Use newImageSnapshot() to get an image from a Canvas

Source/platform/graphics/BitmapPattern.cpp

Index: Source/platform/graphics/BitmapPattern.cpp
diff --git a/Source/platform/graphics/BitmapPattern.cpp b/Source/platform/graphics/BitmapPattern.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..502ab236a3a0c8472c86b6c207715771e803f723
--- /dev/null
+++ b/Source/platform/graphics/BitmapPattern.cpp
@@ -0,0 +1,97 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.

[Justin Novosad, 2014/07/29 14:56:51]

Use the new abbreviated header (see
http://www.chromium.org/blink/coding-style#TOC-License)

[Rémi Piotaix, 2014/07/29 17:18:22]

Done.

+//
+// The Chromium Authors can be found at
+// http://src.chromium.org/svn/trunk/src/AUTHORS
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "config.h"
+#include "platform/graphics/BitmapPattern.h"
+
+
+#include "SkCanvas.h"
+#include "SkColorShader.h"
+#include "platform/graphics/skia/SkiaUtils.h"
+#include <v8.h>
+
+namespace WebCore {

[Justin Novosad, 2014/07/29 14:56:51]

WebCore -> blink

[Rémi Piotaix, 2014/07/29 17:18:22]

Done.

+
+BitmapPattern::BitmapPattern(PassRefPtr<Image> image, bool repeatX, bool repeatY)
+: Pattern(repeatX, repeatY)
+{
+    if (image) {
+        m_tileImage = image->nativeImageForCurrentFrame();
+    }
+}
+
+PassRefPtr<SkShader> BitmapPattern::createShader()
+{
+    SkMatrix localMatrix = affineTransformToSkMatrix(m_patternSpaceTransformation);
+
+    RefPtr<SkShader> shader;
+
+    // If we don't have a bitmap, return a transparent shader.
+    if (!m_tileImage) {
+        shader = adoptRef(new SkColorShader(SK_ColorTRANSPARENT));

[Justin Novosad, 2014/07/29 14:56:51]

Why not just return nullptr to make calling code abort the draw?

[Rémi Piotaix, 2014/07/29 17:18:22]

Done.

+    } else if (m_repeatX && m_repeatY) {
+        shader = adoptRef(SkShader::CreateBitmapShader(m_tileImage->bitmap(), SkShader::kRepeat_TileMode, SkShader::kRepeat_TileMode, &localMatrix));
+    } else {
+        // 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 = m_repeatX ? SkShader::kRepeat_TileMode : SkShader::kClamp_TileMode;
+        SkShader::TileMode tileModeY = m_repeatY ? SkShader::kRepeat_TileMode : SkShader::kClamp_TileMode;
+        int expandW = m_repeatX ? 0 : 1;
+        int expandH = m_repeatY ? 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 = m_tileImage->bitmap().info();
+        info.fWidth += expandW;
+        info.fHeight += expandH;
+        // we explicitly require non-opaquness, since we are going to add a transparent strip.
+        info.fAlphaType = kPremul_SkAlphaType;
+
+        SkBitmap bm2;
+        bm2.allocPixels(info);
+        bm2.eraseARGB(0x00, 0x00, 0x00, 0x00);

[Justin Novosad, 2014/07/29 14:56:51]

Would be more efficient to clear just the border areas

[Rémi Piotaix, 2014/07/30 18:59:12]

Done.

+        SkCanvas canvas(bm2);
+        canvas.drawBitmap(m_tileImage->bitmap(), 0, 0);

[Justin Novosad, 2014/07/29 14:56:51]

You should set-up an SkPaint that uses the Src xfermode to do a direct copy,
without alpha blending. That is necessary if you remove the eraseARGB. Since
m_externalMemoryAllocated is a member of the base class, you should managed in a
centralized way in Pattern. Start by making it private and define a
setExternalMemoryAllocated method that takes car of computing the delta and
updating v8

[Rémi Piotaix, 2014/07/30 18:59:12]

Done.

+        bm2.setImmutable();
+        shader = adoptRef(SkShader::CreateBitmapShader(bm2, tileModeX, tileModeY, &localMatrix));
+
+        // Clamp to int, since that's what the adjust function takes.
+        m_externalMemoryAllocated = static_cast<int> (std::min(static_cast<size_t> (INT_MAX), bm2.getSafeSize()));
+        v8::Isolate::GetCurrent()->AdjustAmountOfExternalAllocatedMemory(m_externalMemoryAllocated);

[Justin Novosad, 2014/07/29 14:56:51]

The adjustment needs to be a delta between the old and new value of
m_externalMemoryAllocated

[Rémi Piotaix, 2014/07/30 18:59:12]

Done.

+    }
+    return shader;

[Justin Novosad, 2014/07/29 14:56:51]

return shader.release();

[Rémi Piotaix, 2014/07/29 17:18:22]

Done.

+}
+
+} // namespace