------------------------------------------------------------------------</span>
<a name="line-213"></a>
<a name="line-214"></a><a name="rgbaAdd"></a><span class='hs-definition'>rgbaAdd</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGBA</span> <span class='hs-varid'>c1</span> <span class='hs-varid'>a1</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>RGBA</span> <span class='hs-varid'>c2</span> <span class='hs-varid'>a2</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-215"></a> <span class='hs-conid'>RGBA</span> <span class='hs-layout'>(</span><span class='hs-varid'>c1</span> <span class='hs-varop'>`mappend`</span> <span class='hs-varid'>c2</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>a1</span> <span class='hs-varop'>`</span><span class='hs-conid'>Chan</span><span class='hs-varop'>.</span><span class='hs-varid'>add</span><span class='hs-varop'>`</span> <span class='hs-varid'>a2</span><span class='hs-layout'>)</span>
</pre></body>
</html>
