add ImageShader, sharing code with its Bitmap cousin

src/image/SkImageShader.cpp

Index: src/image/SkImageShader.cpp
diff --git a/src/image/SkImageShader.cpp b/src/image/SkImageShader.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..5ddc8749401cd225f34b97455bea3cab25d60820
--- /dev/null
+++ b/src/image/SkImageShader.cpp
@@ -0,0 +1,69 @@
+/*
+ * Copyright 2011 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkBitmapProcShader.h"
+#include "SkImage_Base.h"
+#include "SkImageShader.h"
+#include "SkReadBuffer.h"
+#include "SkWriteBuffer.h"
+
+#if SK_SUPPORT_GPU
+#include "effects/GrBicubicEffect.h"
+#include "effects/GrExtractAlphaFragmentProcessor.h"
+#include "effects/GrSimpleTextureEffect.h"
+#endif
+
+SkImageShader::SkImageShader(const SkImage* img, TileMode tmx, TileMode tmy, const SkMatrix* matrix)
+    : INHERITED(matrix)
+    , fImage(SkRef(img))
+    , fTileModeX(tmx)
+    , fTileModeY(tmy)
+{}
+
+SkFlattenable* SkImageShader::CreateProc(SkReadBuffer& buffer) {
+    const TileMode tx = (TileMode)buffer.readUInt();
+    const TileMode ty = (TileMode)buffer.readUInt();
+    SkMatrix matrix;
+    buffer.readMatrix(&matrix);
+    SkAutoTUnref<SkImage> img(buffer.readImage());
+    if (!img) {
+        return nullptr;
+    }
+    return new SkImageShader(img, tx, ty, &matrix);
+}
+
+void SkImageShader::flatten(SkWriteBuffer& buffer) const {
+    buffer.writeUInt(fTileModeX);
+    buffer.writeUInt(fTileModeY);
+    buffer.writeMatrix(this->getLocalMatrix());
+    buffer.writeImage(fImage);
+}
+
+bool SkImageShader::isOpaque() const {
+    return fImage->isOpaque();
+}
+
+size_t SkImageShader::contextSize() const {
+    // we creata a BitmapProcShader::Context, so we defer to it to compute the size
+    return SkBitmapProcShader::ContextSize();
+}
+
+SkShader::Context* SkImageShader::onCreateContext(const ContextRec& rec, void* storage) const {
+    SkBitmap bitmap;
+    if (!as_IB(fImage)->getROPixels(&bitmap)) {
+        return nullptr;
+    }
+    return SkBitmapProcShader::MakeContext(*this, fTileModeX, fTileModeY, bitmap, rec, storage);
+}
+
+SkShader* SkImageShader::Create(const SkImage* image, TileMode tx, TileMode ty,
+                                const SkMatrix* localMatrix) {
+    if (!image) {
+        return nullptr;
+    }
+    return new SkImageShader(image, tx, ty, localMatrix);
+}