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Unified Diff: include/codec/SkAndroidCodec.h

Issue 1406223002: Create an SkAndroidCodec API separate from SkCodec (Closed) Base URL: https://skia.googlesource.com/skia.git@master
Patch Set: Win bot fix Created 5 years, 2 months ago
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Index: include/codec/SkAndroidCodec.h
diff --git a/include/codec/SkAndroidCodec.h b/include/codec/SkAndroidCodec.h
new file mode 100644
index 0000000000000000000000000000000000000000..42e7fa8b9f85229b0aebc25ddf0108e73488820f
--- /dev/null
+++ b/include/codec/SkAndroidCodec.h
@@ -0,0 +1,224 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkAndroidCodec_DEFINED
+#define SkAndroidCodec_DEFINED
+
+#include "SkCodec.h"
+#include "SkEncodedFormat.h"
+#include "SkStream.h"
+#include "SkTypes.h"
+
+/**
+ * Abstract interface defining image codec functionality that is necessary for
+ * Android.
+ */
+class SkAndroidCodec : SkNoncopyable {
+public:
+ /**
+ * If this stream represents an encoded image that we know how to decode,
+ * return an SkAndroidCodec that can decode it. Otherwise return NULL.
+ *
+ * If NULL is returned, the stream is deleted immediately. Otherwise, the
+ * SkCodec takes ownership of it, and will delete it when done with it.
+ */
+ static SkAndroidCodec* NewFromStream(SkStream*);
+
+ /**
+ * If this data represents an encoded image that we know how to decode,
+ * return an SkAndroidCodec that can decode it. Otherwise return NULL.
+ *
+ * Will take a ref if it returns a codec, else will not affect the data.
+ */
+ static SkAndroidCodec* NewFromData(SkData*);
+
+ virtual ~SkAndroidCodec() {}
+
+
+ const SkImageInfo& getInfo() const { return fInfo; }
+
+ /**
+ * Format of the encoded data.
+ */
+ SkEncodedFormat getEncodedFormat() const { return this->onGetEncodedFormat(); }
+
+ /**
+ * Returns the dimensions of the scaled output image, for an input
+ * sampleSize.
+ *
+ * When the sample size divides evenly into the original dimensions, the
+ * scaled output dimensions will simply be equal to the original
+ * dimensions divided by the sample size.
+ *
+ * When the sample size does not divide even into the original
+ * dimensions, the codec may round up or down, depending on what is most
+ * efficient to decode.
+ *
+ * Finally, the codec will always recommend a non-zero output, so the output
+ * dimension will always be one if the sampleSize is greater than the
+ * original dimension.
+ */
+ SkISize getSampledDimensions(int sampleSize) const;
+
+ /**
+ * Return (via desiredSubset) a subset which can decoded from this codec,
+ * or false if the input subset is invalid.
+ *
+ * @param desiredSubset in/out parameter
+ * As input, a desired subset of the original bounds
+ * (as specified by getInfo).
+ * As output, if true is returned, desiredSubset may
+ * have been modified to a subset which is
+ * supported. Although a particular change may have
+ * been made to desiredSubset to create something
+ * supported, it is possible other changes could
+ * result in a valid subset. If false is returned,
+ * desiredSubset's value is undefined.
+ * @return true If the input desiredSubset is valid.
+ * desiredSubset may be modified to a subset
+ * supported by the codec.
+ * false If desiredSubset is invalid (NULL or not fully
+ * contained within the image).
+ */
+ bool getSupportedSubset(SkIRect* desiredSubset) const;
+ // TODO: Rename SkCodec::getValidSubset() to getSupportedSubset()
+
+ /**
+ * Returns the dimensions of the scaled, partial output image, for an
+ * input sampleSize and subset.
+ *
+ * @param sampleSize Factor to scale down by.
+ * @param subset Must be a valid subset of the original image
+ * dimensions and a subset supported by SkAndroidCodec.
+ * getSubset() can be used to obtain a subset supported
+ * by SkAndroidCodec.
+ * @return Size of the scaled partial image. Or zero size
+ * if either of the inputs is invalid.
+ */
+ SkISize getSampledSubsetDimensions(int sampleSize, const SkIRect& subset) const;
+
+ /**
+ * Additional options to pass to getAndroidPixels().
+ */
+ // FIXME: It's a bit redundant to name these AndroidOptions when this class is already
+ // called SkAndroidCodec. On the other hand, it's may be a bit confusing to call
+ // these Options when SkCodec has a slightly different set of Options. Maybe these
+ // should be DecodeOptions or SamplingOptions?
+ struct AndroidOptions {
+ AndroidOptions()
+ : fZeroInitialized(SkCodec::kNo_ZeroInitialized)
+ , fSubset(nullptr)
+ , fColorPtr(nullptr)
+ , fColorCount(nullptr)
+ , fSampleSize(1)
+ {}
+
+ /**
+ * Indicates is destination pixel memory is zero initialized.
+ */
+ SkCodec::ZeroInitialized fZeroInitialized;
+
+ /**
+ * If not NULL, represents a subset of the original image to decode.
+ *
+ * Must be within the bounds returned by getInfo().
+ *
+ * If the EncodedFormat is kWEBP_SkEncodedFormat, the top and left
+ * values must be even.
+ */
+ SkIRect* fSubset;
+
+ /**
+ * If the client has requested a decode to kIndex8_SkColorType
+ * (specified in the SkImageInfo), then the caller must provide
+ * storage for up to 256 SkPMColor values in fColorPtr. On success,
+ * the codec must copy N colors into that storage, (where N is the
+ * logical number of table entries) and set fColorCount to N.
+ *
+ * If the client does not request kIndex8_SkColorType, then the last
+ * two parameters may be NULL. If fColorCount is not null, it will be
+ * set to 0.
+ */
+ SkPMColor* fColorPtr;
+ int* fColorCount;
+
+ /**
+ * The client may provide an integer downscale factor for the decode.
+ * The codec may implement this downscaling by sampling or another
+ * method if it is more efficient.
+ */
+ int fSampleSize;
+ };
+
+ /**
+ * Decode into the given pixels, a block of memory of size at
+ * least (info.fHeight - 1) * rowBytes + (info.fWidth *
+ * bytesPerPixel)
+ *
+ * Repeated calls to this function should give the same results,
+ * allowing the PixelRef to be immutable.
+ *
+ * @param info A description of the format (config, size)
+ * expected by the caller. This can simply be identical
+ * to the info returned by getInfo().
+ *
+ * This contract also allows the caller to specify
+ * different output-configs, which the implementation can
+ * decide to support or not.
+ *
+ * A size that does not match getInfo() implies a request
+ * to scale or subset. If the codec cannot perform this
+ * scaling or subsetting, it will return an error code.
+ *
+ * If info is kIndex8_SkColorType, then the caller must provide storage for up to 256
+ * SkPMColor values in options->fColorPtr. On success the codec must copy N colors into
+ * that storage, (where N is the logical number of table entries) and set
+ * options->fColorCount to N.
+ *
+ * If info is not kIndex8_SkColorType, options->fColorPtr and options->fColorCount may
+ * be nullptr.
+ *
+ * The AndroidOptions object is also used to specify any requested scaling or subsetting
+ * using options->fSampleSize and options->fSubset.
+ *
+ * @return Result kSuccess, or another value explaining the type of failure.
+ */
+ // FIXME: It's a bit redundant to name this getAndroidPixels() when this class is already
+ // called SkAndroidCodec. On the other hand, it's may be a bit confusing to call
+ // this getPixels() when it is a slightly different API than SkCodec's getPixels().
+ // Maybe this should be decode() or decodeSubset()?
+ SkCodec::Result getAndroidPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
+ AndroidOptions* options);
+
+ /**
+ * Simplified version of getAndroidPixels() where we supply the default AndroidOptions.
+ *
+ * This will return an error if the info is kIndex_8_SkColorType and also will not perform
+ * any scaling or subsetting.
+ */
+ SkCodec::Result getAndroidPixels(const SkImageInfo& info, void* pixels, size_t rowBytes);
+
+protected:
+
+ SkAndroidCodec(const SkImageInfo&);
+
+ virtual SkEncodedFormat onGetEncodedFormat() const = 0;
+
+ virtual SkISize onGetSampledDimensions(int sampleSize) const = 0;
+
+ virtual bool onGetSupportedSubset(SkIRect* desiredSubset) const = 0;
+
+ virtual SkCodec::Result onGetAndroidPixels(const SkImageInfo& info, void* pixels,
+ size_t rowBytes, AndroidOptions& options) = 0;
+
+private:
+
+ // This will always be a reference to the info that is contained by the
+ // embedded SkCodec.
+ const SkImageInfo& fInfo;
+};
+#endif // SkAndroidCodec_DEFINED
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