15e9d3e66e
http://codereview.appspot.com/6300114/ git-svn-id: http://skia.googlecode.com/svn/trunk@4291 2bbb7eff-a529-9590-31e7-b0007b416f81
371 lines
14 KiB
C++
371 lines
14 KiB
C++
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/*
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* Copyright 2006 The Android Open Source Project
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkImageDecoder_DEFINED
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#define SkImageDecoder_DEFINED
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#include "SkBitmap.h"
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#include "SkRefCnt.h"
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class SkStream;
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/** \class SkImageDecoder
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Base class for decoding compressed images into a SkBitmap
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*/
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class SkImageDecoder {
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public:
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virtual ~SkImageDecoder();
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enum Format {
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kUnknown_Format,
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kBMP_Format,
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kGIF_Format,
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kICO_Format,
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kJPEG_Format,
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kPNG_Format,
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kWBMP_Format,
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kLastKnownFormat = kWBMP_Format
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};
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/** Return the compressed data's format (see Format enum)
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*/
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virtual Format getFormat() const;
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/** Returns true if the decoder should try to dither the resulting image.
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The default setting is true.
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*/
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bool getDitherImage() const { return fDitherImage; }
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/** Set to true if the the decoder should try to dither the resulting image.
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The default setting is true.
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*/
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void setDitherImage(bool dither) { fDitherImage = dither; }
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/** \class Peeker
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Base class for optional callbacks to retrieve meta/chunk data out of
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an image as it is being decoded.
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*/
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class Peeker : public SkRefCnt {
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public:
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SK_DECLARE_INST_COUNT(Peeker)
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/** Return true to continue decoding, or false to indicate an error, which
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will cause the decoder to not return the image.
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*/
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virtual bool peek(const char tag[], const void* data, size_t length) = 0;
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private:
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typedef SkRefCnt INHERITED;
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};
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Peeker* getPeeker() const { return fPeeker; }
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Peeker* setPeeker(Peeker*);
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/** \class Peeker
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Base class for optional callbacks to retrieve meta/chunk data out of
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an image as it is being decoded.
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*/
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class Chooser : public SkRefCnt {
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public:
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SK_DECLARE_INST_COUNT(Chooser)
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virtual void begin(int count) {}
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virtual void inspect(int index, SkBitmap::Config config, int width, int height) {}
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/** Return the index of the subimage you want, or -1 to choose none of them.
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*/
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virtual int choose() = 0;
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private:
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typedef SkRefCnt INHERITED;
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};
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Chooser* getChooser() const { return fChooser; }
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Chooser* setChooser(Chooser*);
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/** This optional table describes the caller's preferred config based on
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information about the src data. For this table, the src attributes are
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described in terms of depth (index (8), 16, 32/24) and if there is
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per-pixel alpha. These inputs combine to create an index into the
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pref[] table, which contains the caller's preferred config for that
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input, or kNo_Config if there is no preference.
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To specify no preferrence, call setPrefConfigTable(NULL), which is
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the default.
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Note, it is still at the discretion of the codec as to what output
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config is actually returned, as it may not be able to support the
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caller's preference.
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Here is how the index into the table is computed from the src:
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depth [8, 16, 32/24] -> 0, 2, 4
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alpha [no, yes] -> 0, 1
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The two index values are OR'd together.
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src: 8-index, no-alpha -> 0
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src: 8-index, yes-alpha -> 1
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src: 16bit, no-alpha -> 2 // e.g. 565
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src: 16bit, yes-alpha -> 3 // e.g. 1555
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src: 32/24, no-alpha -> 4
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src: 32/24, yes-alpha -> 5
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*/
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void setPrefConfigTable(const SkBitmap::Config pref[6]);
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SkBitmap::Allocator* getAllocator() const { return fAllocator; }
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SkBitmap::Allocator* setAllocator(SkBitmap::Allocator*);
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// sample-size, if set to > 1, tells the decoder to return a smaller than
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// original bitmap, sampling 1 pixel for every size pixels. e.g. if sample
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// size is set to 3, then the returned bitmap will be 1/3 as wide and high,
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// and will contain 1/9 as many pixels as the original.
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// Note: this is a hint, and the codec may choose to ignore this, or only
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// approximate the sample size.
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int getSampleSize() const { return fSampleSize; }
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void setSampleSize(int size);
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/** Reset the sampleSize to its default of 1
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*/
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void resetSampleSize() { this->setSampleSize(1); }
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/** Decoding is synchronous, but for long decodes, a different thread can
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call this method safely. This sets a state that the decoders will
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periodically check, and if they see it changed to cancel, they will
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cancel. This will result in decode() returning false. However, there is
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no guarantee that the decoder will see the state change in time, so
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it is possible that cancelDecode() will be called, but will be ignored
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and decode() will return true (assuming no other problems were
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encountered).
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This state is automatically reset at the beginning of decode().
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*/
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void cancelDecode() {
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// now the subclass must query shouldCancelDecode() to be informed
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// of the request
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fShouldCancelDecode = true;
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}
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/** Passed to the decode method. If kDecodeBounds_Mode is passed, then
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only the bitmap's width/height/config need be set. If kDecodePixels_Mode
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is passed, then the bitmap must have pixels or a pixelRef.
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*/
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enum Mode {
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kDecodeBounds_Mode, //!< only return width/height/config in bitmap
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kDecodePixels_Mode //!< return entire bitmap (including pixels)
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};
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/** Given a stream, decode it into the specified bitmap.
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If the decoder can decompress the image, it calls bitmap.setConfig(),
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and then if the Mode is kDecodePixels_Mode, call allocPixelRef(),
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which will allocated a pixelRef. To access the pixel memory, the codec
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needs to call lockPixels/unlockPixels on the
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bitmap. It can then set the pixels with the decompressed image.
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* If the image cannot be decompressed, return false. After the
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* decoding, the function converts the decoded config in bitmap
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* to pref if possible. Whether a conversion is feasible is
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* tested by Bitmap::canCopyTo(pref).
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note: document use of Allocator, Peeker and Chooser
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*/
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bool decode(SkStream*, SkBitmap* bitmap, SkBitmap::Config pref, Mode);
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bool decode(SkStream* stream, SkBitmap* bitmap, Mode mode) {
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return this->decode(stream, bitmap, SkBitmap::kNo_Config, mode);
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}
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/** Given a stream, this will try to find an appropriate decoder object.
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If none is found, the method returns NULL.
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*/
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static SkImageDecoder* Factory(SkStream*);
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/** Decode the image stored in the specified file, and store the result
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in bitmap. Return true for success or false on failure.
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If pref is kNo_Config, then the decoder is free to choose the most natural
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config given the image data. If pref something other than kNo_Config,
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the decoder will attempt to decode the image into that format, unless
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there is a conflict (e.g. the image has per-pixel alpha and the bitmap's
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config does not support that), in which case the decoder will choose a
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closest match configuration.
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@param format On success, if format is non-null, it is set to the format
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of the decoded file. On failure it is ignored.
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*/
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static bool DecodeFile(const char file[], SkBitmap* bitmap,
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SkBitmap::Config prefConfig, Mode,
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Format* format = NULL);
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static bool DecodeFile(const char file[], SkBitmap* bitmap) {
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return DecodeFile(file, bitmap, SkBitmap::kNo_Config,
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kDecodePixels_Mode, NULL);
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}
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/** Decode the image stored in the specified memory buffer, and store the
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result in bitmap. Return true for success or false on failure.
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If pref is kNo_Config, then the decoder is free to choose the most natural
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config given the image data. If pref something other than kNo_Config,
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the decoder will attempt to decode the image into that format, unless
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there is a conflict (e.g. the image has per-pixel alpha and the bitmap's
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config does not support that), in which case the decoder will choose a
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closest match configuration.
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@param format On success, if format is non-null, it is set to the format
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of the decoded buffer. On failure it is ignored.
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*/
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static bool DecodeMemory(const void* buffer, size_t size, SkBitmap* bitmap,
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SkBitmap::Config prefConfig, Mode,
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Format* format = NULL);
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static bool DecodeMemory(const void* buffer, size_t size, SkBitmap* bitmap){
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return DecodeMemory(buffer, size, bitmap, SkBitmap::kNo_Config,
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kDecodePixels_Mode, NULL);
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}
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/** Decode the image stored in the specified SkStream, and store the result
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in bitmap. Return true for success or false on failure.
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If pref is kNo_Config, then the decoder is free to choose the most
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natural config given the image data. If pref something other than
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kNo_Config, the decoder will attempt to decode the image into that
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format, unless there is a conflict (e.g. the image has per-pixel alpha
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and the bitmap's config does not support that), in which case the
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decoder will choose a closest match configuration.
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@param format On success, if format is non-null, it is set to the format
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of the decoded stream. On failure it is ignored.
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*/
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static bool DecodeStream(SkStream* stream, SkBitmap* bitmap,
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SkBitmap::Config prefConfig, Mode,
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Format* format = NULL);
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static bool DecodeStream(SkStream* stream, SkBitmap* bitmap) {
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return DecodeStream(stream, bitmap, SkBitmap::kNo_Config,
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kDecodePixels_Mode, NULL);
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}
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/** Return the default config for the running device.
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Currently this used as a suggestion to image decoders that need to guess
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what config they should decode into.
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Default is kNo_Config, but this can be changed with SetDeviceConfig()
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*/
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static SkBitmap::Config GetDeviceConfig();
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/** Set the default config for the running device.
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Currently this used as a suggestion to image decoders that need to guess
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what config they should decode into.
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Default is kNo_Config.
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This can be queried with GetDeviceConfig()
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*/
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static void SetDeviceConfig(SkBitmap::Config);
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/** @cond UNIT_TEST */
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SkDEBUGCODE(static void UnitTest();)
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/** @endcond */
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protected:
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// must be overridden in subclasses. This guy is called by decode(...)
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virtual bool onDecode(SkStream*, SkBitmap* bitmap, Mode) = 0;
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/** Can be queried from within onDecode, to see if the user (possibly in
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a different thread) has requested the decode to cancel. If this returns
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true, your onDecode() should stop and return false.
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Each subclass needs to decide how often it can query this, to balance
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responsiveness with performance.
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Calling this outside of onDecode() may return undefined values.
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*/
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public:
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bool shouldCancelDecode() const { return fShouldCancelDecode; }
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protected:
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SkImageDecoder();
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// helper function for decoders to handle the (common) case where there is only
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// once choice available in the image file.
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bool chooseFromOneChoice(SkBitmap::Config config, int width, int height) const;
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/* Helper for subclasses. Call this to allocate the pixel memory given the bitmap's
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width/height/rowbytes/config. Returns true on success. This method handles checking
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for an optional Allocator.
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*/
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bool allocPixelRef(SkBitmap*, SkColorTable*) const;
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enum SrcDepth {
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kIndex_SrcDepth,
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k16Bit_SrcDepth,
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k32Bit_SrcDepth
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};
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/** The subclass, inside onDecode(), calls this to determine the config of
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the returned bitmap. SrcDepth and hasAlpha reflect the raw data of the
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src image. This routine returns the caller's preference given
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srcDepth and hasAlpha, or kNo_Config if there is no preference.
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Note: this also takes into account GetDeviceConfig(), so the subclass
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need not call that.
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*/
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SkBitmap::Config getPrefConfig(SrcDepth, bool hasAlpha) const;
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private:
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Peeker* fPeeker;
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Chooser* fChooser;
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SkBitmap::Allocator* fAllocator;
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int fSampleSize;
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SkBitmap::Config fDefaultPref; // use if fUsePrefTable is false
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SkBitmap::Config fPrefTable[6]; // use if fUsePrefTable is true
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bool fDitherImage;
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bool fUsePrefTable;
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mutable bool fShouldCancelDecode;
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// illegal
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SkImageDecoder(const SkImageDecoder&);
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SkImageDecoder& operator=(const SkImageDecoder&);
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};
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/** Calling newDecoder with a stream returns a new matching imagedecoder
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instance, or NULL if none can be found. The caller must manage its ownership
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of the stream as usual, calling unref() when it is done, as the returned
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decoder may have called ref() (and if so, the decoder is responsible for
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balancing its ownership when it is destroyed).
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*/
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class SkImageDecoderFactory : public SkRefCnt {
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public:
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SK_DECLARE_INST_COUNT(SkImageDecoderFactory)
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virtual SkImageDecoder* newDecoder(SkStream*) = 0;
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private:
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typedef SkRefCnt INHERITED;
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};
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class SkDefaultImageDecoderFactory : SkImageDecoderFactory {
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public:
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// calls SkImageDecoder::Factory(stream)
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virtual SkImageDecoder* newDecoder(SkStream* stream) {
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return SkImageDecoder::Factory(stream);
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}
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};
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// This macro declares a global (i.e., non-class owned) creation entry point
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// for each decoder (e.g., CreateJPEGImageDecoder)
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#define DECLARE_DECODER_CREATOR(codec) \
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SkImageDecoder *Create ## codec ();
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// This macro defines the global creation entry point for each decoder. Each
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// decoder implementation that registers with the decoder factory must call it.
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#define DEFINE_DECODER_CREATOR(codec) \
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SkImageDecoder *Create ## codec () { \
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return SkNEW( Sk ## codec ); \
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}
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// All the decoders known by Skia. Note that, depending on the compiler settings,
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// not all of these will be available
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DECLARE_DECODER_CREATOR(BMPImageDecoder);
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DECLARE_DECODER_CREATOR(GIFImageDecoder);
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DECLARE_DECODER_CREATOR(ICOImageDecoder);
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DECLARE_DECODER_CREATOR(JPEGImageDecoder);
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DECLARE_DECODER_CREATOR(PNGImageDecoder);
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DECLARE_DECODER_CREATOR(WBMPImageDecoder);
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#endif
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