Use newImageSnapshot() to get an image from a Canvas

Source/platform/graphics/BitmapPatternBase.cpp

+// Copyright 2014 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 "config.h"
+#include "platform/graphics/BitmapPatternBase.h"
+
+#include "platform/graphics/skia/SkiaUtils.h"
+#include "third_party/skia/include/core/SkCanvas.h"
+#include "third_party/skia/include/core/SkShader.h"
+
+namespace blink {
+
+BitmapPatternBase::BitmapPatternBase(RepeatMode repeatMode, int64_t externalMemoryAllocated) : Pattern(repeatMode, externalMemoryAllocated) { }
+
+BitmapPatternBase::~BitmapPatternBase() { }
+
+PassRefPtr<SkShader> BitmapPatternBase::createShader()
+{
+    // Skia does not have a "draw the tile only once" option. Clamp_TileMode
+    // repeats the last line of the image after drawing one tile. To avoid
+    // filling the space with arbitrary pixels, this workaround forces the
+    // image to have a line of transparent pixels on the "repeated" edge(s),
+    // thus causing extra space to be transparent filled.
+    SkShader::TileMode tileModeX = isRepeatX() ? SkShader::kRepeat_TileMode : SkShader::kClamp_TileMode;
+    SkShader::TileMode tileModeY = isRepeatY() ? SkShader::kRepeat_TileMode : SkShader::kClamp_TileMode;
+    int expandW = isRepeatX() ? 0 : 1;
+    int expandH = isRepeatY() ? 0 : 1;
+
+    // Create a transparent bitmap 1 pixel wider and/or taller than the
+    // original, then copy the orignal into it.
+    // FIXME: Is there a better way to pad (not scale) an image in skia?
+    SkImageInfo info = this->getBitmapInfo();
+    info.fWidth = info.width() + expandW;
+    info.fHeight = info.height() + expandH;
+    // we explicitly require non-opaquness, since we are going to add a transparent strip.
+    info.fAlphaType = kPremul_SkAlphaType;
+
+    SkBitmap bm2;
+    bm2.allocPixels(info);
+    SkCanvas canvas(bm2);
+
+    SkPaint paint;
+    paint.setXfermodeMode(SkXfermode::kSrc_Mode);
+
+    this->drawBitmapToCanvas(canvas, paint);
+
+    paint.setARGB(0x00, 0x00, 0x00, 0x00);
+    paint.setStyle(SkPaint::kFill_Style);
+
+    if (!isRepeatX())
+        canvas.drawRect(SkRect::MakeXYWH(info.width() - 1, 0, 1, info.height()), paint);
+
+    if (!isRepeatY())
+        canvas.drawRect(SkRect::MakeXYWH(0, info.height() - 1, info.width(), 1), paint);
+
+    bm2.setImmutable();
+
+    adjustExternalMemoryAllocated(bm2.getSafeSize());
+
+    SkMatrix localMatrix = affineTransformToSkMatrix(m_patternSpaceTransformation);
+
+    return adoptRef(SkShader::CreateBitmapShader(bm2, tileModeX, tileModeY, &localMatrix));
+}
+
+} // namespace