| /* |
| * 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 "SkCodec_libgif.h" |
| #include "SkCodecPriv.h" |
| #include "SkColorPriv.h" |
| #include "SkColorTable.h" |
| #include "SkGifInterlaceIter.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(SkStream* stream) { |
| char buf[GIF_STAMP_LEN]; |
| if (stream->read(buf, GIF_STAMP_LEN) == 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; |
| } |
| |
| /* |
| * Warning reporting function |
| */ |
| static void gif_warning(const char* msg) { |
| SkCodecPrintf("Gif Warning: %s\n", msg); |
| } |
| |
| /* |
| * 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) { |
| #if GIFLIB_MAJOR < 5 |
| return DGifOpen(stream, read_bytes_callback); |
| #else |
| return DGifOpen(stream, read_bytes_callback, NULL); |
| #endif |
| } |
| |
| /* |
| * This function cleans up the gif object after the decode completes |
| * It is used in a SkAutoTCallIProc template |
| */ |
| void SkGifCodec::CloseGif(GifFileType* gif) { |
| #if GIFLIB_MAJOR < 5 || (GIFLIB_MAJOR == 5 && GIFLIB_MINOR == 0) |
| DGifCloseFile(gif); |
| #else |
| DGifCloseFile(gif, NULL); |
| #endif |
| } |
| |
| /* |
| * This function free extension data that has been saved to assist the image |
| * decoder |
| */ |
| void SkGifCodec::FreeExtension(SavedImage* image) { |
| if (NULL != image->ExtensionBlocks) { |
| #if GIFLIB_MAJOR < 5 |
| FreeExtension(image); |
| #else |
| GifFreeExtensions(&image->ExtensionBlockCount, &image->ExtensionBlocks); |
| #endif |
| } |
| } |
| |
| /* |
| * 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; |
| } |
| |
| /* |
| * 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 NULL, |
| * codecOut will be set to a new SkGifCodec. |
| * |
| * @param gifOut |
| * If it returned true, and codecOut was NULL, |
| * gifOut must be non-NULL 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 (NULL == gif) { |
| gif_error("DGifOpen failed.\n"); |
| return false; |
| } |
| |
| if (NULL != codecOut) { |
| // Get fields from header |
| const int32_t width = gif->SWidth; |
| const int32_t height = gif->SHeight; |
| if (width <= 0 || height <= 0) { |
| gif_error("Invalid dimensions.\n"); |
| return false; |
| } |
| |
| // Return the codec |
| // kIndex is the most natural color type for gifs, so we set this as |
| // the default. |
| // Many gifs specify a color table index for transparent pixels. Every |
| // other pixel is guaranteed to be opaque. Despite this, because of the |
| // possiblity of transparent pixels, we cannot assume that the image is |
| // opaque. We have the option to set the alpha type as 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. |
| const SkImageInfo& imageInfo = SkImageInfo::Make(width, height, |
| kIndex_8_SkColorType, kPremul_SkAlphaType); |
| *codecOut = SkNEW_ARGS(SkGifCodec, (imageInfo, streamDeleter.detach(), gif.detach())); |
| } else { |
| SkASSERT(NULL != 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 = NULL; |
| if (ReadHeader(stream, &codec, NULL)) { |
| return codec; |
| } |
| return NULL; |
| } |
| |
| SkGifCodec::SkGifCodec(const SkImageInfo& srcInfo, SkStream* stream, |
| GifFileType* gif) |
| : INHERITED(srcInfo, stream) |
| , fGif(gif) |
| {} |
| |
| /* |
| * Checks if the conversion between the input image and the requested output |
| * image has been implemented |
| */ |
| static bool conversion_possible(const SkImageInfo& dst, |
| const SkImageInfo& src) { |
| // Ensure that the profile type is unchanged |
| if (dst.profileType() != src.profileType()) { |
| return false; |
| } |
| |
| // Check for supported color and alpha types |
| switch (dst.colorType()) { |
| case kN32_SkColorType: |
| return kPremul_SkAlphaType == dst.alphaType() || |
| kUnpremul_SkAlphaType == dst.alphaType(); |
| case kIndex_8_SkColorType: |
| return kPremul_SkAlphaType == dst.alphaType() || |
| kUnpremul_SkAlphaType == dst.alphaType(); |
| default: |
| return false; |
| } |
| } |
| |
| /* |
| * Initiates the gif decode |
| */ |
| SkCodec::Result SkGifCodec::onGetPixels(const SkImageInfo& dstInfo, |
| void* dst, size_t dstRowBytes, |
| const Options& opts, |
| SkPMColor* inputColorPtr, |
| int* inputColorCount) { |
| // Rewind if necessary |
| SkCodec::RewindState rewindState = this->rewindIfNeeded(); |
| if (rewindState == kCouldNotRewind_RewindState) { |
| return kCouldNotRewind; |
| } else if (rewindState == kRewound_RewindState) { |
| GifFileType* gifOut = NULL; |
| if (!ReadHeader(this->stream(), NULL, &gifOut)) { |
| return kCouldNotRewind; |
| } else { |
| SkASSERT(NULL != gifOut); |
| fGif.reset(gifOut); |
| } |
| } |
| |
| // Check for valid input parameters |
| if (dstInfo.dimensions() != this->getInfo().dimensions()) { |
| return gif_error("Scaling not supported.\n", kInvalidScale); |
| } |
| if (!conversion_possible(dstInfo, this->getInfo())) { |
| return gif_error("Cannot convert input type to output type.\n", |
| kInvalidConversion); |
| } |
| |
| // 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 = NULL; |
| saveExt.ExtensionBlockCount = 0; |
| GifByteType* extData; |
| #if GIFLIB_MAJOR >= 5 |
| int32_t extFunction; |
| #endif |
| |
| // 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. |
| const int32_t width = dstInfo.width(); |
| const int32_t height = dstInfo.height(); |
| GifRecordType recordType; |
| do { |
| // Get the current record type |
| if (GIF_ERROR == DGifGetRecordType(fGif, &recordType)) { |
| return gif_error("DGifGetRecordType failed.\n", kInvalidInput); |
| } |
| |
| switch (recordType) { |
| case IMAGE_DESC_RECORD_TYPE: { |
| // Read the image descriptor |
| if (GIF_ERROR == DGifGetImageDesc(fGif)) { |
| return gif_error("DGifGetImageDesc failed.\n", |
| kInvalidInput); |
| } |
| |
| // If reading the image descriptor is successful, the image |
| // count will be incremented |
| SkASSERT(fGif->ImageCount >= 1); |
| SavedImage* image = &fGif->SavedImages[fGif->ImageCount - 1]; |
| |
| // Process the descriptor |
| const GifImageDesc& desc = image->ImageDesc; |
| int32_t imageLeft = desc.Left; |
| int32_t imageTop = desc.Top; |
| int32_t innerWidth = desc.Width; |
| int32_t innerHeight = desc.Height; |
| // Fail on non-positive dimensions |
| if (innerWidth <= 0 || innerHeight <= 0) { |
| return gif_error("Invalid dimensions for inner image.\n", |
| kInvalidInput); |
| } |
| // Treat the following cases as warnings and try to fix |
| if (innerWidth > width) { |
| gif_warning("Inner image too wide, shrinking.\n"); |
| innerWidth = width; |
| imageLeft = 0; |
| } else if (imageLeft + innerWidth > width) { |
| gif_warning("Shifting inner image to left to fit.\n"); |
| imageLeft = width - innerWidth; |
| } else if (imageLeft < 0) { |
| gif_warning("Shifting image to right to fit\n"); |
| imageLeft = 0; |
| } |
| if (innerHeight > height) { |
| gif_warning("Inner image too tall, shrinking.\n"); |
| innerHeight = height; |
| imageTop = 0; |
| } else if (imageTop + innerHeight > height) { |
| gif_warning("Shifting inner image up to fit.\n"); |
| imageTop = height - innerHeight; |
| } else if (imageTop < 0) { |
| gif_warning("Shifting image down to fit\n"); |
| imageTop = 0; |
| } |
| |
| // Create a color table to store colors the giflib colorMap |
| SkPMColor alternateColorPtr[256]; |
| SkPMColor* colorTable; |
| SkColorType dstColorType = dstInfo.colorType(); |
| if (kIndex_8_SkColorType == dstColorType) { |
| SkASSERT(NULL != inputColorPtr); |
| SkASSERT(NULL != inputColorCount); |
| colorTable = inputColorPtr; |
| } else { |
| colorTable = alternateColorPtr; |
| } |
| |
| // Set up the color table |
| uint32_t colorCount = 0; |
| // Allocate maximum storage to deal with invalid indices safely |
| const uint32_t maxColors = 256; |
| ColorMapObject* colorMap = fGif->Image.ColorMap; |
| // If there is no local color table, use the global color table |
| if (NULL == colorMap) { |
| colorMap = fGif->SColorMap; |
| } |
| if (NULL != colorMap) { |
| colorCount = colorMap->ColorCount; |
| SkASSERT(colorCount == |
| (unsigned) (1 << (colorMap->BitsPerPixel))); |
| SkASSERT(colorCount <= 256); |
| for (uint32_t i = 0; i < colorCount; i++) { |
| colorTable[i] = SkPackARGB32(0xFF, |
| colorMap->Colors[i].Red, |
| colorMap->Colors[i].Green, |
| colorMap->Colors[i].Blue); |
| } |
| } |
| |
| // This is used to fill unspecified pixels in the image data. |
| uint32_t fillIndex = fGif->SBackGroundColor; |
| ZeroInitialized zeroInit = opts.fZeroInitialized; |
| |
| // Gifs have the option to specify the color at a single |
| // index of the color table as transparent. |
| { |
| // Get the transparent index. If the return value of this |
| // function is greater than the colorCount, we know that |
| // there is no valid transparent color in the color table. |
| // This occurs if there is no graphics control extension or |
| // if the index specified by the graphics control extension |
| // is out of range. |
| uint32_t transIndex = find_trans_index(saveExt); |
| |
| if (transIndex < colorCount) { |
| colorTable[transIndex] = SK_ColorTRANSPARENT; |
| // If there is a transparent index, we also use this as |
| // the fill index. |
| fillIndex = transIndex; |
| } else if (fillIndex >= colorCount) { |
| // If the fill index is invalid, we default to 0. This |
| // behavior is unspecified but matches SkImageDecoder. |
| fillIndex = 0; |
| } |
| } |
| |
| // Check if we can skip filling the background of the image. We |
| // may be able to if the memory is zero initialized. |
| bool skipBackground = |
| ((kN32_SkColorType == dstColorType && colorTable[fillIndex] == 0) || |
| (kIndex_8_SkColorType == dstColorType && fillIndex == 0)) && |
| kYes_ZeroInitialized == zeroInit; |
| |
| |
| // 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++) { |
| colorTable[i] = colorTable[fillIndex]; |
| } |
| |
| // Check if image is only a subset of the image frame |
| SkAutoTDelete<SkSwizzler> swizzler(NULL); |
| if (innerWidth < width || innerHeight < height) { |
| |
| // Modify the destination info |
| const SkImageInfo subsetDstInfo = |
| dstInfo.makeWH(innerWidth, innerHeight); |
| |
| // Fill the destination with the fill color |
| // FIXME: This may not be the behavior that we want for |
| // animated gifs where we draw on top of the |
| // previous frame. |
| if (!skipBackground) { |
| SkSwizzler::Fill(dst, dstInfo, dstRowBytes, height, fillIndex, colorTable); |
| } |
| |
| // Modify the dst pointer |
| const int32_t dstBytesPerPixel = |
| SkColorTypeBytesPerPixel(dstColorType); |
| void* subsetDst = SkTAddOffset<void*>(dst, |
| dstRowBytes * imageTop + |
| dstBytesPerPixel * imageLeft); |
| |
| // Create the subset swizzler |
| swizzler.reset(SkSwizzler::CreateSwizzler( |
| SkSwizzler::kIndex, colorTable, subsetDstInfo, |
| subsetDst, dstRowBytes, zeroInit)); |
| } else { |
| // Create the fully dimensional swizzler |
| swizzler.reset(SkSwizzler::CreateSwizzler( |
| SkSwizzler::kIndex, colorTable, dstInfo, dst, |
| dstRowBytes, zeroInit)); |
| } |
| |
| // Stores output from dgiflib and input to the swizzler |
| SkAutoTDeleteArray<uint8_t> |
| buffer(SkNEW_ARRAY(uint8_t, innerWidth)); |
| |
| // Check the interlace flag and iterate over rows of the input |
| if (fGif->Image.Interlace) { |
| // In interlace mode, the rows of input are rearranged in |
| // the output image. We use an iterator to take care of |
| // the rearranging. |
| SkGifInterlaceIter iter(innerHeight); |
| for (int32_t y = 0; y < innerHeight; y++) { |
| if (GIF_ERROR == DGifGetLine(fGif, buffer.get(), |
| innerWidth)) { |
| // Recover from error by filling remainder of image |
| if (!skipBackground) { |
| memset(buffer.get(), fillIndex, innerWidth); |
| for (; y < innerHeight; y++) { |
| swizzler->next(buffer.get(), iter.nextY()); |
| } |
| } |
| return gif_error(SkStringPrintf( |
| "Could not decode line %d of %d.\n", |
| y, height - 1).c_str(), kIncompleteInput); |
| } |
| swizzler->next(buffer.get(), iter.nextY()); |
| } |
| } else { |
| // Standard mode |
| for (int32_t y = 0; y < innerHeight; y++) { |
| if (GIF_ERROR == DGifGetLine(fGif, buffer.get(), |
| innerWidth)) { |
| if (!skipBackground) { |
| SkSwizzler::Fill(swizzler->getDstRow(), dstInfo, dstRowBytes, |
| innerHeight - y, fillIndex, colorTable); |
| } |
| return gif_error(SkStringPrintf( |
| "Could not decode line %d of %d.\n", |
| y, height - 1).c_str(), kIncompleteInput); |
| } |
| swizzler->next(buffer.get()); |
| } |
| } |
| |
| // 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 GIFLIB_MAJOR < 5 |
| if (GIF_ERROR == |
| DGifGetExtension(fGif, &saveExt.Function, &extData)) { |
| #else |
| if (GIF_ERROR == |
| DGifGetExtension(fGif, &extFunction, &extData)) { |
| #endif |
| return gif_error("Could not get extension.\n", |
| kIncompleteInput); |
| } |
| |
| // Create an extension block with our data |
| while (NULL != extData) { |
| // Add a single block |
| #if GIFLIB_MAJOR < 5 |
| if (GIF_ERROR == AddExtensionBlock(&saveExt, extData[0], |
| &extData[1])) { |
| #else |
| if (GIF_ERROR == |
| GifAddExtensionBlock(&saveExt.ExtensionBlockCount, |
| &saveExt.ExtensionBlocks, extFunction, extData[0], |
| &extData[1])) { |
| #endif |
| return gif_error("Could not add extension block.\n", |
| kIncompleteInput); |
| } |
| // Move to the next block |
| if (GIF_ERROR == DGifGetExtensionNext(fGif, &extData)) { |
| return gif_error("Could not get next extension.\n", |
| kIncompleteInput); |
| } |
| #if GIFLIB_MAJOR < 5 |
| saveExt.Function = 0; |
| #endif |
| } |
| break; |
| |
| // Signals the end of the gif file |
| case TERMINATE_RECORD_TYPE: |
| break; |
| |
| default: |
| // giflib returns an error code if the record type is not known. |
| // We should catch this error immediately. |
| SkASSERT(false); |
| break; |
| } |
| } while (TERMINATE_RECORD_TYPE != recordType); |
| |
| return gif_error("Could not find any images to decode in gif file.\n", |
| kInvalidInput); |
| } |
