diff options
Diffstat (limited to 'thirdparty/libwebp/src/dec/alpha_dec.c')
| -rw-r--r-- | thirdparty/libwebp/src/dec/alpha_dec.c | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/thirdparty/libwebp/src/dec/alpha_dec.c b/thirdparty/libwebp/src/dec/alpha_dec.c new file mode 100644 index 0000000000..bce735bfc2 --- /dev/null +++ b/thirdparty/libwebp/src/dec/alpha_dec.c @@ -0,0 +1,232 @@ +// Copyright 2011 Google Inc. All Rights Reserved. +// +// Use of this source code is governed by a BSD-style license +// that can be found in the COPYING file in the root of the source +// tree. An additional intellectual property rights grant can be found +// in the file PATENTS. All contributing project authors may +// be found in the AUTHORS file in the root of the source tree. +// ----------------------------------------------------------------------------- +// +// Alpha-plane decompression. +// +// Author: Skal (pascal.massimino@gmail.com) + +#include <stdlib.h> +#include "src/dec/alphai_dec.h" +#include "src/dec/vp8i_dec.h" +#include "src/dec/vp8li_dec.h" +#include "src/dsp/dsp.h" +#include "src/utils/quant_levels_dec_utils.h" +#include "src/utils/utils.h" +#include "src/webp/format_constants.h" + +//------------------------------------------------------------------------------ +// ALPHDecoder object. + +// Allocates a new alpha decoder instance. +static ALPHDecoder* ALPHNew(void) { + ALPHDecoder* const dec = (ALPHDecoder*)WebPSafeCalloc(1ULL, sizeof(*dec)); + return dec; +} + +// Clears and deallocates an alpha decoder instance. +static void ALPHDelete(ALPHDecoder* const dec) { + if (dec != NULL) { + VP8LDelete(dec->vp8l_dec_); + dec->vp8l_dec_ = NULL; + WebPSafeFree(dec); + } +} + +//------------------------------------------------------------------------------ +// Decoding. + +// Initialize alpha decoding by parsing the alpha header and decoding the image +// header for alpha data stored using lossless compression. +// Returns false in case of error in alpha header (data too short, invalid +// compression method or filter, error in lossless header data etc). +static int ALPHInit(ALPHDecoder* const dec, const uint8_t* data, + size_t data_size, const VP8Io* const src_io, + uint8_t* output) { + int ok = 0; + const uint8_t* const alpha_data = data + ALPHA_HEADER_LEN; + const size_t alpha_data_size = data_size - ALPHA_HEADER_LEN; + int rsrv; + VP8Io* const io = &dec->io_; + + assert(data != NULL && output != NULL && src_io != NULL); + + VP8FiltersInit(); + dec->output_ = output; + dec->width_ = src_io->width; + dec->height_ = src_io->height; + assert(dec->width_ > 0 && dec->height_ > 0); + + if (data_size <= ALPHA_HEADER_LEN) { + return 0; + } + + dec->method_ = (data[0] >> 0) & 0x03; + dec->filter_ = (WEBP_FILTER_TYPE)((data[0] >> 2) & 0x03); + dec->pre_processing_ = (data[0] >> 4) & 0x03; + rsrv = (data[0] >> 6) & 0x03; + if (dec->method_ < ALPHA_NO_COMPRESSION || + dec->method_ > ALPHA_LOSSLESS_COMPRESSION || + dec->filter_ >= WEBP_FILTER_LAST || + dec->pre_processing_ > ALPHA_PREPROCESSED_LEVELS || + rsrv != 0) { + return 0; + } + + // Copy the necessary parameters from src_io to io + VP8InitIo(io); + WebPInitCustomIo(NULL, io); + io->opaque = dec; + io->width = src_io->width; + io->height = src_io->height; + + io->use_cropping = src_io->use_cropping; + io->crop_left = src_io->crop_left; + io->crop_right = src_io->crop_right; + io->crop_top = src_io->crop_top; + io->crop_bottom = src_io->crop_bottom; + // No need to copy the scaling parameters. + + if (dec->method_ == ALPHA_NO_COMPRESSION) { + const size_t alpha_decoded_size = dec->width_ * dec->height_; + ok = (alpha_data_size >= alpha_decoded_size); + } else { + assert(dec->method_ == ALPHA_LOSSLESS_COMPRESSION); + ok = VP8LDecodeAlphaHeader(dec, alpha_data, alpha_data_size); + } + + return ok; +} + +// Decodes, unfilters and dequantizes *at least* 'num_rows' rows of alpha +// starting from row number 'row'. It assumes that rows up to (row - 1) have +// already been decoded. +// Returns false in case of bitstream error. +static int ALPHDecode(VP8Decoder* const dec, int row, int num_rows) { + ALPHDecoder* const alph_dec = dec->alph_dec_; + const int width = alph_dec->width_; + const int height = alph_dec->io_.crop_bottom; + if (alph_dec->method_ == ALPHA_NO_COMPRESSION) { + int y; + const uint8_t* prev_line = dec->alpha_prev_line_; + const uint8_t* deltas = dec->alpha_data_ + ALPHA_HEADER_LEN + row * width; + uint8_t* dst = dec->alpha_plane_ + row * width; + assert(deltas <= &dec->alpha_data_[dec->alpha_data_size_]); + if (alph_dec->filter_ != WEBP_FILTER_NONE) { + assert(WebPUnfilters[alph_dec->filter_] != NULL); + for (y = 0; y < num_rows; ++y) { + WebPUnfilters[alph_dec->filter_](prev_line, deltas, dst, width); + prev_line = dst; + dst += width; + deltas += width; + } + } else { + for (y = 0; y < num_rows; ++y) { + memcpy(dst, deltas, width * sizeof(*dst)); + prev_line = dst; + dst += width; + deltas += width; + } + } + dec->alpha_prev_line_ = prev_line; + } else { // alph_dec->method_ == ALPHA_LOSSLESS_COMPRESSION + assert(alph_dec->vp8l_dec_ != NULL); + if (!VP8LDecodeAlphaImageStream(alph_dec, row + num_rows)) { + return 0; + } + } + + if (row + num_rows >= height) { + dec->is_alpha_decoded_ = 1; + } + return 1; +} + +static int AllocateAlphaPlane(VP8Decoder* const dec, const VP8Io* const io) { + const int stride = io->width; + const int height = io->crop_bottom; + const uint64_t alpha_size = (uint64_t)stride * height; + assert(dec->alpha_plane_mem_ == NULL); + dec->alpha_plane_mem_ = + (uint8_t*)WebPSafeMalloc(alpha_size, sizeof(*dec->alpha_plane_)); + if (dec->alpha_plane_mem_ == NULL) { + return 0; + } + dec->alpha_plane_ = dec->alpha_plane_mem_; + dec->alpha_prev_line_ = NULL; + return 1; +} + +void WebPDeallocateAlphaMemory(VP8Decoder* const dec) { + assert(dec != NULL); + WebPSafeFree(dec->alpha_plane_mem_); + dec->alpha_plane_mem_ = NULL; + dec->alpha_plane_ = NULL; + ALPHDelete(dec->alph_dec_); + dec->alph_dec_ = NULL; +} + +//------------------------------------------------------------------------------ +// Main entry point. + +const uint8_t* VP8DecompressAlphaRows(VP8Decoder* const dec, + const VP8Io* const io, + int row, int num_rows) { + const int width = io->width; + const int height = io->crop_bottom; + + assert(dec != NULL && io != NULL); + + if (row < 0 || num_rows <= 0 || row + num_rows > height) { + return NULL; // sanity check. + } + + if (!dec->is_alpha_decoded_) { + if (dec->alph_dec_ == NULL) { // Initialize decoder. + dec->alph_dec_ = ALPHNew(); + if (dec->alph_dec_ == NULL) return NULL; + if (!AllocateAlphaPlane(dec, io)) goto Error; + if (!ALPHInit(dec->alph_dec_, dec->alpha_data_, dec->alpha_data_size_, + io, dec->alpha_plane_)) { + goto Error; + } + // if we allowed use of alpha dithering, check whether it's needed at all + if (dec->alph_dec_->pre_processing_ != ALPHA_PREPROCESSED_LEVELS) { + dec->alpha_dithering_ = 0; // disable dithering + } else { + num_rows = height - row; // decode everything in one pass + } + } + + assert(dec->alph_dec_ != NULL); + assert(row + num_rows <= height); + if (!ALPHDecode(dec, row, num_rows)) goto Error; + + if (dec->is_alpha_decoded_) { // finished? + ALPHDelete(dec->alph_dec_); + dec->alph_dec_ = NULL; + if (dec->alpha_dithering_ > 0) { + uint8_t* const alpha = dec->alpha_plane_ + io->crop_top * width + + io->crop_left; + if (!WebPDequantizeLevels(alpha, + io->crop_right - io->crop_left, + io->crop_bottom - io->crop_top, + width, dec->alpha_dithering_)) { + goto Error; + } + } + } + } + + // Return a pointer to the current decoded row. + return dec->alpha_plane_ + row * width; + + Error: + WebPDeallocateAlphaMemory(dec); + return NULL; +} |