/* * 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 "SkBmpCodec.h" #include "SkBmpMaskCodec.h" #include "SkBmpRLECodec.h" #include "SkBmpStandardCodec.h" #include "SkCodecPriv.h" #include "SkColorPriv.h" #include "SkStream.h" /* * Defines the version and type of the second bitmap header */ enum BmpHeaderType { kInfoV1_BmpHeaderType, kInfoV2_BmpHeaderType, kInfoV3_BmpHeaderType, kInfoV4_BmpHeaderType, kInfoV5_BmpHeaderType, kOS2V1_BmpHeaderType, kOS2VX_BmpHeaderType, kUnknown_BmpHeaderType }; /* * Possible bitmap compression types */ enum BmpCompressionMethod { kNone_BmpCompressionMethod = 0, k8BitRLE_BmpCompressionMethod = 1, k4BitRLE_BmpCompressionMethod = 2, kBitMasks_BmpCompressionMethod = 3, kJpeg_BmpCompressionMethod = 4, kPng_BmpCompressionMethod = 5, kAlphaBitMasks_BmpCompressionMethod = 6, kCMYK_BmpCompressionMethod = 11, kCMYK8BitRLE_BmpCompressionMethod = 12, kCMYK4BitRLE_BmpCompressionMethod = 13 }; /* * Used to define the input format of the bmp */ enum BmpInputFormat { kStandard_BmpInputFormat, kRLE_BmpInputFormat, kBitMask_BmpInputFormat, kUnknown_BmpInputFormat }; /* * Checks the start of the stream to see if the image is a bitmap */ bool SkBmpCodec::IsBmp(SkStream* stream) { // TODO: Support "IC", "PT", "CI", "CP", "BA" const char bmpSig[] = { 'B', 'M' }; char buffer[sizeof(bmpSig)]; return stream->read(buffer, sizeof(bmpSig)) == sizeof(bmpSig) && !memcmp(buffer, bmpSig, sizeof(bmpSig)); } /* * Assumes IsBmp was called and returned true * Creates a bmp decoder * Reads enough of the stream to determine the image format */ SkCodec* SkBmpCodec::NewFromStream(SkStream* stream) { return SkBmpCodec::NewFromStream(stream, false); } /* * Creates a bmp decoder for a bmp embedded in ico * Reads enough of the stream to determine the image format */ SkCodec* SkBmpCodec::NewFromIco(SkStream* stream) { return SkBmpCodec::NewFromStream(stream, true); } /* * Read enough of the stream to initialize the SkBmpCodec. Returns a bool * representing success or failure. If it returned true, and codecOut was * not NULL, it will be set to a new SkBmpCodec. * Does *not* take ownership of the passed in SkStream. */ bool SkBmpCodec::ReadHeader(SkStream* stream, bool inIco, SkCodec** codecOut) { // Header size constants static const uint32_t kBmpHeaderBytes = 14; static const uint32_t kBmpHeaderBytesPlusFour = kBmpHeaderBytes + 4; static const uint32_t kBmpOS2V1Bytes = 12; static const uint32_t kBmpOS2V2Bytes = 64; static const uint32_t kBmpInfoBaseBytes = 16; static const uint32_t kBmpInfoV1Bytes = 40; static const uint32_t kBmpInfoV2Bytes = 52; static const uint32_t kBmpInfoV3Bytes = 56; static const uint32_t kBmpInfoV4Bytes = 108; static const uint32_t kBmpInfoV5Bytes = 124; static const uint32_t kBmpMaskBytes = 12; // The total bytes in the bmp file // We only need to use this value for RLE decoding, so we will only // check that it is valid in the RLE case. uint32_t totalBytes; // The offset from the start of the file where the pixel data begins uint32_t offset; // The size of the second (info) header in bytes uint32_t infoBytes; // Bmps embedded in Icos skip the first Bmp header if (!inIco) { // Read the first header and the size of the second header SkAutoTDeleteArray hBuffer( SkNEW_ARRAY(uint8_t, kBmpHeaderBytesPlusFour)); if (stream->read(hBuffer.get(), kBmpHeaderBytesPlusFour) != kBmpHeaderBytesPlusFour) { SkCodecPrintf("Error: unable to read first bitmap header.\n"); return false; } totalBytes = get_int(hBuffer.get(), 2); offset = get_int(hBuffer.get(), 10); if (offset < kBmpHeaderBytes + kBmpOS2V1Bytes) { SkCodecPrintf("Error: invalid starting location for pixel data\n"); return false; } // The size of the second (info) header in bytes // The size is the first field of the second header, so we have already // read the first four infoBytes. infoBytes = get_int(hBuffer.get(), 14); if (infoBytes < kBmpOS2V1Bytes) { SkCodecPrintf("Error: invalid second header size.\n"); return false; } } else { // This value is only used by RLE compression. Bmp in Ico files do not // use RLE. If the compression field is incorrectly signaled as RLE, // we will catch this and signal an error below. totalBytes = 0; // Bmps in Ico cannot specify an offset. We will always assume that // pixel data begins immediately after the color table. This value // will be corrected below. offset = 0; // Read the size of the second header SkAutoTDeleteArray hBuffer( SkNEW_ARRAY(uint8_t, 4)); if (stream->read(hBuffer.get(), 4) != 4) { SkCodecPrintf("Error: unable to read size of second bitmap header.\n"); return false; } infoBytes = get_int(hBuffer.get(), 0); if (infoBytes < kBmpOS2V1Bytes) { SkCodecPrintf("Error: invalid second header size.\n"); return false; } } // We already read the first four bytes of the info header to get the size const uint32_t infoBytesRemaining = infoBytes - 4; // Read the second header SkAutoTDeleteArray iBuffer( SkNEW_ARRAY(uint8_t, infoBytesRemaining)); if (stream->read(iBuffer.get(), infoBytesRemaining) != infoBytesRemaining) { SkCodecPrintf("Error: unable to read second bitmap header.\n"); return false; } // The number of bits used per pixel in the pixel data uint16_t bitsPerPixel; // The compression method for the pixel data uint32_t compression = kNone_BmpCompressionMethod; // Number of colors in the color table, defaults to 0 or max (see below) uint32_t numColors = 0; // Bytes per color in the color table, early versions use 3, most use 4 uint32_t bytesPerColor; // The image width and height int width, height; // Determine image information depending on second header format BmpHeaderType headerType; if (infoBytes >= kBmpInfoBaseBytes) { // Check the version of the header switch (infoBytes) { case kBmpInfoV1Bytes: headerType = kInfoV1_BmpHeaderType; break; case kBmpInfoV2Bytes: headerType = kInfoV2_BmpHeaderType; break; case kBmpInfoV3Bytes: headerType = kInfoV3_BmpHeaderType; break; case kBmpInfoV4Bytes: headerType = kInfoV4_BmpHeaderType; break; case kBmpInfoV5Bytes: headerType = kInfoV5_BmpHeaderType; break; case 16: case 20: case 24: case 28: case 32: case 36: case 42: case 46: case 48: case 60: case kBmpOS2V2Bytes: headerType = kOS2VX_BmpHeaderType; break; default: // We do not signal an error here because there is the // possibility of new or undocumented bmp header types. Most // of the newer versions of bmp headers are similar to and // build off of the older versions, so we may still be able to // decode the bmp. SkCodecPrintf("Warning: unknown bmp header format.\n"); headerType = kUnknown_BmpHeaderType; break; } // We check the size of the header before entering the if statement. // We should not reach this point unless the size is large enough for // these required fields. SkASSERT(infoBytesRemaining >= 12); width = get_int(iBuffer.get(), 0); height = get_int(iBuffer.get(), 4); bitsPerPixel = get_short(iBuffer.get(), 10); // Some versions do not have these fields, so we check before // overwriting the default value. if (infoBytesRemaining >= 16) { compression = get_int(iBuffer.get(), 12); if (infoBytesRemaining >= 32) { numColors = get_int(iBuffer.get(), 28); } } // All of the headers that reach this point, store color table entries // using 4 bytes per pixel. bytesPerColor = 4; } else if (infoBytes >= kBmpOS2V1Bytes) { // The OS2V1 is treated separately because it has a unique format headerType = kOS2V1_BmpHeaderType; width = (int) get_short(iBuffer.get(), 0); height = (int) get_short(iBuffer.get(), 2); bitsPerPixel = get_short(iBuffer.get(), 6); bytesPerColor = 3; } else { // There are no valid bmp headers SkCodecPrintf("Error: second bitmap header size is invalid.\n"); return false; } // Check for valid dimensions from header RowOrder rowOrder = kBottomUp_RowOrder; if (height < 0) { height = -height; rowOrder = kTopDown_RowOrder; } // The height field for bmp in ico is double the actual height because they // contain an XOR mask followed by an AND mask if (inIco) { height /= 2; } if (width <= 0 || height <= 0) { // TODO: Decide if we want to disable really large bmps as well. // https://code.google.com/p/skia/issues/detail?id=3617 SkCodecPrintf("Error: invalid bitmap dimensions.\n"); return false; } // Create mask struct SkMasks::InputMasks inputMasks; memset(&inputMasks, 0, sizeof(SkMasks::InputMasks)); // Determine the input compression format and set bit masks if necessary uint32_t maskBytes = 0; BmpInputFormat inputFormat = kUnknown_BmpInputFormat; switch (compression) { case kNone_BmpCompressionMethod: inputFormat = kStandard_BmpInputFormat; break; case k8BitRLE_BmpCompressionMethod: if (bitsPerPixel != 8) { SkCodecPrintf("Warning: correcting invalid bitmap format.\n"); bitsPerPixel = 8; } inputFormat = kRLE_BmpInputFormat; break; case k4BitRLE_BmpCompressionMethod: if (bitsPerPixel != 4) { SkCodecPrintf("Warning: correcting invalid bitmap format.\n"); bitsPerPixel = 4; } inputFormat = kRLE_BmpInputFormat; break; case kAlphaBitMasks_BmpCompressionMethod: case kBitMasks_BmpCompressionMethod: // Load the masks inputFormat = kBitMask_BmpInputFormat; switch (headerType) { case kInfoV1_BmpHeaderType: { // The V1 header stores the bit masks after the header SkAutoTDeleteArray mBuffer( SkNEW_ARRAY(uint8_t, kBmpMaskBytes)); if (stream->read(mBuffer.get(), kBmpMaskBytes) != kBmpMaskBytes) { SkCodecPrintf("Error: unable to read bit inputMasks.\n"); return false; } maskBytes = kBmpMaskBytes; inputMasks.red = get_int(mBuffer.get(), 0); inputMasks.green = get_int(mBuffer.get(), 4); inputMasks.blue = get_int(mBuffer.get(), 8); break; } case kInfoV2_BmpHeaderType: case kInfoV3_BmpHeaderType: case kInfoV4_BmpHeaderType: case kInfoV5_BmpHeaderType: // Header types are matched based on size. If the header // is V2+, we are guaranteed to be able to read at least // this size. SkASSERT(infoBytesRemaining >= 48); inputMasks.red = get_int(iBuffer.get(), 36); inputMasks.green = get_int(iBuffer.get(), 40); inputMasks.blue = get_int(iBuffer.get(), 44); break; case kOS2VX_BmpHeaderType: // TODO: Decide if we intend to support this. // It is unsupported in the previous version and // in chromium. I have not come across a test case // that uses this format. SkCodecPrintf("Error: huffman format unsupported.\n"); return false; default: SkCodecPrintf("Error: invalid bmp bit masks header.\n"); return false; } break; case kJpeg_BmpCompressionMethod: if (24 == bitsPerPixel) { inputFormat = kRLE_BmpInputFormat; break; } // Fall through case kPng_BmpCompressionMethod: // TODO: Decide if we intend to support this. // It is unsupported in the previous version and // in chromium. I think it is used mostly for printers. SkCodecPrintf("Error: compression format not supported.\n"); return false; case kCMYK_BmpCompressionMethod: case kCMYK8BitRLE_BmpCompressionMethod: case kCMYK4BitRLE_BmpCompressionMethod: // TODO: Same as above. SkCodecPrintf("Error: CMYK not supported for bitmap decoding.\n"); return false; default: SkCodecPrintf("Error: invalid format for bitmap decoding.\n"); return false; } // Most versions of bmps should be rendered as opaque. Either they do // not have an alpha channel, or they expect the alpha channel to be // ignored. V3+ bmp files introduce an alpha mask and allow the creator // of the image to use the alpha channels. However, many of these images // leave the alpha channel blank and expect to be rendered as opaque. This // is the case for almost all V3 images, so we render these as opaque. For // V4+, we will use the alpha channel, and fix the image later if it turns // out to be fully transparent. // As an exception, V3 bmp-in-ico may use an alpha mask. SkAlphaType alphaType = kOpaque_SkAlphaType; if ((kInfoV3_BmpHeaderType == headerType && inIco) || kInfoV4_BmpHeaderType == headerType || kInfoV5_BmpHeaderType == headerType) { // Header types are matched based on size. If the header is // V3+, we are guaranteed to be able to read at least this size. SkASSERT(infoBytesRemaining > 52); inputMasks.alpha = get_int(iBuffer.get(), 48); if (inputMasks.alpha != 0) { alphaType = kUnpremul_SkAlphaType; } } iBuffer.free(); // Additionally, 32 bit bmp-in-icos use the alpha channel. // And, RLE inputs may skip pixels, leaving them as transparent. This // is uncommon, but we cannot be certain that an RLE bmp will be opaque. if ((inIco && 32 == bitsPerPixel) || (kRLE_BmpInputFormat == inputFormat)) { alphaType = kUnpremul_SkAlphaType; } // Check for valid bits per pixel. // At the same time, use this information to choose a suggested color type // and to set default masks. SkColorType colorType = kN32_SkColorType; switch (bitsPerPixel) { // In addition to more standard pixel compression formats, bmp supports // the use of bit masks to determine pixel components. The standard // format for representing 16-bit colors is 555 (XRRRRRGGGGGBBBBB), // which does not map well to any Skia color formats. For this reason, // we will always enable mask mode with 16 bits per pixel. case 16: if (kBitMask_BmpInputFormat != inputFormat) { inputMasks.red = 0x7C00; inputMasks.green = 0x03E0; inputMasks.blue = 0x001F; inputFormat = kBitMask_BmpInputFormat; } break; // We want to decode to kIndex_8 for input formats that are already // designed in index format. case 1: case 2: case 4: case 8: // However, we cannot in RLE format since we may need to leave some // pixels as transparent. Similarly, we also cannot for ICO images // since we may need to apply a transparent mask. if (kRLE_BmpInputFormat != inputFormat && !inIco) { colorType = kIndex_8_SkColorType; } case 24: case 32: break; default: SkCodecPrintf("Error: invalid input value for bits per pixel.\n"); return false; } // Check that input bit masks are valid and create the masks object SkAutoTDelete masks(SkMasks::CreateMasks(inputMasks, bitsPerPixel)); if (NULL == masks) { SkCodecPrintf("Error: invalid input masks.\n"); return false; } // Check for a valid number of total bytes when in RLE mode if (totalBytes <= offset && kRLE_BmpInputFormat == inputFormat) { SkCodecPrintf("Error: RLE requires valid input size.\n"); return false; } const size_t RLEBytes = totalBytes - offset; // Calculate the number of bytes read so far const uint32_t bytesRead = kBmpHeaderBytes + infoBytes + maskBytes; if (!inIco && offset < bytesRead) { SkCodecPrintf("Error: pixel data offset less than header size.\n"); return false; } if (codecOut) { // Set the image info const SkImageInfo& imageInfo = SkImageInfo::Make(width, height, colorType, alphaType); // Return the codec switch (inputFormat) { case kStandard_BmpInputFormat: *codecOut = SkNEW_ARGS(SkBmpStandardCodec, (imageInfo, stream, bitsPerPixel, numColors, bytesPerColor, offset - bytesRead, rowOrder, inIco)); return true; case kBitMask_BmpInputFormat: // Bmp-in-Ico must be standard mode if (inIco) { SkCodecPrintf("Error: Icos may not use bit mask format.\n"); return false; } // Skip to the start of the pixel array. // We can do this here because there is no color table to read // in bit mask mode. if (stream->skip(offset - bytesRead) != offset - bytesRead) { SkCodecPrintf("Error: unable to skip to image data.\n"); return false; } *codecOut = SkNEW_ARGS(SkBmpMaskCodec, (imageInfo, stream, bitsPerPixel, masks.detach(), rowOrder)); return true; case kRLE_BmpInputFormat: // Bmp-in-Ico must be standard mode // When inIco is true, this line cannot be reached, since we // require that RLE Bmps have a valid number of totalBytes, and // Icos skip the header that contains totalBytes. SkASSERT(!inIco); *codecOut = SkNEW_ARGS(SkBmpRLECodec, ( imageInfo, stream, bitsPerPixel, numColors, bytesPerColor, offset - bytesRead, rowOrder, RLEBytes)); return true; default: SkASSERT(false); return false; } } return true; } /* * Creates a bmp decoder * Reads enough of the stream to determine the image format */ SkCodec* SkBmpCodec::NewFromStream(SkStream* stream, bool inIco) { SkAutoTDelete streamDeleter(stream); SkCodec* codec = NULL; if (ReadHeader(stream, inIco, &codec)) { // codec has taken ownership of stream, so we do not need to // delete it. SkASSERT(codec); streamDeleter.detach(); return codec; } return NULL; } SkBmpCodec::SkBmpCodec(const SkImageInfo& info, SkStream* stream, uint16_t bitsPerPixel, RowOrder rowOrder) : INHERITED(info, stream) , fBitsPerPixel(bitsPerPixel) , fRowOrder(rowOrder) {} bool SkBmpCodec::onRewind() { return SkBmpCodec::ReadHeader(this->stream(), this->inIco(), NULL); } /* * Get the destination row to start filling from * Used to fill the remainder of the image on incomplete input for bmps * This is tricky since bmps may be kTopDown or kBottomUp. For kTopDown, * we start filling from where we left off, but for kBottomUp we start * filling at the top of the image. */ void* SkBmpCodec::getDstStartRow(void* dst, size_t dstRowBytes, int32_t y) const { return (kTopDown_RowOrder == fRowOrder) ? SkTAddOffset(dst, y * dstRowBytes) : dst; } /* * Compute the number of colors in the color table */ uint32_t SkBmpCodec::computeNumColors(uint32_t numColors) { // Zero is a default for maxColors // Also set numColors to maxColors when it is too large uint32_t maxColors = 1 << fBitsPerPixel; if (numColors == 0 || numColors >= maxColors) { return maxColors; } return numColors; }