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/*
* 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 "SkBmpRLECodec.h"
#include "SkCodecPriv.h"
#include "SkColorPriv.h"
#include "SkScaledCodec.h"
#include "SkStream.h"
/*
* Creates an instance of the decoder
* Called only by NewFromStream
*/
SkBmpRLECodec::SkBmpRLECodec(const SkImageInfo& info, SkStream* stream,
uint16_t bitsPerPixel, uint32_t numColors,
uint32_t bytesPerColor, uint32_t offset,
SkCodec::SkScanlineOrder rowOrder,
size_t RLEBytes)
: INHERITED(info, stream, bitsPerPixel, rowOrder)
, fColorTable(nullptr)
, fNumColors(this->computeNumColors(numColors))
, fBytesPerColor(bytesPerColor)
, fOffset(offset)
, fStreamBuffer(new uint8_t[RLEBytes])
, fRLEBytes(RLEBytes)
, fCurrRLEByte(0)
, fSampleX(1)
{}
/*
* Initiates the bitmap decode
*/
SkCodec::Result SkBmpRLECodec::onGetPixels(const SkImageInfo& dstInfo,
void* dst, size_t dstRowBytes,
const Options& opts,
SkPMColor* inputColorPtr,
int* inputColorCount) {
if (!this->rewindIfNeeded()) {
return kCouldNotRewind;
}
if (opts.fSubset) {
// Subsets are not supported.
return kUnimplemented;
}
if (dstInfo.dimensions() != this->getInfo().dimensions()) {
SkCodecPrintf("Error: scaling not supported.\n");
return kInvalidScale;
}
if (!conversion_possible(dstInfo, this->getInfo())) {
SkCodecPrintf("Error: cannot convert input type to output type.\n");
return kInvalidConversion;
}
Result result = this->prepareToDecode(dstInfo, opts, inputColorPtr, inputColorCount);
if (kSuccess != result) {
return result;
}
// Perform the decode
return this->decodeRows(dstInfo, dst, dstRowBytes, opts);
}
/*
* Process the color table for the bmp input
*/
bool SkBmpRLECodec::createColorTable(int* numColors) {
// Allocate memory for color table
uint32_t colorBytes = 0;
SkPMColor colorTable[256];
if (this->bitsPerPixel() <= 8) {
// Inform the caller of the number of colors
uint32_t maxColors = 1 << this->bitsPerPixel();
if (nullptr != numColors) {
// We set the number of colors to maxColors in order to ensure
// safe memory accesses. Otherwise, an invalid pixel could
// access memory outside of our color table array.
*numColors = maxColors;
}
// Read the color table from the stream
colorBytes = fNumColors * fBytesPerColor;
SkAutoTDeleteArray<uint8_t> cBuffer(new uint8_t[colorBytes]);
if (stream()->read(cBuffer.get(), colorBytes) != colorBytes) {
SkCodecPrintf("Error: unable to read color table.\n");
return false;
}
// Fill in the color table
uint32_t i = 0;
for (; i < fNumColors; i++) {
uint8_t blue = get_byte(cBuffer.get(), i*fBytesPerColor);
uint8_t green = get_byte(cBuffer.get(), i*fBytesPerColor + 1);
uint8_t red = get_byte(cBuffer.get(), i*fBytesPerColor + 2);
colorTable[i] = SkPackARGB32NoCheck(0xFF, red, green, blue);
}
// To avoid segmentation faults on bad pixel data, fill the end of the
// color table with black. This is the same the behavior as the
// chromium decoder.
for (; i < maxColors; i++) {
colorTable[i] = SkPackARGB32NoCheck(0xFF, 0, 0, 0);
}
// Set the color table
fColorTable.reset(new SkColorTable(colorTable, maxColors));
}
// Check that we have not read past the pixel array offset
if(fOffset < colorBytes) {
// This may occur on OS 2.1 and other old versions where the color
// table defaults to max size, and the bmp tries to use a smaller
// color table. This is invalid, and our decision is to indicate
// an error, rather than try to guess the intended size of the
// color table.
SkCodecPrintf("Error: pixel data offset less than color table size.\n");
return false;
}
// After reading the color table, skip to the start of the pixel array
if (stream()->skip(fOffset - colorBytes) != fOffset - colorBytes) {
SkCodecPrintf("Error: unable to skip to image data.\n");
return false;
}
// Return true on success
return true;
}
bool SkBmpRLECodec::initializeStreamBuffer() {
// Setup a buffer to contain the full input stream
// TODO (msarett): I'm not sure it is smart or optimal to trust fRLEBytes (read from header)
// as the size of our buffer. First of all, the decode fails if fRLEBytes is
// corrupt (negative, zero, or small) when we might be able to decode
// successfully with a fixed size buffer. Additionally, we would save memory
// using a fixed size buffer if the RLE encoding is large. On the other hand,
// we may also waste memory with a fixed size buffer. And determining a
// minimum size for our buffer would depend on the image width (so it's not
// really "fixed" size), and we may end up allocating a buffer that is
// generally larger than the average encoded size anyway.
size_t totalBytes = this->stream()->read(fStreamBuffer.get(), fRLEBytes);
if (totalBytes < fRLEBytes) {
fRLEBytes = totalBytes;
SkCodecPrintf("Warning: incomplete RLE file.\n");
}
if (fRLEBytes == 0) {
SkCodecPrintf("Error: could not read RLE image data.\n");
return false;
}
fCurrRLEByte = 0;
return true;
}
/*
* Before signalling kIncompleteInput, we should attempt to load the
* stream buffer with additional data.
*
* @return the number of bytes remaining in the stream buffer after
* attempting to read more bytes from the stream
*/
size_t SkBmpRLECodec::checkForMoreData() {
const size_t remainingBytes = fRLEBytes - fCurrRLEByte;
uint8_t* buffer = fStreamBuffer.get();
// We will be reusing the same buffer, starting over from the beginning.
// Move any remaining bytes to the start of the buffer.
// We use memmove() instead of memcpy() because there is risk that the dst
// and src memory will overlap in corrupt images.
memmove(buffer, SkTAddOffset<uint8_t>(buffer, fCurrRLEByte), remainingBytes);
// Adjust the buffer ptr to the start of the unfilled data.
buffer += remainingBytes;
// Try to read additional bytes from the stream. There are fCurrRLEByte
// bytes of additional space remaining in the buffer, assuming that we
// have already copied remainingBytes to the start of the buffer.
size_t additionalBytes = this->stream()->read(buffer, fCurrRLEByte);
// Update counters and return the number of bytes we currently have
// available. We are at the start of the buffer again.
fCurrRLEByte = 0;
// If we were unable to fill the buffer, fRLEBytes is no longer equal to
// the size of the buffer. There will be unused space at the end. This
// should be fine, given that there are no more bytes in the stream.
fRLEBytes = remainingBytes + additionalBytes;
return fRLEBytes;
}
/*
* Set an RLE pixel using the color table
*/
void SkBmpRLECodec::setPixel(void* dst, size_t dstRowBytes,
const SkImageInfo& dstInfo, uint32_t x, uint32_t y,
uint8_t index) {
if (is_coord_necessary(x, fSampleX, dstInfo.width())) {
// Set the row
uint32_t row = this->getDstRow(y, dstInfo.height());
// Set the pixel based on destination color type
const int dstX = get_dst_coord(x, fSampleX);
switch (dstInfo.colorType()) {
case kN32_SkColorType: {
SkPMColor* dstRow = SkTAddOffset<SkPMColor>(dst, row * (int) dstRowBytes);
dstRow[dstX] = fColorTable->operator[](index);
break;
}
case kRGB_565_SkColorType: {
uint16_t* dstRow = SkTAddOffset<uint16_t>(dst, row * (int) dstRowBytes);
dstRow[dstX] = SkPixel32ToPixel16(fColorTable->operator[](index));
break;
}
default:
// This case should not be reached. We should catch an invalid
// color type when we check that the conversion is possible.
SkASSERT(false);
break;
}
}
}
/*
* Set an RLE pixel from R, G, B values
*/
void SkBmpRLECodec::setRGBPixel(void* dst, size_t dstRowBytes,
const SkImageInfo& dstInfo, uint32_t x,
uint32_t y, uint8_t red, uint8_t green,
uint8_t blue) {
if (is_coord_necessary(x, fSampleX, dstInfo.width())) {
// Set the row
uint32_t row = this->getDstRow(y, dstInfo.height());
// Set the pixel based on destination color type
const int dstX = get_dst_coord(x, fSampleX);
switch (dstInfo.colorType()) {
case kN32_SkColorType: {
SkPMColor* dstRow = SkTAddOffset<SkPMColor>(dst, row * (int) dstRowBytes);
dstRow[dstX] = SkPackARGB32NoCheck(0xFF, red, green, blue);
break;
}
case kRGB_565_SkColorType: {
uint16_t* dstRow = SkTAddOffset<uint16_t>(dst, row * (int) dstRowBytes);
dstRow[dstX] = SkPack888ToRGB16(red, green, blue);
break;
}
default:
// This case should not be reached. We should catch an invalid
// color type when we check that the conversion is possible.
SkASSERT(false);
break;
}
}
}
SkCodec::Result SkBmpRLECodec::prepareToDecode(const SkImageInfo& dstInfo,
const SkCodec::Options& options, SkPMColor inputColorPtr[], int* inputColorCount) {
// Create the color table if necessary and prepare the stream for decode
// Note that if it is non-NULL, inputColorCount will be modified
if (!this->createColorTable(inputColorCount)) {
SkCodecPrintf("Error: could not create color table.\n");
return SkCodec::kInvalidInput;
}
// Copy the color table to the client if necessary
copy_color_table(dstInfo, this->fColorTable, inputColorPtr, inputColorCount);
// Initialize a buffer for encoded RLE data
if (!this->initializeStreamBuffer()) {
SkCodecPrintf("Error: cannot initialize stream buffer.\n");
return SkCodec::kInvalidConversion;
}
SkScaledCodec::ComputeSampleSize(dstInfo, this->getInfo(), &fSampleX, NULL);
return SkCodec::kSuccess;
}
/*
* 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::decodeRows(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 = this->getInfo().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());
SkSwizzler::Fill(dst, dstInfo, dstRowBytes, height, SK_ColorTRANSPARENT,
NULL, opts.fZeroInitialized);
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;
}
}
}
}
}