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Diffstat (limited to 'src/main/jni/libwebp/dec/alpha.c')
| -rw-r--r-- | src/main/jni/libwebp/dec/alpha.c | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/src/main/jni/libwebp/dec/alpha.c b/src/main/jni/libwebp/dec/alpha.c new file mode 100644 index 000000000..f23ba7d6a --- /dev/null +++ b/src/main/jni/libwebp/dec/alpha.c @@ -0,0 +1,165 @@ +// 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 "./alphai.h" +#include "./vp8i.h" +#include "./vp8li.h" +#include "../utils/quant_levels_dec.h" +#include "../utils/utils.h" +#include "../webp/format_constants.h" + +//------------------------------------------------------------------------------ +// ALPHDecoder object. + +ALPHDecoder* ALPHNew(void) { + ALPHDecoder* const dec = (ALPHDecoder*)WebPSafeCalloc(1ULL, sizeof(*dec)); + return dec; +} + +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, int width, int height, 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; + + assert(width > 0 && height > 0); + assert(data != NULL && output != NULL); + + dec->width_ = width; + dec->height_ = height; + + if (data_size <= ALPHA_HEADER_LEN) { + return 0; + } + + dec->method_ = (data[0] >> 0) & 0x03; + dec->filter_ = (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; + } + + 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, output); + } + 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->height_; + WebPUnfilterFunc unfilter_func = WebPUnfilters[alph_dec->filter_]; + uint8_t* const output = dec->alpha_plane_; + if (alph_dec->method_ == ALPHA_NO_COMPRESSION) { + const size_t offset = row * width; + const size_t num_pixels = num_rows * width; + assert(dec->alpha_data_size_ >= ALPHA_HEADER_LEN + offset + num_pixels); + memcpy(dec->alpha_plane_ + offset, + dec->alpha_data_ + ALPHA_HEADER_LEN + offset, num_pixels); + } else { // alph_dec->method_ == ALPHA_LOSSLESS_COMPRESSION + assert(alph_dec->vp8l_dec_ != NULL); + if (!VP8LDecodeAlphaImageStream(alph_dec, row + num_rows)) { + return 0; + } + } + + if (unfilter_func != NULL) { + unfilter_func(width, height, width, row, num_rows, output); + } + + if (row + num_rows == dec->pic_hdr_.height_) { + dec->is_alpha_decoded_ = 1; + } + return 1; +} + +//------------------------------------------------------------------------------ +// Main entry point. + +const uint8_t* VP8DecompressAlphaRows(VP8Decoder* const dec, + int row, int num_rows) { + const int width = dec->pic_hdr_.width_; + const int height = dec->pic_hdr_.height_; + + if (row < 0 || num_rows <= 0 || row + num_rows > height) { + return NULL; // sanity check. + } + + if (row == 0) { + // Initialize decoding. + assert(dec->alpha_plane_ != NULL); + dec->alph_dec_ = ALPHNew(); + if (dec->alph_dec_ == NULL) return NULL; + if (!ALPHInit(dec->alph_dec_, dec->alpha_data_, dec->alpha_data_size_, + width, height, dec->alpha_plane_)) { + ALPHDelete(dec->alph_dec_); + dec->alph_dec_ = NULL; + return NULL; + } + // 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; // decode everything in one pass + } + } + + if (!dec->is_alpha_decoded_) { + int ok = 0; + assert(dec->alph_dec_ != NULL); + ok = ALPHDecode(dec, row, num_rows); + if (ok && dec->alpha_dithering_ > 0) { + ok = WebPDequantizeLevels(dec->alpha_plane_, width, height, + dec->alpha_dithering_); + } + if (!ok || dec->is_alpha_decoded_) { + ALPHDelete(dec->alph_dec_); + dec->alph_dec_ = NULL; + } + if (!ok) return NULL; // Error. + } + + // Return a pointer to the current decoded row. + return dec->alpha_plane_ + row * width; +} |