docs/develop/servers/app_server/ColorUtils.htm

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  20 <P class="Body" style="margin: 0px"><span class="OBOS-Title">ColorUtils</span><span style="color: rgb(0,0,0); font-size: 24pt"></span></P>
  21 <P class="Body" style="margin: 0px"><BR>
  22 </P>
  23 <P class="Body" style="margin: 0px">These functions are used for general purpose color-related tasks.</P>
  24 <P class="Body" style="margin: 0px"><BR>
  25 <BR>
  26 <HR>
  27 </P>
  28 <P class="Body" style="margin: 0px">Global Functions</P>
  29 <P class="Body" style="margin: 0px"><BR>
  30 void SetRGBColor32(rgb_color *col, uint8 r, uint8 g, uint8 b, uint8 a=255)</P>
  31 <P class="Body" style="margin: 0px">void SetRGBAColor32(rgb_color *col, uint16 color16)</P>
  32 <P class="Body" style="margin: 0px">void SetRGBColor16(uint16 *col, uint8 r, uint8 g, uint8 b)</P>
  33 <P class="Body" style="margin: 0px">void SetRGBAColor15(uint16 *col, uint8 r, uint8 g, uint8 b, bool opaque=true)</P>
  34 <P class="Body" style="margin: 0px"><BR>
  35 uint8 FindClosestColor(rgb_color *palette,rgb_color col)</P>
  36 <P class="Body" style="margin: 0px">uint16 FindClosestColor16(rgb_color col)</P>
  37 <P class="Body" style="margin: 0px">uint16 FindClosestColor15(rgb_color col)</P>
  38 <P class="Body" style="margin: 0px"><BR>
  39 rgb_color MakeBlendColor(rgb_color col, rgb_color col2, float position)</P>
  40 <P class="Body" style="margin: 0px"><BR>
  41 <HR>
  42 </P>
  43 <P class="Body" style="margin: 0px"><span class="OBOS-Function-Def">void SetRGBColor32(rgb_color *col, uint8 r, uint8 g, uint8 b, uint8 a=255)</span></P>
  44 <P class="Body" style="margin: 0px"><BR>
  45 Simply assigns the passed parameters to the internal members of the passed color</P>
  46 <P class="Body" style="margin: 0px"><BR>
  47 <BR>
  48 <span class="OBOS-Function-Def">void SetRGBAColor32(rgb_color *col, uint16 color16)</span></P>
  49 <P class="Body" style="margin: 0px"><BR>
  50 Maps a 16-bit color to a 32-bit one.</P>
  51 <P class="Body" style="margin: 0px"><BR>
  52 gggbbbbb  arrrrrgg</P>
  53 <P class="Body" style="margin: 0px">1) Extract component values using the following calculations:</P>
  54 <P class="Body" style="margin: 0px"><BR>
  55         red16 = (uint8[1] &amp; 124) &gt;&gt;  2</P>
  56 <P class="Body" style="margin: 0px"><BR>
  57         green16 = ((uint8[0] &amp; 224) &gt;&gt; 5) | ((uint8[1] &amp; 3) &lt;&lt; 3)</P>
  58 <P class="Body" style="margin: 0px"><BR>
  59         blue16 = uint8[0] &amp; 31</P>
  60 <P class="Body" style="margin: 0px">2) Use cross-multiplication to map each 16-bit color component from 0-31 space to 0-255 space, i.e. red32 = (red16 / 31) * 255</P>
  61 <P class="Body" style="margin: 0px">3) Assign mapped values to the rgb_color passed to the function</P>
  62 <P class="Body" style="margin: 0px"><BR>
  63 <BR>
  64 <span class="OBOS-Function-Def">void SetRGBColor16(uint16 *col, uint8 r, uint8 g, uint8 b)</span></P>
  65 <P class="Body" style="margin: 0px"><BR>
  66 Used for easy assignment of opaque (B_RGB16) 16-bit colors.</P>
  67 <P class="Body" style="margin: 0px"><BR>
  68 1) Clip parameters via a bitwise AND with 31 (var &amp;=31)</P>
  69 <P class="Body" style="margin: 0px">2) Create a uint8 * to the passed color</P>
  70 <P class="Body" style="margin: 0px">3) Assign as follows and return:</P>
  71 <P class="Body" style="margin: 0px">    a) uint8[0] = ( (g &amp; 7) &lt;&lt; 5) | (b  &amp; 31)</P>
  72 <P class="Body" style="margin: 0px">    b) uint8[1] = ( (r &amp; 31) &lt;&lt; 3) | ( (g &amp; 56) &gt;&gt; 3)</P>
  73 <P class="Body" style="margin: 0px"><BR>
  74 <BR>
  75 <span class="OBOS-Function-Def">void SetRGBAColor15(uint16 *col, uint8 r, uint8 g, uint8 b, bool opaque=true)</span></P>
  76 <P class="Body" style="margin: 0px"><BR>
  77 Used for easy assignment of alpha-aware (B_RGBA16) 16-bit colors.</P>
  78 <P class="Body" style="margin: 0px"><BR>
  79 1) Clip parameters via a bitwise AND with 31 (var &amp;=31)</P>
  80 <P class="Body" style="margin: 0px">2) Create a uint8 * to the passed color</P>
  81 <P class="Body" style="margin: 0px">3) Assign as follows and return:</P>
  82 <P class="Body" style="margin: 0px">    a) uint8[0] = ( (g &amp; 7) &lt;&lt; 5) | (b  &amp; 31)</P>
  83 <P class="Body" style="margin: 0px">    b) uint8[1] = ( (r &amp; 31) &lt;&lt; 2) | ( (g &amp; 24) &gt;&gt; 3) | (a) ? 128 : 0</P>
  84 <P class="Body" style="margin: 0px"><BR>
  85 <BR>
  86 <span class="OBOS-Function-Def">uint8 FindClosestColor(rgb_color *palette,rgb_color col)</span></P>
  87 <P class="Body" style="margin: 0px"><BR>
  88 Finds the color which most closely resembles the given one in the given palette.</P>
  89 <P class="Body" style="margin: 0px"><BR>
  90 1) Set the saved delta value to 765 (maximum difference)</P>
  91 <P class="Body" style="margin: 0px">2) Loop through all the colors in the palette. For each color,</P>
  92 <P class="Body" style="margin: 0px">    a) calculate the delta value for each color component and add them together</P>
  93 <P class="Body" style="margin: 0px">    b) compare the new combined delta with the saved one</P>
  94 <P class="Body" style="margin: 0px">    c) if the delta is 0, immediately return the current index</P>
  95 <P class="Body" style="margin: 0px">    d) if the new one is smaller, save it and also the palette index</P>
  96 <P class="Body" style="margin: 0px"><BR>
  97 <BR>
  98 <span class="OBOS-Function-Def">uint16 FindClosestColor16(rgb_color col)</span></P>
  99 <P class="Body" style="margin: 0px"><BR>
 100 Returns a 16-bit approximation of the given 32-bit color. Alpha values are ignored.</P>
 101 <P class="Body" style="margin: 0px">1) Create an opaque, 16-bit approximation of col using the following calculations:</P>
 102 <P class="Body" style="margin: 0px">    r16=(31*col.red)/255</P>
 103 <P class="Body" style="margin: 0px">    g16=(31*col.green)/255</P>
 104 <P class="Body" style="margin: 0px">    b16=(31*col.blue)/255</P>
 105 <P class="Body" style="margin: 0px">2) Assign it to a uint16 using the same code as in SetRGBColor16() and return it.</P>
 106 <P class="Body" style="margin: 0px"><BR>
 107 <BR>
 108 <span class="OBOS-Function-Def">uint16 FindClosestColor15(rgb_color col)</span></P>
 109 <P class="Body" style="margin: 0px"><BR>
 110 This functions almost exactly like the 16-bit version, but this also takes into account the alpha transparency bit and works in the color space B_RGBA15. Follow the same algorithm as FindClosestColor16(), but assign the return value using SetRGBColor15.</P>
 111 <P class="Body" style="margin: 0px"><BR>
 112 <BR>
 113 <span class="OBOS-Function-Def">rgb_color MakeBlendColor(rgb_color col, rgb_color col2, float position)</span></P>
 114 <P class="Body" style="margin: 0px"><BR>
 115 MakeBlendColor calculates a color that is somewhere between start color col and end color col2, based on position, where 0&lt;= position &lt;= 1. If position is out of these bounds, a color of {0,0,0,0} is returned. If position is 0, the start color is returned. If position is 1, col2 is returned. Otherwise, the color is calculated thus:</P>
 116 <P class="Body" style="margin: 0px"><BR>
 117 1) calculate delta values for each channel, i.e. int16 delta_r=col.red-col2.red</P>
 118 <P class="Body" style="margin: 0px">2) Based on these delta values, calculate the blend values for each channel, i.e. blend_color.red=uint8(col1.red - (delta_r * position) )</P>
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