gfx/src/nsColor.h

   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 #ifndef nsColor_h___
   8 #define nsColor_h___
   9
  10 #include <stdint.h>   // for uint8_t, uint32_t
  11 #include "nsCoord.h"  // for NSToIntRound
  12 #include "nsStringFwd.h"
  13
  14 // A color is a 32 bit unsigned integer with four components: R, G, B
  15 // and A.
  16 typedef uint32_t nscolor;
  17
  18 // Make a color out of r,g,b values. This assumes that the r,g,b values are
  19 // properly constrained to 0-255. This also assumes that a is 255.
  20 #define NS_RGB(_r, _g, _b) \
  21   ((nscolor)((255 << 24) | ((_b) << 16) | ((_g) << 8) | (_r)))
  22
  23 // Make a color out of r,g,b,a values. This assumes that the r,g,b,a
  24 // values are properly constrained to 0-255.
  25 #define NS_RGBA(_r, _g, _b, _a) \
  26   ((nscolor)(((_a) << 24) | ((_b) << 16) | ((_g) << 8) | (_r)))
  27
  28 // Extract color components from nscolor
  29 #define NS_GET_R(_rgba) ((uint8_t)((_rgba) & 0xff))
  30 #define NS_GET_G(_rgba) ((uint8_t)(((_rgba) >> 8) & 0xff))
  31 #define NS_GET_B(_rgba) ((uint8_t)(((_rgba) >> 16) & 0xff))
  32 #define NS_GET_A(_rgba) ((uint8_t)(((_rgba) >> 24) & 0xff))
  33
  34 namespace mozilla {
  35
  36 template <typename T>
  37 inline uint8_t ClampColor(T aColor) {
  38   if (aColor >= 255) {
  39     return 255;
  40   }
  41   if (aColor <= 0) {
  42     return 0;
  43   }
  44   return NSToIntRound(aColor);
  45 }
  46
  47 }  // namespace mozilla
  48
  49 enum class nsHexColorType : uint8_t {
  50   NoAlpha,     // 3 or 6 digit hex colors only
  51   AllowAlpha,  // 3, 4, 6, or 8 digit hex colors
  52 };
  53
  54 // Translate a hex string to a color. Return true if it parses ok,
  55 // otherwise return false.
  56 // This accepts the number of digits specified by aType.
  57 bool NS_HexToRGBA(const nsAString& aBuf, nsHexColorType aType,
  58                   nscolor* aResult);
  59
  60 // Compose one NS_RGB color onto another. The result is what
  61 // you get if you draw aFG on top of aBG with operator OVER.
  62 nscolor NS_ComposeColors(nscolor aBG, nscolor aFG);
  63
  64 namespace mozilla {
  65
  66 inline uint32_t RoundingDivideBy255(uint32_t n) {
  67   // There is an approximate alternative: ((n << 8) + n + 32896) >> 16
  68   // But that is actually slower than this simple expression on a modern
  69   // machine with a modern compiler.
  70   return (n + 127) / 255;
  71 }
  72
  73 }  // namespace mozilla
  74
  75 // Translate a hex string to a color. Return true if it parses ok,
  76 // otherwise return false.
  77 // This version accepts 1 to 9 digits (missing digits are 0)
  78 bool NS_LooseHexToRGB(const nsString& aBuf, nscolor* aResult);
  79
  80 // There is no function to translate a color to a hex string, because
  81 // the hex-string syntax does not support transparency.
  82
  83 #endif /* nsColor_h___ */