3 * Copyright 2006 The Android Open Source Project
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
10 #ifndef SkImageDecoder_DEFINED
11 #define SkImageDecoder_DEFINED
17 #include "SkTRegistry.h"
21 class SkStreamRewindable;
23 /** \class SkImageDecoder
25 Base class for decoding compressed images into a SkBitmap
27 class SkImageDecoder : SkNoncopyable {
29 virtual ~SkImageDecoder();
41 kLastKnownFormat = kWEBP_Format,
44 /** Return the format of image this decoder can decode. If this decoder can decode multiple
45 formats, kUnknown_Format will be returned.
47 virtual Format getFormat() const;
49 /** Return the format of the SkStreamRewindable or kUnknown_Format if it cannot be determined.
50 Rewinds the stream before returning.
52 static Format GetStreamFormat(SkStreamRewindable*);
54 /** Return a readable string of the Format provided.
56 static const char* GetFormatName(Format);
58 /** Return a readable string of the value returned by getFormat().
60 const char* getFormatName() const;
62 /** Whether the decoder should skip writing zeroes to output if possible.
64 bool getSkipWritingZeroes() const { return fSkipWritingZeroes; }
66 /** Set to true if the decoder should skip writing any zeroes when
67 creating the output image.
68 This is a hint that may not be respected by the decoder.
69 It should only be used if it is known that the memory to write
70 to has already been set to 0; otherwise the resulting image will
72 This is ideal for images that contain a lot of completely transparent
73 pixels, but may be a performance hit for an image that has only a
74 few transparent pixels.
77 void setSkipWritingZeroes(bool skip) { fSkipWritingZeroes = skip; }
79 /** Returns true if the decoder should try to dither the resulting image.
80 The default setting is true.
82 bool getDitherImage() const { return fDitherImage; }
84 /** Set to true if the the decoder should try to dither the resulting image.
85 The default setting is true.
87 void setDitherImage(bool dither) { fDitherImage = dither; }
89 /** Returns true if the decoder should try to decode the
90 resulting image to a higher quality even at the expense of
93 bool getPreferQualityOverSpeed() const { return fPreferQualityOverSpeed; }
95 /** Set to true if the the decoder should try to decode the
96 resulting image to a higher quality even at the expense of
99 void setPreferQualityOverSpeed(bool qualityOverSpeed) {
100 fPreferQualityOverSpeed = qualityOverSpeed;
103 /** Set to true to require the decoder to return a bitmap with unpremultiplied
104 colors. The default is false, meaning the resulting bitmap will have its
105 colors premultiplied.
106 NOTE: Passing true to this function may result in a bitmap which cannot
107 be properly used by Skia.
109 void setRequireUnpremultipliedColors(bool request) {
110 fRequireUnpremultipliedColors = request;
113 /** Returns true if the decoder will only return bitmaps with unpremultiplied
116 bool getRequireUnpremultipliedColors() const { return fRequireUnpremultipliedColors; }
120 Base class for optional callbacks to retrieve meta/chunk data out of
121 an image as it is being decoded.
123 class Peeker : public SkRefCnt {
125 SK_DECLARE_INST_COUNT(Peeker)
127 /** Return true to continue decoding, or false to indicate an error, which
128 will cause the decoder to not return the image.
130 virtual bool peek(const char tag[], const void* data, size_t length) = 0;
132 typedef SkRefCnt INHERITED;
135 Peeker* getPeeker() const { return fPeeker; }
136 Peeker* setPeeker(Peeker*);
140 Base class for optional callbacks to choose an image from a format that
141 contains multiple images.
143 class Chooser : public SkRefCnt {
145 SK_DECLARE_INST_COUNT(Chooser)
147 virtual void begin(int count) {}
148 virtual void inspect(int index, SkBitmap::Config config, int width, int height) {}
149 /** Return the index of the subimage you want, or -1 to choose none of them.
151 virtual int choose() = 0;
154 typedef SkRefCnt INHERITED;
157 Chooser* getChooser() const { return fChooser; }
158 Chooser* setChooser(Chooser*);
161 * Optional table describing the caller's preferred config based on
162 * information about the src data. Each field should be set to the
163 * preferred config for a src described in the name of the field. The
164 * src attributes are described in terms of depth (8-index,
165 * 8bit-grayscale, or 8-bits/component) and whether there is per-pixel
166 * alpha (does not apply to grayscale). If the caller has no preference
167 * for a particular src type, its slot should be set to kNo_Config.
169 * NOTE ABOUT PREFERRED CONFIGS:
170 * If a config is preferred, either using a pref table or as a parameter
171 * to some flavor of decode, it is still at the discretion of the codec
172 * as to what output config is actually returned, as it may not be able
173 * to support the caller's preference.
175 * If a bitmap is decoded into SkBitmap::A8_Config, the resulting bitmap
176 * will either be a conversion of the grayscale in the case of a
177 * grayscale source or the alpha channel in the case of a source with
180 struct PrefConfigTable {
181 SkBitmap::Config fPrefFor_8Index_NoAlpha_src;
182 SkBitmap::Config fPrefFor_8Index_YesAlpha_src;
183 SkBitmap::Config fPrefFor_8Gray_src;
184 SkBitmap::Config fPrefFor_8bpc_NoAlpha_src;
185 SkBitmap::Config fPrefFor_8bpc_YesAlpha_src;
189 * Set an optional table for specifying the caller's preferred config
190 * based on information about the src data.
192 * The default is no preference, which will assume the config set by
193 * decode is preferred.
195 void setPrefConfigTable(const PrefConfigTable&);
198 * Do not use a PrefConfigTable to determine the output config. This
199 * is the default, so there is no need to call unless a PrefConfigTable
200 * was previously set.
202 void resetPrefConfigTable() { fUsePrefTable = false; }
204 SkBitmap::Allocator* getAllocator() const { return fAllocator; }
205 SkBitmap::Allocator* setAllocator(SkBitmap::Allocator*);
207 // sample-size, if set to > 1, tells the decoder to return a smaller than
208 // original bitmap, sampling 1 pixel for every size pixels. e.g. if sample
209 // size is set to 3, then the returned bitmap will be 1/3 as wide and high,
210 // and will contain 1/9 as many pixels as the original.
211 // Note: this is a hint, and the codec may choose to ignore this, or only
212 // approximate the sample size.
213 int getSampleSize() const { return fSampleSize; }
214 void setSampleSize(int size);
216 /** Reset the sampleSize to its default of 1
218 void resetSampleSize() { this->setSampleSize(1); }
220 /** Decoding is synchronous, but for long decodes, a different thread can
221 call this method safely. This sets a state that the decoders will
222 periodically check, and if they see it changed to cancel, they will
223 cancel. This will result in decode() returning false. However, there is
224 no guarantee that the decoder will see the state change in time, so
225 it is possible that cancelDecode() will be called, but will be ignored
226 and decode() will return true (assuming no other problems were
229 This state is automatically reset at the beginning of decode().
231 void cancelDecode() {
232 // now the subclass must query shouldCancelDecode() to be informed
234 fShouldCancelDecode = true;
237 /** Passed to the decode method. If kDecodeBounds_Mode is passed, then
238 only the bitmap's width/height/config need be set. If kDecodePixels_Mode
239 is passed, then the bitmap must have pixels or a pixelRef.
242 kDecodeBounds_Mode, //!< only return width/height/config in bitmap
243 kDecodePixels_Mode //!< return entire bitmap (including pixels)
246 /** Given a stream, decode it into the specified bitmap.
247 If the decoder can decompress the image, it calls bitmap.setConfig(),
248 and then if the Mode is kDecodePixels_Mode, call allocPixelRef(),
249 which will allocated a pixelRef. To access the pixel memory, the codec
250 needs to call lockPixels/unlockPixels on the
251 bitmap. It can then set the pixels with the decompressed image.
252 * If the image cannot be decompressed, return false. After the
253 * decoding, the function converts the decoded config in bitmap
254 * to pref if possible. Whether a conversion is feasible is
255 * tested by Bitmap::canCopyTo(pref).
257 If an SkBitmap::Allocator is installed via setAllocator, it will be
258 used to allocate the pixel memory. A clever allocator can be used
259 to allocate the memory from a cache, volatile memory, or even from
260 an existing bitmap's memory.
262 If a Peeker is installed via setPeeker, it may be used to peek into
263 meta data during the decode.
265 If a Chooser is installed via setChooser, it may be used to select
266 which image to return from a format that contains multiple images.
268 bool decode(SkStream*, SkBitmap* bitmap, SkBitmap::Config pref, Mode);
269 bool decode(SkStream* stream, SkBitmap* bitmap, Mode mode) {
270 return this->decode(stream, bitmap, SkBitmap::kNo_Config, mode);
274 * Given a stream, build an index for doing tile-based decode.
275 * The built index will be saved in the decoder, and the image size will
276 * be returned in width and height.
278 * Return true for success or false on failure.
280 bool buildTileIndex(SkStreamRewindable*, int *width, int *height);
283 * Decode a rectangle subset in the image.
284 * The method can only be called after buildTileIndex().
286 * Return true for success.
287 * Return false if the index is never built or failing in decoding.
289 bool decodeSubset(SkBitmap* bm, const SkIRect& subset, SkBitmap::Config pref);
291 /** Given a stream, this will try to find an appropriate decoder object.
292 If none is found, the method returns NULL.
294 static SkImageDecoder* Factory(SkStreamRewindable*);
296 /** Decode the image stored in the specified file, and store the result
297 in bitmap. Return true for success or false on failure.
299 @param prefConfig If the PrefConfigTable is not set, prefer this config.
300 See NOTE ABOUT PREFERRED CONFIGS.
302 @param format On success, if format is non-null, it is set to the format
303 of the decoded file. On failure it is ignored.
305 static bool DecodeFile(const char file[], SkBitmap* bitmap,
306 SkBitmap::Config prefConfig, Mode,
307 Format* format = NULL);
308 static bool DecodeFile(const char file[], SkBitmap* bitmap) {
309 return DecodeFile(file, bitmap, SkBitmap::kNo_Config,
310 kDecodePixels_Mode, NULL);
312 /** Decode the image stored in the specified memory buffer, and store the
313 result in bitmap. Return true for success or false on failure.
315 @param prefConfig If the PrefConfigTable is not set, prefer this config.
316 See NOTE ABOUT PREFERRED CONFIGS.
318 @param format On success, if format is non-null, it is set to the format
319 of the decoded buffer. On failure it is ignored.
321 static bool DecodeMemory(const void* buffer, size_t size, SkBitmap* bitmap,
322 SkBitmap::Config prefConfig, Mode,
323 Format* format = NULL);
324 static bool DecodeMemory(const void* buffer, size_t size, SkBitmap* bitmap){
325 return DecodeMemory(buffer, size, bitmap, SkBitmap::kNo_Config,
326 kDecodePixels_Mode, NULL);
330 * Struct containing information about a pixel destination.
334 * Pre-allocated memory.
339 * Rowbytes of the allocated memory.
344 /** Decode the image stored in the specified SkStreamRewindable, and store the result
345 in bitmap. Return true for success or false on failure.
347 @param prefConfig If the PrefConfigTable is not set, prefer this config.
348 See NOTE ABOUT PREFERRED CONFIGS.
350 @param format On success, if format is non-null, it is set to the format
351 of the decoded stream. On failure it is ignored.
353 static bool DecodeStream(SkStreamRewindable* stream, SkBitmap* bitmap,
354 SkBitmap::Config prefConfig, Mode,
355 Format* format = NULL);
356 static bool DecodeStream(SkStreamRewindable* stream, SkBitmap* bitmap) {
357 return DecodeStream(stream, bitmap, SkBitmap::kNo_Config,
358 kDecodePixels_Mode, NULL);
361 /** Return the default config for the running device.
362 Currently this used as a suggestion to image decoders that need to guess
363 what config they should decode into.
364 Default is kNo_Config, but this can be changed with SetDeviceConfig()
366 static SkBitmap::Config GetDeviceConfig();
367 /** Set the default config for the running device.
368 Currently this used as a suggestion to image decoders that need to guess
369 what config they should decode into.
370 Default is kNo_Config.
371 This can be queried with GetDeviceConfig()
373 static void SetDeviceConfig(SkBitmap::Config);
376 // must be overridden in subclasses. This guy is called by decode(...)
377 virtual bool onDecode(SkStream*, SkBitmap* bitmap, Mode) = 0;
379 // If the decoder wants to support tiled based decoding,
380 // this method must be overridden. This guy is called by buildTileIndex(...)
381 virtual bool onBuildTileIndex(SkStreamRewindable*, int *width, int *height) {
385 // If the decoder wants to support tiled based decoding,
386 // this method must be overridden. This guy is called by decodeRegion(...)
387 virtual bool onDecodeSubset(SkBitmap* bitmap, const SkIRect& rect) {
392 * Crop a rectangle from the src Bitmap to the dest Bitmap. src and dst are
393 * both sampled by sampleSize from an original Bitmap.
395 * @param dst the destination bitmap.
396 * @param src the source bitmap that is sampled by sampleSize from the
398 * @param sampleSize the sample size that src is sampled from the original bitmap.
399 * @param (dstX, dstY) the upper-left point of the dest bitmap in terms of
400 * the coordinate in the original bitmap.
401 * @param (width, height) the width and height of the unsampled dst.
402 * @param (srcX, srcY) the upper-left point of the src bitmap in terms of
403 * the coordinate in the original bitmap.
404 * @return bool Whether or not it succeeded.
406 bool cropBitmap(SkBitmap *dst, SkBitmap *src, int sampleSize,
407 int dstX, int dstY, int width, int height,
411 * Copy all fields on this decoder to the other decoder. Used by subclasses
412 * to decode a subimage using a different decoder, but with the same settings.
414 void copyFieldsToOther(SkImageDecoder* other);
417 * Return the default preference being used by the current or latest call to
420 SkBitmap::Config getDefaultPref() { return fDefaultPref; }
422 /** Can be queried from within onDecode, to see if the user (possibly in
423 a different thread) has requested the decode to cancel. If this returns
424 true, your onDecode() should stop and return false.
425 Each subclass needs to decide how often it can query this, to balance
426 responsiveness with performance.
428 Calling this outside of onDecode() may return undefined values.
432 bool shouldCancelDecode() const { return fShouldCancelDecode; }
437 // helper function for decoders to handle the (common) case where there is only
438 // once choice available in the image file.
439 bool chooseFromOneChoice(SkBitmap::Config config, int width, int height) const;
441 /* Helper for subclasses. Call this to allocate the pixel memory given the bitmap's
442 width/height/rowbytes/config. Returns true on success. This method handles checking
443 for an optional Allocator.
445 bool allocPixelRef(SkBitmap*, SkColorTable*) const;
448 * The raw data of the src image.
453 // Grayscale in 8 bits.
455 // 8 bits per component. Used for 24 bit if there is no alpha.
458 /** The subclass, inside onDecode(), calls this to determine the config of
459 the returned bitmap. SrcDepth and hasAlpha reflect the raw data of the
460 src image. This routine returns the caller's preference given
461 srcDepth and hasAlpha, or kNo_Config if there is no preference.
463 Note: this also takes into account GetDeviceConfig(), so the subclass
466 SkBitmap::Config getPrefConfig(SrcDepth, bool hasAlpha) const;
471 SkBitmap::Allocator* fAllocator;
473 SkBitmap::Config fDefaultPref; // use if fUsePrefTable is false
474 PrefConfigTable fPrefTable; // use if fUsePrefTable is true
477 bool fSkipWritingZeroes;
478 mutable bool fShouldCancelDecode;
479 bool fPreferQualityOverSpeed;
480 bool fRequireUnpremultipliedColors;
483 /** Calling newDecoder with a stream returns a new matching imagedecoder
484 instance, or NULL if none can be found. The caller must manage its ownership
485 of the stream as usual, calling unref() when it is done, as the returned
486 decoder may have called ref() (and if so, the decoder is responsible for
487 balancing its ownership when it is destroyed).
489 class SkImageDecoderFactory : public SkRefCnt {
491 SK_DECLARE_INST_COUNT(SkImageDecoderFactory)
493 virtual SkImageDecoder* newDecoder(SkStreamRewindable*) = 0;
496 typedef SkRefCnt INHERITED;
499 class SkDefaultImageDecoderFactory : SkImageDecoderFactory {
501 // calls SkImageDecoder::Factory(stream)
502 virtual SkImageDecoder* newDecoder(SkStreamRewindable* stream) {
503 return SkImageDecoder::Factory(stream);
507 // This macro declares a global (i.e., non-class owned) creation entry point
508 // for each decoder (e.g., CreateJPEGImageDecoder)
509 #define DECLARE_DECODER_CREATOR(codec) \
510 SkImageDecoder *Create ## codec ();
512 // This macro defines the global creation entry point for each decoder. Each
513 // decoder implementation that registers with the decoder factory must call it.
514 #define DEFINE_DECODER_CREATOR(codec) \
515 SkImageDecoder *Create ## codec () { \
516 return SkNEW( Sk ## codec ); \
519 // All the decoders known by Skia. Note that, depending on the compiler settings,
520 // not all of these will be available
521 DECLARE_DECODER_CREATOR(BMPImageDecoder);
522 DECLARE_DECODER_CREATOR(GIFImageDecoder);
523 DECLARE_DECODER_CREATOR(ICOImageDecoder);
524 DECLARE_DECODER_CREATOR(JPEGImageDecoder);
525 DECLARE_DECODER_CREATOR(PNGImageDecoder);
526 DECLARE_DECODER_CREATOR(WBMPImageDecoder);
527 DECLARE_DECODER_CREATOR(WEBPImageDecoder);
530 // Typedefs to make registering decoder and formatter callbacks easier.
531 // These have to be defined outside SkImageDecoder. :(
532 typedef SkTRegistry<SkImageDecoder*(*)(SkStreamRewindable*)> SkImageDecoder_DecodeReg;
533 typedef SkTRegistry<SkImageDecoder::Format(*)(SkStreamRewindable*)> SkImageDecoder_FormatReg;