Add bitmap manipulation functions in advance of themes.

skia/ext/skia_utils.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "skia/ext/skia_utils.h"
+#include "skia/include/SkColorPriv.h"
 
 #include "SkGradientShader.h"
 
 namespace skia {
 
 SkShader* CreateGradientShader(int start_point,
                                int end_point,
                                SkColor start_color,
                                SkColor end_color) {
   SkColor grad_colors[2] = { start_color, end_color};
   SkPoint grad_points[2];
   grad_points[0].set(SkIntToScalar(0), SkIntToScalar(start_point));
   grad_points[1].set(SkIntToScalar(0), SkIntToScalar(end_point));
 
   return SkGradientShader::CreateLinear(
       grad_points, grad_colors, NULL, 2, SkShader::kRepeat_TileMode);
 }
 
+// Helper function for HSLToSKColor.
+static inline double calcHue(double temp1, double temp2, double hueVal) {
+  if (hueVal < 0.0)
+    hueVal++;
+  else if (hueVal > 1.0)
+    hueVal--;
+
+  if (hueVal * 6.0 < 1.0)
+    return temp1 + (temp2 - temp1) * hueVal * 6.0;
+  if (hueVal * 2.0 < 1.0)
+    return temp2;
+  if (hueVal * 3.0 < 2.0)
+    return temp1 + (temp2 - temp1) * (2.0 / 3.0 - hueVal) * 6.0;
+
+  return temp1;
+}
+
+SkColor HSLToSKColor(U8CPU alpha, float hsl[3]) {
+  double hue = SkScalarToDouble(hsl[0]);
+  double saturation = SkScalarToDouble(hsl[1]);
+  double lightness = SkScalarToDouble(hsl[2]);
+  double scaleFactor = 256.0;
+
+  // If there's no color, we don't care about hue and can do everything based
+  // on brightness.
+  if (!saturation) {
+    U8CPU lightness;
+
+    if (hsl[2] < 0)
+      lightness = 0;
+    else if (hsl[2] >= SK_Scalar1)
+      lightness = 255;
+    else
+      lightness = SkScalarToFixed(hsl[2]) >> 8;
+
+    unsigned greyValue = SkAlphaMul(lightness, alpha);
+    return SkColorSetARGB(alpha, greyValue, greyValue, greyValue);
+  }
+
+  double temp2 = (lightness < 0.5) ?
+      lightness * (1.0 + saturation) :
+      lightness + saturation - (lightness * saturation);
+  double temp1 = 2.0 * lightness - temp2;
+
+  double rh = calcHue(temp1, temp2, hue + 1.0 / 3.0);
+  double gh = calcHue(temp1, temp2, hue);
+  double bh = calcHue(temp1, temp2, hue - 1.0 / 3.0);
+
+  return SkColorSetARGB(alpha,
+      SkAlphaMul(static_cast<int>(rh * scaleFactor), alpha),
+      SkAlphaMul(static_cast<int>(gh * scaleFactor), alpha),
+      SkAlphaMul(static_cast<int>(bh * scaleFactor), alpha));
+}
+
+void SkColorToHSL(SkColor c, float hsl[3]) {
+  double r = SkColorGetR(c) / 255.0;
+  double g = SkColorGetG(c) / 255.0;
+  double b = SkColorGetB(c) / 255.0;
+
+  double h, s, l;
+
+  double vmax = r > g ? r : g;
+  vmax = vmax > b ? vmax : b;
+  double vmin = r < g ? r : g;
+  vmin = vmin < b ? vmin : b;
+  double delta = vmax - vmin;
+
+  l = (vmax + vmin) / 2;
+
+  if (delta == 0) {
+    h = 0;
+    s = 0;
+  } else {
+    if (l < 0.5)
+      s = delta / (vmax + vmin);
+    else
+      s = delta / (2 - vmax - vmin);
+
+    double dr = (((vmax - r) / 6.0) + (delta / 2.0)) / delta;
+    double dg = (((vmax - g) / 6.0) + (delta / 2.0)) / delta;
+    double db = (((vmax - b) / 6.0) + (delta / 2.0)) / delta;
+
+    if (r == vmax)
+      h = db - dg;
+    else if (g == vmax)
+      h = (1.0 / 3.0) + dr - db;
+    else if (b == vmax)
+      h = (2.0 / 3.0) + dg - dr;
+
+    if (h < 0) h += 1;
+    if (h > 1) h -= 1;
+  }
+
+  hsl[0] = h;
+  hsl[1] = s;
+  hsl[2] = l;
+}
+
+
 }  // namespace skia