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| 1 /* | |
| 2 * Copyright 2015 Google Inc. | |
| 3 * | |
| 4 * Use of this source code is governed by a BSD-style license that can be | |
| 5 * found in the LICENSE file. | |
| 6 */ | |
| 7 | |
| 8 #include "SkCodec.h" | |
| 9 #include "SkColorTable.h" | |
| 10 #include "SkImageInfo.h" | |
| 11 #include "SkSwizzler.h" | |
| 12 | |
| 13 #include "gif_lib.h" | |
| 14 | |
| 15 /* | |
| 16 * | |
| 17 * This class implements the decoding for gif images | |
| 18 * | |
| 19 */ | |
| 20 class SkGifCodec : public SkCodec { | |
| 21 public: | |
| 22 static bool IsGif(const void*, size_t); | |
| 23 | |
| 24 /* | |
| 25 * Assumes IsGif was called and returned true | |
| 26 * Creates a gif decoder | |
| 27 * Reads enough of the stream to determine the image format | |
| 28 */ | |
| 29 static SkCodec* NewFromStream(SkStream*); | |
| 30 | |
| 31 protected: | |
| 32 | |
| 33 /* | |
| 34 * Read enough of the stream to initialize the SkGifCodec. | |
| 35 * Returns a bool representing success or failure. | |
| 36 * | |
| 37 * @param codecOut | |
| 38 * If it returned true, and codecOut was not nullptr, | |
| 39 * codecOut will be set to a new SkGifCodec. | |
| 40 * | |
| 41 * @param gifOut | |
| 42 * If it returned true, and codecOut was nullptr, | |
| 43 * gifOut must be non-nullptr and gifOut will be set to a new | |
| 44 * GifFileType pointer. | |
| 45 * | |
| 46 * @param stream | |
| 47 * Deleted on failure. | |
| 48 * codecOut will take ownership of it in the case where we created a codec. | |
| 49 * Ownership is unchanged when we returned a gifOut. | |
| 50 * | |
| 51 */ | |
| 52 static bool ReadHeader(SkStream* stream, SkCodec** codecOut, | |
| 53 GifFileType** gifOut); | |
| 54 | |
| 55 /* | |
| 56 * Performs the full gif decode | |
| 57 */ | |
| 58 Result onGetPixels(const SkImageInfo&, void*, size_t, const Options&, | |
| 59 SkPMColor*, int*, int*) override; | |
| 60 | |
| 61 SkEncodedFormat onGetEncodedFormat() const override { | |
| 62 return kGIF_SkEncodedFormat; | |
| 63 } | |
| 64 | |
| 65 bool onRewind() override; | |
| 66 | |
| 67 uint32_t onGetFillValue(SkColorType colorType, SkAlphaType alphaType) const
override; | |
| 68 | |
| 69 int onOutputScanline(int inputScanline) const override; | |
| 70 | |
| 71 private: | |
| 72 | |
| 73 /* | |
| 74 * A gif can contain multiple image frames. We will only decode the first | |
| 75 * frame. This function reads up to the first image frame, processing | |
| 76 * transparency and/or animation information that comes before the image | |
| 77 * data. | |
| 78 * | |
| 79 * @param gif Pointer to the library type that manages the gif decode | |
| 80 * @param transIndex This call will set the transparent index based on the | |
| 81 * extension data. | |
| 82 */ | |
| 83 static Result ReadUpToFirstImage(GifFileType* gif, uint32_t* transIndex); | |
| 84 | |
| 85 /* | |
| 86 * A gif may contain many image frames, all of different sizes. | |
| 87 * This function checks if the gif dimensions are valid, based on the frame | |
| 88 * dimensions, and corrects the gif dimensions if necessary. | |
| 89 * | |
| 90 * @param gif Pointer to the library type that manages the gif decode | |
| 91 * @param size Size of the image that we will decode. | |
| 92 * Will be set by this function if the return value is tru
e. | |
| 93 * @param frameRect Contains the dimenions and offset of the first image fr
ame. | |
| 94 * Will be set by this function if the return value is tru
e. | |
| 95 * | |
| 96 * @return true on success, false otherwise | |
| 97 */ | |
| 98 static bool GetDimensions(GifFileType* gif, SkISize* size, SkIRect* frameRe
ct); | |
| 99 | |
| 100 /* | |
| 101 * Initializes the color table that we will use for decoding. | |
| 102 * | |
| 103 * @param dstInfo Contains the requested dst color type. | |
| 104 * @param inputColorPtr Copies the encoded color table to the client's | |
| 105 * input color table if the client requests kIndex8. | |
| 106 * @param inputColorCount If the client requests kIndex8, sets | |
| 107 * inputColorCount to 256. Since gifs always | |
| 108 * contain 8-bit indices, we need a 256 entry color | |
| 109 * table to ensure that indexing is always in | |
| 110 * bounds. | |
| 111 */ | |
| 112 void initializeColorTable(const SkImageInfo& dstInfo, SkPMColor* colorPtr, | |
| 113 int* inputColorCount); | |
| 114 | |
| 115 /* | |
| 116 * Checks for invalid inputs and calls setFrameDimensions(), and | |
| 117 * initializeColorTable() in the proper sequence. | |
| 118 */ | |
| 119 Result prepareToDecode(const SkImageInfo& dstInfo, SkPMColor* inputColorPtr, | |
| 120 int* inputColorCount, const Options& opts); | |
| 121 | |
| 122 /* | |
| 123 * Initializes the swizzler. | |
| 124 * | |
| 125 * @param dstInfo Output image information. Dimensions may have been | |
| 126 * adjusted if the image frame size does not match the size | |
| 127 * indicated in the header. | |
| 128 * @param options Informs the swizzler if destination memory is zero initia
lized. | |
| 129 * Contains subset information. | |
| 130 */ | |
| 131 Result initializeSwizzler(const SkImageInfo& dstInfo, | |
| 132 const Options& options); | |
| 133 | |
| 134 SkSampler* getSampler(bool createIfNecessary) override { | |
| 135 SkASSERT(fSwizzler); | |
| 136 return fSwizzler; | |
| 137 } | |
| 138 | |
| 139 /* | |
| 140 * @return true if the read is successful and false if the read fails. | |
| 141 */ | |
| 142 bool readRow(); | |
| 143 | |
| 144 Result onStartScanlineDecode(const SkImageInfo& dstInfo, const Options& opts
, | |
| 145 SkPMColor inputColorPtr[], int* inputColorCount) override; | |
| 146 | |
| 147 int onGetScanlines(void* dst, int count, size_t rowBytes) override; | |
| 148 | |
| 149 bool onSkipScanlines(int count) override; | |
| 150 | |
| 151 /* | |
| 152 * For a scanline decode of "count" lines, this function indicates how | |
| 153 * many of the "count" lines should be skipped until we reach the top of | |
| 154 * the image frame and how many of the "count" lines are actually inside | |
| 155 * the image frame. | |
| 156 * | |
| 157 * @param count The number of scanlines requested. | |
| 158 * @param rowsBeforeFrame Output variable. The number of lines before | |
| 159 * we reach the top of the image frame. | |
| 160 * @param rowsInFrame Output variable. The number of lines to decode | |
| 161 * inside the image frame. | |
| 162 */ | |
| 163 void handleScanlineFrame(int count, int* rowsBeforeFrame, int* rowsInFrame); | |
| 164 | |
| 165 SkScanlineOrder onGetScanlineOrder() const override; | |
| 166 | |
| 167 /* | |
| 168 * This function cleans up the gif object after the decode completes | |
| 169 * It is used in a SkAutoTCallIProc template | |
| 170 */ | |
| 171 static void CloseGif(GifFileType* gif); | |
| 172 | |
| 173 /* | |
| 174 * Frees any extension data used in the decode | |
| 175 * Used in a SkAutoTCallVProc | |
| 176 */ | |
| 177 static void FreeExtension(SavedImage* image); | |
| 178 | |
| 179 /* | |
| 180 * Creates an instance of the decoder | |
| 181 * Called only by NewFromStream | |
| 182 * | |
| 183 * @param srcInfo contains the source width and height | |
| 184 * @param stream the stream of image data | |
| 185 * @param gif pointer to library type that manages gif decode | |
| 186 * takes ownership | |
| 187 * @param transIndex The transparent index. An invalid value | |
| 188 * indicates that there is no transparent index. | |
| 189 */ | |
| 190 SkGifCodec(const SkImageInfo& srcInfo, SkStream* stream, GifFileType* gif, u
int32_t transIndex, | |
| 191 const SkIRect& frameRect, bool frameIsSubset); | |
| 192 | |
| 193 SkAutoTCallVProc<GifFileType, CloseGif> fGif; // owned | |
| 194 SkAutoTDeleteArray<uint8_t> fSrcBuffer; | |
| 195 const SkIRect fFrameRect; | |
| 196 const uint32_t fTransIndex; | |
| 197 uint32_t fFillIndex; | |
| 198 const bool fFrameIsSubset; | |
| 199 SkAutoTDelete<SkSwizzler> fSwizzler; | |
| 200 SkAutoTUnref<SkColorTable> fColorTable; | |
| 201 | |
| 202 typedef SkCodec INHERITED; | |
| 203 }; | |
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Chromium Code Reviews
Issue 1567863003:
Rename SkGifCodec, SkIcoCodec, SkWbmpCodec (Closed)
Base URL: https://skia.googlesource.com/skia.git@master