1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "chrome/browser/ui/libgtk2ui/skia_utils_gtk2.h"
6
7#include <gdk/gdk.h>
8
9#include "base/basictypes.h"
10#include "base/logging.h"
11#include "third_party/skia/include/core/SkBitmap.h"
12#include "third_party/skia/include/core/SkUnPreMultiply.h"
13
14namespace libgtk2ui {
15
16// GDK_COLOR_RGB multiplies by 257 (= 0x10001) to distribute the bits evenly
17// See: http://www.mindcontrol.org/~hplus/graphics/expand-bits.html
18// To get back, we can just right shift by eight
19// (or, formulated differently, i == (i*257)/256 for all i < 256).
20
21SkColor GdkColorToSkColor(GdkColor color) {
22  return SkColorSetRGB(color.red >> 8, color.green >> 8, color.blue >> 8);
23}
24
25GdkColor SkColorToGdkColor(SkColor color) {
26  GdkColor gdk_color = {
27      0,
28      static_cast<guint16>(SkColorGetR(color) * kSkiaToGDKMultiplier),
29      static_cast<guint16>(SkColorGetG(color) * kSkiaToGDKMultiplier),
30      static_cast<guint16>(SkColorGetB(color) * kSkiaToGDKMultiplier)
31  };
32  return gdk_color;
33}
34
35const SkBitmap GdkPixbufToImageSkia(GdkPixbuf* pixbuf) {
36  // TODO(erg): What do we do in the case where the pixbuf fails these dchecks?
37  // I would prefer to use our gtk based canvas, but that would require
38  // recompiling half of our skia extensions with gtk support, which we can't
39  // do in this build.
40  DCHECK_EQ(GDK_COLORSPACE_RGB, gdk_pixbuf_get_colorspace(pixbuf));
41
42  int n_channels = gdk_pixbuf_get_n_channels(pixbuf);
43  int w = gdk_pixbuf_get_width(pixbuf);
44  int h = gdk_pixbuf_get_height(pixbuf);
45
46  SkBitmap ret;
47  ret.allocN32Pixels(w, h);
48  ret.eraseColor(0);
49
50  uint32_t* skia_data = static_cast<uint32_t*>(ret.getAddr(0, 0));
51
52  if (n_channels == 4) {
53    int total_length = w * h;
54    guchar* gdk_pixels = gdk_pixbuf_get_pixels(pixbuf);
55
56    // Now here's the trick: we need to convert the gdk data (which is RGBA and
57    // isn't premultiplied) to skia (which can be anything and premultiplied).
58    for (int i = 0; i < total_length; ++i, gdk_pixels += 4) {
59      const unsigned char& red = gdk_pixels[0];
60      const unsigned char& green = gdk_pixels[1];
61      const unsigned char& blue = gdk_pixels[2];
62      const unsigned char& alpha = gdk_pixels[3];
63
64      skia_data[i] = SkPreMultiplyARGB(alpha, red, green, blue);
65    }
66  } else if (n_channels == 3) {
67    // Because GDK makes rowstrides word aligned, we need to do something a bit
68    // more complex when a pixel isn't perfectly a word of memory.
69    int rowstride = gdk_pixbuf_get_rowstride(pixbuf);
70    guchar* gdk_pixels = gdk_pixbuf_get_pixels(pixbuf);
71    for (int y = 0; y < h; ++y) {
72      int row = y * rowstride;
73
74      for (int x = 0; x < w; ++x) {
75        guchar* pixel = gdk_pixels + row + (x * 3);
76        const unsigned char& red = pixel[0];
77        const unsigned char& green = pixel[1];
78        const unsigned char& blue = pixel[2];
79
80        skia_data[y * w + x] = SkPreMultiplyARGB(255, red, green, blue);
81      }
82    }
83  } else {
84    NOTREACHED();
85  }
86
87  return ret;
88}
89
90GdkPixbuf* GdkPixbufFromSkBitmap(const SkBitmap& bitmap) {
91  if (bitmap.isNull())
92    return NULL;
93
94  SkAutoLockPixels lock_pixels(bitmap);
95
96  int width = bitmap.width();
97  int height = bitmap.height();
98
99  GdkPixbuf* pixbuf =
100      gdk_pixbuf_new(GDK_COLORSPACE_RGB,  // The only colorspace gtk supports.
101                     TRUE,                // There is an alpha channel.
102                     8,
103                     width,
104                     height);
105
106  // SkBitmaps are premultiplied, we need to unpremultiply them.
107  const int kBytesPerPixel = 4;
108  uint8* divided = gdk_pixbuf_get_pixels(pixbuf);
109
110  for (int y = 0, i = 0; y < height; y++) {
111    for (int x = 0; x < width; x++) {
112      uint32 pixel = bitmap.getAddr32(0, y)[x];
113
114      int alpha = SkColorGetA(pixel);
115      if (alpha != 0 && alpha != 255) {
116        SkColor unmultiplied = SkUnPreMultiply::PMColorToColor(pixel);
117        divided[i + 0] = SkColorGetR(unmultiplied);
118        divided[i + 1] = SkColorGetG(unmultiplied);
119        divided[i + 2] = SkColorGetB(unmultiplied);
120        divided[i + 3] = alpha;
121      } else {
122        divided[i + 0] = SkColorGetR(pixel);
123        divided[i + 1] = SkColorGetG(pixel);
124        divided[i + 2] = SkColorGetB(pixel);
125        divided[i + 3] = alpha;
126      }
127      i += kBytesPerPixel;
128    }
129  }
130
131  return pixbuf;
132}
133
134}  // namespace libgtk2ui
135