161 lines
5.1 KiB
C
161 lines
5.1 KiB
C
// 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 "../webp/format_constants.h"
|
|
|
|
//------------------------------------------------------------------------------
|
|
// ALPHDecoder object.
|
|
|
|
ALPHDecoder* ALPHNew(void) {
|
|
ALPHDecoder* const dec = (ALPHDecoder*)calloc(1, sizeof(*dec));
|
|
return dec;
|
|
}
|
|
|
|
void ALPHDelete(ALPHDecoder* const dec) {
|
|
if (dec != NULL) {
|
|
VP8LDelete(dec->vp8l_dec_);
|
|
dec->vp8l_dec_ = NULL;
|
|
free(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 (alph_dec->pre_processing_ == ALPHA_PREPROCESSED_LEVELS) {
|
|
if (!DequantizeLevels(output, width, height, row, num_rows)) {
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
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 (!dec->is_alpha_decoded_) {
|
|
int ok = 0;
|
|
assert(dec->alph_dec_ != NULL);
|
|
ok = ALPHDecode(dec, row, num_rows);
|
|
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;
|
|
}
|
|
|