2 * Copyright 2006 The Android Open Source Project
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
9 #include "SkColorPriv.h"
10 #include "SkColorTable.h"
11 #include "SkImageDecoder.h"
13 #include "SkScaledBitmapSampler.h"
15 #include "SkTemplates.h"
20 class SkGIFImageDecoder : public SkImageDecoder {
22 virtual Format getFormat() const SK_OVERRIDE {
27 virtual Result onDecode(SkStream* stream, SkBitmap* bm, Mode mode) SK_OVERRIDE;
30 typedef SkImageDecoder INHERITED;
33 static const uint8_t gStartingIterlaceYValue[] = {
36 static const uint8_t gDeltaIterlaceYValue[] = {
40 SK_CONF_DECLARE(bool, c_suppressGIFImageDecoderWarnings,
41 "images.gif.suppressDecoderWarnings", true,
42 "Suppress GIF warnings and errors when calling image decode "
46 /* Implement the GIF interlace algorithm in an iterator.
47 1) grab every 8th line beginning at 0
48 2) grab every 8th line beginning at 4
49 3) grab every 4th line beginning at 2
50 4) grab every 2nd line beginning at 1
52 class GifInterlaceIter {
54 GifInterlaceIter(int height) : fHeight(height) {
55 fStartYPtr = gStartingIterlaceYValue;
56 fDeltaYPtr = gDeltaIterlaceYValue;
58 fCurrY = *fStartYPtr++;
59 fDeltaY = *fDeltaYPtr++;
72 int y = fCurrY + fDeltaY;
73 // We went from an if statement to a while loop so that we iterate
74 // through fStartYPtr until a valid row is found. This is so that images
75 // that are smaller than 5x5 will not trash memory.
76 while (y >= fHeight) {
77 if (gStartingIterlaceYValue +
78 SK_ARRAY_COUNT(gStartingIterlaceYValue) == fStartYPtr) {
80 SkDEBUGCODE(fStartYPtr = NULL;)
81 SkDEBUGCODE(fDeltaYPtr = NULL;)
85 fDeltaY = *fDeltaYPtr++;
95 const uint8_t* fStartYPtr;
96 const uint8_t* fDeltaYPtr;
99 ///////////////////////////////////////////////////////////////////////////////
101 static int DecodeCallBackProc(GifFileType* fileType, GifByteType* out,
103 SkStream* stream = (SkStream*) fileType->UserData;
104 return (int) stream->read(out, size);
107 void CheckFreeExtension(SavedImage* Image) {
108 if (Image->ExtensionBlocks) {
110 FreeExtension(Image);
112 GifFreeExtensions(&Image->ExtensionBlockCount, &Image->ExtensionBlocks);
117 // return NULL on failure
118 static const ColorMapObject* find_colormap(const GifFileType* gif) {
119 const ColorMapObject* cmap = gif->Image.ColorMap;
121 cmap = gif->SColorMap;
128 // some sanity checks
129 if (cmap && ((unsigned)cmap->ColorCount > 256 ||
130 cmap->ColorCount != (1 << cmap->BitsPerPixel))) {
136 // return -1 if not found (i.e. we're completely opaque)
137 static int find_transpIndex(const SavedImage& image, int colorCount) {
138 int transpIndex = -1;
139 for (int i = 0; i < image.ExtensionBlockCount; ++i) {
140 const ExtensionBlock* eb = image.ExtensionBlocks + i;
141 if (eb->Function == 0xF9 && eb->ByteCount == 4) {
142 if (eb->Bytes[0] & 1) {
143 transpIndex = (unsigned char)eb->Bytes[3];
144 // check for valid transpIndex
145 if (transpIndex >= colorCount) {
155 static SkImageDecoder::Result error_return(const SkBitmap& bm, const char msg[]) {
156 if (!c_suppressGIFImageDecoderWarnings) {
157 SkDebugf("libgif error [%s] bitmap [%d %d] pixels %p colortable %p\n",
158 msg, bm.width(), bm.height(), bm.getPixels(),
161 return SkImageDecoder::kFailure;
164 static void gif_warning(const SkBitmap& bm, const char msg[]) {
165 if (!c_suppressGIFImageDecoderWarnings) {
166 SkDebugf("libgif warning [%s] bitmap [%d %d] pixels %p colortable %p\n",
167 msg, bm.width(), bm.height(), bm.getPixels(),
173 * Skip rows in the source gif image.
174 * @param gif Source image.
175 * @param dst Scratch output needed by gif library call. Must be >= width bytes.
176 * @param width Bytes per row in the source image.
177 * @param rowsToSkip Number of rows to skip.
178 * @return True on success, false on GIF_ERROR.
180 static bool skip_src_rows(GifFileType* gif, uint8_t* dst, int width, int rowsToSkip) {
181 for (int i = 0; i < rowsToSkip; i++) {
182 if (DGifGetLine(gif, dst, width) == GIF_ERROR) {
190 * GIFs with fewer then 256 color entries will sometimes index out of
191 * bounds of the color table (this is malformed, but libgif does not
192 * check sicne it is rare). This function checks for this error and
193 * fixes it. This makes the output image consistantly deterministic.
195 static void sanitize_indexed_bitmap(SkBitmap* bm) {
196 if ((kIndex_8_SkColorType == bm->colorType()) && !(bm->empty())) {
197 SkAutoLockPixels alp(*bm);
198 if (bm->getPixels()) {
199 SkColorTable* ct = bm->getColorTable(); // Index8 must have it.
200 SkASSERT(ct != NULL);
201 uint32_t count = ct->count();
203 SkASSERT(count <= 0x100);
204 if (count != 0x100) { // Full colortables can't go wrong.
205 // Count is a power of 2; asserted elsewhere.
206 uint8_t byteMask = (~(count - 1));
207 bool warning = false;
208 uint8_t* addr = static_cast<uint8_t*>(bm->getPixels());
209 int height = bm->height();
210 int width = bm->width();
211 size_t rowBytes = bm->rowBytes();
212 while (--height >= 0) {
216 if (0 != ((*ptr) & byteMask)) {
225 gif_warning(*bm, "Index out of bounds.");
232 SkImageDecoder::Result SkGIFImageDecoder::onDecode(SkStream* sk_stream, SkBitmap* bm, Mode mode) {
234 GifFileType* gif = DGifOpen(sk_stream, DecodeCallBackProc);
236 GifFileType* gif = DGifOpen(sk_stream, DecodeCallBackProc, NULL);
239 return error_return(*bm, "DGifOpen");
242 SkAutoTCallIProc<GifFileType, DGifCloseFile> acp(gif);
244 SavedImage temp_save;
245 temp_save.ExtensionBlocks=NULL;
246 temp_save.ExtensionBlockCount=0;
247 SkAutoTCallVProc<SavedImage, CheckFreeExtension> acp2(&temp_save);
250 GifRecordType recType;
251 GifByteType *extData;
252 #if GIFLIB_MAJOR >= 5
255 int transpIndex = -1; // -1 means we don't have it (yet)
256 int fillIndex = gif->SBackGroundColor;
259 if (DGifGetRecordType(gif, &recType) == GIF_ERROR) {
260 return error_return(*bm, "DGifGetRecordType");
264 case IMAGE_DESC_RECORD_TYPE: {
265 if (DGifGetImageDesc(gif) == GIF_ERROR) {
266 return error_return(*bm, "IMAGE_DESC_RECORD_TYPE");
269 if (gif->ImageCount < 1) { // sanity check
270 return error_return(*bm, "ImageCount < 1");
274 height = gif->SHeight;
276 SavedImage* image = &gif->SavedImages[gif->ImageCount-1];
277 const GifImageDesc& desc = image->ImageDesc;
279 int imageLeft = desc.Left;
280 int imageTop = desc.Top;
281 const int innerWidth = desc.Width;
282 const int innerHeight = desc.Height;
283 if (innerWidth <= 0 || innerHeight <= 0) {
284 return error_return(*bm, "invalid dimensions");
287 // check for valid descriptor
288 if (innerWidth > width) {
289 gif_warning(*bm, "image too wide, expanding output to size");
292 } else if (imageLeft + innerWidth > width) {
293 gif_warning(*bm, "shifting image left to fit");
294 imageLeft = width - innerWidth;
295 } else if (imageLeft < 0) {
296 gif_warning(*bm, "shifting image right to fit");
301 if (innerHeight > height) {
302 gif_warning(*bm, "image too tall, expanding output to size");
303 height = innerHeight;
305 } else if (imageTop + innerHeight > height) {
306 gif_warning(*bm, "shifting image up to fit");
307 imageTop = height - innerHeight;
308 } else if (imageTop < 0) {
309 gif_warning(*bm, "shifting image down to fit");
313 #ifdef SK_SUPPORT_LEGACY_IMAGEDECODER_CHOOSER
314 // FIXME: We could give the caller a choice of images or configs.
315 if (!this->chooseFromOneChoice(kIndex_8_SkColorType, width, height)) {
316 return error_return(*bm, "chooseFromOneChoice");
320 SkScaledBitmapSampler sampler(width, height, this->getSampleSize());
322 bm->setInfo(SkImageInfo::Make(sampler.scaledWidth(), sampler.scaledHeight(),
323 kIndex_8_SkColorType, kPremul_SkAlphaType));
325 if (SkImageDecoder::kDecodeBounds_Mode == mode) {
330 // now we decode the colortable
333 // Declare colorPtr here for scope.
334 SkPMColor colorPtr[256]; // storage for worst-case
335 const ColorMapObject* cmap = find_colormap(gif);
337 SkASSERT(cmap->ColorCount == (1 << (cmap->BitsPerPixel)));
338 colorCount = cmap->ColorCount;
339 if (colorCount > 256) {
340 colorCount = 256; // our kIndex8 can't support more
342 for (int index = 0; index < colorCount; index++) {
343 colorPtr[index] = SkPackARGB32(0xFF,
344 cmap->Colors[index].Red,
345 cmap->Colors[index].Green,
346 cmap->Colors[index].Blue);
349 // find_colormap() returned NULL. Some (rare, broken)
350 // GIFs don't have a color table, so we force one.
351 gif_warning(*bm, "missing colormap");
353 sk_memset32(colorPtr, SK_ColorWHITE, colorCount);
355 transpIndex = find_transpIndex(temp_save, colorCount);
356 if (transpIndex >= 0) {
357 colorPtr[transpIndex] = SK_ColorTRANSPARENT; // ram in a transparent SkPMColor
358 fillIndex = transpIndex;
359 } else if (fillIndex >= colorCount) {
360 // gif->SBackGroundColor should be less than colorCount.
361 fillIndex = 0; // If not, fix it.
364 SkAutoTUnref<SkColorTable> ctable(SkNEW_ARGS(SkColorTable, (colorPtr, colorCount)));
365 if (!this->allocPixelRef(bm, ctable)) {
366 return error_return(*bm, "allocPixelRef");
370 // abort if either inner dimension is <= 0
371 if (innerWidth <= 0 || innerHeight <= 0) {
372 return error_return(*bm, "non-pos inner width/height");
375 SkAutoLockPixels alp(*bm);
377 SkAutoMalloc storage(innerWidth);
378 uint8_t* scanline = (uint8_t*) storage.get();
380 // GIF has an option to store the scanlines of an image, plus a larger background,
381 // filled by a fill color. In this case, we will use a subset of the larger bitmap
384 SkBitmap* workingBitmap;
385 // are we only a subset of the total bounds?
386 if ((imageTop | imageLeft) > 0 ||
387 innerWidth < width || innerHeight < height) {
388 // Fill the background.
389 memset(bm->getPixels(), fillIndex, bm->getSize());
391 // Create a subset of the bitmap.
392 SkIRect subsetRect(SkIRect::MakeXYWH(imageLeft / sampler.srcDX(),
393 imageTop / sampler.srcDY(),
394 innerWidth / sampler.srcDX(),
395 innerHeight / sampler.srcDY()));
396 if (!bm->extractSubset(&subset, subsetRect)) {
397 return error_return(*bm, "Extract failed.");
399 // Update the sampler. We'll now be only sampling into the subset.
400 sampler = SkScaledBitmapSampler(innerWidth, innerHeight, this->getSampleSize());
401 workingBitmap = ⊂
406 // bm is already locked, but if we had to take a subset, it must be locked also,
407 // so that getPixels() will point to its pixels.
408 SkAutoLockPixels alpWorking(*workingBitmap);
410 if (!sampler.begin(workingBitmap, SkScaledBitmapSampler::kIndex, *this)) {
411 return error_return(*bm, "Sampler failed to begin.");
414 // now decode each scanline
415 if (gif->Image.Interlace) {
416 // Iterate over the height of the source data. The sampler will
417 // take care of skipping unneeded rows.
418 GifInterlaceIter iter(innerHeight);
419 for (int y = 0; y < innerHeight; y++) {
420 if (DGifGetLine(gif, scanline, innerWidth) == GIF_ERROR) {
421 gif_warning(*bm, "interlace DGifGetLine");
422 memset(scanline, fillIndex, innerWidth);
423 for (; y < innerHeight; y++) {
424 sampler.sampleInterlaced(scanline, iter.currY());
427 return kPartialSuccess;
429 sampler.sampleInterlaced(scanline, iter.currY());
433 // easy, non-interlace case
434 const int outHeight = workingBitmap->height();
435 skip_src_rows(gif, scanline, innerWidth, sampler.srcY0());
436 for (int y = 0; y < outHeight; y++) {
437 if (DGifGetLine(gif, scanline, innerWidth) == GIF_ERROR) {
438 gif_warning(*bm, "DGifGetLine");
439 memset(scanline, fillIndex, innerWidth);
440 for (; y < outHeight; y++) {
441 sampler.next(scanline);
443 return kPartialSuccess;
445 // scanline now contains the raw data. Sample it.
446 sampler.next(scanline);
447 if (y < outHeight - 1) {
448 skip_src_rows(gif, scanline, innerWidth, sampler.srcDY() - 1);
451 // skip the rest of the rows (if any)
452 int read = (outHeight - 1) * sampler.srcDY() + sampler.srcY0() + 1;
453 SkASSERT(read <= innerHeight);
454 skip_src_rows(gif, scanline, innerWidth, innerHeight - read);
456 sanitize_indexed_bitmap(bm);
460 case EXTENSION_RECORD_TYPE:
462 if (DGifGetExtension(gif, &temp_save.Function,
463 &extData) == GIF_ERROR) {
465 if (DGifGetExtension(gif, &extFunction, &extData) == GIF_ERROR) {
467 return error_return(*bm, "DGifGetExtension");
470 while (extData != NULL) {
471 /* Create an extension block with our data */
473 if (AddExtensionBlock(&temp_save, extData[0],
474 &extData[1]) == GIF_ERROR) {
476 if (GifAddExtensionBlock(&gif->ExtensionBlockCount,
477 &gif->ExtensionBlocks,
480 &extData[1]) == GIF_ERROR) {
482 return error_return(*bm, "AddExtensionBlock");
484 if (DGifGetExtensionNext(gif, &extData) == GIF_ERROR) {
485 return error_return(*bm, "DGifGetExtensionNext");
488 temp_save.Function = 0;
493 case TERMINATE_RECORD_TYPE:
496 default: /* Should be trapped by DGifGetRecordType */
499 } while (recType != TERMINATE_RECORD_TYPE);
501 sanitize_indexed_bitmap(bm);
505 ///////////////////////////////////////////////////////////////////////////////
506 DEFINE_DECODER_CREATOR(GIFImageDecoder);
507 ///////////////////////////////////////////////////////////////////////////////
509 static bool is_gif(SkStreamRewindable* stream) {
510 char buf[GIF_STAMP_LEN];
511 if (stream->read(buf, GIF_STAMP_LEN) == GIF_STAMP_LEN) {
512 if (memcmp(GIF_STAMP, buf, GIF_STAMP_LEN) == 0 ||
513 memcmp(GIF87_STAMP, buf, GIF_STAMP_LEN) == 0 ||
514 memcmp(GIF89_STAMP, buf, GIF_STAMP_LEN) == 0) {
521 static SkImageDecoder* sk_libgif_dfactory(SkStreamRewindable* stream) {
522 if (is_gif(stream)) {
523 return SkNEW(SkGIFImageDecoder);
528 static SkImageDecoder_DecodeReg gReg(sk_libgif_dfactory);
530 static SkImageDecoder::Format get_format_gif(SkStreamRewindable* stream) {
531 if (is_gif(stream)) {
532 return SkImageDecoder::kGIF_Format;
534 return SkImageDecoder::kUnknown_Format;
537 static SkImageDecoder_FormatReg gFormatReg(get_format_gif);