add ImageGenerator::NewFromData to porting layer

src/ports/SkImageGenerator_skia.cpp

+/*
+ * Copyright 2015 The Android Open Source Project

[hal.canary, 2015/01/06 20:06:40]

 * 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 "SkData.h"
+#include "SkImageDecoder.h"
+#include "SkImageGenerator.h"
+#include "SkStream.h"
+
+class BareMemoryAllocator : public SkBitmap::Allocator {
+    const SkImageInfo   fInfo;
+    void* const         fMemory;
+    const size_t        fRowBytes;
+
+public:
+    BareMemoryAllocator(const SkImageInfo& info, void* memory, size_t rowBytes)
+        : fInfo(info), fMemory(memory), fRowBytes(rowBytes)
+    {}
+
+protected:
+    bool allocPixelRef(SkBitmap* bm, SkColorTable* ctable) SK_OVERRIDE {
+        const SkImageInfo bmi = bm->info();
+        if (bmi.width() != fInfo.width() || bmi.height() != fInfo.height() ||
+            bmi.colorType() != fInfo.colorType())
+        {
+            return false;
+        }
+        return bm->installPixels(bmi, fMemory, fRowBytes, ctable, NULL, NULL);
+    }
+};
+
+class SkImageDecoderGenerator : public SkImageGenerator {
+    const SkImageInfo               fInfo;
+    SkAutoTDelete<SkImageDecoder>   fDecoder;
+    SkAutoTUnref<SkData>            fData;
+
+public:
+    SkImageDecoderGenerator(const SkImageInfo& info, SkImageDecoder* decoder, SkData* data)
+        : fInfo(info), fDecoder(decoder), fData(SkRef(data))
+    {}
+
+protected:
+    SkData* onRefEncodedData() SK_OVERRIDE {
+        return SkRef(fData.get());
+    }
+
+    virtual bool onGetInfo(SkImageInfo* info) {
+        *info = fInfo;
+        return true;
+    }
+
+    virtual bool onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
+                             SkPMColor ctableEntries[], int* ctableCount) {
+        SkMemoryStream stream(fData->data(), fData->size(), false);
+        SkAutoTUnref<BareMemoryAllocator> allocator(SkNEW_ARGS(BareMemoryAllocator,

[scroggo, 2015/01/06 19:50:15]

You could put the BareMemoryAllocator on the stack if you remove it after
decoding.

+                                                               (info, pixels, rowBytes)));
+        fDecoder->setAllocator(allocator);
+        fDecoder->setRequireUnpremultipliedColors(kUnpremul_SkAlphaType == info.alphaType());
+
+        SkBitmap bm;
+        SkImageDecoder::Result result = fDecoder->decode(&stream, &bm, info.colorType(),
+                                                         SkImageDecoder::kDecodePixels_Mode);
+        switch (result) {
+            case SkImageDecoder::kSuccess:
+                break;
+            default:
+                return false;
+        }
+
+        SkASSERT(info.colorType() == bm.info().colorType());
+
+        if (kIndex_8_SkColorType == info.colorType()) {
+            SkASSERT(ctableEntries);
+
+            SkColorTable* ctable = bm.getColorTable();
+            if (NULL == ctable) {
+                return false;
+            }
+            const int count = ctable->count();
+            memcpy(ctableEntries, ctable->readColors(), count * sizeof(SkPMColor));
+            *ctableCount = count;
+        }
+        return true;
+    }
+
+    bool onGetYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3],
+                         SkYUVColorSpace* colorSpace) SK_OVERRIDE {
+        SkMemoryStream stream(fData->data(), fData->size(), false);

[hal.canary, 2015/01/06 20:06:40]

    SkMemoryStream stream(fData);

is simpler.

+        return fDecoder->decodeYUV8Planes(&stream, sizes, planes, rowBytes, colorSpace);
+    }
+    
+};
+
+SkImageGenerator* SkImageGenerator::NewFromData(SkData* data) {
+    if (NULL == data) {
+        return NULL;
+    }
+
+    SkMemoryStream stream(data->data(), data->size(), false);
+    SkImageDecoder* decoder = SkImageDecoder::Factory(&stream);
+    if (NULL == decoder) {
+        return NULL;
+    }
+
+    SkBitmap bm;
+    stream.rewind();
+    if (!decoder->decode(&stream, &bm, kUnknown_SkColorType, SkImageDecoder::kDecodeBounds_Mode)) {
+        SkDELETE(decoder);
+        return NULL;
+    }
+
+    return SkNEW_ARGS(SkImageDecoderGenerator, (bm.info(), decoder, data));
+}