diff options
Diffstat (limited to 'src/plugins/imageformats/gif/qgifhandler.cpp')
| -rw-r--r-- | src/plugins/imageformats/gif/qgifhandler.cpp | 235 |
1 files changed, 234 insertions, 1 deletions
diff --git a/src/plugins/imageformats/gif/qgifhandler.cpp b/src/plugins/imageformats/gif/qgifhandler.cpp index 6f049be..6cd7841 100644 --- a/src/plugins/imageformats/gif/qgifhandler.cpp +++ b/src/plugins/imageformats/gif/qgifhandler.cpp @@ -72,6 +72,7 @@ public: int decode(QImage *image, const uchar* buffer, int length, int *nextFrameDelay, int *loopCount, QSize *nextSize); + static int imageCount(QIODevice *device); bool newFrame; bool partialNewFrame; @@ -645,6 +646,234 @@ int QGIFFormat::decode(QImage *image, const uchar *buffer, int length, return initial-length; } +/*! + Returns the number of images that can be read from \a device. +*/ + +int QGIFFormat::imageCount(QIODevice *device) +{ + if (!device) + return 0; + + qint64 oldPos = device->pos(); + if (!device->seek(0)) + return 0; + + int colorCount = 0; + int localColorCount = 0; + int globalColorCount = 0; + int colorReadCount = 0; + bool localColormap = false; + bool globalColormap = false; + int count = 0; + int blockSize = 0; + bool done = false; + uchar hold[16]; + int imageCount = 0; + State state = Header; + + const int readBufferSize = 40960; // 40k read buffer + QByteArray readBuffer(device->read(readBufferSize)); + + if (readBuffer.isEmpty()) + return 0; + + // this is a specialized version of the state machine from decode(), + // which doesn't do any image decoding or mallocing, and has an + // optimized way of skipping SkipBlocks, ImageDataBlocks and + // Global/LocalColorMaps. + + while (!readBuffer.isEmpty()) { + int length = readBuffer.size(); + const uchar *buffer = (const uchar *) readBuffer.constData(); + while (!done && length) { + length--; + uchar ch = *buffer++; + switch (state) { + case Header: + hold[count++] = ch; + if (count == 6) { + state = LogicalScreenDescriptor; + count = 0; + } + break; + case LogicalScreenDescriptor: + hold[count++] = ch; + if (count == 7) { + globalColormap = !!(hold[4] & 0x80); + globalColorCount = 2 << (hold[4] & 0x7); + count = 0; + colorCount = globalColorCount; + if (globalColormap) { + int colorTableSize = 3 * globalColorCount; + if (length >= colorTableSize) { + // skip the global color table in one go + length -= colorTableSize; + buffer += colorTableSize; + state = Introducer; + } else { + colorReadCount = 0; + state = GlobalColorMap; + } + } else { + state=Introducer; + } + } + break; + case GlobalColorMap: + case LocalColorMap: + hold[count++] = ch; + if (count == 3) { + if (++colorReadCount >= colorCount) { + if (state == LocalColorMap) + state = TableImageLZWSize; + else + state = Introducer; + } + count = 0; + } + break; + case Introducer: + hold[count++] = ch; + switch (ch) { + case 0x2c: + state = ImageDescriptor; + break; + case 0x21: + state = ExtensionLabel; + break; + case 0x3b: + state = Done; + break; + default: + done = true; + state = Error; + } + break; + case ImageDescriptor: + hold[count++] = ch; + if (count == 10) { + localColormap = !!(hold[9] & 0x80); + localColorCount = localColormap ? (2 << (hold[9] & 0x7)) : 0; + if (localColorCount) + colorCount = localColorCount; + else + colorCount = globalColorCount; + imageCount++; + + count = 0; + if (localColormap) { + int colorTableSize = 3 * localColorCount; + if (length >= colorTableSize) { + // skip the local color table in one go + length -= colorTableSize; + buffer += colorTableSize; + state = TableImageLZWSize; + } else { + colorReadCount = 0; + state = LocalColorMap; + } + } else { + state = TableImageLZWSize; + } + } + break; + case TableImageLZWSize: + if (ch > max_lzw_bits) + state = Error; + else + state = ImageDataBlockSize; + count = 0; + break; + case ImageDataBlockSize: + blockSize = ch; + if (blockSize) { + if (length >= blockSize) { + // we can skip the block in one go + length -= blockSize; + buffer += blockSize; + count = 0; + } else { + state = ImageDataBlock; + } + } else { + state = Introducer; + } + break; + case ImageDataBlock: + ++count; + if (count == blockSize) { + count = 0; + state = ImageDataBlockSize; + } + break; + case ExtensionLabel: + switch (ch) { + case 0xf9: + state = GraphicControlExtension; + break; + case 0xff: + state = ApplicationExtension; + break; + default: + state = SkipBlockSize; + } + count = 0; + break; + case ApplicationExtension: + if (count < 11) + hold[count] = ch; + ++count; + if (count == hold[0] + 1) { + state = SkipBlockSize; + count = 0; + } + break; + case GraphicControlExtension: + if (count < 5) + hold[count] = ch; + ++count; + if (count == hold[0] + 1) { + count = 0; + state = SkipBlockSize; + } + break; + case NetscapeExtensionBlockSize: // fallthrough + case SkipBlockSize: + blockSize = ch; + count = 0; + if (blockSize) { + if (length >= blockSize) { + // we can skip the block in one go + length -= blockSize; + buffer += blockSize; + } else { + state = SkipBlock; + } + } else { + state = Introducer; + } + break; + case NetscapeExtensionBlock: // fallthrough + case SkipBlock: + ++count; + if (count == blockSize) + state = SkipBlockSize; + break; + case Done: + done = true; + break; + case Error: + device->seek(oldPos); + return 0; + } + } + readBuffer = device->read(readBufferSize); + } + device->seek(oldPos); + return imageCount; +} + void QGIFFormat::fillRect(QImage *image, int col, int row, int w, int h, QRgb color) { if (w>0) { @@ -766,6 +995,7 @@ QGifHandler::QGifHandler() loopCnt = 0; frameNumber = -1; nextSize = QSize(); + imageCnt = -1; } QGifHandler::~QGifHandler() @@ -883,7 +1113,10 @@ int QGifHandler::nextImageDelay() const int QGifHandler::imageCount() const { - return 0; // Don't know + if (imageCnt != -1) + return imageCnt; + imageCnt = QGIFFormat::imageCount(device()); + return imageCnt; } int QGifHandler::loopCount() const |