Android 颜色计算

/**

• 合并颜色，支持 argb8888

• @param fg 前景色

• @param bg 背景色
  */
  public static int blendColor(int fg, int bg) {
  int scr = Color.red(fg);
  int scg = Color.green(fg);
  int scb = Color.blue(fg);
  int sa = fg >>> 24;
  int dcr = Color.red(bg);
  int dcg = Color.green(bg);
  int dcb = Color.blue(bg);
  int color_r = dcr * (0xff - sa) / 0xff + scr * sa / 0xff;
  int color_g = dcg * (0xff - sa) / 0xff + scg * sa / 0xff;
  int color_b = dcb * (0xff - sa) / 0xff + scb * sa / 0xff;
  return ((color_r << 16) + (color_g << 8) + color_b) | (0xff000000);
  }

  /** Calculates the constrast between two colors, using the algorithm provided by the WCAG v2. */
  public static float computeContrastBetweenColors(int bg, int fg) {
  float bgR = Color.red(bg) / 255f;
  float bgG = Color.green(bg) / 255f;
  float bgB = Color.blue(bg) / 255f;
  bgR = (bgR < 0.03928f) ? bgR / 12.92f : (float) Math.pow((bgR + 0.055f) / 1.055f, 2.4f);
  bgG = (bgG < 0.03928f) ? bgG / 12.92f : (float) Math.pow((bgG + 0.055f) / 1.055f, 2.4f);
  bgB = (bgB < 0.03928f) ? bgB / 12.92f : (float) Math.pow((bgB + 0.055f) / 1.055f, 2.4f);
  float bgL = 0.2126f * bgR + 0.7152f * bgG + 0.0722f * bgB;

   float fgR = Color.red(fg) / 255f;
   float fgG = Color.green(fg) / 255f;
   float fgB = Color.blue(fg) / 255f;
   fgR = (fgR < 0.03928f) ? fgR / 12.92f : (float) Math.pow((fgR + 0.055f) / 1.055f, 2.4f);
   fgG = (fgG < 0.03928f) ? fgG / 12.92f : (float) Math.pow((fgG + 0.055f) / 1.055f, 2.4f);
   fgB = (fgB < 0.03928f) ? fgB / 12.92f : (float) Math.pow((fgB + 0.055f) / 1.055f, 2.4f);
   float fgL = 0.2126f * fgR + 0.7152f * fgG + 0.0722f * fgB;
  
   return Math.abs((fgL + 0.05f) / (bgL + 0.05f));
  

  }
  //判断是否是深色
  isDark = computeContrastBetweenColors(color,Color.WHITE) > 3f;