layout/base/nsCSSColorUtils.cpp

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  37
  38 /* functions that manipulate colors */
  39
  40 #include "nsCSSColorUtils.h"
  41 #include "nsDebug.h"
  42 #include <math.h>
  43
  44 // Weird color computing code stolen from winfe which was stolen
  45 // from the xfe which was written originally by Eric Bina. So there.
  46
  47 #define RED_LUMINOSITY        299
  48 #define GREEN_LUMINOSITY      587
  49 #define BLUE_LUMINOSITY       114
  50 #define INTENSITY_FACTOR      25
  51 #define LIGHT_FACTOR          0
  52 #define LUMINOSITY_FACTOR     75
  53
  54 #define MAX_COLOR             255
  55 #define COLOR_DARK_THRESHOLD  51
  56 #define COLOR_LIGHT_THRESHOLD 204
  57
  58 #define COLOR_LITE_BS_FACTOR 45
  59 #define COLOR_LITE_TS_FACTOR 70
  60
  61 #define COLOR_DARK_BS_FACTOR 30
  62 #define COLOR_DARK_TS_FACTOR 50
  63
  64 #define LIGHT_GRAY NS_RGB(192, 192, 192)
  65 #define DARK_GRAY  NS_RGB(96, 96, 96)
  66 #define WHITE      NS_RGB(255, 255, 255)
  67 #define BLACK      NS_RGB(0, 0, 0)
  68
  69 #define MAX_BRIGHTNESS  254
  70 #define MAX_DARKNESS     0
  71
  72 void NS_GetSpecial3DColors(nscolor aResult[2],
  73                            nscolor aBackgroundColor,
  74                            nscolor aBorderColor)
  75 {
  76
  77   PRUint8 f0, f1;
  78   PRUint8 r, g, b;
  79
  80   PRUint8 rb = NS_GET_R(aBorderColor);
  81   PRUint8 gb = NS_GET_G(aBorderColor);
  82   PRUint8 bb = NS_GET_B(aBorderColor);
  83
  84   PRUint8 a = NS_GET_A(aBorderColor);
  85
  86   // This needs to be optimized.
  87   // Calculating background brightness again and again is
  88   // a waste of time!!!. Just calculate it only once.
  89   // .....somehow!!!
  90
  91   PRUint8 red = NS_GET_R(aBackgroundColor);
  92   PRUint8 green = NS_GET_G(aBackgroundColor);
  93   PRUint8 blue = NS_GET_B(aBackgroundColor);
  94
  95   PRUint8 elementBrightness = NS_GetBrightness(rb,gb,bb);
  96   PRUint8 backgroundBrightness = NS_GetBrightness(red, green, blue);
  97
  98
  99   if (backgroundBrightness < COLOR_DARK_THRESHOLD) {
 100     f0 = COLOR_DARK_BS_FACTOR;
 101     f1 = COLOR_DARK_TS_FACTOR;
 102         if(elementBrightness == MAX_DARKNESS)
 103         {
 104        rb = NS_GET_R(DARK_GRAY);
 105        gb = NS_GET_G(DARK_GRAY);
 106        bb = NS_GET_B(DARK_GRAY);
 107         }
 108   }else if (backgroundBrightness > COLOR_LIGHT_THRESHOLD) {
 109     f0 = COLOR_LITE_BS_FACTOR;
 110     f1 = COLOR_LITE_TS_FACTOR;
 111         if(elementBrightness == MAX_BRIGHTNESS)
 112         {
 113        rb = NS_GET_R(LIGHT_GRAY);
 114        gb = NS_GET_G(LIGHT_GRAY);
 115        bb = NS_GET_B(LIGHT_GRAY);
 116         }
 117   }else {
 118     f0 = COLOR_DARK_BS_FACTOR +
 119       (backgroundBrightness *
 120        (COLOR_LITE_BS_FACTOR - COLOR_DARK_BS_FACTOR) / MAX_COLOR);
 121     f1 = COLOR_DARK_TS_FACTOR +
 122       (backgroundBrightness *
 123        (COLOR_LITE_TS_FACTOR - COLOR_DARK_TS_FACTOR) / MAX_COLOR);
 124   }
 125
 126
 127   r = rb - (f0 * rb / 100);
 128   g = gb - (f0 * gb / 100);
 129   b = bb - (f0 * bb / 100);
 130   aResult[0] = NS_RGBA(r, g, b, a);
 131
 132   r = rb + (f1 * (MAX_COLOR - rb) / 100);
 133   g = gb + (f1 * (MAX_COLOR - gb) / 100);
 134   b = bb + (f1 * (MAX_COLOR - bb) / 100);
 135   aResult[1] = NS_RGBA(r, g, b, a);
 136 }
 137
 138 int NS_GetBrightness(PRUint8 aRed, PRUint8 aGreen, PRUint8 aBlue)
 139 {
 140
 141   PRUint8 intensity = (aRed + aGreen + aBlue) / 3;
 142
 143   PRUint8 luminosity = NS_GetLuminosity(NS_RGB(aRed, aGreen, aBlue)) / 1000;
 144
 145   return ((intensity * INTENSITY_FACTOR) +
 146           (luminosity * LUMINOSITY_FACTOR)) / 100;
 147 }
 148
 149 PRInt32 NS_GetLuminosity(nscolor aColor)
 150 {
 151   // When aColor is not opaque, the perceived luminosity will depend
 152   // on what color(s) aColor is ultimately drawn on top of, which we
 153   // do not know.
 154   NS_ASSERTION(NS_GET_A(aColor) == 255,
 155                "impossible to compute luminosity of a non-opaque color");
 156
 157   return (NS_GET_R(aColor) * RED_LUMINOSITY +
 158           NS_GET_G(aColor) * GREEN_LUMINOSITY +
 159           NS_GET_B(aColor) * BLUE_LUMINOSITY);
 160 }
 161
 162 // Function to convert RGB color space into the HSV colorspace
 163 // Hue is the primary color defined from 0 to 359 degrees
 164 // Saturation is defined from 0 to 255.  The higher the number.. the deeper
 165 // the color Value is the brightness of the color. 0 is black, 255 is white.
 166 void NS_RGB2HSV(nscolor aColor, PRUint16 &aHue, PRUint16 &aSat,
 167                 PRUint16 &aValue, PRUint8 &aAlpha)
 168 {
 169   PRUint8 r, g, b;
 170   PRInt16 delta, min, max, r1, b1, g1;
 171   float   hue;
 172
 173   r = NS_GET_R(aColor);
 174   g = NS_GET_G(aColor);
 175   b = NS_GET_B(aColor);
 176
 177   if (r>g) {
 178     max = r;
 179     min = g;
 180   } else {
 181     max = g;
 182     min = r;
 183   }
 184
 185   if (b>max) {
 186     max = b;
 187   }
 188   if (b<min) {
 189     min = b;
 190   }
 191
 192   // value or brightness will always be the max of all the colors(RGB)
 193   aValue = max;
 194   delta = max-min;
 195   aSat = (max!=0)?((delta*255)/max):0;
 196   r1 = r;
 197   b1 = b;
 198   g1 = g;
 199
 200   if (aSat==0) {
 201     hue = 1000;
 202   } else {
 203     if(r==max){
 204       hue=(float)(g1-b1)/(float)delta;
 205     } else if (g1==max) {
 206       hue= 2.0f+(float)(b1-r1)/(float)delta;
 207     } else {
 208       hue = 4.0f+(float)(r1-g1)/(float)delta;
 209     }
 210   }
 211
 212   if(hue<999) {
 213     hue*=60;
 214     if(hue<0){
 215       hue+=360;
 216     }
 217   } else {
 218     hue=0;
 219   }
 220
 221   aHue = (PRUint16)hue;
 222
 223   aAlpha = NS_GET_A(aColor);
 224 }
 225
 226 // Function to convert HSV color space into the RGB colorspace
 227 // Hue is the primary color defined from 0 to 359 degrees
 228 // Saturation is defined from 0 to 255.  The higher the number.. the deeper
 229 // the color Value is the brightness of the color. 0 is black, 255 is white.
 230 void NS_HSV2RGB(nscolor &aColor, PRUint16 aHue, PRUint16 aSat, PRUint16 aValue,
 231                 PRUint8 aAlpha)
 232 {
 233   PRUint16  r = 0, g = 0, b = 0;
 234   PRUint16  i, p, q, t;
 235   double    h, f, percent;
 236
 237   if ( aSat == 0 ){
 238     // achromatic color, no hue is defined
 239     r = aValue;
 240     g = aValue;
 241     b = aValue;
 242   } else {
 243     // hue in in degrees around the color wheel defined from
 244     // 0 to 360 degrees.
 245     if (aHue >= 360) {
 246       aHue = 0;
 247     }
 248
 249     // we break the color wheel into 6 areas.. these
 250     // areas define how the saturation and value define the color.
 251     // reds behave differently than the blues
 252     h = (double)aHue / 60.0;
 253     i = (PRUint16) floor(h);
 254     f = h-(double)i;
 255     percent = ((double)aValue/255.0);   // this needs to be a value from 0 to 1, so a percentage
 256                                         // can be calculated of the saturation.
 257     p = (PRUint16)(percent*(255-aSat));
 258     q = (PRUint16)(percent*(255-(aSat*f)));
 259     t = (PRUint16)(percent*(255-(aSat*(1.0-f))));
 260
 261     // i is guaranteed to never be larger than 5.
 262     switch(i){
 263       case 0: r = aValue; g = t; b = p;break;
 264       case 1: r = q; g = aValue; b = p;break;
 265       case 2: r = p; g = aValue; b = t;break;
 266       case 3: r = p; g = q; b = aValue;break;
 267       case 4: r = t; g = p; b = aValue;break;
 268       case 5: r = aValue; g = p; b = q;break;
 269     }
 270   }
 271   aColor = NS_RGBA(r, g, b, aAlpha);
 272 }