1 2 /* 3 * Copyright 2006 The Android Open Source Project 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 9 10 #include "SkImageDecoder.h" 11 #include "SkColor.h" 12 #include "SkColorPriv.h" 13 #include "SkStream.h" 14 #include "SkTemplates.h" 15 #include "SkPackBits.h" 16 17 #include "gif_lib.h" 18 19 class SkGIFImageDecoder : public SkImageDecoder { 20 public: 21 virtual Format getFormat() const { 22 return kGIF_Format; 23 } 24 25 protected: 26 virtual bool onDecode(SkStream* stream, SkBitmap* bm, Mode mode); 27 }; 28 29 static const uint8_t gStartingIterlaceYValue[] = { 30 0, 4, 2, 1 31 }; 32 static const uint8_t gDeltaIterlaceYValue[] = { 33 8, 8, 4, 2 34 }; 35 36 /* Implement the GIF interlace algorithm in an iterator. 37 1) grab every 8th line beginning at 0 38 2) grab every 8th line beginning at 4 39 3) grab every 4th line beginning at 2 40 4) grab every 2nd line beginning at 1 41 */ 42 class GifInterlaceIter { 43 public: 44 GifInterlaceIter(int height) : fHeight(height) { 45 fStartYPtr = gStartingIterlaceYValue; 46 fDeltaYPtr = gDeltaIterlaceYValue; 47 48 fCurrY = *fStartYPtr++; 49 fDeltaY = *fDeltaYPtr++; 50 } 51 52 int currY() const { 53 SkASSERT(fStartYPtr); 54 SkASSERT(fDeltaYPtr); 55 return fCurrY; 56 } 57 58 void next() { 59 SkASSERT(fStartYPtr); 60 SkASSERT(fDeltaYPtr); 61 62 int y = fCurrY + fDeltaY; 63 // We went from an if statement to a while loop so that we iterate 64 // through fStartYPtr until a valid row is found. This is so that images 65 // that are smaller than 5x5 will not trash memory. 66 while (y >= fHeight) { 67 if (gStartingIterlaceYValue + 68 SK_ARRAY_COUNT(gStartingIterlaceYValue) == fStartYPtr) { 69 // we done 70 SkDEBUGCODE(fStartYPtr = NULL;) 71 SkDEBUGCODE(fDeltaYPtr = NULL;) 72 y = 0; 73 } else { 74 y = *fStartYPtr++; 75 fDeltaY = *fDeltaYPtr++; 76 } 77 } 78 fCurrY = y; 79 } 80 81 private: 82 const int fHeight; 83 int fCurrY; 84 int fDeltaY; 85 const uint8_t* fStartYPtr; 86 const uint8_t* fDeltaYPtr; 87 }; 88 89 /////////////////////////////////////////////////////////////////////////////// 90 91 //#define GIF_STAMP "GIF" /* First chars in file - GIF stamp. */ 92 //#define GIF_STAMP_LEN (sizeof(GIF_STAMP) - 1) 93 94 static int DecodeCallBackProc(GifFileType* fileType, GifByteType* out, 95 int size) { 96 SkStream* stream = (SkStream*) fileType->UserData; 97 return (int) stream->read(out, size); 98 } 99 100 void CheckFreeExtension(SavedImage* Image) { 101 if (Image->ExtensionBlocks) { 102 FreeExtension(Image); 103 } 104 } 105 106 // return NULL on failure 107 static const ColorMapObject* find_colormap(const GifFileType* gif) { 108 const ColorMapObject* cmap = gif->Image.ColorMap; 109 if (NULL == cmap) { 110 cmap = gif->SColorMap; 111 } 112 113 if (NULL == cmap) { 114 // no colormap found 115 return NULL; 116 } 117 // some sanity checks 118 if (cmap && ((unsigned)cmap->ColorCount > 256 || 119 cmap->ColorCount != (1 << cmap->BitsPerPixel))) { 120 cmap = NULL; 121 } 122 return cmap; 123 } 124 125 // return -1 if not found (i.e. we're completely opaque) 126 static int find_transpIndex(const SavedImage& image, int colorCount) { 127 int transpIndex = -1; 128 for (int i = 0; i < image.ExtensionBlockCount; ++i) { 129 const ExtensionBlock* eb = image.ExtensionBlocks + i; 130 if (eb->Function == 0xF9 && eb->ByteCount == 4) { 131 if (eb->Bytes[0] & 1) { 132 transpIndex = (unsigned char)eb->Bytes[3]; 133 // check for valid transpIndex 134 if (transpIndex >= colorCount) { 135 transpIndex = -1; 136 } 137 break; 138 } 139 } 140 } 141 return transpIndex; 142 } 143 144 static bool error_return(GifFileType* gif, const SkBitmap& bm, 145 const char msg[]) { 146 #if 0 147 SkDebugf("libgif error <%s> bitmap [%d %d] pixels %p colortable %p\n", 148 msg, bm.width(), bm.height(), bm.getPixels(), bm.getColorTable()); 149 #endif 150 return false; 151 } 152 153 bool SkGIFImageDecoder::onDecode(SkStream* sk_stream, SkBitmap* bm, Mode mode) { 154 GifFileType* gif = DGifOpen(sk_stream, DecodeCallBackProc); 155 if (NULL == gif) { 156 return error_return(gif, *bm, "DGifOpen"); 157 } 158 159 SkAutoTCallIProc<GifFileType, DGifCloseFile> acp(gif); 160 161 SavedImage temp_save; 162 temp_save.ExtensionBlocks=NULL; 163 temp_save.ExtensionBlockCount=0; 164 SkAutoTCallVProc<SavedImage, CheckFreeExtension> acp2(&temp_save); 165 166 int width, height; 167 GifRecordType recType; 168 GifByteType *extData; 169 int transpIndex = -1; // -1 means we don't have it (yet) 170 171 do { 172 if (DGifGetRecordType(gif, &recType) == GIF_ERROR) { 173 return error_return(gif, *bm, "DGifGetRecordType"); 174 } 175 176 switch (recType) { 177 case IMAGE_DESC_RECORD_TYPE: { 178 if (DGifGetImageDesc(gif) == GIF_ERROR) { 179 return error_return(gif, *bm, "IMAGE_DESC_RECORD_TYPE"); 180 } 181 182 if (gif->ImageCount < 1) { // sanity check 183 return error_return(gif, *bm, "ImageCount < 1"); 184 } 185 186 width = gif->SWidth; 187 height = gif->SHeight; 188 if (width <= 0 || height <= 0 || 189 !this->chooseFromOneChoice(SkBitmap::kIndex8_Config, 190 width, height)) { 191 return error_return(gif, *bm, "chooseFromOneChoice"); 192 } 193 194 if (SkImageDecoder::kDecodeBounds_Mode == mode) { 195 bm->setConfig(SkBitmap::kIndex8_Config, width, height); 196 return true; 197 } 198 #ifdef SK_BUILD_FOR_ANDROID 199 // No Bitmap reuse supported for this format 200 if (!bm->isNull()) { 201 return false; 202 } 203 #endif 204 205 bm->setConfig(SkBitmap::kIndex8_Config, width, height); 206 SavedImage* image = &gif->SavedImages[gif->ImageCount-1]; 207 const GifImageDesc& desc = image->ImageDesc; 208 209 // check for valid descriptor 210 if ( (desc.Top | desc.Left) < 0 || 211 desc.Left + desc.Width > width || 212 desc.Top + desc.Height > height) { 213 return error_return(gif, *bm, "TopLeft"); 214 } 215 216 // now we decode the colortable 217 int colorCount = 0; 218 { 219 const ColorMapObject* cmap = find_colormap(gif); 220 if (NULL == cmap) { 221 return error_return(gif, *bm, "null cmap"); 222 } 223 224 colorCount = cmap->ColorCount; 225 SkColorTable* ctable = SkNEW_ARGS(SkColorTable, (colorCount)); 226 SkPMColor* colorPtr = ctable->lockColors(); 227 for (int index = 0; index < colorCount; index++) 228 colorPtr[index] = SkPackARGB32(0xFF, 229 cmap->Colors[index].Red, 230 cmap->Colors[index].Green, 231 cmap->Colors[index].Blue); 232 233 transpIndex = find_transpIndex(temp_save, colorCount); 234 if (transpIndex < 0) 235 ctable->setFlags(ctable->getFlags() | SkColorTable::kColorsAreOpaque_Flag); 236 else 237 colorPtr[transpIndex] = 0; // ram in a transparent SkPMColor 238 ctable->unlockColors(true); 239 240 SkAutoUnref aurts(ctable); 241 if (!this->allocPixelRef(bm, ctable)) { 242 return error_return(gif, *bm, "allocPixelRef"); 243 } 244 } 245 246 SkAutoLockPixels alp(*bm); 247 248 // time to decode the scanlines 249 // 250 uint8_t* scanline = bm->getAddr8(0, 0); 251 const int rowBytes = bm->rowBytes(); 252 const int innerWidth = desc.Width; 253 const int innerHeight = desc.Height; 254 255 // abort if either inner dimension is <= 0 256 if (innerWidth <= 0 || innerHeight <= 0) { 257 return error_return(gif, *bm, "non-pos inner width/height"); 258 } 259 260 // are we only a subset of the total bounds? 261 if ((desc.Top | desc.Left) > 0 || 262 innerWidth < width || innerHeight < height) 263 { 264 int fill; 265 if (transpIndex >= 0) { 266 fill = transpIndex; 267 } else { 268 fill = gif->SBackGroundColor; 269 } 270 // check for valid fill index/color 271 if (static_cast<unsigned>(fill) >= 272 static_cast<unsigned>(colorCount)) { 273 fill = 0; 274 } 275 memset(scanline, fill, bm->getSize()); 276 // bump our starting address 277 scanline += desc.Top * rowBytes + desc.Left; 278 } 279 280 // now decode each scanline 281 if (gif->Image.Interlace) 282 { 283 GifInterlaceIter iter(innerHeight); 284 for (int y = 0; y < innerHeight; y++) 285 { 286 uint8_t* row = scanline + iter.currY() * rowBytes; 287 if (DGifGetLine(gif, row, innerWidth) == GIF_ERROR) { 288 return error_return(gif, *bm, "interlace DGifGetLine"); 289 } 290 iter.next(); 291 } 292 } 293 else 294 { 295 // easy, non-interlace case 296 for (int y = 0; y < innerHeight; y++) { 297 if (DGifGetLine(gif, scanline, innerWidth) == GIF_ERROR) { 298 return error_return(gif, *bm, "DGifGetLine"); 299 } 300 scanline += rowBytes; 301 } 302 } 303 goto DONE; 304 } break; 305 306 case EXTENSION_RECORD_TYPE: 307 if (DGifGetExtension(gif, &temp_save.Function, 308 &extData) == GIF_ERROR) { 309 return error_return(gif, *bm, "DGifGetExtension"); 310 } 311 312 while (extData != NULL) { 313 /* Create an extension block with our data */ 314 if (AddExtensionBlock(&temp_save, extData[0], 315 &extData[1]) == GIF_ERROR) { 316 return error_return(gif, *bm, "AddExtensionBlock"); 317 } 318 if (DGifGetExtensionNext(gif, &extData) == GIF_ERROR) { 319 return error_return(gif, *bm, "DGifGetExtensionNext"); 320 } 321 temp_save.Function = 0; 322 } 323 break; 324 325 case TERMINATE_RECORD_TYPE: 326 break; 327 328 default: /* Should be trapped by DGifGetRecordType */ 329 break; 330 } 331 } while (recType != TERMINATE_RECORD_TYPE); 332 333 DONE: 334 return true; 335 } 336 337 /////////////////////////////////////////////////////////////////////////////// 338 339 #include "SkTRegistry.h" 340 341 static SkImageDecoder* Factory(SkStream* stream) { 342 char buf[GIF_STAMP_LEN]; 343 if (stream->read(buf, GIF_STAMP_LEN) == GIF_STAMP_LEN) { 344 if (memcmp(GIF_STAMP, buf, GIF_STAMP_LEN) == 0 || 345 memcmp(GIF87_STAMP, buf, GIF_STAMP_LEN) == 0 || 346 memcmp(GIF89_STAMP, buf, GIF_STAMP_LEN) == 0) { 347 return SkNEW(SkGIFImageDecoder); 348 } 349 } 350 return NULL; 351 } 352 353 static SkTRegistry<SkImageDecoder*, SkStream*> gReg(Factory); 354
