skia2/include/codec/SkAndroidCodec.h
scroggo 7b5e5536a1 Add SkAndroidCodec::getPixels
This is a synonym for the version of getAndroidPixels that accepts
only three parameters (i.e. no AndroidOptions). It is very similar
to SkCodec::getPixels, so I think the motivation for naming the
version with options differently does not apply here.

Add comments to the header describing defaults.

Update the test to use a template, and delete a lot of redundant code.

Rename a variable to stop shadowing another variable.

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1647153002

Review URL: https://codereview.chromium.org/1647153002
2016-02-04 06:14:24 -08:00

265 lines
10 KiB
C++

/*
* 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.
*
* The SkPngChunkReader handles unknown chunks in PNGs.
* See SkCodec.h for more details.
*
* 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*, SkPngChunkReader* = NULL);
/**
* If this data represents an encoded image that we know how to decode,
* return an SkAndroidCodec that can decode it. Otherwise return NULL.
*
* The SkPngChunkReader handles unknown chunks in PNGs.
* See SkCodec.h for more details.
*
* Will take a ref if it returns a codec, else will not affect the data.
*/
static SkAndroidCodec* NewFromData(SkData*, SkPngChunkReader* = NULL);
virtual ~SkAndroidCodec() {}
const SkImageInfo& getInfo() const { return fInfo; }
/**
* Format of the encoded data.
*/
SkEncodedFormat getEncodedFormat() const { return fCodec->getEncodedFormat(); }
/**
* @param requestedColorType Color type requested by the client
*
* If it is possible to decode to requestedColorType, this returns
* requestedColorType. Otherwise, this returns whichever color type
* is suggested by the codec as the best match for the encoded data.
*/
SkColorType computeOutputColorType(SkColorType requestedColorType);
/**
* @param requestedUnpremul Indicates if the client requested
* unpremultiplied output
*
* Returns the appropriate alpha type to decode to. If the image
* has alpha, the value of requestedUnpremul will be honored.
*/
SkAlphaType computeOutputAlphaType(bool requestedUnpremul);
/**
* 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.
*
* The default is SkCodec::kNo_ZeroInitialized.
*/
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.
*
* The default is NULL, meaning a decode of the entire image.
*/
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.
*
* The default is NULL for both pointers.
*/
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.
*
* The default is 1, representing no downscaling.
*/
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. If NULL, the defaults (as specified above
* for AndroidOptions) are used.
*
* @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,
const AndroidOptions* options);
/**
* Simplified version of getAndroidPixels() where we supply the default AndroidOptions as
* specified above for 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);
SkCodec::Result getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes) {
return this->getAndroidPixels(info, pixels, rowBytes);
}
protected:
SkAndroidCodec(SkCodec*);
SkCodec* codec() const { return fCodec.get(); }
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, const AndroidOptions& options) = 0;
private:
// This will always be a reference to the info that is contained by the
// embedded SkCodec.
const SkImageInfo& fInfo;
SkAutoTDelete<SkCodec> fCodec;
};
#endif // SkAndroidCodec_DEFINED