// Copyright 2012 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.
// -----------------------------------------------------------------------------
//
// main entry for the decoder
//
// Authors: Vikas Arora (vikaas.arora@gmail.com)
// Jyrki Alakuijala (jyrki@google.com)
#include <stdlib.h>
#include "./alphai.h"
#include "./vp8li.h"
#include "../dsp/dsp.h"
#include "../dsp/lossless.h"
#include "../dsp/yuv.h"
#include "../utils/huffman.h"
#include "../utils/utils.h"
#define NUM_ARGB_CACHE_ROWS 16
static const int kCodeLengthLiterals = 16;
static const int kCodeLengthRepeatCode = 16;
static const int kCodeLengthExtraBits[3] = { 2, 3, 7 };
static const int kCodeLengthRepeatOffsets[3] = { 3, 3, 11 };
// -----------------------------------------------------------------------------
// Five Huffman codes are used at each meta code:
// 1. green + length prefix codes + color cache codes,
// 2. alpha,
// 3. red,
// 4. blue, and,
// 5. distance prefix codes.
typedef enum {
GREEN = 0,
RED = 1,
BLUE = 2,
ALPHA = 3,
DIST = 4
} HuffIndex;
static const uint16_t kAlphabetSize[HUFFMAN_CODES_PER_META_CODE] = {
NUM_LITERAL_CODES + NUM_LENGTH_CODES,
NUM_LITERAL_CODES, NUM_LITERAL_CODES, NUM_LITERAL_CODES,
NUM_DISTANCE_CODES
};
#define NUM_CODE_LENGTH_CODES 19
static const uint8_t kCodeLengthCodeOrder[NUM_CODE_LENGTH_CODES] = {
17, 18, 0, 1, 2, 3, 4, 5, 16, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
};
#define CODE_TO_PLANE_CODES 120
static const uint8_t kCodeToPlane[CODE_TO_PLANE_CODES] = {
0x18, 0x07, 0x17, 0x19, 0x28, 0x06, 0x27, 0x29, 0x16, 0x1a,
0x26, 0x2a, 0x38, 0x05, 0x37, 0x39, 0x15, 0x1b, 0x36, 0x3a,
0x25, 0x2b, 0x48, 0x04, 0x47, 0x49, 0x14, 0x1c, 0x35, 0x3b,
0x46, 0x4a, 0x24, 0x2c, 0x58, 0x45, 0x4b, 0x34, 0x3c, 0x03,
0x57, 0x59, 0x13, 0x1d, 0x56, 0x5a, 0x23, 0x2d, 0x44, 0x4c,
0x55, 0x5b, 0x33, 0x3d, 0x68, 0x02, 0x67, 0x69, 0x12, 0x1e,
0x66, 0x6a, 0x22, 0x2e, 0x54, 0x5c, 0x43, 0x4d, 0x65, 0x6b,
0x32, 0x3e, 0x78, 0x01, 0x77, 0x79, 0x53, 0x5d, 0x11, 0x1f,
0x64, 0x6c, 0x42, 0x4e, 0x76, 0x7a, 0x21, 0x2f, 0x75, 0x7b,
0x31, 0x3f, 0x63, 0x6d, 0x52, 0x5e, 0x00, 0x74, 0x7c, 0x41,
0x4f, 0x10, 0x20, 0x62, 0x6e, 0x30, 0x73, 0x7d, 0x51, 0x5f,
0x40, 0x72, 0x7e, 0x61, 0x6f, 0x50, 0x71, 0x7f, 0x60, 0x70
};
static int DecodeImageStream(int xsize, int ysize,
int is_level0,
VP8LDecoder* const dec,
uint32_t** const decoded_data);
//------------------------------------------------------------------------------
int VP8LCheckSignature(const uint8_t* const data, size_t size) {
return (size >= VP8L_FRAME_HEADER_SIZE &&
data[0] == VP8L_MAGIC_BYTE &&
(data[4] >> 5) == 0); // version
}
static int ReadImageInfo(VP8LBitReader* const br,
int* const width, int* const height,
int* const has_alpha) {
if (VP8LReadBits(br, 8) != VP8L_MAGIC_BYTE) return 0;
*width = VP8LReadBits(br, VP8L_IMAGE_SIZE_BITS) + 1;
*height = VP8LReadBits(br, VP8L_IMAGE_SIZE_BITS) + 1;
*has_alpha = VP8LReadBits(br, 1);
if (VP8LReadBits(br, VP8L_VERSION_BITS) != 0) return 0;
return 1;
}
int VP8LGetInfo(const uint8_t* data, size_t data_size,
int* const width, int* const height, int* const has_alpha) {
if (data == NULL || data_size < VP8L_FRAME_HEADER_SIZE) {
return 0; // not enough data
} else if (!VP8LCheckSignature(data, data_size)) {
return 0; // bad signature
} else {
int w, h, a;
VP8LBitReader br;
VP8LInitBitReader(&br, data, data_size);
if (!ReadImageInfo(&br, &w, &h, &a)) {
return 0;
}
if (width != NULL) *width = w;
if (height != NULL) *height = h;
if (has_alpha != NULL) *has_alpha = a;
return 1;
}
}
//------------------------------------------------------------------------------
static WEBP_INLINE int GetCopyDistance(int distance_symbol,
VP8LBitReader* const br) {
int extra_bits, offset;
if (distance_symbol < 4) {
return distance_symbol + 1;
}
extra_bits = (distance_symbol - 2) >> 1;
offset = (2 + (distance_symbol & 1)) << extra_bits;
return offset + VP8LReadBits(br, extra_bits) + 1;
}
static WEBP_INLINE int GetCopyLength(int length_symbol,
VP8LBitReader* const br) {
// Length and distance prefixes are encoded the same way.
return GetCopyDistance(length_symbol, br);
}
static WEBP_INLINE int PlaneCodeToDistance(int xsize, int plane_code) {
if (plane_code > CODE_TO_PLANE_CODES) {
return plane_code - CODE_TO_PLANE_CODES;
} else {
const int dist_code = kCodeToPlane[plane_code - 1];
const int yoffset = dist_code >> 4;
const int xoffset = 8 - (dist_code & 0xf);
const int dist = yoffset * xsize + xoffset;
return (dist >= 1) ? dist : 1; // dist<1 can happen if xsize is very small
}
}
//------------------------------------------------------------------------------
// Decodes the next Huffman code from bit-stream.
// FillBitWindow(br) needs to be called at minimum every second call
// to ReadSymbol, in order to pre-fetch enough bits.
static WEBP_INLINE int ReadSymbol(const HuffmanTree* tree,
VP8LBitReader* const br) {
const HuffmanTreeNode* node = tree->root_;
uint32_t bits = VP8LPrefetchBits(br);
int bitpos = br->bit_pos_;
// Check if we find the bit combination from the Huffman lookup table.
const int lut_ix = bits & (HUFF_LUT - 1);
const int lut_bits = tree->lut_bits_[lut_ix];
if (lut_bits <= HUFF_LUT_BITS) {
VP8LSetBitPos(br, bitpos + lut_bits);
return tree->lut_symbol_[lut_ix];
}
node += tree->lut_jump_[lut_ix];
bitpos += HUFF_LUT_BITS;
bits >>= HUFF_LUT_BITS;
// Decode the value from a binary tree.
assert(node != NULL);
do {
node = HuffmanTreeNextNode(node, bits & 1);
bits >>= 1;
++bitpos;
} while (HuffmanTreeNodeIsNotLeaf(node));
VP8LSetBitPos(br, bitpos);
return node->symbol_;
}
static int ReadHuffmanCodeLengths(
VP8LDecoder* const dec, const int* const code_length_code_lengths,
int num_symbols, int* const code_lengths) {
int ok = 0;
VP8LBitReader* const br = &dec->br_;
int symbol;
int max_symbol;
int prev_code_len = DEFAULT_CODE_LENGTH;
HuffmanTree tree;
int huff_codes[NUM_CODE_LENGTH_CODES] = { 0 };
if (!VP8LHuffmanTreeBuildImplicit(&tree, code_length_code_lengths,
huff_codes, NUM_CODE_LENGTH_CODES)) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
return 0;
}
if (VP8LReadBits(br, 1)) { // use length
const int length_nbits = 2 + 2 * VP8LReadBits(br, 3);
max_symbol = 2 + VP8LReadBits(br, length_nbits);
if (max_symbol > num_symbols) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
goto End;
}
} else {
max_symbol = num_symbols;
}
symbol = 0;
while (symbol < num_symbols) {
int code_len;
if (max_symbol-- == 0) break;
VP8LFillBitWindow(br);
code_len = ReadSymbol(&tree, br);
if (code_len < kCodeLengthLiterals) {
code_lengths[symbol++] = code_len;
if (code_len != 0) prev_code_len = code_len;
} else {
const int use_prev = (code_len == kCodeLengthRepeatCode);
const int slot = code_len - kCodeLengthLiterals;
const int extra_bits = kCodeLengthExtraBits[slot];
const int repeat_offset = kCodeLengthRepeatOffsets[slot];
int repeat = VP8LReadBits(br, extra_bits) + repeat_offset;
if (symbol + repeat > num_symbols) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
goto End;
} else {
const int length = use_prev ? prev_code_len : 0;
while (repeat-- > 0) code_lengths[symbol++] = length;
}
}
}
ok = 1;
End:
VP8LHuffmanTreeFree(&tree);
return ok;
}
// 'code_lengths' is pre-allocated temporary buffer, used for creating Huffman
// tree.
static int ReadHuffmanCode(int alphabet_size, VP8LDecoder* const dec,
int* const code_lengths, int* const huff_codes,
HuffmanTree* const tree) {
int ok = 0;
VP8LBitReader* const br = &dec->br_;
const int simple_code = VP8LReadBits(br, 1);
if (simple_code) { // Read symbols, codes & code lengths directly.
int symbols[2];
int codes[2];
const int num_symbols = VP8LReadBits(br, 1) + 1;
const int first_symbol_len_code = VP8LReadBits(br, 1);
// The first code is either 1 bit or 8 bit code.
symbols[0] = VP8LReadBits(br, (first_symbol_len_code == 0) ? 1 : 8);
codes[0] = 0;
code_lengths[0] = num_symbols - 1;
// The second code (if present), is always 8 bit long.
if (num_symbols == 2) {
symbols[1] = VP8LReadBits(br, 8);
codes[1] = 1;
code_lengths[1] = num_symbols - 1;
}
ok = VP8LHuffmanTreeBuildExplicit(tree, code_lengths, codes, symbols,
alphabet_size, num_symbols);
} else { // Decode Huffman-coded code lengths.
int i;
int code_length_code_lengths[NUM_CODE_LENGTH_CODES] = { 0 };
const int num_codes = VP8LReadBits(br, 4) + 4;
if (num_codes > NUM_CODE_LENGTH_CODES) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
return 0;
}
memset(code_lengths, 0, alphabet_size * sizeof(*code_lengths));
for (i = 0; i < num_codes; ++i) {
code_length_code_lengths[kCodeLengthCodeOrder[i]] = VP8LReadBits(br, 3);
}
ok = ReadHuffmanCodeLengths(dec, code_length_code_lengths, alphabet_size,
code_lengths);
ok = ok && VP8LHuffmanTreeBuildImplicit(tree, code_lengths, huff_codes,
alphabet_size);
}
ok = ok && !br->error_;
if (!ok) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
return 0;
}
return 1;
}
static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize,
int color_cache_bits, int allow_recursion) {
int i, j;
VP8LBitReader* const br = &dec->br_;
VP8LMetadata* const hdr = &dec->hdr_;
uint32_t* huffman_image = NULL;
HTreeGroup* htree_groups = NULL;
int num_htree_groups = 1;
int max_alphabet_size = 0;
int* code_lengths = NULL;
int* huff_codes = NULL;
if (allow_recursion && VP8LReadBits(br, 1)) {
// use meta Huffman codes.
const int huffman_precision = VP8LReadBits(br, 3) + 2;
const int huffman_xsize = VP8LSubSampleSize(xsize, huffman_precision);
const int huffman_ysize = VP8LSubSampleSize(ysize, huffman_precision);
const int huffman_pixs = huffman_xsize * huffman_ysize;
if (!DecodeImageStream(huffman_xsize, huffman_ysize, 0, dec,
&huffman_image)) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
goto Error;
}
hdr->huffman_subsample_bits_ = huffman_precision;
for (i = 0; i < huffman_pixs; ++i) {
// The huffman data is stored in red and green bytes.
const int group = (huffman_image[i] >> 8) & 0xffff;
huffman_image[i] = group;
if (group >= num_htree_groups) {
num_htree_groups = group + 1;
}
}
}
if (br->error_) goto Error;
// Find maximum alphabet size for the htree group.
for (j = 0; j < HUFFMAN_CODES_PER_META_CODE; ++j) {
int alphabet_size = kAlphabetSize[j];
if (j == 0 && color_cache_bits > 0) {
alphabet_size += 1 << color_cache_bits;
}
if (max_alphabet_size < alphabet_size) {
max_alphabet_size = alphabet_size;
}
}
htree_groups = VP8LHtreeGroupsNew(num_htree_groups);
code_lengths =
(int*)WebPSafeCalloc((uint64_t)max_alphabet_size, sizeof(*code_lengths));
huff_codes =
(int*)WebPSafeMalloc((uint64_t)max_alphabet_size, sizeof(*huff_codes));
if (htree_groups == NULL || code_lengths == NULL || huff_codes == NULL) {
dec->status_ = VP8_STATUS_OUT_OF_MEMORY;
goto Error;
}
for (i = 0; i < num_htree_groups; ++i) {
HuffmanTree* const htrees = htree_groups[i].htrees_;
for (j = 0; j < HUFFMAN_CODES_PER_META_CODE; ++j) {
int alphabet_size = kAlphabetSize[j];
HuffmanTree* const htree = htrees + j;
if (j == 0 && color_cache_bits > 0) {
alphabet_size += 1 << color_cache_bits;
}
if (!ReadHuffmanCode(alphabet_size, dec, code_lengths, huff_codes,
htree)) {
goto Error;
}
}
}
WebPSafeFree(huff_codes);
WebPSafeFree(code_lengths);
// All OK. Finalize pointers and return.
hdr->huffman_image_ = huffman_image;
hdr->num_htree_groups_ = num_htree_groups;
hdr->htree_groups_ = htree_groups;
return 1;
Error:
WebPSafeFree(huff_codes);
WebPSafeFree(code_lengths);
WebPSafeFree(huffman_image);
VP8LHtreeGroupsFree(htree_groups, num_htree_groups);
return 0;
}
//------------------------------------------------------------------------------
// Scaling.
static int AllocateAndInitRescaler(VP8LDecoder* const dec, VP8Io* const io) {
const int num_channels = 4;
const int in_width = io->mb_w;
const int out_width = io->scaled_width;
const int in_height = io->mb_h;
const int out_height = io->scaled_height;
const uint64_t work_size = 2 * num_channels * (uint64_t)out_width;
int32_t* work; // Rescaler work area.
const uint64_t scaled_data_size = num_channels * (uint64_t)out_width;
uint32_t* scaled_data; // Temporary storage for scaled BGRA data.
const uint64_t memory_size = sizeof(*dec->rescaler) +
work_size * sizeof(*work) +
scaled_data_size * sizeof(*scaled_data);
uint8_t* memory = (uint8_t*)WebPSafeCalloc(memory_size, sizeof(*memory));
if (memory == NULL) {
dec->status_ = VP8_STATUS_OUT_OF_MEMORY;
return 0;
}
assert(dec->rescaler_memory == NULL);
dec->rescaler_memory = memory;
dec->rescaler = (WebPRescaler*)memory;
memory += sizeof(*dec->rescaler);
work = (int32_t*)memory;
memory += work_size * sizeof(*work);
scaled_data = (uint32_t*)memory;
WebPRescalerInit(dec->rescaler, in_width, in_height, (uint8_t*)scaled_data,
out_width, out_height, 0, num_channels,
in_width, out_width, in_height, out_height, work);
return 1;
}
//------------------------------------------------------------------------------
// Export to ARGB
// We have special "export" function since we need to convert from BGRA
static int Export(WebPRescaler* const rescaler, WEBP_CSP_MODE colorspace,
int rgba_stride, uint8_t* const rgba) {
uint32_t* const src = (uint32_t*)rescaler->dst;
const int dst_width = rescaler->dst_width;
int num_lines_out = 0;
while (WebPRescalerHasPendingOutput(rescaler)) {
uint8_t* const dst = rgba + num_lines_out * rgba_stride;
WebPRescalerExportRow(rescaler, 0);
WebPMultARGBRow(src, dst_width, 1);
VP8LConvertFromBGRA(src, dst_width, colorspace, dst);
++num_lines_out;
}
return num_lines_out;
}
// Emit scaled rows.
static int EmitRescaledRowsRGBA(const VP8LDecoder* const dec,
uint8_t* in, int in_stride, int mb_h,
uint8_t* const out, int out_stride) {
const WEBP_CSP_MODE colorspace = dec->output_->colorspace;
int num_lines_in = 0;
int num_lines_out = 0;
while (num_lines_in < mb_h) {
uint8_t* const row_in = in + num_lines_in * in_stride;
uint8_t* const row_out = out + num_lines_out * out_stride;
const int lines_left = mb_h - num_lines_in;
const int needed_lines = WebPRescaleNeededLines(dec->rescaler, lines_left);
assert(needed_lines > 0 && needed_lines <= lines_left);
WebPMultARGBRows(row_in, in_stride,
dec->rescaler->src_width, needed_lines, 0);
WebPRescalerImport(dec->rescaler, lines_left, row_in, in_stride);
num_lines_in += needed_lines;
num_lines_out += Export(dec->rescaler, colorspace, out_stride, row_out);
}
return num_lines_out;
}
// Emit rows without any scaling.
static int EmitRows(WEBP_CSP_MODE colorspace,
const uint8_t* row_in, int in_stride,
int mb_w, int mb_h,
uint8_t* const out, int out_stride) {
int lines = mb_h;
uint8_t* row_out = out;
while (lines-- > 0) {
VP8LConvertFromBGRA((const uint32_t*)row_in, mb_w, colorspace, row_out);
row_in += in_stride;
row_out += out_stride;
}
return mb_h; // Num rows out == num rows in.
}
//------------------------------------------------------------------------------
// Export to YUVA
// TODO(skal): should be in yuv.c
static void ConvertToYUVA(const uint32_t* const src, int width, int y_pos,
const WebPDecBuffer* const output) {
const WebPYUVABuffer* const buf = &output->u.YUVA;
// first, the luma plane
{
int i;
uint8_t* const y = buf->y + y_pos * buf->y_stride;
for (i = 0; i < width; ++i) {
const uint32_t p = src[i];
y[i] = VP8RGBToY((p >> 16) & 0xff, (p >> 8) & 0xff, (p >> 0) & 0xff,
YUV_HALF);
}
}
// then U/V planes
{
uint8_t* const u = buf->u + (y_pos >> 1) * buf->u_stride;
uint8_t* const v = buf->v + (y_pos >> 1) * buf->v_stride;
const int uv_width = width >> 1;
int i;
for (i = 0; i < uv_width; ++i) {
const uint32_t v0 = src[2 * i + 0];
const uint32_t v1 = src[2 * i + 1];
// VP8RGBToU/V expects four accumulated pixels. Hence we need to
// scale r/g/b value by a factor 2. We just shift v0/v1 one bit less.
const int r = ((v0 >> 15) & 0x1fe) + ((v1 >> 15) & 0x1fe);
const int g = ((v0 >> 7) & 0x1fe) + ((v1 >> 7) & 0x1fe);
const int b = ((v0 << 1) & 0x1fe) + ((v1 << 1) & 0x1fe);
if (!(y_pos & 1)) { // even lines: store values
u[i] = VP8RGBToU(r, g, b, YUV_HALF << 2);
v[i] = VP8RGBToV(r, g, b, YUV_HALF << 2);
} else { // odd lines: average with previous values
const int tmp_u = VP8RGBToU(r, g, b, YUV_HALF << 2);
const int tmp_v = VP8RGBToV(r, g, b, YUV_HALF << 2);
// Approximated average-of-four. But it's an acceptable diff.
u[i] = (u[i] + tmp_u + 1) >> 1;
v[i] = (v[i] + tmp_v + 1) >> 1;
}
}
if (width & 1) { // last pixel
const uint32_t v0 = src[2 * i + 0];
const int r = (v0 >> 14) & 0x3fc;
const int g = (v0 >> 6) & 0x3fc;
const int b = (v0 << 2) & 0x3fc;
if (!(y_pos & 1)) { // even lines
u[i] = VP8RGBToU(r, g, b, YUV_HALF << 2);
v[i] = VP8RGBToV(r, g, b, YUV_HALF << 2);
} else { // odd lines (note: we could just skip this)
const int tmp_u = VP8RGBToU(r, g, b, YUV_HALF << 2);
const int tmp_v = VP8RGBToV(r, g, b, YUV_HALF << 2);
u[i] = (u[i] + tmp_u + 1) >> 1;
v[i] = (v[i] + tmp_v + 1) >> 1;
}
}
}
// Lastly, store alpha if needed.
if (buf->a != NULL) {
int i;
uint8_t* const a = buf->a + y_pos * buf->a_stride;
for (i = 0; i < width; ++i) a[i] = (src[i] >> 24);
}
}
static int ExportYUVA(const VP8LDecoder* const dec, int y_pos) {
WebPRescaler* const rescaler = dec->rescaler;
uint32_t* const src = (uint32_t*)rescaler->dst;
const int dst_width = rescaler->dst_width;
int num_lines_out = 0;
while (WebPRescalerHasPendingOutput(rescaler)) {
WebPRescalerExportRow(rescaler, 0);
WebPMultARGBRow(src, dst_width, 1);
ConvertToYUVA(src, dst_width, y_pos, dec->output_);
++y_pos;
++num_lines_out;
}
return num_lines_out;
}
static int EmitRescaledRowsYUVA(const VP8LDecoder* const dec,
uint8_t* in, int in_stride, int mb_h) {
int num_lines_in = 0;
int y_pos = dec->last_out_row_;
while (num_lines_in < mb_h) {
const int lines_left = mb_h - num_lines_in;
const int needed_lines = WebPRescaleNeededLines(dec->rescaler, lines_left);
WebPMultARGBRows(in, in_stride, dec->rescaler->src_width, needed_lines, 0);
WebPRescalerImport(dec->rescaler, lines_left, in, in_stride);
num_lines_in += needed_lines;
in += needed_lines * in_stride;
y_pos += ExportYUVA(dec, y_pos);
}
return y_pos;
}
static int EmitRowsYUVA(const VP8LDecoder* const dec,
const uint8_t* in, int in_stride,
int mb_w, int num_rows) {
int y_pos = dec->last_out_row_;
while (num_rows-- > 0) {
ConvertToYUVA((const uint32_t*)in, mb_w, y_pos, dec->output_);
in += in_stride;
++y_pos;
}
return y_pos;
}
//------------------------------------------------------------------------------
// Cropping.
// Sets io->mb_y, io->mb_h & io->mb_w according to start row, end row and
// crop options. Also updates the input data pointer, so that it points to the
// start of the cropped window. Note that pixels are in ARGB format even if
// 'in_data' is uint8_t*.
// Returns true if the crop window is not empty.
static int SetCropWindow(VP8Io* const io, int y_start, int y_end,
uint8_t** const in_data, int pixel_stride) {
assert(y_start < y_end);
assert(io->crop_left < io->crop_right);
if (y_end > io->crop_bottom) {
y_end = io->crop_bottom; // make sure we don't overflow on last row.
}
if (y_start < io->crop_top) {
const int delta = io->crop_top - y_start;
y_start = io->crop_top;
*in_data += delta * pixel_stride;
}
if (y_start >= y_end) return 0; // Crop window is empty.
*in_data += io->crop_left * sizeof(uint32_t);
io->mb_y = y_start - io->crop_top;
io->mb_w = io->crop_right - io->crop_left;
io->mb_h = y_end - y_start;
return 1; // Non-empty crop window.
}
//------------------------------------------------------------------------------
static WEBP_INLINE int GetMetaIndex(
const uint32_t* const image, int xsize, int bits, int x, int y) {
if (bits == 0) return 0;
return image[xsize * (y >> bits) + (x >> bits)];
}
static WEBP_INLINE HTreeGroup* GetHtreeGroupForPos(VP8LMetadata* const hdr,
int x, int y) {
const int meta_index = GetMetaIndex(hdr->huffman_image_, hdr->huffman_xsize_,
hdr->huffman_subsample_bits_, x, y);
assert(meta_index < hdr->num_htree_groups_);
return hdr->htree_groups_ + meta_index;
}
//------------------------------------------------------------------------------
// Main loop, with custom row-processing function
typedef void (*ProcessRowsFunc)(VP8LDecoder* const dec, int row);
static void ApplyInverseTransforms(VP8LDecoder* const dec, int num_rows,
const uint32_t* const rows) {
int n = dec->next_transform_;
const int cache_pixs = dec->width_ * num_rows;
const int start_row = dec->last_row_;
const int end_row = start_row + num_rows;
const uint32_t* rows_in = rows;
uint32_t* const rows_out = dec->argb_cache_;
// Inverse transforms.
// TODO: most transforms only need to operate on the cropped region only.
memcpy(rows_out, rows_in, cache_pixs * sizeof(*rows_out));
while (n-- > 0) {
VP8LTransform* const transform = &dec->transforms_[n];
VP8LInverseTransform(transform, start_row, end_row, rows_in, rows_out);
rows_in = rows_out;
}
}
// Special method for paletted alpha data.
static void ApplyInverseTransformsAlpha(VP8LDecoder* const dec, int num_rows,
const uint8_t* const rows) {
const int start_row = dec->last_row_;
const int end_row = start_row + num_rows;
const uint8_t* rows_in = rows;
uint8_t* rows_out = (uint8_t*)dec->io_->opaque + dec->io_->width * start_row;
VP8LTransform* const transform = &dec->transforms_[0];
assert(dec->next_transform_ == 1);
assert(transform->type_ == COLOR_INDEXING_TRANSFORM);
VP8LColorIndexInverseTransformAlpha(transform, start_row, end_row, rows_in,
rows_out);
}
// Processes (transforms, scales & color-converts) the rows decoded after the
// last call.
static void ProcessRows(VP8LDecoder* const dec, int row) {
const uint32_t* const rows = dec->pixels_ + dec->width_ * dec->last_row_;
const int num_rows = row - dec->last_row_;
if (num_rows <= 0) return; // Nothing to be done.
ApplyInverseTransforms(dec, num_rows, rows);
// Emit output.
{
VP8Io* const io = dec->io_;
uint8_t* rows_data = (uint8_t*)dec->argb_cache_;
const int in_stride = io->width * sizeof(uint32_t); // in unit of RGBA
if (!SetCropWindow(io, dec->last_row_, row, &rows_data, in_stride)) {
// Nothing to output (this time).
} else {
const WebPDecBuffer* const output = dec->output_;
if (output->colorspace < MODE_YUV) { // convert to RGBA
const WebPRGBABuffer* const buf = &output->u.RGBA;
uint8_t* const rgba = buf->rgba + dec->last_out_row_ * buf->stride;
const int num_rows_out = io->use_scaling ?
EmitRescaledRowsRGBA(dec, rows_data, in_stride, io->mb_h,
rgba, buf->stride) :
EmitRows(output->colorspace, rows_data, in_stride,
io->mb_w, io->mb_h, rgba, buf->stride);
// Update 'last_out_row_'.
dec->last_out_row_ += num_rows_out;
} else { // convert to YUVA
dec->last_out_row_ = io->use_scaling ?
EmitRescaledRowsYUVA(dec, rows_data, in_stride, io->mb_h) :
EmitRowsYUVA(dec, rows_data, in_stride, io->mb_w, io->mb_h);
}
assert(dec->last_out_row_ <= output->height);
}
}
// Update 'last_row_'.
dec->last_row_ = row;
assert(dec->last_row_ <= dec->height_);
}
// Row-processing for the special case when alpha data contains only one
// transform (color indexing), and trivial non-green literals.
static int Is8bOptimizable(const VP8LMetadata* const hdr) {
int i;
if (hdr->color_cache_size_ > 0) return 0;
// When the Huffman tree contains only one symbol, we can skip the
// call to ReadSymbol() for red/blue/alpha channels.
for (i = 0; i < hdr->num_htree_groups_; ++i) {
const HuffmanTree* const htrees = hdr->htree_groups_[i].htrees_;
if (htrees[RED].num_nodes_ > 1) return 0;
if (htrees[BLUE].num_nodes_ > 1) return 0;
if (htrees[ALPHA].num_nodes_ > 1) return 0;
}
return 1;
}
static void ExtractPalettedAlphaRows(VP8LDecoder* const dec, int row) {
const int num_rows = row - dec->last_row_;
const uint8_t* const in =
(uint8_t*)dec->pixels_ + dec->width_ * dec->last_row_;
if (num_rows > 0) {
ApplyInverseTransformsAlpha(dec, num_rows, in);
}
dec->last_row_ = dec->last_out_row_ = row;
}
static int DecodeAlphaData(VP8LDecoder* const dec, uint8_t* const data,
int width, int height, int last_row) {
int ok = 1;
int row = dec->last_pixel_ / width;
int col = dec->last_pixel_ % width;
VP8LBitReader* const br = &dec->br_;
VP8LMetadata* const hdr = &dec->hdr_;
const HTreeGroup* htree_group = GetHtreeGroupForPos(hdr, col, row);
int pos = dec->last_pixel_; // current position
const int end = width * height; // End of data
const int last = width * last_row; // Last pixel to decode
const int len_code_limit = NUM_LITERAL_CODES + NUM_LENGTH_CODES;
const int mask = hdr->huffman_mask_;
assert(htree_group != NULL);
assert(pos < end);
assert(last_row <= height);
assert(Is8bOptimizable(hdr));
while (!br->eos_ && pos < last) {
int code;
// Only update when changing tile.
if ((col & mask) == 0) {
htree_group = GetHtreeGroupForPos(hdr, col, row);
}
VP8LFillBitWindow(br);
code = ReadSymbol(&htree_group->htrees_[GREEN], br);
if (code < NUM_LITERAL_CODES) { // Literal
data[pos] = code;
++pos;
++col;
if (col >= width) {
col = 0;
++row;
if (row % NUM_ARGB_CACHE_ROWS == 0) {
ExtractPalettedAlphaRows(dec, row);
}
}
} else if (code < len_code_limit) { // Backward reference
int dist_code, dist;
const int length_sym = code - NUM_LITERAL_CODES;
const int length = GetCopyLength(length_sym, br);
const int dist_symbol = ReadSymbol(&htree_group->htrees_[DIST], br);
VP8LFillBitWindow(br);
dist_code = GetCopyDistance(dist_symbol, br);
dist = PlaneCodeToDistance(width, dist_code);
if (pos >= dist && end - pos >= length) {
int i;
for (i = 0; i < length; ++i) data[pos + i] = data[pos + i - dist];
} else {
ok = 0;
goto End;
}
pos += length;
col += length;
while (col >= width) {
col -= width;
++row;
if (row % NUM_ARGB_CACHE_ROWS == 0) {
ExtractPalettedAlphaRows(dec, row);
}
}
if (pos < last && (col & mask)) {
htree_group = GetHtreeGroupForPos(hdr, col, row);
}
} else { // Not reached
ok = 0;
goto End;
}
ok = !br->error_;
if (!ok) goto End;
}
// Process the remaining rows corresponding to last row-block.
ExtractPalettedAlphaRows(dec, row);
End:
if (br->error_ || !ok || (br->eos_ && pos < end)) {
ok = 0;
dec->status_ = br->eos_ ? VP8_STATUS_SUSPENDED
: VP8_STATUS_BITSTREAM_ERROR;
} else {
dec->last_pixel_ = (int)pos;
if (pos == end) dec->state_ = READ_DATA;
}
return ok;
}
static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
int width, int height, int last_row,
ProcessRowsFunc process_func) {
int ok = 1;
int row = dec->last_pixel_ / width;
int col = dec->last_pixel_ % width;
VP8LBitReader* const br = &dec->br_;
VP8LMetadata* const hdr = &dec->hdr_;
HTreeGroup* htree_group = GetHtreeGroupForPos(hdr, col, row);
uint32_t* src = data + dec->last_pixel_;
uint32_t* last_cached = src;
uint32_t* const src_end = data + width * height; // End of data
uint32_t* const src_last = data + width * last_row; // Last pixel to decode
const int len_code_limit = NUM_LITERAL_CODES + NUM_LENGTH_CODES;
const int color_cache_limit = len_code_limit + hdr->color_cache_size_;
VP8LColorCache* const color_cache =
(hdr->color_cache_size_ > 0) ? &hdr->color_cache_ : NULL;
const int mask = hdr->huffman_mask_;
assert(htree_group != NULL);
assert(src < src_end);
assert(src_last <= src_end);
while (!br->eos_ && src < src_last) {
int code;
// Only update when changing tile. Note we could use this test:
// if "((((prev_col ^ col) | prev_row ^ row)) > mask)" -> tile changed
// but that's actually slower and needs storing the previous col/row.
if ((col & mask) == 0) {
htree_group = GetHtreeGroupForPos(hdr, col, row);
}
VP8LFillBitWindow(br);
code = ReadSymbol(&htree_group->htrees_[GREEN], br);
if (code < NUM_LITERAL_CODES) { // Literal
int red, green, blue, alpha;
red = ReadSymbol(&htree_group->htrees_[RED], br);
green = code;
VP8LFillBitWindow(br);
blue = ReadSymbol(&htree_group->htrees_[BLUE], br);
alpha = ReadSymbol(&htree_group->htrees_[ALPHA], br);
*src = ((uint32_t)alpha << 24) | (red << 16) | (green << 8) | blue;
AdvanceByOne:
++src;
++col;
if (col >= width) {
col = 0;
++row;
if ((row % NUM_ARGB_CACHE_ROWS == 0) && (process_func != NULL)) {
process_func(dec, row);
}
if (color_cache != NULL) {
while (last_cached < src) {
VP8LColorCacheInsert(color_cache, *last_cached++);
}
}
}
} else if (code < len_code_limit) { // Backward reference
int dist_code, dist;
const int length_sym = code - NUM_LITERAL_CODES;
const int length = GetCopyLength(length_sym, br);
const int dist_symbol = ReadSymbol(&htree_group->htrees_[DIST], br);
VP8LFillBitWindow(br);
dist_code = GetCopyDistance(dist_symbol, br);
dist = PlaneCodeToDistance(width, dist_code);
if (src - data < (ptrdiff_t)dist || src_end - src < (ptrdiff_t)length) {
ok = 0;
goto End;
} else {
int i;
for (i = 0; i < length; ++i) src[i] = src[i - dist];
src += length;
}
col += length;
while (col >= width) {
col -= width;
++row;
if ((row % NUM_ARGB_CACHE_ROWS == 0) && (process_func != NULL)) {
process_func(dec, row);
}
}
if (src < src_last) {
if (col & mask) htree_group = GetHtreeGroupForPos(hdr, col, row);
if (color_cache != NULL) {
while (last_cached < src) {
VP8LColorCacheInsert(color_cache, *last_cached++);
}
}
}
} else if (code < color_cache_limit) { // Color cache
const int key = code - len_code_limit;
assert(color_cache != NULL);
while (last_cached < src) {
VP8LColorCacheInsert(color_cache, *last_cached++);
}
*src = VP8LColorCacheLookup(color_cache, key);
goto AdvanceByOne;
} else { // Not reached
ok = 0;
goto End;
}
ok = !br->error_;
if (!ok) goto End;
}
// Process the remaining rows corresponding to last row-block.
if (process_func != NULL) process_func(dec, row);
End:
if (br->error_ || !ok || (br->eos_ && src < src_end)) {
ok = 0;
dec->status_ = br->eos_ ? VP8_STATUS_SUSPENDED
: VP8_STATUS_BITSTREAM_ERROR;
} else {
dec->last_pixel_ = (int)(src - data);
if (src == src_end) dec->state_ = READ_DATA;
}
return ok;
}
// -----------------------------------------------------------------------------
// VP8LTransform
static void ClearTransform(VP8LTransform* const transform) {
WebPSafeFree(transform->data_);
transform->data_ = NULL;
}
// For security reason, we need to remap the color map to span
// the total possible bundled values, and not just the num_colors.
static int ExpandColorMap(int num_colors, VP8LTransform* const transform) {
int i;
const int final_num_colors = 1 << (8 >> transform->bits_);
uint32_t* const new_color_map =
(uint32_t*)WebPSafeMalloc((uint64_t)final_num_colors,
sizeof(*new_color_map));
if (new_color_map == NULL) {
return 0;
} else {
uint8_t* const data = (uint8_t*)transform->data_;
uint8_t* const new_data = (uint8_t*)new_color_map;
new_color_map[0] = transform->data_[0];
for (i = 4; i < 4 * num_colors; ++i) {
// Equivalent to AddPixelEq(), on a byte-basis.
new_data[i] = (data[i] + new_data[i - 4]) & 0xff;
}
for (; i < 4 * final_num_colors; ++i)
new_data[i] = 0; // black tail.
WebPSafeFree(transform->data_);
transform->data_ = new_color_map;
}
return 1;
}
static int ReadTransform(int* const xsize, int const* ysize,
VP8LDecoder* const dec) {
int ok = 1;
VP8LBitReader* const br = &dec->br_;
VP8LTransform* transform = &dec->transforms_[dec->next_transform_];
const VP8LImageTransformType type =
(VP8LImageTransformType)VP8LReadBits(br, 2);
// Each transform type can only be present once in the stream.
if (dec->transforms_seen_ & (1U << type)) {
return 0; // Already there, let's not accept the second same transform.
}
dec->transforms_seen_ |= (1U << type);
transform->type_ = type;
transform->xsize_ = *xsize;
transform->ysize_ = *ysize;
transform->data_ = NULL;
++dec->next_transform_;
assert(dec->next_transform_ <= NUM_TRANSFORMS);
switch (type) {
case PREDICTOR_TRANSFORM:
case CROSS_COLOR_TRANSFORM:
transform->bits_ = VP8LReadBits(br, 3) + 2;
ok = DecodeImageStream(VP8LSubSampleSize(transform->xsize_,
transform->bits_),
VP8LSubSampleSize(transform->ysize_,
transform->bits_),
0, dec, &transform->data_);
break;
case COLOR_INDEXING_TRANSFORM: {
const int num_colors = VP8LReadBits(br, 8) + 1;
const int bits = (num_colors > 16) ? 0
: (num_colors > 4) ? 1
: (num_colors > 2) ? 2
: 3;
*xsize = VP8LSubSampleSize(transform->xsize_, bits);
transform->bits_ = bits;
ok = DecodeImageStream(num_colors, 1, 0, dec, &transform->data_);
ok = ok && ExpandColorMap(num_colors, transform);
break;
}
case SUBTRACT_GREEN:
break;
default:
assert(0); // can't happen
break;
}
return ok;
}
// -----------------------------------------------------------------------------
// VP8LMetadata
static void InitMetadata(VP8LMetadata* const hdr) {
assert(hdr);
memset(hdr, 0, sizeof(*hdr));
}
static void ClearMetadata(VP8LMetadata* const hdr) {
assert(hdr);
WebPSafeFree(hdr->huffman_image_);
VP8LHtreeGroupsFree(hdr->htree_groups_, hdr->num_htree_groups_);
VP8LColorCacheClear(&hdr->color_cache_);
InitMetadata(hdr);
}
// -----------------------------------------------------------------------------
// VP8LDecoder
VP8LDecoder* VP8LNew(void) {
VP8LDecoder* const dec = (VP8LDecoder*)WebPSafeCalloc(1ULL, sizeof(*dec));
if (dec == NULL) return NULL;
dec->status_ = VP8_STATUS_OK;
dec->action_ = READ_DIM;
dec->state_ = READ_DIM;
VP8LDspInit(); // Init critical function pointers.
return dec;
}
void VP8LClear(VP8LDecoder* const dec) {
int i;
if (dec == NULL) return;
ClearMetadata(&dec->hdr_);
WebPSafeFree(dec->pixels_);
dec->pixels_ = NULL;
for (i = 0; i < dec->next_transform_; ++i) {
ClearTransform(&dec->transforms_[i]);
}
dec->next_transform_ = 0;
dec->transforms_seen_ = 0;
WebPSafeFree(dec->rescaler_memory);
dec->rescaler_memory = NULL;
dec->output_ = NULL; // leave no trace behind
}
void VP8LDelete(VP8LDecoder* const dec) {
if (dec != NULL) {
VP8LClear(dec);
WebPSafeFree(dec);
}
}
static void UpdateDecoder(VP8LDecoder* const dec, int width, int height) {
VP8LMetadata* const hdr = &dec->hdr_;
const int num_bits = hdr->huffman_subsample_bits_;
dec->width_ = width;
dec->height_ = height;
hdr->huffman_xsize_ = VP8LSubSampleSize(width, num_bits);
hdr->huffman_mask_ = (num_bits == 0) ? ~0 : (1 << num_bits) - 1;
}
static int DecodeImageStream(int xsize, int ysize,
int is_level0,
VP8LDecoder* const dec,
uint32_t** const decoded_data) {
int ok = 1;
int transform_xsize = xsize;
int transform_ysize = ysize;
VP8LBitReader* const br = &dec->br_;
VP8LMetadata* const hdr = &dec->hdr_;
uint32_t* data = NULL;
int color_cache_bits = 0;
// Read the transforms (may recurse).
if (is_level0) {
while (ok && VP8LReadBits(br, 1)) {
ok = ReadTransform(&transform_xsize, &transform_ysize, dec);
}
}
// Color cache
if (ok && VP8LReadBits(br, 1)) {
color_cache_bits = VP8LReadBits(br, 4);
ok = (color_cache_bits >= 1 && color_cache_bits <= MAX_CACHE_BITS);
if (!ok) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
goto End;
}
}
// Read the Huffman codes (may recurse).
ok = ok && ReadHuffmanCodes(dec, transform_xsize, transform_ysize,
color_cache_bits, is_level0);
if (!ok) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
goto End;
}
// Finish setting up the color-cache
if (color_cache_bits > 0) {
hdr->color_cache_size_ = 1 << color_cache_bits;
if (!VP8LColorCacheInit(&hdr->color_cache_, color_cache_bits)) {
dec->status_ = VP8_STATUS_OUT_OF_MEMORY;
ok = 0;
goto End;
}
} else {
hdr->color_cache_size_ = 0;
}
UpdateDecoder(dec, transform_xsize, transform_ysize);
if (is_level0) { // level 0 complete
dec->state_ = READ_HDR;
goto End;
}
{
const uint64_t total_size = (uint64_t)transform_xsize * transform_ysize;
data = (uint32_t*)WebPSafeMalloc(total_size, sizeof(*data));
if (data == NULL) {
dec->status_ = VP8_STATUS_OUT_OF_MEMORY;
ok = 0;
goto End;
}
}
// Use the Huffman trees to decode the LZ77 encoded data.
ok = DecodeImageData(dec, data, transform_xsize, transform_ysize,
transform_ysize, NULL);
ok = ok && !br->error_;
End:
if (!ok) {
WebPSafeFree(data);
ClearMetadata(hdr);
// If not enough data (br.eos_) resulted in BIT_STREAM_ERROR, update the
// status appropriately.
if (dec->status_ == VP8_STATUS_BITSTREAM_ERROR && dec->br_.eos_) {
dec->status_ = VP8_STATUS_SUSPENDED;
}
} else {
if (decoded_data != NULL) {
*decoded_data = data;
} else {
// We allocate image data in this function only for transforms. At level 0
// (that is: not the transforms), we shouldn't have allocated anything.
assert(data == NULL);
assert(is_level0);
}
dec->last_pixel_ = 0; // Reset for future DECODE_DATA_FUNC() calls.
if (!is_level0) ClearMetadata(hdr); // Clean up temporary data behind.
}
return ok;
}
//------------------------------------------------------------------------------
// Allocate internal buffers dec->pixels_ and dec->argb_cache_.
static int AllocateInternalBuffers32b(VP8LDecoder* const dec, int final_width) {
const uint64_t num_pixels = (uint64_t)dec->width_ * dec->height_;
// Scratch buffer corresponding to top-prediction row for transforming the
// first row in the row-blocks. Not needed for paletted alpha.
const uint64_t cache_top_pixels = (uint16_t)final_width;
// Scratch buffer for temporary BGRA storage. Not needed for paletted alpha.
const uint64_t cache_pixels = (uint64_t)final_width * NUM_ARGB_CACHE_ROWS;
const uint64_t total_num_pixels =
num_pixels + cache_top_pixels + cache_pixels;
assert(dec->width_ <= final_width);
dec->pixels_ = (uint32_t*)WebPSafeMalloc(total_num_pixels, sizeof(uint32_t));
if (dec->pixels_ == NULL) {
dec->argb_cache_ = NULL; // for sanity check
dec->status_ = VP8_STATUS_OUT_OF_MEMORY;
return 0;
}
dec->argb_cache_ = dec->pixels_ + num_pixels + cache_top_pixels;
return 1;
}
static int AllocateInternalBuffers8b(VP8LDecoder* const dec) {
const uint64_t total_num_pixels = (uint64_t)dec->width_ * dec->height_;
dec->argb_cache_ = NULL; // for sanity check
dec->pixels_ = (uint32_t*)WebPSafeMalloc(total_num_pixels, sizeof(uint8_t));
if (dec->pixels_ == NULL) {
dec->status_ = VP8_STATUS_OUT_OF_MEMORY;
return 0;
}
return 1;
}
//------------------------------------------------------------------------------
// Special row-processing that only stores the alpha data.
static void ExtractAlphaRows(VP8LDecoder* const dec, int row) {
const int num_rows = row - dec->last_row_;
const uint32_t* const in = dec->pixels_ + dec->width_ * dec->last_row_;
if (num_rows <= 0) return; // Nothing to be done.
ApplyInverseTransforms(dec, num_rows, in);
// Extract alpha (which is stored in the green plane).
{
const int width = dec->io_->width; // the final width (!= dec->width_)
const int cache_pixs = width * num_rows;
uint8_t* const dst = (uint8_t*)dec->io_->opaque + width * dec->last_row_;
const uint32_t* const src = dec->argb_cache_;
int i;
for (i = 0; i < cache_pixs; ++i) dst[i] = (src[i] >> 8) & 0xff;
}
dec->last_row_ = dec->last_out_row_ = row;
}
int VP8LDecodeAlphaHeader(ALPHDecoder* const alph_dec,
const uint8_t* const data, size_t data_size,
uint8_t* const output) {
int ok = 0;
VP8LDecoder* dec;
VP8Io* io;
assert(alph_dec != NULL);
alph_dec->vp8l_dec_ = VP8LNew();
if (alph_dec->vp8l_dec_ == NULL) return 0;
dec = alph_dec->vp8l_dec_;
dec->width_ = alph_dec->width_;
dec->height_ = alph_dec->height_;
dec->io_ = &alph_dec->io_;
io = dec->io_;
VP8InitIo(io);
WebPInitCustomIo(NULL, io); // Just a sanity Init. io won't be used.
io->opaque = output;
io->width = alph_dec->width_;
io->height = alph_dec->height_;
dec->status_ = VP8_STATUS_OK;
VP8LInitBitReader(&dec->br_, data, data_size);
dec->action_ = READ_HDR;
if (!DecodeImageStream(alph_dec->width_, alph_dec->height_, 1, dec, NULL)) {
goto Err;
}
// Special case: if alpha data uses only the color indexing transform and
// doesn't use color cache (a frequent case), we will use DecodeAlphaData()
// method that only needs allocation of 1 byte per pixel (alpha channel).
if (dec->next_transform_ == 1 &&
dec->transforms_[0].type_ == COLOR_INDEXING_TRANSFORM &&
Is8bOptimizable(&dec->hdr_)) {
alph_dec->use_8b_decode = 1;
ok = AllocateInternalBuffers8b(dec);
} else {
// Allocate internal buffers (note that dec->width_ may have changed here).
alph_dec->use_8b_decode = 0;
ok = AllocateInternalBuffers32b(dec, alph_dec->width_);
}
if (!ok) goto Err;
dec->action_ = READ_DATA;
return 1;
Err:
VP8LDelete(alph_dec->vp8l_dec_);
alph_dec->vp8l_dec_ = NULL;
return 0;
}
int VP8LDecodeAlphaImageStream(ALPHDecoder* const alph_dec, int last_row) {
VP8LDecoder* const dec = alph_dec->vp8l_dec_;
assert(dec != NULL);
assert(dec->action_ == READ_DATA);
assert(last_row <= dec->height_);
if (dec->last_pixel_ == dec->width_ * dec->height_) {
return 1; // done
}
// Decode (with special row processing).
return alph_dec->use_8b_decode ?
DecodeAlphaData(dec, (uint8_t*)dec->pixels_, dec->width_, dec->height_,
last_row) :
DecodeImageData(dec, dec->pixels_, dec->width_, dec->height_,
last_row, ExtractAlphaRows);
}
//------------------------------------------------------------------------------
int VP8LDecodeHeader(VP8LDecoder* const dec, VP8Io* const io) {
int width, height, has_alpha;
if (dec == NULL) return 0;
if (io == NULL) {
dec->status_ = VP8_STATUS_INVALID_PARAM;
return 0;
}
dec->io_ = io;
dec->status_ = VP8_STATUS_OK;
VP8LInitBitReader(&dec->br_, io->data, io->data_size);
if (!ReadImageInfo(&dec->br_, &width, &height, &has_alpha)) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
goto Error;
}
dec->state_ = READ_DIM;
io->width = width;
io->height = height;
dec->action_ = READ_HDR;
if (!DecodeImageStream(width, height, 1, dec, NULL)) goto Error;
return 1;
Error:
VP8LClear(dec);
assert(dec->status_ != VP8_STATUS_OK);
return 0;
}
int VP8LDecodeImage(VP8LDecoder* const dec) {
VP8Io* io = NULL;
WebPDecParams* params = NULL;
// Sanity checks.
if (dec == NULL) return 0;
io = dec->io_;
assert(io != NULL);
params = (WebPDecParams*)io->opaque;
assert(params != NULL);
dec->output_ = params->output;
assert(dec->output_ != NULL);
// Initialization.
if (!WebPIoInitFromOptions(params->options, io, MODE_BGRA)) {
dec->status_ = VP8_STATUS_INVALID_PARAM;
goto Err;
}
if (!AllocateInternalBuffers32b(dec, io->width)) goto Err;
if (io->use_scaling && !AllocateAndInitRescaler(dec, io)) goto Err;
if (io->use_scaling || WebPIsPremultipliedMode(dec->output_->colorspace)) {
// need the alpha-multiply functions for premultiplied output or rescaling
WebPInitAlphaProcessing();
}
// Decode.
dec->action_ = READ_DATA;
if (!DecodeImageData(dec, dec->pixels_, dec->width_, dec->height_,
dec->height_, ProcessRows)) {
goto Err;
}
// Cleanup.
params->last_y = dec->last_out_row_;
VP8LClear(dec);
return 1;
Err:
VP8LClear(dec);
assert(dec->status_ != VP8_STATUS_OK);
return 0;
}
//------------------------------------------------------------------------------