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..58eddf3f7d69e76a5bb0999166e870c83c7b839e
--- /dev/null
+++ b/src/image/SkImageShader.cpp
@@ -0,0 +1,145 @@
+/*
+ * Copyright 2015 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 "SkBitmapProvider.h"
+#include "SkImage_Base.h"
+#include "SkImageShader.h"
+#include "SkReadBuffer.h"
+#include "SkWriteBuffer.h"
+
+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 {
+    return SkBitmapProcShader::ContextSize();
+}
+
+SkShader::Context* SkImageShader::onCreateContext(const ContextRec& rec, void* storage) const {
+    return SkBitmapProcShader::MakeContext(*this, fTileModeX, fTileModeY,
+                                           SkBitmapProvider(fImage), 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);
+}
+
+#ifndef SK_IGNORE_TO_STRING
+void SkImageShader::toString(SkString* str) const {
+    const char* gTileModeName[SkShader::kTileModeCount] = {
+        "clamp", "repeat", "mirror"
+    };
+
+    str->appendf("ImageShader: ((%s %s) ", gTileModeName[fTileModeX], gTileModeName[fTileModeY]);
+    fImage->toString(str);
+    this->INHERITED::toString(str);
+    str->append(")");
+}
+#endif
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+#if SK_SUPPORT_GPU
+
+#include "GrTextureAccess.h"
+#include "SkGr.h"
+#include "effects/GrSimpleTextureEffect.h"
+#include "effects/GrBicubicEffect.h"
+#include "effects/GrExtractAlphaFragmentProcessor.h"
+#include "effects/GrSimpleTextureEffect.h"
+
+const GrFragmentProcessor* SkImageShader::asFragmentProcessor(GrContext* context,
+                                                              const SkMatrix& viewM,
+                                                              const SkMatrix* localMatrix,
+                                                              SkFilterQuality filterQuality,
+                                                              GrProcessorDataManager* mgr) const {
+    SkMatrix matrix;
+    matrix.setIDiv(fImage->width(), fImage->height());
+
+    SkMatrix lmInverse;
+    if (!this->getLocalMatrix().invert(&lmInverse)) {
+        return nullptr;
+    }
+    if (localMatrix) {
+        SkMatrix inv;
+        if (!localMatrix->invert(&inv)) {
+            return nullptr;
+        }
+        lmInverse.postConcat(inv);
+    }
+    matrix.preConcat(lmInverse);
+
+    SkShader::TileMode tm[] = { fTileModeX, fTileModeY };
+
+    // Must set wrap and filter on the sampler before requesting a texture. In two places below
+    // we check the matrix scale factors to determine how to interpret the filter quality setting.
+    // This completely ignores the complexity of the drawVertices case where explicit local coords
+    // are provided by the caller.
+    bool doBicubic;
+    GrTextureParams::FilterMode textureFilterMode =
+    GrSkFilterQualityToGrFilterMode(filterQuality, viewM, this->getLocalMatrix(), &doBicubic);
+    GrTextureParams params(tm, textureFilterMode);
+
+    SkImageUsageType usageType;
+    if (kClamp_TileMode == fTileModeX && kClamp_TileMode == fTileModeY) {
+        usageType = kUntiled_SkImageUsageType;
+    } else if (GrTextureParams::kNone_FilterMode == textureFilterMode) {
+        usageType = kTiled_Unfiltered_SkImageUsageType;
+    } else {
+        usageType = kTiled_Filtered_SkImageUsageType;
+    }
+
+    SkAutoTUnref<GrTexture> texture(as_IB(fImage)->asTextureRef(context, usageType));
+    if (!texture) {
+        return nullptr;
+    }
+
+    SkAutoTUnref<GrFragmentProcessor> inner;
+    if (doBicubic) {
+        inner.reset(GrBicubicEffect::Create(mgr, texture, matrix, tm));
+    } else {
+        inner.reset(GrSimpleTextureEffect::Create(mgr, texture, matrix, params));
+    }
+
+    if (GrPixelConfigIsAlphaOnly(texture->config())) {
+        return SkRef(inner.get());
+    }
+    return GrExtractAlphaFragmentProcessor::Create(inner);
+}
+
+#endif