Create an SkAndroidCodec API separate from SkCodec

src/codec/SkAndroidCodec.cpp

+/*
+ * 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 "SkAndroidCodec.h"
+#include "SkCodec.h"
+#include "SkCodecPriv.h"
+#include "SkSampledCodec.h"
+#include "SkWebpAdapterCodec.h"
+
+static bool is_valid_sample_size(int sampleSize) {
+    // FIXME: As Leon has mentioned elsewhere, surely there is also a maximum sampleSize?

[scroggo, 2015/10/20 13:51:59]

Maybe it's bigger than the width/height of the image, which will fail later?

[msarett, 2015/10/20 14:47:27]

We actually don't even fail in this case.  We'll always suggest a size of at
least 1, and when we decode, we will modify the input sample size to the true
sample size that we actually need to get an output size of 1.

Assuming the logic that handles this isn't buggy, we can support arbitrarily
large sample sizes and return 1x1 images.  I think this is what SkImageDecoder
tried to do (but didn't always work).  I'm not sure if we want to set the
precedent of supporting this (but IIRC a few bugs were filed because clients
were already expecting this behavior).

+    return sampleSize > 0;
+}
+
+SkAndroidCodec::SkAndroidCodec(const SkImageInfo& info)
+    : fInfo(info)
+{}
+
+SkAndroidCodec* SkAndroidCodec::NewFromStream(SkStream* stream) {
+    SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(stream));
+    if (nullptr == codec) {
+        return nullptr;
+    }
+
+    switch (codec->getEncodedFormat()) {
+        case kWEBP_SkEncodedFormat:
+            return new SkWebpAdapterCodec((SkWebpCodec*) codec.detach());
+        case kPNG_SkEncodedFormat:
+        case kJPEG_SkEncodedFormat:
+            return new SkSampledCodec(codec.detach());
+        default:
+            // FIXME: SkSampledCodec is temporarily disabled for other formats
+            // while focusing on the formats that are supported by
+            // BitmapRegionDecoder.
+            return nullptr;
+    }
+}
+
+SkAndroidCodec* SkAndroidCodec::NewFromData(SkData* data) {
+    if (!data) {
+        return nullptr;
+    }
+
+    return NewFromStream(new SkMemoryStream(data));
+}
+
+SkISize SkAndroidCodec::getSampledDimensions(int sampleSize) const {
+    if (!is_valid_sample_size(sampleSize)) {
+        return SkISize::Make(0, 0);
+    }
+
+    return this->onGetSampledDimensions(sampleSize);
+}
+
+bool SkAndroidCodec::getSupportedSubset(SkIRect* desiredSubset) const {
+    if (!desiredSubset || !is_valid_subset(*desiredSubset, fInfo.dimensions())) {
+        return false;
+    }
+
+    return this->onGetSupportedSubset(desiredSubset);
+}
+
+SkISize SkAndroidCodec::getSampledSubsetDimensions(int sampleSize, const SkIRect& subset) const {
+    if (!is_valid_sample_size(sampleSize)) {
+        return SkISize::Make(0, 0);
+    }
+
+    // We require that the input subset is a subset that is supported by SkAndroidCodec.
+    // We test this by calling getSupportedSubset() and verifying that no modifications
+    // are made to the subset.
+    SkIRect copySubset = subset;
+    if (!this->getSupportedSubset(&copySubset) || copySubset != subset) {
+        return SkISize::Make(0, 0);
+    }
+
+    // If the subset is the entire image, for consistency, use onGetSampledDimensions().
+    if (fInfo.dimensions() == subset.size()) {
+        return onGetSampledDimensions(sampleSize);
+    }
+
+    return SkISize::Make(get_scaled_dimension(subset.width(), sampleSize),

[scroggo, 2015/10/20 13:51:59]

Maybe a note that this should perhaps be a virtual
(onGetSampledSubsetDimensions) but both subclasses want the same implementation?

[msarett, 2015/10/20 14:47:27]

Yes I think this is a good idea.

+                get_scaled_dimension(subset.height(), sampleSize));
+}
+
+SkCodec::Result SkAndroidCodec::getAndroidPixels(const SkImageInfo& info, void* pixels,
+        size_t rowBytes, AndroidOptions* options) {
+    if (!pixels) {
+        return SkCodec::kInvalidParameters;
+    }
+    if (rowBytes < info.minRowBytes()) {
+        return SkCodec::kInvalidParameters;
+    }
+
+    AndroidOptions defaultOptions;
+    if (!options) {
+        options = &defaultOptions;
+    } else if (options->fSubset) {
+        if (!is_valid_subset(*options->fSubset, fInfo.dimensions())) {
+            return SkCodec::kInvalidParameters;
+        }
+    }
+
+    return this->onGetAndroidPixels(info, pixels, rowBytes, *options);
+}
+
+SkCodec::Result SkAndroidCodec::getAndroidPixels(const SkImageInfo& info, void* pixels,
+        size_t rowBytes) {
+    return this->getAndroidPixels(info, pixels, rowBytes, nullptr);
+}