gfx/src/nsColor.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "mozilla/ArrayUtils.h"         // for ArrayLength
   7 #include "mozilla/mozalloc.h"           // for operator delete, etc
   8
   9 #include "nsColor.h"
  10 #include <sys/types.h>                  // for int32_t
  11 #include "nsColorNames.h"               // for nsColorNames
  12 #include "nsDebug.h"                    // for NS_ASSERTION, etc
  13 #include "nsStaticNameTable.h"
  14 #include "nsString.h"                   // for nsAutoCString, nsString, etc
  15 #include "nscore.h"                     // for nsAString, etc
  16
  17 using namespace mozilla;
  18
  19 // define an array of all color names
  20 #define GFX_COLOR(_name, _value) #_name,
  21 static const char* const kColorNames[] = {
  22 #include "nsColorNameList.h"
  23 };
  24 #undef GFX_COLOR
  25
  26 // define an array of all color name values
  27 #define GFX_COLOR(_name, _value) _value,
  28 static const nscolor kColors[] = {
  29 #include "nsColorNameList.h"
  30 };
  31 #undef GFX_COLOR
  32
  33 #define eColorName_COUNT (ArrayLength(kColorNames))
  34 #define eColorName_UNKNOWN (-1)
  35
  36 static nsStaticCaseInsensitiveNameTable* gColorTable = nullptr;
  37
  38 void nsColorNames::AddRefTable(void)
  39 {
  40   NS_ASSERTION(!gColorTable, "pre existing array!");
  41   if (!gColorTable) {
  42     gColorTable = new nsStaticCaseInsensitiveNameTable();
  43     if (gColorTable) {
  44 #ifdef DEBUG
  45     {
  46       // let's verify the table...
  47       for (uint32_t index = 0; index < eColorName_COUNT; ++index) {
  48         nsAutoCString temp1(kColorNames[index]);
  49         nsAutoCString temp2(kColorNames[index]);
  50         ToLowerCase(temp1);
  51         NS_ASSERTION(temp1.Equals(temp2), "upper case char in table");
  52       }
  53     }
  54 #endif
  55       gColorTable->Init(kColorNames, eColorName_COUNT);
  56     }
  57   }
  58 }
  59
  60 void nsColorNames::ReleaseTable(void)
  61 {
  62   if (gColorTable) {
  63     delete gColorTable;
  64     gColorTable = nullptr;
  65   }
  66 }
  67
  68 static int ComponentValue(const char16_t* aColorSpec, int aLen, int color, int dpc)
  69 {
  70   int component = 0;
  71   int index = (color * dpc);
  72   if (2 < dpc) {
  73     dpc = 2;
  74   }
  75   while (--dpc >= 0) {
  76     char16_t ch = ((index < aLen) ? aColorSpec[index++] : '0');
  77     if (('0' <= ch) && (ch <= '9')) {
  78       component = (component * 16) + (ch - '0');
  79     } else if ((('a' <= ch) && (ch <= 'f')) ||
  80                (('A' <= ch) && (ch <= 'F'))) {
  81       // "ch&7" handles lower and uppercase hex alphabetics
  82       component = (component * 16) + (ch & 7) + 9;
  83     }
  84     else {  // not a hex digit, treat it like 0
  85       component = (component * 16);
  86     }
  87   }
  88   return component;
  89 }
  90
  91 NS_GFX_(bool) NS_HexToRGB(const nsAString& aColorSpec,
  92                                        nscolor* aResult)
  93 {
  94   const char16_t* buffer = aColorSpec.BeginReading();
  95
  96   int nameLen = aColorSpec.Length();
  97   if ((nameLen == 3) || (nameLen == 6)) {
  98     // Make sure the digits are legal
  99     for (int i = 0; i < nameLen; i++) {
 100       char16_t ch = buffer[i];
 101       if (((ch >= '0') && (ch <= '9')) ||
 102           ((ch >= 'a') && (ch <= 'f')) ||
 103           ((ch >= 'A') && (ch <= 'F'))) {
 104         // Legal character
 105         continue;
 106       }
 107       // Whoops. Illegal character.
 108       return false;
 109     }
 110
 111     // Convert the ascii to binary
 112     int dpc = ((3 == nameLen) ? 1 : 2);
 113     // Translate components from hex to binary
 114     int r = ComponentValue(buffer, nameLen, 0, dpc);
 115     int g = ComponentValue(buffer, nameLen, 1, dpc);
 116     int b = ComponentValue(buffer, nameLen, 2, dpc);
 117     if (dpc == 1) {
 118       // Scale single digit component to an 8 bit value. Replicate the
 119       // single digit to compute the new value.
 120       r = (r << 4) | r;
 121       g = (g << 4) | g;
 122       b = (b << 4) | b;
 123     }
 124     NS_ASSERTION((r >= 0) && (r <= 255), "bad r");
 125     NS_ASSERTION((g >= 0) && (g <= 255), "bad g");
 126     NS_ASSERTION((b >= 0) && (b <= 255), "bad b");
 127     *aResult = NS_RGB(r, g, b);
 128     return true;
 129   }
 130
 131   // Improperly formatted color value
 132   return false;
 133 }
 134
 135 // This implements part of the algorithm for legacy behavior described in
 136 // http://www.whatwg.org/specs/web-apps/current-work/complete/common-microsyntaxes.html#rules-for-parsing-a-legacy-color-value
 137 NS_GFX_(bool) NS_LooseHexToRGB(const nsString& aColorSpec, nscolor* aResult)
 138 {
 139   if (aColorSpec.EqualsLiteral("transparent")) {
 140     return false;
 141   }
 142
 143   int nameLen = aColorSpec.Length();
 144   const char16_t* colorSpec = aColorSpec.get();
 145   if (nameLen > 128) {
 146     nameLen = 128;
 147   }
 148
 149   if ('#' == colorSpec[0]) {
 150     ++colorSpec;
 151     --nameLen;
 152   }
 153
 154   // digits per component
 155   int dpc = (nameLen + 2) / 3;
 156   int newdpc = dpc;
 157
 158   // Use only the rightmost 8 characters of each component.
 159   if (newdpc > 8) {
 160     nameLen -= newdpc - 8;
 161     colorSpec += newdpc - 8;
 162     newdpc = 8;
 163   }
 164
 165   // And then keep trimming characters at the left until we'd trim one
 166   // that would leave a nonzero value, but not past 2 characters per
 167   // component.
 168   while (newdpc > 2) {
 169     bool haveNonzero = false;
 170     for (int c = 0; c < 3; ++c) {
 171       NS_ABORT_IF_FALSE(c * dpc < nameLen,
 172                         "should not pass end of string while newdpc > 2");
 173       char16_t ch = colorSpec[c * dpc];
 174       if (('1' <= ch && ch <= '9') ||
 175           ('A' <= ch && ch <= 'F') ||
 176           ('a' <= ch && ch <= 'f')) {
 177         haveNonzero = true;
 178         break;
 179       }
 180     }
 181     if (haveNonzero) {
 182       break;
 183     }
 184     --newdpc;
 185     --nameLen;
 186     ++colorSpec;
 187   }
 188
 189   // Translate components from hex to binary
 190   int r = ComponentValue(colorSpec, nameLen, 0, dpc);
 191   int g = ComponentValue(colorSpec, nameLen, 1, dpc);
 192   int b = ComponentValue(colorSpec, nameLen, 2, dpc);
 193   NS_ASSERTION((r >= 0) && (r <= 255), "bad r");
 194   NS_ASSERTION((g >= 0) && (g <= 255), "bad g");
 195   NS_ASSERTION((b >= 0) && (b <= 255), "bad b");
 196
 197   *aResult = NS_RGB(r, g, b);
 198   return true;
 199 }
 200
 201 NS_GFX_(bool) NS_ColorNameToRGB(const nsAString& aColorName, nscolor* aResult)
 202 {
 203   if (!gColorTable) return false;
 204
 205   int32_t id = gColorTable->Lookup(aColorName);
 206   if (eColorName_UNKNOWN < id) {
 207     NS_ASSERTION(uint32_t(id) < eColorName_COUNT,
 208                  "gColorTable->Lookup messed up");
 209     if (aResult) {
 210       *aResult = kColors[id];
 211     }
 212     return true;
 213   }
 214   return false;
 215 }
 216
 217 // Returns kColorNames, an array of all possible color names, and sets
 218 // *aSizeArray to the size of that array. Do NOT call free() on this array.
 219 NS_GFX_(const char * const *) NS_AllColorNames(size_t *aSizeArray)
 220 {
 221   *aSizeArray = ArrayLength(kColorNames);
 222   return kColorNames;
 223 }
 224
 225 // Macro to blend two colors
 226 //
 227 // equivalent to target = (bg*(255-fgalpha) + fg*fgalpha)/255
 228 #define MOZ_BLEND(target, bg, fg, fgalpha)       \
 229   FAST_DIVIDE_BY_255(target, (bg)*(255-fgalpha) + (fg)*(fgalpha))
 230
 231 NS_GFX_(nscolor)
 232 NS_ComposeColors(nscolor aBG, nscolor aFG)
 233 {
 234   // This function uses colors that are non premultiplied alpha.
 235   int r, g, b, a;
 236
 237   int bgAlpha = NS_GET_A(aBG);
 238   int fgAlpha = NS_GET_A(aFG);
 239
 240   // Compute the final alpha of the blended color
 241   // a = fgAlpha + bgAlpha*(255 - fgAlpha)/255;
 242   FAST_DIVIDE_BY_255(a, bgAlpha*(255-fgAlpha));
 243   a = fgAlpha + a;
 244   int blendAlpha;
 245   if (a == 0) {
 246     // In this case the blended color is totally trasparent,
 247     // we preserve the color information of the foreground color.
 248     blendAlpha = 255;
 249   } else {
 250     blendAlpha = (fgAlpha*255)/a;
 251   }
 252   MOZ_BLEND(r, NS_GET_R(aBG), NS_GET_R(aFG), blendAlpha);
 253   MOZ_BLEND(g, NS_GET_G(aBG), NS_GET_G(aFG), blendAlpha);
 254   MOZ_BLEND(b, NS_GET_B(aBG), NS_GET_B(aFG), blendAlpha);
 255
 256   return NS_RGBA(r, g, b, a);
 257 }
 258
 259 // Functions to convert from HSL color space to RGB color space.
 260 // This is the algorithm described in the CSS3 specification
 261
 262 // helper
 263 static float
 264 HSL_HueToRGB(float m1, float m2, float h)
 265 {
 266   if (h < 0.0f)
 267     h += 1.0f;
 268   if (h > 1.0f)
 269     h -= 1.0f;
 270   if (h < (float)(1.0/6.0))
 271     return m1 + (m2 - m1)*h*6.0f;
 272   if (h < (float)(1.0/2.0))
 273     return m2;
 274   if (h < (float)(2.0/3.0))
 275     return m1 + (m2 - m1)*((float)(2.0/3.0) - h)*6.0f;
 276   return m1;
 277 }
 278
 279 // The float parameters are all expected to be in the range 0-1
 280 NS_GFX_(nscolor)
 281 NS_HSL2RGB(float h, float s, float l)
 282 {
 283   uint8_t r, g, b;
 284   float m1, m2;
 285   if (l <= 0.5f) {
 286     m2 = l*(s+1);
 287   } else {
 288     m2 = l + s - l*s;
 289   }
 290   m1 = l*2 - m2;
 291   r = uint8_t(255 * HSL_HueToRGB(m1, m2, h + 1.0f/3.0f));
 292   g = uint8_t(255 * HSL_HueToRGB(m1, m2, h));
 293   b = uint8_t(255 * HSL_HueToRGB(m1, m2, h - 1.0f/3.0f));
 294   return NS_RGB(r, g, b);
 295 }
 296
 297 NS_GFX_(const char*)
 298 NS_RGBToColorName(nscolor aColor)
 299 {
 300   for (size_t idx = 0; idx < ArrayLength(kColors); ++idx) {
 301     if (kColors[idx] == aColor) {
 302       return kColorNames[idx];
 303     }
 304   }
 305
 306   return nullptr;
 307 }