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Diffstat (limited to 'WebCore/platform/image-decoders/skia/BMPImageReader.cpp')
| -rw-r--r-- | WebCore/platform/image-decoders/skia/BMPImageReader.cpp | 835 |
1 files changed, 835 insertions, 0 deletions
diff --git a/WebCore/platform/image-decoders/skia/BMPImageReader.cpp b/WebCore/platform/image-decoders/skia/BMPImageReader.cpp new file mode 100644 index 0000000..829b107 --- /dev/null +++ b/WebCore/platform/image-decoders/skia/BMPImageReader.cpp @@ -0,0 +1,835 @@ +/* + * Copyright (c) 2008, 2009, Google Inc. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * * Redistributions in binary form must reproduce the above + * copyright notice, this list of conditions and the following disclaimer + * in the documentation and/or other materials provided with the + * distribution. + * * Neither the name of Google Inc. nor the names of its + * contributors may be used to endorse or promote products derived from + * this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "config.h" +#include "BMPImageReader.h" + +namespace WebCore { + +BMPImageReader::BMPImageReader() + : m_decodedOffset(0) + , m_headerOffset(0) + , m_imgDataOffset(0) + , m_andMaskState(None) + , m_isOS21x(false) + , m_isOS22x(false) + , m_isTopDown(false) + , m_needToProcessBitmasks(false) + , m_needToProcessColorTable(false) + , m_tableSizeInBytes(0) + , m_seenNonZeroAlphaPixel(false) + , m_seenZeroAlphaPixel(false) +{ + m_frameBufferCache.resize(1); + + // Clue-in decodeBMP() that we need to detect the correct info header size. + memset(&m_infoHeader, 0, sizeof(m_infoHeader)); +} + +void BMPImageReader::setData(SharedBuffer* data, bool allDataReceived) +{ + ImageDecoder::setData(data, allDataReceived); + + // NOTE: This function intentionally uses frameBufferAtIndex() instead of + // checking m_frameBufferCache.first() directly, so that it will do the + // right thing for ICOImageDecoder, which needs to override this accessor + // to support ICOs which contain PNGs. + + // Return quickly when we can't do any more work. + if (m_failed || data->isEmpty() + || (frameBufferAtIndex(0)->status() == RGBA32Buffer::FrameComplete)) + return; + + // Decode as much as we can. This assumes |data| starts at the beginning + // of the image data, rather than containing just the latest chunk. + decodeImage(data); + if (m_failed) { + // Handle failure before getting the framebuffer below. + m_colorTable.clear(); + return; + } + + // If we got all the data but couldn't finish decoding, fail. + const bool finished = + (frameBufferAtIndex(0)->status() == RGBA32Buffer::FrameComplete); + if (allDataReceived && !finished) + m_failed = true; + + // Release the color table when we no longer need it. + if (finished || m_failed) + m_colorTable.clear(); +} + +RGBA32Buffer* BMPImageReader::frameBufferAtIndex(size_t index) +{ + return index ? 0 : &m_frameBufferCache.first(); +} + +void BMPImageReader::decodeBMP(SharedBuffer* data) +{ + // Calculate size of info header. + if (!m_infoHeader.biSize && !getInfoHeaderSize(data)) + return; + + // Read and process info header. + if ((m_decodedOffset < (m_headerOffset + m_infoHeader.biSize)) + && !processInfoHeader(data)) + return; + + // Read and process the bitmasks, if needed. + if (m_needToProcessBitmasks && !processBitmasks(data)) + return; + + // Read and process the color table, if needed. + if (m_needToProcessColorTable && !processColorTable(data)) + return; + + // Initialize frame buffer state, if needed. + if (m_frameBufferCache.first().status() == RGBA32Buffer::FrameEmpty) { + m_frameBufferCache.first().setRect(IntRect(IntPoint(), size())); + m_frameBufferCache.first().setStatus(RGBA32Buffer::FramePartial); + if (!m_frameBufferCache.first().setSize(m_infoHeader.biWidth, + m_infoHeader.biHeight)) { + // Unable to allocate. + m_failed = true; + return; + } + + // setSize() calls eraseARGB(), which resets the alpha flag, so we force + // it back to false here. We'll set it true below in all cases where + // these 0s could actually show through. + m_frameBufferCache.first().setHasAlpha(false); + if (!m_isTopDown) + m_coord.setY(size().height() - 1); + } + + // Decode the data. + if ((m_andMaskState != Decoding) && !pastEndOfImage(0)) { + if ((m_infoHeader.biCompression == RLE4) + || (m_infoHeader.biCompression == RLE8) + || (m_infoHeader.biCompression == RLE24)) { + if (!processRLEData(data)) + return; + } else if (!processNonRLEData(data, false, 0)) + return; + } + + // If the image has an AND mask and there was no alpha data, process the + // mask. + if ((m_andMaskState == NotYetDecoded) + && !m_frameBufferCache.first().hasAlpha()) { + // Reset decoding coordinates to start of image. + m_coord.setX(0); + m_coord.setY(m_isTopDown ? 0 : (size().height() - 1)); + + // The AND mask is stored as 1-bit data. + m_infoHeader.biBitCount = 1; + + m_andMaskState = Decoding; + } + if ((m_andMaskState == Decoding) && !processNonRLEData(data, false, 0)) + return; + + // Done! + m_frameBufferCache.first().setStatus(RGBA32Buffer::FrameComplete); +} + +bool BMPImageReader::getInfoHeaderSize(SharedBuffer* data) +{ + // Get size of info header. + ASSERT(m_decodedOffset == m_headerOffset); + if ((m_decodedOffset > data->size()) + || ((data->size() - m_decodedOffset) < 4)) + return false; + m_infoHeader.biSize = readUint32(data, 0); + // Don't increment m_decodedOffset here, it just makes the code in + // processInfoHeader() more confusing. + + // Don't allow the header to overflow (which would be harmless here, but + // problematic or at least confusing in other places), or to overrun the + // image data. + if (((m_headerOffset + m_infoHeader.biSize) < m_headerOffset) + || (m_imgDataOffset + && (m_imgDataOffset < (m_headerOffset + m_infoHeader.biSize)))) { + m_failed = true; + return false; + } + + // See if this is a header size we understand: + // OS/2 1.x: 12 + if (m_infoHeader.biSize == 12) + m_isOS21x = true; + // Windows V3: 40 + else if ((m_infoHeader.biSize == 40) || isWindowsV4Plus()) + ; + // OS/2 2.x: any multiple of 4 between 16 and 64, inclusive, or 42 or 46 + else if ((m_infoHeader.biSize >= 16) && (m_infoHeader.biSize <= 64) + && (((m_infoHeader.biSize & 3) == 0) || (m_infoHeader.biSize == 42) + || (m_infoHeader.biSize == 46))) + m_isOS22x = true; + else + m_failed = true; + + return !m_failed; +} + +bool BMPImageReader::processInfoHeader(SharedBuffer* data) +{ + // Read info header. + ASSERT(m_decodedOffset == m_headerOffset); + if ((m_decodedOffset > data->size()) + || ((data->size() - m_decodedOffset) < m_infoHeader.biSize) + || !readInfoHeader(data)) + return false; + m_decodedOffset += m_infoHeader.biSize; + + // Sanity-check header values. + if (!isInfoHeaderValid()) { + m_failed = true; + return false; + } + + // Make our size available to the caller. + if (!setSize(m_infoHeader.biWidth, m_infoHeader.biHeight)) { + m_failed = true; + return false; + } + + // For paletted images, bitmaps can set biClrUsed to 0 to mean "all + // colors", so set it to the maximum number of colors for this bit depth. + // Also do this for bitmaps that put too large a value here. + if (m_infoHeader.biBitCount < 16) { + const uint32_t maxColors = + static_cast<uint32_t>(1) << m_infoHeader.biBitCount; + if ((m_infoHeader.biClrUsed == 0) + || (m_infoHeader.biClrUsed > maxColors)) + m_infoHeader.biClrUsed = maxColors; + } + + // For any bitmaps that set their BitCount to the wrong value, reset the + // counts now that we've calculated the number of necessary colors, since + // other code relies on this value being correct. + if (m_infoHeader.biCompression == RLE8) + m_infoHeader.biBitCount = 8; + else if (m_infoHeader.biCompression == RLE4) + m_infoHeader.biBitCount = 4; + + // Tell caller what still needs to be processed. + if (m_infoHeader.biBitCount >= 16) + m_needToProcessBitmasks = true; + else if (m_infoHeader.biBitCount > 0) + m_needToProcessColorTable = true; + + return true; +} + +bool BMPImageReader::readInfoHeader(SharedBuffer* data) +{ + // Pre-initialize some fields that not all headers set. + m_infoHeader.biCompression = RGB; + m_infoHeader.biClrUsed = 0; + + if (m_isOS21x) { + m_infoHeader.biWidth = readUint16(data, 4); + m_infoHeader.biHeight = readUint16(data, 6); + ASSERT(m_andMaskState == None); // ICO is a Windows format, not OS/2! + m_infoHeader.biBitCount = readUint16(data, 10); + return true; + } + + m_infoHeader.biWidth = readUint32(data, 4); + m_infoHeader.biHeight = readUint32(data, 8); + if (m_andMaskState != None) + m_infoHeader.biHeight /= 2; + m_infoHeader.biBitCount = readUint16(data, 14); + + // Read compression type, if present. + if (m_infoHeader.biSize >= 20) { + uint32_t biCompression = readUint32(data, 16); + + // Detect OS/2 2.x-specific compression types. + if ((biCompression == 3) && (m_infoHeader.biBitCount == 1)) { + m_infoHeader.biCompression = HUFFMAN1D; + m_isOS22x = true; + } else if ((biCompression == 4) && (m_infoHeader.biBitCount == 24)) { + m_infoHeader.biCompression = RLE24; + m_isOS22x = true; + } else if (biCompression > 5) { + // Some type we don't understand. + m_failed = true; + return false; + } else + m_infoHeader.biCompression = static_cast<CompressionType>(biCompression); + } + + // Read colors used, if present. + if (m_infoHeader.biSize >= 36) + m_infoHeader.biClrUsed = readUint32(data, 32); + + // Windows V4+ can safely read the four bitmasks from 40-56 bytes in, so do + // that here. If the bit depth is less than 16, these values will be + // ignored by the image data decoders. If the bit depth is at least 16 but + // the compression format isn't BITFIELDS, these values will be ignored and + // overwritten* in processBitmasks(). + // NOTE: We allow alpha here. Microsoft doesn't really document this well, + // but some BMPs appear to use it. + // + // For non-Windows V4+, m_bitMasks[] et. al will be initialized later + // during processBitmasks(). + // + // *Except the alpha channel. Bizarrely, some RGB bitmaps expect decoders + // to pay attention to the alpha mask here, so there's a special case in + // processBitmasks() that doesn't always overwrite that value. + if (isWindowsV4Plus()) { + m_bitMasks[0] = readUint32(data, 40); + m_bitMasks[1] = readUint32(data, 44); + m_bitMasks[2] = readUint32(data, 48); + m_bitMasks[3] = readUint32(data, 52); + } + + // Detect top-down BMPs. + if (m_infoHeader.biHeight < 0) { + m_isTopDown = true; + m_infoHeader.biHeight = -m_infoHeader.biHeight; + } + + return true; +} + +bool BMPImageReader::isInfoHeaderValid() const +{ + // Non-positive widths/heights are invalid. (We've already flipped the + // sign of the height for top-down bitmaps.) + if ((m_infoHeader.biWidth <= 0) || (m_infoHeader.biHeight == 0)) + return false; + + // Only Windows V3+ has top-down bitmaps. + if (m_isTopDown && (m_isOS21x || m_isOS22x)) + return false; + + // Only bit depths of 1, 4, 8, or 24 are universally supported. + if ((m_infoHeader.biBitCount != 1) && (m_infoHeader.biBitCount != 4) + && (m_infoHeader.biBitCount != 8) + && (m_infoHeader.biBitCount != 24)) { + // Windows V3+ additionally supports bit depths of 0 (for embedded + // JPEG/PNG images), 16, and 32. + if (m_isOS21x || m_isOS22x) + return false; + if ((m_infoHeader.biBitCount != 0) + && (m_infoHeader.biBitCount != 16) + && (m_infoHeader.biBitCount != 32)) + return false; + } + + // Each compression type is only valid with certain bit depths (except RGB, + // which can be used with any bit depth). Also, some formats do not + // some compression types. + switch (m_infoHeader.biCompression) { + case RGB: + if (m_infoHeader.biBitCount == 0) + return false; + break; + + case RLE8: + // Supposedly there are undocumented formats like "BitCount = 1, + // Compression = RLE4" (which means "4 bit, but with a 2-color table"), + // so also allow the paletted RLE compression types to have too low a + // bit count; we'll correct this later. + if (m_infoHeader.biBitCount == 0 || m_infoHeader.biBitCount > 8) + return false; + break; + + case RLE4: + // See comments in RLE8. + if (m_infoHeader.biBitCount == 0 || m_infoHeader.biBitCount > 4) + return false; + break; + + case BITFIELDS: + // Only valid for Windows V3+. + if (m_isOS21x || m_isOS22x) + return false; + if ((m_infoHeader.biBitCount != 16) && (m_infoHeader.biBitCount != 32)) + return false; + break; + + case JPEG: + case PNG: + // Only valid for Windows V3+. + if (m_isOS21x || m_isOS22x) + return false; + if (m_infoHeader.biBitCount != 0) + return false; + break; + + case HUFFMAN1D: + // Only valid for OS/2 2.x. + if (!m_isOS22x) + return false; + if (m_infoHeader.biBitCount != 1) + return false; + break; + + case RLE24: + // Only valid for OS/2 2.x. + if (!m_isOS22x) + return false; + if (m_infoHeader.biBitCount != 24) + return false; + break; + + default: + // Some type we don't understand. This should have been caught in + // readInfoHeader(). + ASSERT_NOT_REACHED(); + return false; + } + + // Top-down bitmaps cannot be compressed; they must be RGB or BITFIELDS. + if (m_isTopDown && (m_infoHeader.biCompression != RGB) + && (m_infoHeader.biCompression != BITFIELDS)) + return false; + + // Reject the following valid bitmap types that we don't currently bother + // decoding. Few other people decode these either, they're unlikely to be + // in much use. + // TODO(pkasting): Consider supporting these someday. + // * Bitmaps larger than 2^16 pixels in either dimension (Windows + // probably doesn't draw these well anyway, and the decoded data would + // take a lot of memory). + if ((m_infoHeader.biWidth >= (1 << 16)) + || (m_infoHeader.biHeight >= (1 << 16))) + return false; + // * Windows V3+ JPEG-in-BMP and PNG-in-BMP bitmaps (supposedly not found + // in the wild, only used to send data to printers?). + if ((m_infoHeader.biCompression == JPEG) + || (m_infoHeader.biCompression == PNG)) + return false; + // * OS/2 2.x Huffman-encoded monochrome bitmaps (see + // http://www.fileformat.info/mirror/egff/ch09_05.htm , re: "G31D" + // algorithm). + if (m_infoHeader.biCompression == HUFFMAN1D) + return false; + + return true; +} + +bool BMPImageReader::processBitmasks(SharedBuffer* data) +{ + // Create m_bitMasks[] values. + if (m_infoHeader.biCompression != BITFIELDS) { + // The format doesn't actually use bitmasks. To simplify the decode + // logic later, create bitmasks for the RGB data. For Windows V4+, + // this overwrites the masks we read from the header, which are + // supposed to be ignored in non-BITFIELDS cases. + // 16 bits: MSB <- xRRRRRGG GGGBBBBB -> LSB + // 24/32 bits: MSB <- [AAAAAAAA] RRRRRRRR GGGGGGGG BBBBBBBB -> LSB + const int numBits = (m_infoHeader.biBitCount == 16) ? 5 : 8; + for (int i = 0; i <= 2; ++i) { + m_bitMasks[i] = + ((static_cast<uint32_t>(1) << (numBits * (3 - i))) - 1) ^ + ((static_cast<uint32_t>(1) << (numBits * (2 - i))) - 1); + } + + // For Windows V4+ 32-bit RGB, don't overwrite the alpha mask from the + // header (see note in readInfoHeader()). + if (m_infoHeader.biBitCount < 32) + m_bitMasks[3] = 0; + else if (!isWindowsV4Plus()) + m_bitMasks[3] = static_cast<uint32_t>(0xff000000); + } else if (!isWindowsV4Plus()) { + // For Windows V4+ BITFIELDS mode bitmaps, this was already done when + // we read the info header. + + // Fail if we don't have enough file space for the bitmasks. + static const int SIZEOF_BITMASKS = 12; + if (((m_headerOffset + m_infoHeader.biSize + SIZEOF_BITMASKS) < (m_headerOffset + m_infoHeader.biSize)) + || (m_imgDataOffset && (m_imgDataOffset < (m_headerOffset + m_infoHeader.biSize + SIZEOF_BITMASKS)))) { + m_failed = true; + return false; + } + + // Read bitmasks. + if ((data->size() - m_decodedOffset) < SIZEOF_BITMASKS) + return false; + m_bitMasks[0] = readUint32(data, 0); + m_bitMasks[1] = readUint32(data, 4); + m_bitMasks[2] = readUint32(data, 8); + // No alpha in anything other than Windows V4+. + m_bitMasks[3] = 0; + + m_decodedOffset += SIZEOF_BITMASKS; + } + + // We've now decoded all the non-image data we care about. Skip anything + // else before the actual raster data. + if (m_imgDataOffset) + m_decodedOffset = m_imgDataOffset; + m_needToProcessBitmasks = false; + + // Check masks and set shift values. + for (int i = 0; i < 4; ++i) { + // Trim the mask to the allowed bit depth. Some Windows V4+ BMPs + // specify a bogus alpha channel in bits that don't exist in the pixel + // data (for example, bits 25-31 in a 24-bit RGB format). + if (m_infoHeader.biBitCount < 32) + m_bitMasks[i] &= ((static_cast<uint32_t>(1) << m_infoHeader.biBitCount) - 1); + + // For empty masks (common on the alpha channel, especially after the + // trimming above), quickly clear the shifts and continue, to avoid an + // infinite loop in the counting code below. + uint32_t tempMask = m_bitMasks[i]; + if (!tempMask) { + m_bitShiftsRight[i] = m_bitShiftsLeft[i] = 0; + continue; + } + + // Make sure bitmask does not overlap any other bitmasks. + for (int j = 0; j < i; ++j) { + if (tempMask & m_bitMasks[j]) { + m_failed = true; + return false; + } + } + + // Count offset into pixel data. + for (m_bitShiftsRight[i] = 0; !(tempMask & 1); tempMask >>= 1) + ++m_bitShiftsRight[i]; + + // Count size of mask. + for (m_bitShiftsLeft[i] = 8; tempMask & 1; tempMask >>= 1) + --m_bitShiftsLeft[i]; + + // Make sure bitmask is contiguous. + if (tempMask) { + m_failed = true; + return false; + } + + // Since RGBABuffer tops out at 8 bits per channel, adjust the shift + // amounts to use the most significant 8 bits of the channel. + if (m_bitShiftsLeft[i] < 0) { + m_bitShiftsRight[i] -= m_bitShiftsLeft[i]; + m_bitShiftsLeft[i] = 0; + } + } + + return true; +} + +bool BMPImageReader::processColorTable(SharedBuffer* data) +{ + m_tableSizeInBytes = m_infoHeader.biClrUsed * (m_isOS21x ? 3 : 4); + + // Fail if we don't have enough file space for the color table. + if (((m_headerOffset + m_infoHeader.biSize + m_tableSizeInBytes) < (m_headerOffset + m_infoHeader.biSize)) + || (m_imgDataOffset && (m_imgDataOffset < (m_headerOffset + m_infoHeader.biSize + m_tableSizeInBytes)))) { + m_failed = true; + return false; + } + + // Read color table. + if ((m_decodedOffset > data->size()) + || ((data->size() - m_decodedOffset) < m_tableSizeInBytes)) + return false; + m_colorTable.resize(m_infoHeader.biClrUsed); + for (size_t i = 0; i < m_infoHeader.biClrUsed; ++i) { + m_colorTable[i].rgbBlue = data->data()[m_decodedOffset++]; + m_colorTable[i].rgbGreen = data->data()[m_decodedOffset++]; + m_colorTable[i].rgbRed = data->data()[m_decodedOffset++]; + // Skip padding byte (not present on OS/2 1.x). + if (!m_isOS21x) + ++m_decodedOffset; + } + + // We've now decoded all the non-image data we care about. Skip anything + // else before the actual raster data. + if (m_imgDataOffset) + m_decodedOffset = m_imgDataOffset; + m_needToProcessColorTable = false; + + return true; +} + +bool BMPImageReader::processRLEData(SharedBuffer* data) +{ + if (m_decodedOffset > data->size()) + return false; + + // RLE decoding is poorly specified. Two main problems: + // (1) Are EOL markers necessary? What happens when we have too many + // pixels for one row? + // http://www.fileformat.info/format/bmp/egff.htm says extra pixels + // should wrap to the next line. Real BMPs I've encountered seem to + // instead expect extra pixels to be ignored until the EOL marker is + // seen, although this has only happened in a few cases and I suspect + // those BMPs may be invalid. So we only change lines on EOL (or Delta + // with dy > 0), and fail in most cases when pixels extend past the end + // of the line. + // (2) When Delta, EOL, or EOF are seen, what happens to the "skipped" + // pixels? + // http://www.daubnet.com/formats/BMP.html says these should be filled + // with color 0. However, the "do nothing" and "don't care" comments + // of other references suggest leaving these alone, i.e. letting them + // be transparent to the background behind the image. This seems to + // match how MSPAINT treats BMPs, so we do that. Note that when we + // actually skip pixels for a case like this, we need to note on the + // framebuffer that we have alpha. + + // Impossible to decode row-at-a-time, so just do things as a stream of + // bytes. + while (true) { + // Every entry takes at least two bytes; bail if there isn't enough + // data. + if ((data->size() - m_decodedOffset) < 2) + return false; + + // For every entry except EOF, we'd better not have reached the end of + // the image. + const uint8_t count = data->data()[m_decodedOffset]; + const uint8_t code = data->data()[m_decodedOffset + 1]; + if (((count != 0) || (code != 1)) && pastEndOfImage(0)) { + m_failed = true; + return false; + } + + // Decode. + if (count == 0) { + switch (code) { + case 0: // Magic token: EOL + // Skip any remaining pixels in this row. + if (m_coord.x() < size().width()) + m_frameBufferCache.first().setHasAlpha(true); + moveBufferToNextRow(); + + m_decodedOffset += 2; + break; + + case 1: // Magic token: EOF + // Skip any remaining pixels in the image. + if ((m_coord.x() < size().width()) + || (m_isTopDown ? (m_coord.y() < (size().height() - 1)) : (m_coord.y() > 0))) + m_frameBufferCache.first().setHasAlpha(true); + return true; + + case 2: { // Magic token: Delta + // The next two bytes specify dx and dy. Bail if there isn't + // enough data. + if ((data->size() - m_decodedOffset) < 4) + return false; + + // Fail if this takes us past the end of the desired row or + // past the end of the image. + const uint8_t dx = data->data()[m_decodedOffset + 2]; + const uint8_t dy = data->data()[m_decodedOffset + 3]; + if ((dx != 0) || (dy != 0)) + m_frameBufferCache.first().setHasAlpha(true); + if (((m_coord.x() + dx) > size().width()) || + pastEndOfImage(dy)) { + m_failed = true; + return false; + } + + // Skip intervening pixels. + m_coord.move(dx, m_isTopDown ? dy : -dy); + + m_decodedOffset += 4; + break; + } + + default: // Absolute mode + // |code| pixels specified as in BI_RGB, zero-padded at the end + // to a multiple of 16 bits. + // Because processNonRLEData() expects m_decodedOffset to + // point to the beginning of the pixel data, bump it past + // the escape bytes and then reset if decoding failed. + m_decodedOffset += 2; + if (!processNonRLEData(data, true, code)) { + m_decodedOffset -= 2; + return false; + } + break; + } + } else { // Encoded mode + // The following color data is repeated for |count| total pixels. + // Strangely, some BMPs seem to specify excessively large counts + // here; ignore pixels past the end of the row. + const int endX = std::min(m_coord.x() + count, size().width()); + + if (m_infoHeader.biCompression == RLE24) { + // Bail if there isn't enough data. + if ((data->size() - m_decodedOffset) < 4) + return false; + + // One BGR triple that we copy |count| times. + fillRGBA(endX, data->data()[m_decodedOffset + 3], + data->data()[m_decodedOffset + 2], code, 0xff); + m_decodedOffset += 4; + } else { + // RLE8 has one color index that gets repeated; RLE4 has two + // color indexes in the upper and lower 4 bits of the byte, + // which are alternated. + size_t colorIndexes[2] = {code, code}; + if (m_infoHeader.biCompression == RLE4) { + colorIndexes[0] = (colorIndexes[0] >> 4) & 0xf; + colorIndexes[1] &= 0xf; + } + if ((colorIndexes[0] >= m_infoHeader.biClrUsed) + || (colorIndexes[1] >= m_infoHeader.biClrUsed)) { + m_failed = true; + return false; + } + for (int which = 0; m_coord.x() < endX; ) { + setI(colorIndexes[which]); + which = !which; + } + + m_decodedOffset += 2; + } + } + } +} + +bool BMPImageReader::processNonRLEData(SharedBuffer* data, bool inRLE, int numPixels) +{ + if (m_decodedOffset > data->size()) + return false; + + if (!inRLE) + numPixels = size().width(); + + // Fail if we're being asked to decode more pixels than remain in the row. + const int endX = m_coord.x() + numPixels; + if (endX > size().width()) { + m_failed = true; + return false; + } + + // Determine how many bytes of data the requested number of pixels + // requires. + const size_t pixelsPerByte = 8 / m_infoHeader.biBitCount; + const size_t bytesPerPixel = m_infoHeader.biBitCount / 8; + const size_t unpaddedNumBytes = (m_infoHeader.biBitCount < 16) + ? ((numPixels + pixelsPerByte - 1) / pixelsPerByte) + : (numPixels * bytesPerPixel); + // RLE runs are zero-padded at the end to a multiple of 16 bits. Non-RLE + // data is in rows and is zero-padded to a multiple of 32 bits. + const size_t alignBits = inRLE ? 1 : 3; + const size_t paddedNumBytes = (unpaddedNumBytes + alignBits) & ~alignBits; + + // Decode as many rows as we can. (For RLE, where we only want to decode + // one row, we've already checked that this condition is true.) + while (!pastEndOfImage(0)) { + // Bail if we don't have enough data for the desired number of pixels. + if ((data->size() - m_decodedOffset) < paddedNumBytes) + return false; + + if (m_infoHeader.biBitCount < 16) { + // Paletted data. Pixels are stored little-endian within bytes. + // Decode pixels one byte at a time, left to right (so, starting at + // the most significant bits in the byte). + const uint8_t mask = (1 << m_infoHeader.biBitCount) - 1; + for (size_t byte = 0; byte < unpaddedNumBytes; ++byte) { + uint8_t pixelData = data->data()[m_decodedOffset + byte]; + for (size_t pixel = 0; (pixel < pixelsPerByte) && (m_coord.x() < endX); ++pixel) { + const size_t colorIndex = + (pixelData >> (8 - m_infoHeader.biBitCount)) & mask; + if (m_andMaskState == Decoding) { + // There's no way to accurately represent an AND + XOR + // operation as an RGBA image, so where the AND values + // are 1, we simply set the framebuffer pixels to fully + // transparent, on the assumption that most ICOs on the + // web will not be doing a lot of inverting. + if (colorIndex) { + setRGBA(0, 0, 0, 0); + m_frameBufferCache.first().setHasAlpha(true); + } else + m_coord.move(1, 0); + } else { + if (colorIndex >= m_infoHeader.biClrUsed) { + m_failed = true; + return false; + } + setI(colorIndex); + } + pixelData <<= m_infoHeader.biBitCount; + } + } + } else { + // RGB data. Decode pixels one at a time, left to right. + while (m_coord.x() < endX) { + const uint32_t pixel = readCurrentPixel(data, bytesPerPixel); + + // Some BMPs specify an alpha channel but don't actually use it + // (it contains all 0s). To avoid displaying these images as + // fully-transparent, decode as if images are fully opaque + // until we actually see a non-zero alpha value; at that point, + // reset any previously-decoded pixels to fully transparent and + // continue decoding based on the real alpha channel values. + // As an optimization, avoid setting "hasAlpha" to true for + // images where all alpha values are 255; opaque images are + // faster to draw. + int alpha = getAlpha(pixel); + if (!m_seenNonZeroAlphaPixel && (alpha == 0)) { + m_seenZeroAlphaPixel = true; + alpha = 255; + } else { + m_seenNonZeroAlphaPixel = true; + if (m_seenZeroAlphaPixel) { + // The eraseARGB() call here also sets "hasAlpha" true. + m_frameBufferCache.first().bitmap().eraseARGB(0, 0, 0, + 0); + m_seenZeroAlphaPixel = false; + } else if (alpha != 255) + m_frameBufferCache.first().setHasAlpha(true); + } + + setRGBA(getComponent(pixel, 0), getComponent(pixel, 1), + getComponent(pixel, 2), alpha); + } + } + + // Success, keep going. + m_decodedOffset += paddedNumBytes; + if (inRLE) + return true; + moveBufferToNextRow(); + } + + // Finished decoding whole image. + return true; +} + +void BMPImageReader::moveBufferToNextRow() +{ + m_coord.move(-m_coord.x(), m_isTopDown ? 1 : -1); +} + +} // namespace WebCore |