layout/base/nsCSSColorUtils.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /* functions that manipulate colors */
   8
   9 #include "nsCSSColorUtils.h"
  10 #include "nsDebug.h"
  11 #include <math.h>
  12
  13 // Weird color computing code stolen from winfe which was stolen
  14 // from the xfe which was written originally by Eric Bina. So there.
  15
  16 #define RED_LUMINOSITY 299
  17 #define GREEN_LUMINOSITY 587
  18 #define BLUE_LUMINOSITY 114
  19 #define INTENSITY_FACTOR 25
  20 #define LUMINOSITY_FACTOR 75
  21
  22 void NS_GetSpecial3DColors(nscolor aResult[2], nscolor aBorderColor) {
  23   const float kDarkerScale = 2.0f / 3.0f;
  24
  25   uint8_t r = NS_GET_R(aBorderColor);
  26   uint8_t g = NS_GET_G(aBorderColor);
  27   uint8_t b = NS_GET_B(aBorderColor);
  28   uint8_t a = NS_GET_A(aBorderColor);
  29   if (r == 0 && g == 0 && b == 0) {
  30     // 0.3 * black
  31     aResult[0] = NS_RGBA(76, 76, 76, a);
  32     // 0.7 * black
  33     aResult[1] = NS_RGBA(178, 178, 178, a);
  34     return;
  35   }
  36
  37   aResult[0] = NS_RGBA(uint8_t(r * kDarkerScale), uint8_t(g * kDarkerScale),
  38                        uint8_t(b * kDarkerScale), a);
  39   aResult[1] = aBorderColor;
  40 }
  41
  42 int NS_GetBrightness(uint8_t aRed, uint8_t aGreen, uint8_t aBlue) {
  43   uint8_t intensity = (aRed + aGreen + aBlue) / 3;
  44
  45   uint8_t luminosity = NS_GetLuminosity(NS_RGB(aRed, aGreen, aBlue)) / 1000;
  46
  47   return ((intensity * INTENSITY_FACTOR) + (luminosity * LUMINOSITY_FACTOR)) /
  48          100;
  49 }
  50
  51 int32_t NS_GetLuminosity(nscolor aColor) {
  52   // When aColor is not opaque, the perceived luminosity will depend
  53   // on what color(s) aColor is ultimately drawn on top of, which we
  54   // do not know.
  55   NS_ASSERTION(NS_GET_A(aColor) == 255,
  56                "impossible to compute luminosity of a non-opaque color");
  57
  58   return (NS_GET_R(aColor) * RED_LUMINOSITY +
  59           NS_GET_G(aColor) * GREEN_LUMINOSITY +
  60           NS_GET_B(aColor) * BLUE_LUMINOSITY);
  61 }
  62
  63 // Function to convert RGB color space into the HSV colorspace
  64 // Hue is the primary color defined from 0 to 359 degrees
  65 // Saturation is defined from 0 to 255.  The higher the number.. the deeper
  66 // the color Value is the brightness of the color. 0 is black, 255 is white.
  67 void NS_RGB2HSV(nscolor aColor, uint16_t& aHue, uint16_t& aSat,
  68                 uint16_t& aValue, uint8_t& aAlpha) {
  69   uint8_t r, g, b;
  70   int16_t delta, min, max, r1, b1, g1;
  71   float hue;
  72
  73   r = NS_GET_R(aColor);
  74   g = NS_GET_G(aColor);
  75   b = NS_GET_B(aColor);
  76
  77   if (r > g) {
  78     max = r;
  79     min = g;
  80   } else {
  81     max = g;
  82     min = r;
  83   }
  84
  85   if (b > max) {
  86     max = b;
  87   }
  88   if (b < min) {
  89     min = b;
  90   }
  91
  92   // value or brightness will always be the max of all the colors(RGB)
  93   aValue = max;
  94   delta = max - min;
  95   aSat = (max != 0) ? ((delta * 255) / max) : 0;
  96   r1 = r;
  97   b1 = b;
  98   g1 = g;
  99
 100   if (aSat == 0) {
 101     hue = 1000;
 102   } else {
 103     if (r == max) {
 104       hue = (float)(g1 - b1) / (float)delta;
 105     } else if (g1 == max) {
 106       hue = 2.0f + (float)(b1 - r1) / (float)delta;
 107     } else {
 108       hue = 4.0f + (float)(r1 - g1) / (float)delta;
 109     }
 110   }
 111
 112   if (hue < 999) {
 113     hue *= 60;
 114     if (hue < 0) {
 115       hue += 360;
 116     }
 117   } else {
 118     hue = 0;
 119   }
 120
 121   aHue = (uint16_t)hue;
 122
 123   aAlpha = NS_GET_A(aColor);
 124 }
 125
 126 // Function to convert HSV color space into the RGB colorspace
 127 // Hue is the primary color defined from 0 to 359 degrees
 128 // Saturation is defined from 0 to 255.  The higher the number.. the deeper
 129 // the color Value is the brightness of the color. 0 is black, 255 is white.
 130 void NS_HSV2RGB(nscolor& aColor, uint16_t aHue, uint16_t aSat, uint16_t aValue,
 131                 uint8_t aAlpha) {
 132   uint16_t r = 0, g = 0, b = 0;
 133   uint16_t i, p, q, t;
 134   double h, f, percent;
 135
 136   if (aSat == 0) {
 137     // achromatic color, no hue is defined
 138     r = aValue;
 139     g = aValue;
 140     b = aValue;
 141   } else {
 142     // hue in in degrees around the color wheel defined from
 143     // 0 to 360 degrees.
 144     if (aHue >= 360) {
 145       aHue = 0;
 146     }
 147
 148     // we break the color wheel into 6 areas.. these
 149     // areas define how the saturation and value define the color.
 150     // reds behave differently than the blues
 151     h = (double)aHue / 60.0;
 152     i = (uint16_t)floor(h);
 153     f = h - (double)i;
 154     percent = ((double)aValue /
 155                255.0);  // this needs to be a value from 0 to 1, so a percentage
 156                         // can be calculated of the saturation.
 157     p = (uint16_t)(percent * (255 - aSat));
 158     q = (uint16_t)(percent * (255 - (aSat * f)));
 159     t = (uint16_t)(percent * (255 - (aSat * (1.0 - f))));
 160
 161     // i is guaranteed to never be larger than 5.
 162     switch (i) {
 163       case 0:
 164         r = aValue;
 165         g = t;
 166         b = p;
 167         break;
 168       case 1:
 169         r = q;
 170         g = aValue;
 171         b = p;
 172         break;
 173       case 2:
 174         r = p;
 175         g = aValue;
 176         b = t;
 177         break;
 178       case 3:
 179         r = p;
 180         g = q;
 181         b = aValue;
 182         break;
 183       case 4:
 184         r = t;
 185         g = p;
 186         b = aValue;
 187         break;
 188       case 5:
 189         r = aValue;
 190         g = p;
 191         b = q;
 192         break;
 193     }
 194   }
 195   aColor = NS_RGBA(r, g, b, aAlpha);
 196 }
 197
 198 #undef RED_LUMINOSITY
 199 #undef GREEN_LUMINOSITY
 200 #undef BLUE_LUMINOSITY
 201 #undef INTENSITY_FACTOR
 202 #undef LUMINOSITY_FACTOR