Move functions from skia/ext to app/gfx where possible: most of skia_utils.* and image_operations.* can be moved because they are not used by WebKit code.

This also fixes the spelling of "Convolusion" to "Convolution" and updates some copyrights.

BUG=none
TEST=none
Review URL: http://codereview.chromium.org/207059

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@26975 0039d316-1c4b-4281-b951-d872f2087c98

7 files changed, 914 insertions, 0 deletions

diff --git a/app/app.gyp b/app/app.gyp
index 18edb94..7c61d17 100644
--- a/app/app.gyp
+++ b/app/app.gyp
@@ -86,6 +86,8 @@
         'gfx/path_gtk.cc',
         'gfx/path_win.cc',
         'gfx/path.h',
+        'gfx/skbitmap_operations.cc',
+        'gfx/skbitmap_operations.h',
         'gfx/text_elider.cc',
         'gfx/text_elider.h',
         'gtk_dnd_util.cc',
@@ -199,8 +201,10 @@
       ],
       'sources': [
         'animation_unittest.cc',
+        'gfx/color_utils_unittest.cc',
         'gfx/font_unittest.cc',
         'gfx/icon_util_unittest.cc',
+        'gfx/skbitmap_operations_unittest.cc',
         'gfx/text_elider_unittest.cc',
         'l10n_util_mac_unittest.mm',
         'l10n_util_unittest.cc',
diff --git a/app/gfx/color_utils.cc b/app/gfx/color_utils.cc
index 48a13ca..1d6cfe4 100644
--- a/app/gfx/color_utils.cc
+++ b/app/gfx/color_utils.cc
@@ -23,6 +23,22 @@ namespace color_utils {
 
 namespace {
 
+double calcHue(double temp1, double temp2, double hue) {
+  if (hue < 0.0)
+    ++hue;
+  else if (hue > 1.0)
+    --hue;
+
+  if (hue * 6.0 < 1.0)
+    return temp1 + (temp2 - temp1) * hue * 6.0;
+  if (hue * 2.0 < 1.0)
+    return temp2;
+  if (hue * 3.0 < 2.0)
+    return temp1 + (temp2 - temp1) * (2.0 / 3.0 - hue) * 6.0;
+
+  return temp1;
+}
+
 int GetLumaForColor(SkColor* color) {
   int luma = static_cast<int>((0.3 * SkColorGetR(*color)) +
                               (0.59 * SkColorGetG(*color)) +
@@ -56,6 +72,109 @@ double ContrastRatio(SkColor color1, SkColor color2) {
 
 // ----------------------------------------------------------------------------
 
+void SkColorToHSL(SkColor c, HSL* hsl) {
+  double r = static_cast<double>(SkColorGetR(c)) / 255.0;
+  double g = static_cast<double>(SkColorGetG(c)) / 255.0;
+  double b = static_cast<double>(SkColorGetB(c)) / 255.0;
+  double vmax = std::max(std::max(r, g), b);
+  double vmin = std::min(std::min(r, g), b);
+  double delta = vmax - vmin;
+  hsl->l = (vmax + vmin) / 2;
+  if (delta) {
+    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)
+      hsl->h = db - dg;
+    else if (g == vmax)
+      hsl->h = (1.0 / 3.0) + dr - db;
+    else if (b == vmax)
+      hsl->h = (2.0 / 3.0) + dg - dr;
+
+    if (hsl->h < 0.0)
+      ++hsl->h;
+    else if (hsl->h > 1.0)
+      --hsl->h;
+
+    hsl->s = delta / ((hsl->l < 0.5) ? (vmax + vmin) : (2 - vmax - vmin));
+  } else {
+    hsl->h = hsl->s = 0;
+  }
+}
+
+SkColor HSLToSkColor(const HSL& hsl, SkAlpha alpha) {
+  double hue = hsl.h;
+  double saturation = hsl.s;
+  double lightness = hsl.l;
+
+  // If there's no color, we don't care about hue and can do everything based
+  // on brightness.
+  if (!saturation) {
+    uint8 light;
+
+    if (lightness < 0)
+      light = 0;
+    else if (lightness >= 1.0)
+      light = 255;
+    else
+      light = SkDoubleToFixed(lightness) >> 8;
+
+    return SkColorSetARGB(alpha, light, light, light);
+  }
+
+  double temp2 = (lightness < 0.5) ?
+      (lightness * (1.0 + saturation)) :
+      (lightness + saturation - (lightness * saturation));
+  double temp1 = 2.0 * lightness - temp2;
+  return SkColorSetARGB(alpha,
+      static_cast<int>(calcHue(temp1, temp2, hue + 1.0 / 3.0) * 255),
+      static_cast<int>(calcHue(temp1, temp2, hue) * 255),
+      static_cast<int>(calcHue(temp1, temp2, hue - 1.0 / 3.0) * 255));
+}
+
+SkColor HSLShift(SkColor color, const HSL& shift) {
+  HSL hsl;
+  int alpha = SkColorGetA(color);
+  SkColorToHSL(color, &hsl);
+
+  // Replace the hue with the tint's hue.
+  if (shift.h >= 0)
+    hsl.h = shift.h;
+
+  // Change the saturation.
+  if (shift.s >= 0) {
+    if (shift.s <= 0.5)
+      hsl.s *= shift.s * 2.0;
+    else
+      hsl.s += (1.0 - hsl.s) * ((shift.s - 0.5) * 2.0);
+  }
+
+  SkColor result = HSLToSkColor(hsl, alpha);
+
+  if (shift.l < 0)
+    return result;
+
+  // Lightness shifts in the style of popular image editors aren't
+  // actually represented in HSL - the L value does have some effect
+  // on saturation.
+  double r = static_cast<double>(SkColorGetR(result));
+  double g = static_cast<double>(SkColorGetG(result));
+  double b = static_cast<double>(SkColorGetB(result));
+  if (shift.l <= 0.5) {
+    r *= (shift.l * 2.0);
+    g *= (shift.l * 2.0);
+    b *= (shift.l * 2.0);
+  } else {
+    r += (255.0 - r) * ((shift.l - 0.5) * 2.0);
+    g += (255.0 - g) * ((shift.l - 0.5) * 2.0);
+    b += (255.0 - b) * ((shift.l - 0.5) * 2.0);
+  }
+  return SkColorSetARGB(alpha,
+                        static_cast<int>(r),
+                        static_cast<int>(g),
+                        static_cast<int>(b));
+}
+
 bool IsColorCloseToTransparent(SkAlpha alpha) {
   const int kCloseToBoundary = 64;
   return alpha < kCloseToBoundary;
diff --git a/app/gfx/color_utils.h b/app/gfx/color_utils.h
index 30e9e52..682062f 100644
--- a/app/gfx/color_utils.h
+++ b/app/gfx/color_utils.h
@@ -11,6 +11,33 @@ class SkBitmap;
 
 namespace color_utils {
 
+// Represents an HSL color.
+struct HSL {
+  double h;
+  double s;
+  double l;
+};
+
+// Note: these transformations assume sRGB as the source color space
+void SkColorToHSL(SkColor c, HSL* hsl);
+SkColor HSLToSkColor(const HSL& hsl, SkAlpha alpha);
+
+// HSL-Shift an SkColor. The shift values are in the range of 0-1, with the
+// option to specify -1 for 'no change'. The shift values are defined as:
+// hsl_shift[0] (hue): The absolute hue value - 0 and 1 map
+//    to 0 and 360 on the hue color wheel (red).
+// hsl_shift[1] (saturation): A saturation shift, with the
+//    following key values:
+//    0 = remove all color.
+//    0.5 = leave unchanged.
+//    1 = fully saturate the image.
+// hsl_shift[2] (lightness): A lightness shift, with the
+//    following key values:
+//    0 = remove all lightness (make all pixels black).
+//    0.5 = leave unchanged.
+//    1 = full lightness (make all pixels white).
+SkColor HSLShift(SkColor color, const HSL& shift);
+
 // Determine if a given alpha value is nearly completely transparent.
 bool IsColorCloseToTransparent(SkAlpha alpha);
 
diff --git a/app/gfx/color_utils_unittest.cc b/app/gfx/color_utils_unittest.cc
new file mode 100644
index 0000000..4e7f414
--- /dev/null
+++ b/app/gfx/color_utils_unittest.cc
@@ -0,0 +1,38 @@
+// 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 <stdlib.h>
+
+#include "app/gfx/color_utils.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "third_party/skia/include/core/SkColorPriv.h"
+
+TEST(ColorUtils, SkColorToHSLRed) {
+  color_utils::HSL hsl = { 0, 0, 0 };
+  color_utils::SkColorToHSL(SK_ColorRED, &hsl);
+  EXPECT_EQ(hsl.h, 0);
+  EXPECT_EQ(hsl.s, 1);
+  EXPECT_EQ(hsl.l, 0.5);
+}
+
+TEST(ColorUtils, SkColorToHSLGrey) {
+  color_utils::HSL hsl = { 0, 0, 0 };
+  color_utils::SkColorToHSL(SkColorSetARGB(255, 128, 128, 128), &hsl);
+  EXPECT_EQ(hsl.h, 0);
+  EXPECT_EQ(hsl.s, 0);
+  EXPECT_EQ(static_cast<int>(hsl.l * 100),
+            static_cast<int>(0.5 * 100));  // Accurate to two decimal places.
+}
+
+TEST(ColorUtils, HSLToSkColorWithAlpha) {
+  SkColor red = SkColorSetARGB(128, 255, 0, 0);
+  color_utils::HSL hsl = { 0, 1, 0.5 };
+  SkColor result = color_utils::HSLToSkColor(hsl, 128);
+  EXPECT_EQ(SkColorGetA(red), SkColorGetA(result));
+  EXPECT_EQ(SkColorGetR(red), SkColorGetR(result));
+  EXPECT_EQ(SkColorGetG(red), SkColorGetG(result));
+  EXPECT_EQ(SkColorGetB(red), SkColorGetB(result));
+}
+
diff --git a/app/gfx/skbitmap_operations.cc b/app/gfx/skbitmap_operations.cc
new file mode 100644
index 0000000..174df68
--- /dev/null
+++ b/app/gfx/skbitmap_operations.cc
@@ -0,0 +1,296 @@
+// Copyright (c) 2009 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 "app/gfx/skbitmap_operations.h"
+
+#include "base/logging.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "third_party/skia/include/core/SkColorPriv.h"
+#include "third_party/skia/include/core/SkUnPreMultiply.h"
+
+// static
+SkBitmap SkBitmapOperations::CreateBlendedBitmap(const SkBitmap& first,
+                                                 const SkBitmap& second,
+                                                 double alpha) {
+  DCHECK((alpha >= 0) && (alpha <= 1));
+  DCHECK(first.width() == second.width());
+  DCHECK(first.height() == second.height());
+  DCHECK(first.bytesPerPixel() == second.bytesPerPixel());
+  DCHECK(first.config() == SkBitmap::kARGB_8888_Config);
+
+  // Optimize for case where we won't need to blend anything.
+  static const double alpha_min = 1.0 / 255;
+  static const double alpha_max = 254.0 / 255;
+  if (alpha < alpha_min)
+    return first;
+  else if (alpha > alpha_max)
+    return second;
+
+  SkAutoLockPixels lock_first(first);
+  SkAutoLockPixels lock_second(second);
+
+  SkBitmap blended;
+  blended.setConfig(SkBitmap::kARGB_8888_Config, first.width(), first.height(),
+                    0);
+  blended.allocPixels();
+  blended.eraseARGB(0, 0, 0, 0);
+
+  double first_alpha = 1 - alpha;
+
+  for (int y = 0; y < first.height(); ++y) {
+    uint32* first_row = first.getAddr32(0, y);
+    uint32* second_row = second.getAddr32(0, y);
+    uint32* dst_row = blended.getAddr32(0, y);
+
+    for (int x = 0; x < first.width(); ++x) {
+      uint32 first_pixel = first_row[x];
+      uint32 second_pixel = second_row[x];
+
+      int a = static_cast<int>((SkColorGetA(first_pixel) * first_alpha) +
+                               (SkColorGetA(second_pixel) * alpha));
+      int r = static_cast<int>((SkColorGetR(first_pixel) * first_alpha) +
+                               (SkColorGetR(second_pixel) * alpha));
+      int g = static_cast<int>((SkColorGetG(first_pixel) * first_alpha) +
+                               (SkColorGetG(second_pixel) * alpha));
+      int b = static_cast<int>((SkColorGetB(first_pixel) * first_alpha) +
+                               (SkColorGetB(second_pixel) * alpha));
+
+      dst_row[x] = SkColorSetARGB(a, r, g, b);
+    }
+  }
+
+  return blended;
+}
+
+// static
+SkBitmap SkBitmapOperations::CreateMaskedBitmap(const SkBitmap& rgb,
+                                                const SkBitmap& alpha) {
+  DCHECK(rgb.width() == alpha.width());
+  DCHECK(rgb.height() == alpha.height());
+  DCHECK(rgb.bytesPerPixel() == alpha.bytesPerPixel());
+  DCHECK(rgb.config() == SkBitmap::kARGB_8888_Config);
+  DCHECK(alpha.config() == SkBitmap::kARGB_8888_Config);
+
+  SkBitmap masked;
+  masked.setConfig(SkBitmap::kARGB_8888_Config, rgb.width(), rgb.height(), 0);
+  masked.allocPixels();
+  masked.eraseARGB(0, 0, 0, 0);
+
+  SkAutoLockPixels lock_rgb(rgb);
+  SkAutoLockPixels lock_alpha(alpha);
+  SkAutoLockPixels lock_masked(masked);
+
+  for (int y = 0; y < masked.height(); ++y) {
+    uint32* rgb_row = rgb.getAddr32(0, y);
+    uint32* alpha_row = alpha.getAddr32(0, y);
+    uint32* dst_row = masked.getAddr32(0, y);
+
+    for (int x = 0; x < masked.width(); ++x) {
+      SkColor rgb_pixel = SkUnPreMultiply::PMColorToColor(rgb_row[x]);
+      int alpha = SkAlphaMul(SkColorGetA(rgb_pixel), SkColorGetA(alpha_row[x]));
+      dst_row[x] = SkColorSetARGB(alpha,
+                                  SkAlphaMul(SkColorGetR(rgb_pixel), alpha),
+                                  SkAlphaMul(SkColorGetG(rgb_pixel), alpha),
+                                  SkAlphaMul(SkColorGetB(rgb_pixel), alpha));
+    }
+  }
+
+  return masked;
+}
+
+// static
+SkBitmap SkBitmapOperations::CreateButtonBackground(SkColor color,
+                                                    const SkBitmap& image,
+                                                    const SkBitmap& mask) {
+  DCHECK(image.config() == SkBitmap::kARGB_8888_Config);
+  DCHECK(mask.config() == SkBitmap::kARGB_8888_Config);
+
+  SkBitmap background;
+  background.setConfig(
+      SkBitmap::kARGB_8888_Config, mask.width(), mask.height(), 0);
+  background.allocPixels();
+
+  double bg_a = SkColorGetA(color);
+  double bg_r = SkColorGetR(color);
+  double bg_g = SkColorGetG(color);
+  double bg_b = SkColorGetB(color);
+
+  SkAutoLockPixels lock_mask(mask);
+  SkAutoLockPixels lock_image(image);
+  SkAutoLockPixels lock_background(background);
+
+  for (int y = 0; y < mask.height(); ++y) {
+    uint32* dst_row = background.getAddr32(0, y);
+    uint32* image_row = image.getAddr32(0, y % image.height());
+    uint32* mask_row = mask.getAddr32(0, y);
+
+    for (int x = 0; x < mask.width(); ++x) {
+      uint32 image_pixel = image_row[x % image.width()];
+
+      double img_a = SkColorGetA(image_pixel);
+      double img_r = SkColorGetR(image_pixel);
+      double img_g = SkColorGetG(image_pixel);
+      double img_b = SkColorGetB(image_pixel);
+
+      double img_alpha = static_cast<double>(img_a) / 255.0;
+      double img_inv = 1 - img_alpha;
+
+      double mask_a = static_cast<double>(SkColorGetA(mask_row[x])) / 255.0;
+
+      dst_row[x] = SkColorSetARGB(
+          static_cast<int>(std::min(255.0, bg_a + img_a) * mask_a),
+          static_cast<int>(((bg_r * img_inv) + (img_r * img_alpha)) * mask_a),
+          static_cast<int>(((bg_g * img_inv) + (img_g * img_alpha)) * mask_a),
+          static_cast<int>(((bg_b * img_inv) + (img_b * img_alpha)) * mask_a));
+    }
+  }
+
+  return background;
+}
+
+
+// static
+SkBitmap SkBitmapOperations::CreateHSLShiftedBitmap(
+    const SkBitmap& bitmap,
+    color_utils::HSL hsl_shift) {
+  DCHECK(bitmap.empty() == false);
+  DCHECK(bitmap.config() == SkBitmap::kARGB_8888_Config);
+
+  SkBitmap shifted;
+  shifted.setConfig(SkBitmap::kARGB_8888_Config, bitmap.width(),
+                    bitmap.height(), 0);
+  shifted.allocPixels();
+  shifted.eraseARGB(0, 0, 0, 0);
+  shifted.setIsOpaque(false);
+
+  SkAutoLockPixels lock_bitmap(bitmap);
+  SkAutoLockPixels lock_shifted(shifted);
+
+  // Loop through the pixels of the original bitmap.
+  for (int y = 0; y < bitmap.height(); ++y) {
+    SkPMColor* pixels = bitmap.getAddr32(0, y);
+    SkPMColor* tinted_pixels = shifted.getAddr32(0, y);
+
+    for (int x = 0; x < bitmap.width(); ++x) {
+      tinted_pixels[x] = SkPreMultiplyColor(color_utils::HSLShift(
+          SkUnPreMultiply::PMColorToColor(pixels[x]), hsl_shift));
+    }
+  }
+
+  return shifted;
+}
+
+// static
+SkBitmap SkBitmapOperations::CreateTiledBitmap(const SkBitmap& source,
+                                               int src_x, int src_y,
+                                               int dst_w, int dst_h) {
+  DCHECK(source.getConfig() == SkBitmap::kARGB_8888_Config);
+
+  SkBitmap cropped;
+  cropped.setConfig(SkBitmap::kARGB_8888_Config, dst_w, dst_h, 0);
+  cropped.allocPixels();
+  cropped.eraseARGB(0, 0, 0, 0);
+
+  SkAutoLockPixels lock_source(source);
+  SkAutoLockPixels lock_cropped(cropped);
+
+  // Loop through the pixels of the original bitmap.
+  for (int y = 0; y < dst_h; ++y) {
+    int y_pix = (src_y + y) % source.height();
+    while (y_pix < 0)
+      y_pix += source.height();
+
+    uint32* source_row = source.getAddr32(0, y_pix);
+    uint32* dst_row = cropped.getAddr32(0, y);
+
+    for (int x = 0; x < dst_w; ++x) {
+      int x_pix = (src_x + x) % source.width();
+      while (x_pix < 0)
+        x_pix += source.width();
+
+      dst_row[x] = source_row[x_pix];
+    }
+  }
+
+  return cropped;
+}
+
+// static
+SkBitmap SkBitmapOperations::DownsampleByTwoUntilSize(const SkBitmap& bitmap,
+                                                      int min_w, int min_h) {
+  if ((bitmap.width() <= min_w) || (bitmap.height() <= min_h) ||
+      (min_w < 0) || (min_h < 0))
+    return bitmap;
+
+  // Since bitmaps are refcounted, this copy will be fast.
+  SkBitmap current = bitmap;
+  while ((current.width() >= min_w * 2) && (current.height() >= min_h * 2) &&
+         (current.width() > 1) && (current.height() > 1))
+    current = DownsampleByTwo(current);
+  return current;
+}
+
+// static
+SkBitmap SkBitmapOperations::DownsampleByTwo(const SkBitmap& bitmap) {
+  // Handle the nop case.
+  if ((bitmap.width() <= 1) || (bitmap.height() <= 1))
+    return bitmap;
+
+  SkBitmap result;
+  result.setConfig(SkBitmap::kARGB_8888_Config,
+                   (bitmap.width() + 1) / 2, (bitmap.height() + 1) / 2);
+  result.allocPixels();
+
+  SkAutoLockPixels lock(bitmap);
+  for (int dest_y = 0; dest_y < result.height(); ++dest_y) {
+    for (int dest_x = 0; dest_x < result.width(); ++dest_x) {
+      // This code is based on downsampleby2_proc32 in SkBitmap.cpp. It is very
+      // clever in that it does two channels at once: alpha and green ("ag")
+      // and red and blue ("rb"). Each channel gets averaged across 4 pixels
+      // to get the result.
+      int src_x = dest_x << 1;
+      int src_y = dest_y << 1;
+      const SkPMColor* cur_src = bitmap.getAddr32(src_x, src_y);
+      SkPMColor tmp, ag, rb;
+
+      // Top left pixel of the 2x2 block.
+      tmp = *cur_src;
+      ag = (tmp >> 8) & 0xFF00FF;
+      rb = tmp & 0xFF00FF;
+      if (src_x < (bitmap.width() - 1))
+        ++cur_src;
+
+      // Top right pixel of the 2x2 block.
+      tmp = *cur_src;
+      ag += (tmp >> 8) & 0xFF00FF;
+      rb += tmp & 0xFF00FF;
+      if (src_y < (bitmap.height() - 1))
+        cur_src = bitmap.getAddr32(src_x, src_y + 1);
+      else
+        cur_src = bitmap.getAddr32(src_x, src_y);  // Move back to the first.
+
+      // Bottom left pixel of the 2x2 block.
+      tmp = *cur_src;
+      ag += (tmp >> 8) & 0xFF00FF;
+      rb += tmp & 0xFF00FF;
+      if (src_x < (bitmap.width() - 1))
+        ++cur_src;
+
+      // Bottom right pixel of the 2x2 block.
+      tmp = *cur_src;
+      ag += (tmp >> 8) & 0xFF00FF;
+      rb += tmp & 0xFF00FF;
+
+      // Put the channels back together, dividing each by 4 to get the average.
+      // |ag| has the alpha and green channels shifted right by 8 bits from
+      // there they should end up, so shifting left by 6 gives them in the
+      // correct position divided by 4.
+      *result.getAddr32(dest_x, dest_y) =
+          ((rb >> 2) & 0xFF00FF) | ((ag << 6) & 0xFF00FF00);
+    }
+  }
+
+  return result;
+}
+
diff --git a/app/gfx/skbitmap_operations.h b/app/gfx/skbitmap_operations.h
new file mode 100644
index 0000000..d6bb5d3
--- /dev/null
+++ b/app/gfx/skbitmap_operations.h
@@ -0,0 +1,82 @@
+// Copyright (c) 2009 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.
+
+#ifndef APP_GFX_SKBITMAP_OPERATIONS_H_
+#define APP_GFX_SKBITMAP_OPERATIONS_H_
+
+#include "app/gfx/color_utils.h"
+#include "testing/gtest/include/gtest/gtest_prod.h"
+
+class SkBitmap;
+
+class SkBitmapOperations {
+ public:
+  // Create a bitmap that is a blend of two others. The alpha argument
+  // specifies the opacity of the second bitmap. The provided bitmaps must
+  // use have the kARGB_8888_Config config and be of equal dimensions.
+  static SkBitmap CreateBlendedBitmap(const SkBitmap& first,
+                                      const SkBitmap& second,
+                                      double alpha);
+
+  // Create a bitmap that is the original bitmap masked out by the mask defined
+  // in the alpha bitmap. The images must use the kARGB_8888_Config config and
+  // be of equal dimensions.
+  static SkBitmap CreateMaskedBitmap(const SkBitmap& first,
+                                     const SkBitmap& alpha);
+
+  // We create a button background image by compositing the color and image
+  // together, then applying the mask. This is a highly specialized composite
+  // operation that is the equivalent of drawing a background in |color|,
+  // tiling |image| over the top, and then masking the result out with |mask|.
+  // The images must use kARGB_8888_Config config.
+  static SkBitmap CreateButtonBackground(SkColor color,
+                                         const SkBitmap& image,
+                                         const SkBitmap& mask);
+
+  // Shift a bitmap's HSL values. The shift values are in the range of 0-1,
+  // with the option to specify -1 for 'no change'. The shift values are
+  // defined as:
+  // hsl_shift[0] (hue): The absolute hue value for the image - 0 and 1 map
+  //    to 0 and 360 on the hue color wheel (red).
+  // hsl_shift[1] (saturation): A saturation shift for the image, with the
+  //    following key values:
+  //    0 = remove all color.
+  //    0.5 = leave unchanged.
+  //    1 = fully saturate the image.
+  // hsl_shift[2] (lightness): A lightness shift for the image, with the
+  //    following key values:
+  //    0 = remove all lightness (make all pixels black).
+  //    0.5 = leave unchanged.
+  //    1 = full lightness (make all pixels white).
+  static SkBitmap CreateHSLShiftedBitmap(const SkBitmap& bitmap,
+                                         color_utils::HSL hsl_shift);
+
+  // Create a bitmap that is cropped from another bitmap. This is special
+  // because it tiles the original bitmap, so your coordinates can extend
+  // outside the bounds of the original image.
+  static SkBitmap CreateTiledBitmap(const SkBitmap& bitmap,
+                                    int src_x, int src_y,
+                                    int dst_w, int dst_h);
+
+  // Iteratively downsamples by 2 until the bitmap is no smaller than the
+  // input size. The normal use of this is to downsample the bitmap "close" to
+  // the final size, and then use traditional resampling on the result.
+  // Because the bitmap will be closer to the final size, it will be faster,
+  // and linear interpolation will generally work well as a second step.
+  static SkBitmap DownsampleByTwoUntilSize(const SkBitmap& bitmap,
+                                           int min_w, int min_h);
+
+ private:
+  SkBitmapOperations();  // Class for scoping only.
+
+  // Makes a bitmap half has large in each direction by averaging groups of
+  // 4 pixels. This is one step in generating a mipmap.
+  static SkBitmap DownsampleByTwo(const SkBitmap& bitmap);
+
+  FRIEND_TEST(SkBitmapOperationsTest, DownsampleByTwo);
+  FRIEND_TEST(SkBitmapOperationsTest, DownsampleByTwoSmall);
+};
+
+#endif  // APP_GFX_SKBITMAP_OPERATIONS_H_
+
diff --git a/app/gfx/skbitmap_operations_unittest.cc b/app/gfx/skbitmap_operations_unittest.cc
new file mode 100644
index 0000000..feb288c
--- /dev/null
+++ b/app/gfx/skbitmap_operations_unittest.cc
@@ -0,0 +1,348 @@
+// Copyright (c) 2009 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 "app/gfx/skbitmap_operations.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "third_party/skia/include/core/SkColorPriv.h"
+#include "third_party/skia/include/core/SkUnPreMultiply.h"
+
+namespace {
+
+// Returns true if each channel of the given two colors are "close." This is
+// used for comparing colors where rounding errors may cause off-by-one.
+bool ColorsClose(uint32_t a, uint32_t b) {
+  return abs(static_cast<int>(SkColorGetB(a) - SkColorGetB(b))) < 2 &&
+         abs(static_cast<int>(SkColorGetG(a) - SkColorGetG(b))) < 2 &&
+         abs(static_cast<int>(SkColorGetR(a) - SkColorGetR(b))) < 2 &&
+         abs(static_cast<int>(SkColorGetA(a) - SkColorGetA(b))) < 2;
+}
+
+void FillDataToBitmap(int w, int h, SkBitmap* bmp) {
+  bmp->setConfig(SkBitmap::kARGB_8888_Config, w, h);
+  bmp->allocPixels();
+
+  unsigned char* src_data =
+      reinterpret_cast<unsigned char*>(bmp->getAddr32(0, 0));
+  for (int i = 0; i < w * h; i++) {
+    src_data[i * 4 + 0] = static_cast<unsigned char>(i % 255);
+    src_data[i * 4 + 1] = static_cast<unsigned char>(i % 255);
+    src_data[i * 4 + 2] = static_cast<unsigned char>(i % 255);
+    src_data[i * 4 + 3] = static_cast<unsigned char>(i % 255);
+  }
+}
+
+}  // namespace
+
+// Blend two bitmaps together at 50% alpha and verify that the result
+// is the middle-blend of the two.
+TEST(SkBitmapOperationsTest, CreateBlendedBitmap) {
+  int src_w = 16, src_h = 16;
+  SkBitmap src_a;
+  src_a.setConfig(SkBitmap::kARGB_8888_Config, src_w, src_h);
+  src_a.allocPixels();
+
+  SkBitmap src_b;
+  src_b.setConfig(SkBitmap::kARGB_8888_Config, src_w, src_h);
+  src_b.allocPixels();
+
+  for (int y = 0, i = 0; y < src_h; y++) {
+    for (int x = 0; x < src_w; x++) {
+      *src_a.getAddr32(x, y) = SkColorSetARGB(255, 0, i * 2 % 255, i % 255);
+      *src_b.getAddr32(x, y) =
+          SkColorSetARGB((255 - i) % 255, i % 255, i * 4 % 255, 0);
+      i++;
+    }
+  }
+
+  // Shift to red.
+  SkBitmap blended = SkBitmapOperations::CreateBlendedBitmap(
+    src_a, src_b, 0.5);
+  SkAutoLockPixels srca_lock(src_a);
+  SkAutoLockPixels srcb_lock(src_b);
+  SkAutoLockPixels blended_lock(blended);
+
+  for (int y = 0; y < src_h; y++) {
+    for (int x = 0; x < src_w; x++) {
+      int i = y * src_w + x;
+      EXPECT_EQ(static_cast<unsigned int>((255 + ((255 - i) % 255)) / 2),
+                SkColorGetA(*blended.getAddr32(x, y)));
+      EXPECT_EQ(static_cast<unsigned int>(i % 255 / 2),
+                SkColorGetR(*blended.getAddr32(x, y)));
+      EXPECT_EQ((static_cast<unsigned int>((i * 2) % 255 + (i * 4) % 255) / 2),
+                SkColorGetG(*blended.getAddr32(x, y)));
+      EXPECT_EQ(static_cast<unsigned int>(i % 255 / 2),
+                SkColorGetB(*blended.getAddr32(x, y)));
+    }
+  }
+}
+
+// Test our masking functions.
+TEST(SkBitmapOperationsTest, CreateMaskedBitmap) {
+  int src_w = 16, src_h = 16;
+
+  SkBitmap src;
+  FillDataToBitmap(src_w, src_h, &src);
+
+  // Generate alpha mask
+  SkBitmap alpha;
+  alpha.setConfig(SkBitmap::kARGB_8888_Config, src_w, src_h);
+  alpha.allocPixels();
+  for (int y = 0, i = 0; y < src_h; y++) {
+    for (int x = 0; x < src_w; x++) {
+      *alpha.getAddr32(x, y) = SkColorSetARGB((i + 128) % 255,
+                                              (i + 128) % 255,
+                                              (i + 64) % 255,
+                                              (i + 0) % 255);
+      i++;
+    }
+  }
+
+  SkBitmap masked = SkBitmapOperations::CreateMaskedBitmap(src, alpha);
+
+  SkAutoLockPixels src_lock(src);
+  SkAutoLockPixels alpha_lock(alpha);
+  SkAutoLockPixels masked_lock(masked);
+  for (int y = 0; y < src_h; y++) {
+    for (int x = 0; x < src_w; x++) {
+      // Test that the alpha is equal.
+      SkColor src_pixel = SkUnPreMultiply::PMColorToColor(*src.getAddr32(x, y));
+      SkColor alpha_pixel =
+          SkUnPreMultiply::PMColorToColor(*alpha.getAddr32(x, y));
+      SkColor masked_pixel = *masked.getAddr32(x, y);
+
+      int alpha_value = SkAlphaMul(SkColorGetA(src_pixel),
+                                   SkColorGetA(alpha_pixel));
+      SkColor expected_pixel = SkColorSetARGB(
+          alpha_value,
+          SkAlphaMul(SkColorGetR(src_pixel), alpha_value),
+          SkAlphaMul(SkColorGetG(src_pixel), alpha_value),
+          SkAlphaMul(SkColorGetB(src_pixel), alpha_value));
+
+      EXPECT_TRUE(ColorsClose(expected_pixel, masked_pixel));
+    }
+  }
+}
+
+// Make sure that when shifting a bitmap without any shift parameters,
+// the end result is close enough to the original (rounding errors
+// notwithstanding).
+TEST(SkBitmapOperationsTest, CreateHSLShiftedBitmapToSame) {
+  int src_w = 4, src_h = 4;
+  SkBitmap src;
+  src.setConfig(SkBitmap::kARGB_8888_Config, src_w, src_h);
+  src.allocPixels();
+
+  for (int y = 0, i = 0; y < src_h; y++) {
+    for (int x = 0; x < src_w; x++) {
+      *src.getAddr32(x, y) = SkColorSetARGB(i + 128 % 255,
+          i + 128 % 255, i + 64 % 255, i + 0 % 255);
+      i++;
+    }
+  }
+
+  color_utils::HSL hsl = { -1, -1, -1 };
+
+  SkBitmap shifted = SkBitmapOperations::CreateHSLShiftedBitmap(src, hsl);
+
+  SkAutoLockPixels src_lock(src);
+  SkAutoLockPixels shifted_lock(shifted);
+
+  for (int y = 0; y < src_w; y++) {
+    for (int x = 0; x < src_h; x++) {
+      SkColor src_pixel = *src.getAddr32(x, y);
+      SkColor shifted_pixel = *shifted.getAddr32(x, y);
+      EXPECT_TRUE(ColorsClose(src_pixel, shifted_pixel));
+    }
+  }
+}
+
+// Shift a blue bitmap to red.
+TEST(SkBitmapOperationsTest, CreateHSLShiftedBitmapHueOnly) {
+  int src_w = 16, src_h = 16;
+  SkBitmap src;
+  src.setConfig(SkBitmap::kARGB_8888_Config, src_w, src_h);
+  src.allocPixels();
+
+  for (int y = 0, i = 0; y < src_h; y++) {
+    for (int x = 0; x < src_w; x++) {
+      *src.getAddr32(x, y) = SkColorSetARGB(255, 0, 0, i % 255);
+      i++;
+    }
+  }
+
+  // Shift to red.
+  color_utils::HSL hsl = { 0, -1, -1 };
+
+  SkBitmap shifted = SkBitmapOperations::CreateHSLShiftedBitmap(src, hsl);
+
+  SkAutoLockPixels src_lock(src);
+  SkAutoLockPixels shifted_lock(shifted);
+
+  for (int y = 0, i = 0; y < src_h; y++) {
+    for (int x = 0; x < src_w; x++) {
+      EXPECT_TRUE(ColorsClose(*shifted.getAddr32(x, y),
+                              SkColorSetARGB(255, i % 255, 0, 0)));
+      i++;
+    }
+  }
+}
+
+// Test our cropping.
+TEST(SkBitmapOperationsTest, CreateCroppedBitmap) {
+  int src_w = 16, src_h = 16;
+  SkBitmap src;
+  FillDataToBitmap(src_w, src_h, &src);
+
+  SkBitmap cropped = SkBitmapOperations::CreateTiledBitmap(src, 4, 4,
+                                                              8, 8);
+  ASSERT_EQ(8, cropped.width());
+  ASSERT_EQ(8, cropped.height());
+
+  SkAutoLockPixels src_lock(src);
+  SkAutoLockPixels cropped_lock(cropped);
+  for (int y = 4; y < 12; y++) {
+    for (int x = 4; x < 12; x++) {
+      EXPECT_EQ(*src.getAddr32(x, y),
+                *cropped.getAddr32(x - 4, y - 4));
+    }
+  }
+}
+
+// Test whether our cropping correctly wraps across image boundaries.
+TEST(SkBitmapOperationsTest, CreateCroppedBitmapWrapping) {
+  int src_w = 16, src_h = 16;
+  SkBitmap src;
+  FillDataToBitmap(src_w, src_h, &src);
+
+  SkBitmap cropped = SkBitmapOperations::CreateTiledBitmap(
+      src, src_w / 2, src_h / 2, src_w, src_h);
+  ASSERT_EQ(src_w, cropped.width());
+  ASSERT_EQ(src_h, cropped.height());
+
+  SkAutoLockPixels src_lock(src);
+  SkAutoLockPixels cropped_lock(cropped);
+  for (int y = 0; y < src_h; y++) {
+    for (int x = 0; x < src_w; x++) {
+      EXPECT_EQ(*src.getAddr32(x, y),
+                *cropped.getAddr32((x + src_w / 2) % src_w,
+                                   (y + src_h / 2) % src_h));
+    }
+  }
+}
+
+TEST(SkBitmapOperationsTest, DownsampleByTwo) {
+  // Use an odd-sized bitmap to make sure the edge cases where there isn't a
+  // 2x2 block of pixels is handled correctly.
+  // Here's the ARGB example
+  //
+  //    50% transparent green             opaque 50% blue           white
+  //        80008000                         FF000080              FFFFFFFF
+  //
+  //    50% transparent red               opaque 50% gray           black
+  //        80800000                         80808080              FF000000
+  //
+  //         black                            white                50% gray
+  //        FF000000                         FFFFFFFF              FF808080
+  //
+  // The result of this computation should be:
+  //        A0404040  FF808080
+  //        FF808080  FF808080
+  SkBitmap input;
+  input.setConfig(SkBitmap::kARGB_8888_Config, 3, 3);
+  input.allocPixels();
+
+  // The color order may be different, but we don't care (the channels are
+  // trated the same).
+  *input.getAddr32(0, 0) = 0x80008000;
+  *input.getAddr32(1, 0) = 0xFF000080;
+  *input.getAddr32(2, 0) = 0xFFFFFFFF;
+  *input.getAddr32(0, 1) = 0x80800000;
+  *input.getAddr32(1, 1) = 0x80808080;
+  *input.getAddr32(2, 1) = 0xFF000000;
+  *input.getAddr32(0, 2) = 0xFF000000;
+  *input.getAddr32(1, 2) = 0xFFFFFFFF;
+  *input.getAddr32(2, 2) = 0xFF808080;
+
+  SkBitmap result = SkBitmapOperations::DownsampleByTwo(input);
+  EXPECT_EQ(2, result.width());
+  EXPECT_EQ(2, result.height());
+
+  // Some of the values are off-by-one due to rounding.
+  SkAutoLockPixels lock(result);
+  EXPECT_EQ(0x9f404040, *result.getAddr32(0, 0));
+  EXPECT_EQ(0xFF7f7f7f, *result.getAddr32(1, 0));
+  EXPECT_EQ(0xFF7f7f7f, *result.getAddr32(0, 1));
+  EXPECT_EQ(0xFF808080, *result.getAddr32(1, 1));
+}
+
+// Test edge cases for DownsampleByTwo.
+TEST(SkBitmapOperationsTest, DownsampleByTwoSmall) {
+  SkPMColor reference = 0xFF4080FF;
+
+  // Test a 1x1 bitmap.
+  SkBitmap one_by_one;
+  one_by_one.setConfig(SkBitmap::kARGB_8888_Config, 1, 1);
+  one_by_one.allocPixels();
+  *one_by_one.getAddr32(0, 0) = reference;
+  SkBitmap result = SkBitmapOperations::DownsampleByTwo(one_by_one);
+  SkAutoLockPixels lock1(result);
+  EXPECT_EQ(1, result.width());
+  EXPECT_EQ(1, result.height());
+  EXPECT_EQ(reference, *result.getAddr32(0, 0));
+
+  // Test an n by 1 bitmap.
+  SkBitmap one_by_n;
+  one_by_n.setConfig(SkBitmap::kARGB_8888_Config, 300, 1);
+  one_by_n.allocPixels();
+  result = SkBitmapOperations::DownsampleByTwo(one_by_n);
+  SkAutoLockPixels lock2(result);
+  EXPECT_EQ(300, result.width());
+  EXPECT_EQ(1, result.height());
+
+  // Test a 1 by n bitmap.
+  SkBitmap n_by_one;
+  n_by_one.setConfig(SkBitmap::kARGB_8888_Config, 1, 300);
+  n_by_one.allocPixels();
+  result = SkBitmapOperations::DownsampleByTwo(n_by_one);
+  SkAutoLockPixels lock3(result);
+  EXPECT_EQ(1, result.width());
+  EXPECT_EQ(300, result.height());
+
+  // Test an empty bitmap
+  SkBitmap empty;
+  result = SkBitmapOperations::DownsampleByTwo(empty);
+  EXPECT_TRUE(result.isNull());
+  EXPECT_EQ(0, result.width());
+  EXPECT_EQ(0, result.height());
+}
+
+// Here we assume DownsampleByTwo works correctly (it's tested above) and
+// just make sure that the wrapper function does the right thing.
+TEST(SkBitmapOperationsTest, DownsampleByTwoUntilSize) {
+  // First make sure a "too small" bitmap doesn't get modified at all.
+  SkBitmap too_small;
+  too_small.setConfig(SkBitmap::kARGB_8888_Config, 10, 10);
+  too_small.allocPixels();
+  SkBitmap result = SkBitmapOperations::DownsampleByTwoUntilSize(
+      too_small, 16, 16);
+  EXPECT_EQ(10, result.width());
+  EXPECT_EQ(10, result.height());
+
+  // Now make sure giving it a 0x0 target returns something reasonable.
+  result = SkBitmapOperations::DownsampleByTwoUntilSize(too_small, 0, 0);
+  EXPECT_EQ(1, result.width());
+  EXPECT_EQ(1, result.height());
+
+  // Test multiple steps of downsampling.
+  SkBitmap large;
+  large.setConfig(SkBitmap::kARGB_8888_Config, 100, 43);
+  large.allocPixels();
+  result = SkBitmapOperations::DownsampleByTwoUntilSize(large, 6, 6);
+
+  // The result should be divided in half 100x43 -> 50x22 -> 25x11
+  EXPECT_EQ(25, result.width());
+  EXPECT_EQ(11, result.height());
+}