VP8StatusCode WebPAllocateDecBuffer(int w, int h,
const WebPDecoderOptions* const options,
WebPDecBuffer* const out) {
VP8StatusCode status;
if (out == NULL || w <= 0 || h <= 0) {
return VP8_STATUS_INVALID_PARAM;
}
if (options != NULL) { // First, apply options if there is any.
if (options->use_cropping) {
const int cw = options->crop_width;
const int ch = options->crop_height;
const int x = options->crop_left & ~1;
const int y = options->crop_top & ~1;
if (x < 0 || y < 0 || cw <= 0 || ch <= 0 || x + cw > w || y + ch > h) {
return VP8_STATUS_INVALID_PARAM; // out of frame boundary.
}
w = cw;
h = ch;
}
if (options->use_scaling) {
int scaled_width = options->scaled_width;
int scaled_height = options->scaled_height;
if (!WebPRescalerGetScaledDimensions(
w, h, &scaled_width, &scaled_height)) {
return VP8_STATUS_INVALID_PARAM;
}
w = scaled_width;
h = scaled_height;
}
}
out->width = w;
out->height = h;
// Then, allocate buffer for real.
status = AllocateBuffer(out);
if (status != VP8_STATUS_OK) return status;
// Use the stride trick if vertical flip is needed.
if (options != NULL && options->flip) {
status = WebPFlipBuffer(out);
}
return status;
}
// Main flow
static VP8StatusCode DecodeInto(const uint8_t* const data, size_t data_size,
WebPDecParams* const params) {
VP8StatusCode status;
VP8Io io;
WebPHeaderStructure headers;
headers.data = data;
headers.data_size = data_size;
headers.have_all_data = 1;
status = WebPParseHeaders(&headers); // Process Pre-VP8 chunks.
if (status != VP8_STATUS_OK) {
return status;
}
assert(params != NULL);
VP8InitIo(&io);
io.data = headers.data + headers.offset;
io.data_size = headers.data_size - headers.offset;
WebPInitCustomIo(params, &io); // Plug the I/O functions.
if (!headers.is_lossless) {
VP8Decoder* const dec = VP8New();
if (dec == NULL) {
return VP8_STATUS_OUT_OF_MEMORY;
}
dec->alpha_data_ = headers.alpha_data;
dec->alpha_data_size_ = headers.alpha_data_size;
// Decode bitstream header, update io->width/io->height.
if (!VP8GetHeaders(dec, &io)) {
status = dec->status_; // An error occurred. Grab error status.
} else {
// Allocate/check output buffers.
status = WebPAllocateDecBuffer(io.width, io.height, params->options,
params->output);
if (status == VP8_STATUS_OK) { // Decode
// This change must be done before calling VP8Decode()
dec->mt_method_ = VP8GetThreadMethod(params->options, &headers,
io.width, io.height);
VP8InitDithering(params->options, dec);
if (!VP8Decode(dec, &io)) {
status = dec->status_;
}
}
}
VP8Delete(dec);
} else {
VP8LDecoder* const dec = VP8LNew();
if (dec == NULL) {
return VP8_STATUS_OUT_OF_MEMORY;
}
if (!VP8LDecodeHeader(dec, &io)) {
status = dec->status_; // An error occurred. Grab error status.
} else {
// Allocate/check output buffers.
status = WebPAllocateDecBuffer(io.width, io.height, params->options,
params->output);
if (status == VP8_STATUS_OK) { // Decode
if (!VP8LDecodeImage(dec)) {
status = dec->status_;
}
}
}
VP8LDelete(dec);
}
if (status != VP8_STATUS_OK) {
WebPFreeDecBuffer(params->output);
} else {
if (params->options != NULL && params->options->flip) {
// This restores the original stride values if options->flip was used
// during the call to WebPAllocateDecBuffer above.
status = WebPFlipBuffer(params->output);
}
}
return status;
}
