/*
* Performs the decoding
*/
SkCodec::Result SkBmpMaskCodec::decode(const SkImageInfo& dstInfo,
void* dst, size_t dstRowBytes,
const Options& opts) {
// Set constant values
const int width = dstInfo.width();
const int height = dstInfo.height();
const size_t rowBytes = SkAlign4(compute_row_bytes(width, this->bitsPerPixel()));
// Iterate over rows of the image
uint8_t* srcRow = fSrcBuffer.get();
for (int y = 0; y < height; y++) {
// Read a row of the input
if (this->stream()->read(srcRow, rowBytes) != rowBytes) {
SkCodecPrintf("Warning: incomplete input stream.\n");
// Fill the destination image on failure
SkPMColor fillColor = dstInfo.alphaType() == kOpaque_SkAlphaType ?
SK_ColorBLACK : SK_ColorTRANSPARENT;
if (kNo_ZeroInitialized == opts.fZeroInitialized || 0 != fillColor) {
void* dstStart = this->getDstStartRow(dst, dstRowBytes, y);
SkSwizzler::Fill(dstStart, dstInfo, dstRowBytes, dstInfo.height() - y, fillColor,
nullptr);
}
return kIncompleteInput;
}
// Decode the row in destination format
int row = SkBmpCodec::kBottomUp_RowOrder == this->rowOrder() ? height - 1 - y : y;
void* dstRow = SkTAddOffset<void>(dst, row * dstRowBytes);
fMaskSwizzler->swizzle(dstRow, srcRow);
}
// Finished decoding the entire image
return kSuccess;
}
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 SkBmpMaskCodec::initializeSwizzler(const SkImageInfo& dstInfo) {
// Allocate space for a row buffer
const size_t rowBytes = SkAlign4(compute_row_bytes(dstInfo.width(), this->bitsPerPixel()));
fSrcBuffer.reset(new uint8_t[rowBytes]);
// Create the swizzler
fMaskSwizzler.reset(SkMaskSwizzler::CreateMaskSwizzler(
dstInfo, fMasks, this->bitsPerPixel()));
if (nullptr == fMaskSwizzler.get()) {
return false;
}
return true;
}
/*
* Performs the bitmap decoding for RLE input format
* RLE decoding is performed all at once, rather than a one row at a time
*/
SkCodec::Result SkBmpRLECodec::decode(const SkImageInfo& dstInfo,
void* dst, size_t dstRowBytes,
const Options& opts) {
// Set RLE flags
static const uint8_t RLE_ESCAPE = 0;
static const uint8_t RLE_EOL = 0;
static const uint8_t RLE_EOF = 1;
static const uint8_t RLE_DELTA = 2;
// Set constant values
const int width = dstInfo.width();
const int height = dstInfo.height();
// Destination parameters
int x = 0;
int y = 0;
// Set the background as transparent. Then, if the RLE code skips pixels,
// the skipped pixels will be transparent.
// Because of the need for transparent pixels, kN32 is the only color
// type that makes sense for the destination format.
SkASSERT(kN32_SkColorType == dstInfo.colorType());
if (kNo_ZeroInitialized == opts.fZeroInitialized) {
SkSwizzler::Fill(dst, dstInfo, dstRowBytes, height, SK_ColorTRANSPARENT, NULL);
}
while (true) {
// If we have reached a row that is beyond the requested height, we have
// succeeded.
if (y >= height) {
// It would be better to check for the EOF marker before returning
// success, but we may be performing a scanline decode, which
// may require us to stop before decoding the full height.
return kSuccess;
}
// Every entry takes at least two bytes
if ((int) fRLEBytes - fCurrRLEByte < 2) {
SkCodecPrintf("Warning: might be incomplete RLE input.\n");
if (this->checkForMoreData() < 2) {
return kIncompleteInput;
}
}
// Read the next two bytes. These bytes have different meanings
// depending on their values. In the first interpretation, the first
// byte is an escape flag and the second byte indicates what special
// task to perform.
const uint8_t flag = fStreamBuffer.get()[fCurrRLEByte++];
const uint8_t task = fStreamBuffer.get()[fCurrRLEByte++];
// Perform decoding
if (RLE_ESCAPE == flag) {
switch (task) {
case RLE_EOL:
x = 0;
y++;
break;
case RLE_EOF:
return kSuccess;
case RLE_DELTA: {
// Two bytes are needed to specify delta
if ((int) fRLEBytes - fCurrRLEByte < 2) {
SkCodecPrintf("Warning: might be incomplete RLE input.\n");
if (this->checkForMoreData() < 2) {
return kIncompleteInput;
}
}
// Modify x and y
const uint8_t dx = fStreamBuffer.get()[fCurrRLEByte++];
const uint8_t dy = fStreamBuffer.get()[fCurrRLEByte++];
x += dx;
y += dy;
if (x > width || y > height) {
SkCodecPrintf("Warning: invalid RLE input.\n");
return kInvalidInput;
}
break;
}
default: {
// If task does not match any of the above signals, it
// indicates that we have a sequence of non-RLE pixels.
// Furthermore, the value of task is equal to the number
// of pixels to interpret.
uint8_t numPixels = task;
const size_t rowBytes = compute_row_bytes(numPixels,
this->bitsPerPixel());
// Abort if setting numPixels moves us off the edge of the
// image.
if (x + numPixels > width) {
SkCodecPrintf("Warning: invalid RLE input.\n");
return kInvalidInput;
}
// Also abort if there are not enough bytes
// remaining in the stream to set numPixels.
if ((int) fRLEBytes - fCurrRLEByte < SkAlign2(rowBytes)) {
SkCodecPrintf("Warning: might be incomplete RLE input.\n");
if (this->checkForMoreData() < SkAlign2(rowBytes)) {
return kIncompleteInput;
}
}
// Set numPixels number of pixels
while (numPixels > 0) {
switch(this->bitsPerPixel()) {
case 4: {
SkASSERT(fCurrRLEByte < fRLEBytes);
uint8_t val = fStreamBuffer.get()[fCurrRLEByte++];
setPixel(dst, dstRowBytes, dstInfo, x++,
y, val >> 4);
numPixels--;
if (numPixels != 0) {
setPixel(dst, dstRowBytes, dstInfo,
x++, y, val & 0xF);
numPixels--;
}
break;
}
case 8:
SkASSERT(fCurrRLEByte < fRLEBytes);
setPixel(dst, dstRowBytes, dstInfo, x++,
y, fStreamBuffer.get()[fCurrRLEByte++]);
numPixels--;
break;
case 24: {
SkASSERT(fCurrRLEByte + 2 < fRLEBytes);
uint8_t blue = fStreamBuffer.get()[fCurrRLEByte++];
uint8_t green = fStreamBuffer.get()[fCurrRLEByte++];
uint8_t red = fStreamBuffer.get()[fCurrRLEByte++];
setRGBPixel(dst, dstRowBytes, dstInfo,
x++, y, red, green, blue);
numPixels--;
}
default:
SkASSERT(false);
return kInvalidInput;
}
}
// Skip a byte if necessary to maintain alignment
if (!SkIsAlign2(rowBytes)) {
fCurrRLEByte++;
}
break;
}
}
} else {
// If the first byte read is not a flag, it indicates the number of
// pixels to set in RLE mode.
const uint8_t numPixels = flag;
const int endX = SkTMin<int>(x + numPixels, width);
if (24 == this->bitsPerPixel()) {
// In RLE24, the second byte read is part of the pixel color.
// There are two more required bytes to finish encoding the
// color.
if ((int) fRLEBytes - fCurrRLEByte < 2) {
SkCodecPrintf("Warning: might be incomplete RLE input.\n");
if (this->checkForMoreData() < 2) {
return kIncompleteInput;
}
}
// Fill the pixels up to endX with the specified color
uint8_t blue = task;
uint8_t green = fStreamBuffer.get()[fCurrRLEByte++];
uint8_t red = fStreamBuffer.get()[fCurrRLEByte++];
while (x < endX) {
setRGBPixel(dst, dstRowBytes, dstInfo, x++, y, red,
green, blue);
}
} else {
// In RLE8 or RLE4, the second byte read gives the index in the
// color table to look up the pixel color.
// RLE8 has one color index that gets repeated
// RLE4 has two color indexes in the upper and lower 4 bits of
// the bytes, which are alternated
uint8_t indices[2] = { task, task };
if (4 == this->bitsPerPixel()) {
indices[0] >>= 4;
indices[1] &= 0xf;
}
// Set the indicated number of pixels
for (int which = 0; x < endX; x++) {
setPixel(dst, dstRowBytes, dstInfo, x, y,
indices[which]);
which = !which;
}
}
}
