/*
* 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(const void* buffer, size_t bytesRead) {
// TODO: Support "IC", "PT", "CI", "CP", "BA"
const char bmpSig[] = { 'B', 'M' };
return bytesRead >= 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 nullptr, 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<uint8_t> hBuffer(new 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<uint8_t> hBuffer(new 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<uint8_t> iBuffer(new 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
SkCodec::SkScanlineOrder rowOrder = SkCodec::kBottomUp_SkScanlineOrder;
if (height < 0) {
height = -height;
rowOrder = SkCodec::kTopDown_SkScanlineOrder;
}
// 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<uint8_t> mBuffer(new 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+ images in kMask mode, we will use the alpha mask.
//
// skbug.com/4116: We should perhaps also apply the alpha mask in kStandard
// mode. We just haven't seen any images that expect this
// behavior.
//
// Additionally, V3 bmp-in-ico may use the 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.
// FIXME (msarett): Don't all 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;
}
// Mask bmps must have 16, 24, or 32 bits per pixel.
if (kBitMask_BmpInputFormat == inputFormat) {
SkCodecPrintf("Error: invalid input value of bits per pixel for mask bmp.\n");
return false;
}
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<SkMasks>
masks(SkMasks::CreateMasks(inputMasks, bitsPerPixel));
if (nullptr == 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) {
// TODO (msarett): Do we really want to fail if the offset in the header is invalid?
// Seems like we can just assume that the offset is zero and try to decode?
// Maybe we don't want to try to decode corrupt images?
SkCodecPrintf("Error: pixel data offset less than header size.\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 (!inIco && kBitMask_BmpInputFormat == inputFormat) {
if (stream->skip(offset - bytesRead) != offset - bytesRead) {
SkCodecPrintf("Error: unable to skip to image data.\n");
return false;
}
}
if (codecOut) {
// BMPs-in-ICOs contain an alpha mask after the image which means we
// cannot guarantee that an image is opaque, even if the bmp thinks
// it is.
bool isOpaque = kOpaque_SkAlphaType == alphaType;
if (inIco) {
alphaType = kUnpremul_SkAlphaType;
}
// Set the image info
const SkImageInfo& imageInfo = SkImageInfo::Make(width, height,
colorType, alphaType);
// Return the codec
switch (inputFormat) {
case kStandard_BmpInputFormat:
// We require streams to have a memory base for Bmp-in-Ico decodes.
SkASSERT(!inIco || nullptr != stream->getMemoryBase());
*codecOut = new SkBmpStandardCodec(imageInfo, stream, bitsPerPixel, numColors,
bytesPerColor, offset - bytesRead, rowOrder, isOpaque, 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;
}
*codecOut = new 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 = new 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<SkStream> streamDeleter(stream);
SkCodec* codec = nullptr;
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 nullptr;
}
SkBmpCodec::SkBmpCodec(const SkImageInfo& info, SkStream* stream,
uint16_t bitsPerPixel, SkCodec::SkScanlineOrder rowOrder)
: INHERITED(info, stream)
, fBitsPerPixel(bitsPerPixel)
, fRowOrder(rowOrder)
, fSrcRowBytes(SkAlign4(compute_row_bytes(info.width(), fBitsPerPixel)))
{}
bool SkBmpCodec::onRewind() {
return SkBmpCodec::ReadHeader(this->stream(), this->inIco(), nullptr);
}
int32_t SkBmpCodec::getDstRow(int32_t y, int32_t height) const {
if (SkCodec::kTopDown_SkScanlineOrder == fRowOrder) {
return y;
}
SkASSERT(SkCodec::kBottomUp_SkScanlineOrder == fRowOrder);
return height - y - 1;
}
SkCodec::Result SkBmpCodec::onStartScanlineDecode(const SkImageInfo& dstInfo,
const SkCodec::Options& options, SkPMColor inputColorPtr[], int* inputColorCount) {
if (!conversion_possible(dstInfo, this->getInfo())) {
SkCodecPrintf("Error: cannot convert input type to output type.\n");
return kInvalidConversion;
}
return prepareToDecode(dstInfo, options, inputColorPtr, inputColorCount);
}
int SkBmpCodec::onGetScanlines(void* dst, int count, size_t rowBytes) {
// Create a new image info representing the portion of the image to decode
SkImageInfo rowInfo = this->dstInfo().makeWH(this->dstInfo().width(), count);
// Decode the requested rows
return this->decodeRows(rowInfo, dst, rowBytes, this->options());
}
bool SkBmpCodec::skipRows(int count) {
const size_t bytesToSkip = count * fSrcRowBytes;
return this->stream()->skip(bytesToSkip) == bytesToSkip;
}
bool SkBmpCodec::onSkipScanlines(int count) {
return this->skipRows(count);
}