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/*
* Copyright 2013 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkDecodingImageGenerator_DEFINED
#define SkDecodingImageGenerator_DEFINED
#include "SkBitmap.h"
#include "SkImageGenerator.h"
class SkData;
class SkStreamRewindable;
/**
* An implementation of SkImageGenerator that calls into
* SkImageDecoder.
*/
class SkDecodingImageGenerator : public SkImageGenerator {
public:
virtual ~SkDecodingImageGenerator();
virtual SkData* refEncodedData() SK_OVERRIDE;
// This implementaion of getInfo() always returns true.
virtual bool getInfo(SkImageInfo* info) SK_OVERRIDE;
virtual bool getPixels(const SkImageInfo& info,
void* pixels,
size_t rowBytes) SK_OVERRIDE;
/**
* These options will be passed on to the image decoder. The
* defaults are sensible.
*
* @param fSampleSize If set to > 1, tells the decoder to return a
* smaller than original bitmap, sampling 1 pixel for
* every size pixels. e.g. if sample size is set to 3,
* then the returned bitmap will be 1/3 as wide and high,
* and will contain 1/9 as many pixels as the original.
* Note: this is a hint, and the codec may choose to
* ignore this, or only approximate the sample size.
*
* @param fDitherImage Set to true if the the decoder should try to
* dither the resulting image when decoding to a smaller
* color-space. The default is true.
*
* @param fRequestedColorType If not given, then use whichever
* config the decoder wants. Else try to use this color
* type. If the decoder won't support this color type,
* SkDecodingImageGenerator::Create will return
* NULL. kIndex_8_SkColorType is not supported.
*/
struct Options {
Options()
: fSampleSize(1)
, fDitherImage(true)
, fUseRequestedColorType(false)
, fRequestedColorType() { }
Options(int sampleSize, bool dither)
: fSampleSize(sampleSize)
, fDitherImage(dither)
, fUseRequestedColorType(false)
, fRequestedColorType() { }
Options(int sampleSize, bool dither, SkColorType colorType)
: fSampleSize(sampleSize)
, fDitherImage(dither)
, fUseRequestedColorType(true)
, fRequestedColorType(colorType) { }
const int fSampleSize;
const bool fDitherImage;
const bool fUseRequestedColorType;
const SkColorType fRequestedColorType;
};
/**
* These two functions return a SkImageGenerator that calls into
* SkImageDecoder. They return NULL on failure.
*
* The SkData version of this function is preferred. If the stream
* has an underlying SkData (such as a SkMemoryStream) pass that in.
*
* This object will unref the stream when done or on failure. Since
* streams have internal state (position), the caller should not pass
* a shared stream in. Pass either a new duplicated stream in or
* transfer ownership of the stream. This factory asserts
* stream->unique().
*
* For example:
* SkStreamRewindable* stream;
* ...
* SkImageGenerator* gen
* = SkDecodingImageGenerator::Create(
* stream->duplicate(), SkDecodingImageGenerator::Options());
* ...
* SkDELETE(gen);
*
* @param Options (see above)
*
* @return NULL on failure, a new SkImageGenerator on success.
*/
static SkImageGenerator* Create(SkStreamRewindable* stream,
const Options& opt);
/**
* @param data Contains the encoded image data that will be used by
* the SkDecodingImageGenerator. Will be ref()ed by the
* SkImageGenerator constructor and and unref()ed on deletion.
*/
static SkImageGenerator* Create(SkData* data, const Options& opt);
private:
SkData* fData;
SkStreamRewindable* fStream;
const SkImageInfo fInfo;
const int fSampleSize;
const bool fDitherImage;
SkDecodingImageGenerator(SkData* data,
SkStreamRewindable* stream,
const SkImageInfo& info,
int sampleSize,
bool ditherImage);
static SkImageGenerator* Create(SkData*, SkStreamRewindable*,
const Options&);
typedef SkImageGenerator INHERITED;
};
// // Example of most basic use case:
//
// bool install_data(SkData* data, SkBitmap* dst) {
// return SkInstallDiscardablePixelRef(
// SkDecodingImageGenerator::Create(
// data, SkDecodingImageGenerator::Options()), dst, NULL);
// }
// bool install_stream(SkStreamRewindable* stream, SkBitmap* dst) {
// return SkInstallDiscardablePixelRef(
// SkDecodingImageGenerator::Create(
// stream, SkDecodingImageGenerator::Options()), dst, NULL);
// }
#endif // SkDecodingImageGenerator_DEFINED
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