| /* |
| * Copyright 2015 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "SkCodecPriv.h" |
| #include "SkColorPriv.h" |
| #include "SkColorTable.h" |
| #include "SkGifCodec.h" |
| #include "SkStream.h" |
| #include "SkSwizzler.h" |
| #include "SkUtils.h" |
| |
| /* |
| * Checks the start of the stream to see if the image is a gif |
| */ |
| bool SkGifCodec::IsGif(const void* buf, size_t bytesRead) { |
| if (bytesRead >= GIF_STAMP_LEN) { |
| if (memcmp(GIF_STAMP, buf, GIF_STAMP_LEN) == 0 || |
| memcmp(GIF87_STAMP, buf, GIF_STAMP_LEN) == 0 || |
| memcmp(GIF89_STAMP, buf, GIF_STAMP_LEN) == 0) |
| { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /* |
| * Error function |
| */ |
| static SkCodec::Result gif_error(const char* msg, SkCodec::Result result = SkCodec::kInvalidInput) { |
| SkCodecPrintf("Gif Error: %s\n", msg); |
| return result; |
| } |
| |
| |
| /* |
| * Read function that will be passed to gif_lib |
| */ |
| static int32_t read_bytes_callback(GifFileType* fileType, GifByteType* out, int32_t size) { |
| SkStream* stream = (SkStream*) fileType->UserData; |
| return (int32_t) stream->read(out, size); |
| } |
| |
| /* |
| * Open the gif file |
| */ |
| static GifFileType* open_gif(SkStream* stream) { |
| return DGifOpen(stream, read_bytes_callback, nullptr); |
| } |
| |
| /* |
| * Check if a there is an index of the color table for a transparent pixel |
| */ |
| static uint32_t find_trans_index(const SavedImage& image) { |
| // If there is a transparent index specified, it will be contained in an |
| // extension block. We will loop through extension blocks in reverse order |
| // to check the most recent extension blocks first. |
| for (int32_t i = image.ExtensionBlockCount - 1; i >= 0; i--) { |
| // Get an extension block |
| const ExtensionBlock& extBlock = image.ExtensionBlocks[i]; |
| |
| // Specifically, we need to check for a graphics control extension, |
| // which may contain transparency information. Also, note that a valid |
| // graphics control extension is always four bytes. The fourth byte |
| // is the transparent index (if it exists), so we need at least four |
| // bytes. |
| if (GRAPHICS_EXT_FUNC_CODE == extBlock.Function && extBlock.ByteCount >= 4) { |
| // Check the transparent color flag which indicates whether a |
| // transparent index exists. It is the least significant bit of |
| // the first byte of the extension block. |
| if (1 == (extBlock.Bytes[0] & 1)) { |
| // Use uint32_t to prevent sign extending |
| return extBlock.Bytes[3]; |
| } |
| |
| // There should only be one graphics control extension for the image frame |
| break; |
| } |
| } |
| |
| // Use maximum unsigned int (surely an invalid index) to indicate that a valid |
| // index was not found. |
| return SK_MaxU32; |
| } |
| |
| inline uint32_t ceil_div(uint32_t a, uint32_t b) { |
| return (a + b - 1) / b; |
| } |
| |
| /* |
| * Gets the output row corresponding to the encoded row for interlaced gifs |
| */ |
| inline uint32_t get_output_row_interlaced(uint32_t encodedRow, uint32_t height) { |
| SkASSERT(encodedRow < height); |
| // First pass |
| if (encodedRow * 8 < height) { |
| return encodedRow * 8; |
| } |
| // Second pass |
| if (encodedRow * 4 < height) { |
| return 4 + 8 * (encodedRow - ceil_div(height, 8)); |
| } |
| // Third pass |
| if (encodedRow * 2 < height) { |
| return 2 + 4 * (encodedRow - ceil_div(height, 4)); |
| } |
| // Fourth pass |
| return 1 + 2 * (encodedRow - ceil_div(height, 2)); |
| } |
| |
| /* |
| * This function cleans up the gif object after the decode completes |
| * It is used in a SkAutoTCallIProc template |
| */ |
| void SkGifCodec::CloseGif(GifFileType* gif) { |
| DGifCloseFile(gif, NULL); |
| } |
| |
| /* |
| * This function free extension data that has been saved to assist the image |
| * decoder |
| */ |
| void SkGifCodec::FreeExtension(SavedImage* image) { |
| if (NULL != image->ExtensionBlocks) { |
| GifFreeExtensions(&image->ExtensionBlockCount, &image->ExtensionBlocks); |
| } |
| } |
| |
| /* |
| * Read enough of the stream to initialize the SkGifCodec. |
| * Returns a bool representing success or failure. |
| * |
| * @param codecOut |
| * If it returned true, and codecOut was not nullptr, |
| * codecOut will be set to a new SkGifCodec. |
| * |
| * @param gifOut |
| * If it returned true, and codecOut was nullptr, |
| * gifOut must be non-nullptr and gifOut will be set to a new |
| * GifFileType pointer. |
| * |
| * @param stream |
| * Deleted on failure. |
| * codecOut will take ownership of it in the case where we created a codec. |
| * Ownership is unchanged when we returned a gifOut. |
| * |
| */ |
| bool SkGifCodec::ReadHeader(SkStream* stream, SkCodec** codecOut, GifFileType** gifOut) { |
| SkAutoTDelete<SkStream> streamDeleter(stream); |
| |
| // Read gif header, logical screen descriptor, and global color table |
| SkAutoTCallVProc<GifFileType, CloseGif> gif(open_gif(stream)); |
| |
| if (nullptr == gif) { |
| gif_error("DGifOpen failed.\n"); |
| return false; |
| } |
| |
| // Read through gif extensions to get to the image data. Set the |
| // transparent index based on the extension data. |
| uint32_t transIndex; |
| SkCodec::Result result = ReadUpToFirstImage(gif, &transIndex); |
| if (kSuccess != result){ |
| return false; |
| } |
| |
| // Read the image descriptor |
| if (GIF_ERROR == DGifGetImageDesc(gif)) { |
| return false; |
| } |
| // If reading the image descriptor is successful, the image count will be |
| // incremented. |
| SkASSERT(gif->ImageCount >= 1); |
| |
| if (nullptr != codecOut) { |
| SkISize size; |
| SkIRect frameRect; |
| if (!GetDimensions(gif, &size, &frameRect)) { |
| gif_error("Invalid gif size.\n"); |
| return false; |
| } |
| bool frameIsSubset = (size != frameRect.size()); |
| |
| // Determine the recommended alpha type. The transIndex might be valid if it less |
| // than 256. We are not certain that the index is valid until we process the color |
| // table, since some gifs have color tables with less than 256 colors. If |
| // there might be a valid transparent index, we must indicate that the image has |
| // alpha. |
| // In the case where we must support alpha, we have the option to set the |
| // suggested alpha type to kPremul or kUnpremul. Both are valid since the alpha |
| // component will always be 0xFF or the entire 32-bit pixel will be set to zero. |
| // We prefer kPremul because we support kPremul, and it is more efficient to use |
| // kPremul directly even when kUnpremul is supported. |
| SkAlphaType alphaType = (transIndex < 256) ? kPremul_SkAlphaType : kOpaque_SkAlphaType; |
| |
| // Return the codec |
| // kIndex is the most natural color type for gifs, so we set this as |
| // the default. |
| SkImageInfo imageInfo = SkImageInfo::Make(size.width(), size.height(), kIndex_8_SkColorType, |
| alphaType); |
| *codecOut = new SkGifCodec(imageInfo, streamDeleter.detach(), gif.detach(), transIndex, |
| frameRect, frameIsSubset); |
| } else { |
| SkASSERT(nullptr != gifOut); |
| streamDeleter.detach(); |
| *gifOut = gif.detach(); |
| } |
| return true; |
| } |
| |
| /* |
| * Assumes IsGif was called and returned true |
| * Creates a gif decoder |
| * Reads enough of the stream to determine the image format |
| */ |
| SkCodec* SkGifCodec::NewFromStream(SkStream* stream) { |
| SkCodec* codec = nullptr; |
| if (ReadHeader(stream, &codec, nullptr)) { |
| return codec; |
| } |
| return nullptr; |
| } |
| |
| SkGifCodec::SkGifCodec(const SkImageInfo& srcInfo, SkStream* stream, GifFileType* gif, |
| uint32_t transIndex, const SkIRect& frameRect, bool frameIsSubset) |
| : INHERITED(srcInfo, stream) |
| , fGif(gif) |
| , fSrcBuffer(new uint8_t[this->getInfo().width()]) |
| , fFrameRect(frameRect) |
| // If it is valid, fTransIndex will be used to set fFillIndex. We don't know if |
| // fTransIndex is valid until we process the color table, since fTransIndex may |
| // be greater than the size of the color table. |
| , fTransIndex(transIndex) |
| // Default fFillIndex is 0. We will overwrite this if fTransIndex is valid, or if |
| // there is a valid background color. |
| , fFillIndex(0) |
| , fFrameIsSubset(frameIsSubset) |
| , fSwizzler(NULL) |
| , fColorTable(NULL) |
| {} |
| |
| bool SkGifCodec::onRewind() { |
| GifFileType* gifOut = nullptr; |
| if (!ReadHeader(this->stream(), nullptr, &gifOut)) { |
| return false; |
| } |
| |
| SkASSERT(nullptr != gifOut); |
| fGif.reset(gifOut); |
| return true; |
| } |
| |
| SkCodec::Result SkGifCodec::ReadUpToFirstImage(GifFileType* gif, uint32_t* transIndex) { |
| // Use this as a container to hold information about any gif extension |
| // blocks. This generally stores transparency and animation instructions. |
| SavedImage saveExt; |
| SkAutoTCallVProc<SavedImage, FreeExtension> autoFreeExt(&saveExt); |
| saveExt.ExtensionBlocks = nullptr; |
| saveExt.ExtensionBlockCount = 0; |
| GifByteType* extData; |
| int32_t extFunction; |
| |
| // We will loop over components of gif images until we find an image. Once |
| // we find an image, we will decode and return it. While many gif files |
| // contain more than one image, we will simply decode the first image. |
| GifRecordType recordType; |
| do { |
| // Get the current record type |
| if (GIF_ERROR == DGifGetRecordType(gif, &recordType)) { |
| return gif_error("DGifGetRecordType failed.\n", kInvalidInput); |
| } |
| switch (recordType) { |
| case IMAGE_DESC_RECORD_TYPE: { |
| *transIndex = find_trans_index(saveExt); |
| |
| // FIXME: Gif files may have multiple images stored in a single |
| // file. This is most commonly used to enable |
| // animations. Since we are leaving animated gifs as a |
| // TODO, we will return kSuccess after decoding the |
| // first image in the file. This is the same behavior |
| // as SkImageDecoder_libgif. |
| // |
| // Most times this works pretty well, but sometimes it |
| // doesn't. For example, I have an animated test image |
| // where the first image in the file is 1x1, but the |
| // subsequent images are meaningful. This currently |
| // displays the 1x1 image, which is not ideal. Right |
| // now I am leaving this as an issue that will be |
| // addressed when we implement animated gifs. |
| // |
| // It is also possible (not explicitly disallowed in the |
| // specification) that gif files provide multiple |
| // images in a single file that are all meant to be |
| // displayed in the same frame together. I will |
| // currently leave this unimplemented until I find a |
| // test case that expects this behavior. |
| return kSuccess; |
| } |
| // Extensions are used to specify special properties of the image |
| // such as transparency or animation. |
| case EXTENSION_RECORD_TYPE: |
| // Read extension data |
| if (GIF_ERROR == DGifGetExtension(gif, &extFunction, &extData)) { |
| return gif_error("Could not get extension.\n", kIncompleteInput); |
| } |
| |
| // Create an extension block with our data |
| while (nullptr != extData) { |
| // Add a single block |
| if (GIF_ERROR == GifAddExtensionBlock(&saveExt.ExtensionBlockCount, |
| &saveExt.ExtensionBlocks, |
| extFunction, extData[0], &extData[1])) |
| { |
| return gif_error("Could not add extension block.\n", kIncompleteInput); |
| } |
| // Move to the next block |
| if (GIF_ERROR == DGifGetExtensionNext(gif, &extData)) { |
| return gif_error("Could not get next extension.\n", kIncompleteInput); |
| } |
| } |
| break; |
| |
| // Signals the end of the gif file |
| case TERMINATE_RECORD_TYPE: |
| break; |
| |
| default: |
| // DGifGetRecordType returns an error if the record type does |
| // not match one of the above cases. This should not be |
| // reached. |
| SkASSERT(false); |
| break; |
| } |
| } while (TERMINATE_RECORD_TYPE != recordType); |
| |
| return gif_error("Could not find any images to decode in gif file.\n", kInvalidInput); |
| } |
| |
| bool SkGifCodec::GetDimensions(GifFileType* gif, SkISize* size, SkIRect* frameRect) { |
| // Get the encoded dimension values |
| SavedImage* image = &gif->SavedImages[gif->ImageCount - 1]; |
| const GifImageDesc& desc = image->ImageDesc; |
| int frameLeft = desc.Left; |
| int frameTop = desc.Top; |
| int frameWidth = desc.Width; |
| int frameHeight = desc.Height; |
| int width = gif->SWidth; |
| int height = gif->SHeight; |
| |
| // Ensure that the decode dimensions are large enough to contain the frame |
| width = SkTMax(width, frameWidth + frameLeft); |
| height = SkTMax(height, frameHeight + frameTop); |
| |
| // All of these dimensions should be positive, as they are encoded as unsigned 16-bit integers. |
| // It is unclear why giflib casts them to ints. We will go ahead and check that they are |
| // in fact positive. |
| if (frameLeft < 0 || frameTop < 0 || frameWidth < 0 || frameHeight < 0 || width <= 0 || |
| height <= 0) { |
| return false; |
| } |
| |
| frameRect->setXYWH(frameLeft, frameTop, frameWidth, frameHeight); |
| size->set(width, height); |
| return true; |
| } |
| |
| void SkGifCodec::initializeColorTable(const SkImageInfo& dstInfo, SkPMColor* inputColorPtr, |
| int* inputColorCount) { |
| // Set up our own color table |
| const uint32_t maxColors = 256; |
| SkPMColor colorPtr[256]; |
| if (NULL != inputColorCount) { |
| // We set the number of colors to maxColors in order to ensure |
| // safe memory accesses. Otherwise, an invalid pixel could |
| // access memory outside of our color table array. |
| *inputColorCount = maxColors; |
| } |
| |
| // Get local color table |
| ColorMapObject* colorMap = fGif->Image.ColorMap; |
| // If there is no local color table, use the global color table |
| if (NULL == colorMap) { |
| colorMap = fGif->SColorMap; |
| } |
| |
| uint32_t colorCount = 0; |
| if (NULL != colorMap) { |
| colorCount = colorMap->ColorCount; |
| // giflib guarantees these properties |
| SkASSERT(colorCount == (unsigned) (1 << (colorMap->BitsPerPixel))); |
| SkASSERT(colorCount <= 256); |
| for (uint32_t i = 0; i < colorCount; i++) { |
| colorPtr[i] = SkPackARGB32(0xFF, colorMap->Colors[i].Red, |
| colorMap->Colors[i].Green, colorMap->Colors[i].Blue); |
| } |
| } |
| |
| // Gifs have the option to specify the color at a single index of the color |
| // table as transparent. If the transparent index is greater than the |
| // colorCount, we know that there is no valid transparent color in the color |
| // table. If there is not valid transparent index, we will try to use the |
| // backgroundIndex as the fill index. If the backgroundIndex is also not |
| // valid, we will let fFillIndex default to 0 (it is set to zero in the |
| // constructor). This behavior is not specified but matches |
| // SkImageDecoder_libgif. |
| uint32_t backgroundIndex = fGif->SBackGroundColor; |
| if (fTransIndex < colorCount) { |
| colorPtr[fTransIndex] = SK_ColorTRANSPARENT; |
| fFillIndex = fTransIndex; |
| } else if (backgroundIndex < colorCount) { |
| fFillIndex = backgroundIndex; |
| } |
| |
| // Fill in the color table for indices greater than color count. |
| // This allows for predictable, safe behavior. |
| for (uint32_t i = colorCount; i < maxColors; i++) { |
| colorPtr[i] = colorPtr[fFillIndex]; |
| } |
| |
| fColorTable.reset(new SkColorTable(colorPtr, maxColors)); |
| copy_color_table(dstInfo, this->fColorTable, inputColorPtr, inputColorCount); |
| } |
| |
| SkCodec::Result SkGifCodec::prepareToDecode(const SkImageInfo& dstInfo, SkPMColor* inputColorPtr, |
| int* inputColorCount, const Options& opts) { |
| // Check for valid input parameters |
| if (!conversion_possible(dstInfo, this->getInfo())) { |
| return gif_error("Cannot convert input type to output type.\n", |
| kInvalidConversion); |
| } |
| |
| // Initialize color table and copy to the client if necessary |
| this->initializeColorTable(dstInfo, inputColorPtr, inputColorCount); |
| |
| return this->initializeSwizzler(dstInfo, opts); |
| } |
| |
| SkCodec::Result SkGifCodec::initializeSwizzler(const SkImageInfo& dstInfo, const Options& opts) { |
| const SkPMColor* colorPtr = get_color_ptr(fColorTable.get()); |
| const SkIRect* frameRect = fFrameIsSubset ? &fFrameRect : nullptr; |
| fSwizzler.reset(SkSwizzler::CreateSwizzler(SkSwizzler::kIndex, colorPtr, dstInfo, opts, |
| frameRect)); |
| |
| if (nullptr != fSwizzler.get()) { |
| return kSuccess; |
| } |
| return kUnimplemented; |
| } |
| |
| bool SkGifCodec::readRow() { |
| return GIF_ERROR != DGifGetLine(fGif, fSrcBuffer.get(), fFrameRect.width()); |
| } |
| |
| /* |
| * Initiates the gif decode |
| */ |
| SkCodec::Result SkGifCodec::onGetPixels(const SkImageInfo& dstInfo, |
| void* dst, size_t dstRowBytes, |
| const Options& opts, |
| SkPMColor* inputColorPtr, |
| int* inputColorCount, |
| int* rowsDecoded) { |
| Result result = this->prepareToDecode(dstInfo, inputColorPtr, inputColorCount, opts); |
| if (kSuccess != result) { |
| return result; |
| } |
| |
| if (dstInfo.dimensions() != this->getInfo().dimensions()) { |
| return gif_error("Scaling not supported.\n", kInvalidScale); |
| } |
| |
| // Initialize the swizzler |
| if (fFrameIsSubset) { |
| // Fill the background |
| SkSampler::Fill(dstInfo, dst, dstRowBytes, |
| this->getFillValue(dstInfo.colorType(), dstInfo.alphaType()), |
| opts.fZeroInitialized); |
| } |
| |
| // Iterate over rows of the input |
| for (int y = fFrameRect.top(); y < fFrameRect.bottom(); y++) { |
| if (!this->readRow()) { |
| *rowsDecoded = y; |
| return gif_error("Could not decode line.\n", kIncompleteInput); |
| } |
| void* dstRow = SkTAddOffset<void>(dst, dstRowBytes * this->outputScanline(y)); |
| fSwizzler->swizzle(dstRow, fSrcBuffer.get()); |
| } |
| return kSuccess; |
| } |
| |
| // FIXME: This is similar to the implementation for bmp and png. Can we share more code or |
| // possibly make this non-virtual? |
| uint32_t SkGifCodec::onGetFillValue(SkColorType colorType, SkAlphaType alphaType) const { |
| const SkPMColor* colorPtr = get_color_ptr(fColorTable.get()); |
| return get_color_table_fill_value(colorType, colorPtr, fFillIndex); |
| } |
| |
| SkCodec::Result SkGifCodec::onStartScanlineDecode(const SkImageInfo& dstInfo, |
| const SkCodec::Options& opts, SkPMColor inputColorPtr[], int* inputColorCount) { |
| return this->prepareToDecode(dstInfo, inputColorPtr, inputColorCount, this->options()); |
| } |
| |
| void SkGifCodec::handleScanlineFrame(int count, int* rowsBeforeFrame, int* rowsInFrame) { |
| if (fFrameIsSubset) { |
| const int currRow = this->currScanline(); |
| |
| // The number of rows that remain to be skipped before reaching rows that we |
| // actually must decode into. |
| // This must be at least zero. We also make sure that it is less than or |
| // equal to count, since we will skip at most count rows. |
| *rowsBeforeFrame = SkTMin(count, SkTMax(0, fFrameRect.top() - currRow)); |
| |
| // Rows left to decode once we reach the start of the frame. |
| const int rowsLeft = count - *rowsBeforeFrame; |
| |
| // Count the number of that extend beyond the bottom of the frame. We do not |
| // need to decode into these rows. |
| const int rowsAfterFrame = SkTMax(0, currRow + rowsLeft - fFrameRect.bottom()); |
| |
| // Set the actual number of source rows that we need to decode. |
| *rowsInFrame = rowsLeft - rowsAfterFrame; |
| } else { |
| *rowsBeforeFrame = 0; |
| *rowsInFrame = count; |
| } |
| } |
| |
| int SkGifCodec::onGetScanlines(void* dst, int count, size_t rowBytes) { |
| int rowsBeforeFrame; |
| int rowsInFrame; |
| this->handleScanlineFrame(count, &rowsBeforeFrame, &rowsInFrame); |
| |
| if (fFrameIsSubset) { |
| // Fill the requested rows |
| SkImageInfo fillInfo = this->dstInfo().makeWH(this->dstInfo().width(), count); |
| uint32_t fillValue = this->onGetFillValue(this->dstInfo().colorType(), |
| this->dstInfo().alphaType()); |
| fSwizzler->fill(fillInfo, dst, rowBytes, fillValue, this->options().fZeroInitialized); |
| |
| // Start to write pixels at the start of the image frame |
| dst = SkTAddOffset<void>(dst, rowBytes * rowsBeforeFrame); |
| } |
| |
| for (int i = 0; i < rowsInFrame; i++) { |
| if (!this->readRow()) { |
| return i + rowsBeforeFrame; |
| } |
| fSwizzler->swizzle(dst, fSrcBuffer.get()); |
| dst = SkTAddOffset<void>(dst, rowBytes); |
| } |
| |
| return count; |
| } |
| |
| bool SkGifCodec::onSkipScanlines(int count) { |
| int rowsBeforeFrame; |
| int rowsInFrame; |
| this->handleScanlineFrame(count, &rowsBeforeFrame, &rowsInFrame); |
| |
| for (int i = 0; i < rowsInFrame; i++) { |
| if (!this->readRow()) { |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| |
| SkCodec::SkScanlineOrder SkGifCodec::onGetScanlineOrder() const { |
| if (fGif->Image.Interlace) { |
| return kOutOfOrder_SkScanlineOrder; |
| } |
| return kTopDown_SkScanlineOrder; |
| } |
| |
| int SkGifCodec::onOutputScanline(int inputScanline) const { |
| if (fGif->Image.Interlace) { |
| if (inputScanline < fFrameRect.top() || inputScanline >= fFrameRect.bottom()) { |
| return inputScanline; |
| } |
| return get_output_row_interlaced(inputScanline - fFrameRect.top(), fFrameRect.height()) + |
| fFrameRect.top(); |
| } |
| return inputScanline; |
| } |
