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godot/thirdparty/libwebp/enc/vp8l.c

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// 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 lossless encoder.
//
// Author: Vikas Arora (vikaas.arora@gmail.com)
//
#include <assert.h>
#include <stdlib.h>
#include "./backward_references.h"
#include "./histogram.h"
#include "./vp8enci.h"
#include "./vp8li.h"
#include "../dsp/lossless.h"
#include "../utils/bit_writer.h"
#include "../utils/huffman_encode.h"
#include "../utils/utils.h"
#include "../webp/format_constants.h"
#include "./delta_palettization.h"
#define PALETTE_KEY_RIGHT_SHIFT 22 // Key for 1K buffer.
// Maximum number of histogram images (sub-blocks).
#define MAX_HUFF_IMAGE_SIZE 2600
// Palette reordering for smaller sum of deltas (and for smaller storage).
static int PaletteCompareColorsForQsort(const void* p1, const void* p2) {
const uint32_t a = WebPMemToUint32(p1);
const uint32_t b = WebPMemToUint32(p2);
assert(a != b);
return (a < b) ? -1 : 1;
}
static WEBP_INLINE uint32_t PaletteComponentDistance(uint32_t v) {
return (v <= 128) ? v : (256 - v);
}
// Computes a value that is related to the entropy created by the
// palette entry diff.
//
// Note that the last & 0xff is a no-operation in the next statement, but
// removed by most compilers and is here only for regularity of the code.
static WEBP_INLINE uint32_t PaletteColorDistance(uint32_t col1, uint32_t col2) {
const uint32_t diff = VP8LSubPixels(col1, col2);
const int kMoreWeightForRGBThanForAlpha = 9;
uint32_t score;
score = PaletteComponentDistance((diff >> 0) & 0xff);
score += PaletteComponentDistance((diff >> 8) & 0xff);
score += PaletteComponentDistance((diff >> 16) & 0xff);
score *= kMoreWeightForRGBThanForAlpha;
score += PaletteComponentDistance((diff >> 24) & 0xff);
return score;
}
static WEBP_INLINE void SwapColor(uint32_t* const col1, uint32_t* const col2) {
const uint32_t tmp = *col1;
*col1 = *col2;
*col2 = tmp;
}
static void GreedyMinimizeDeltas(uint32_t palette[], int num_colors) {
// Find greedily always the closest color of the predicted color to minimize
// deltas in the palette. This reduces storage needs since the
// palette is stored with delta encoding.
uint32_t predict = 0x00000000;
int i, k;
for (i = 0; i < num_colors; ++i) {
int best_ix = i;
uint32_t best_score = ~0U;
for (k = i; k < num_colors; ++k) {
const uint32_t cur_score = PaletteColorDistance(palette[k], predict);
if (best_score > cur_score) {
best_score = cur_score;
best_ix = k;
}
}
SwapColor(&palette[best_ix], &palette[i]);
predict = palette[i];
}
}
// The palette has been sorted by alpha. This function checks if the other
// components of the palette have a monotonic development with regards to
// position in the palette. If all have monotonic development, there is
// no benefit to re-organize them greedily. A monotonic development
// would be spotted in green-only situations (like lossy alpha) or gray-scale
// images.
static int PaletteHasNonMonotonousDeltas(uint32_t palette[], int num_colors) {
uint32_t predict = 0x000000;
int i;
uint8_t sign_found = 0x00;
for (i = 0; i < num_colors; ++i) {
const uint32_t diff = VP8LSubPixels(palette[i], predict);
const uint8_t rd = (diff >> 16) & 0xff;
const uint8_t gd = (diff >> 8) & 0xff;
const uint8_t bd = (diff >> 0) & 0xff;
if (rd != 0x00) {
sign_found |= (rd < 0x80) ? 1 : 2;
}
if (gd != 0x00) {
sign_found |= (gd < 0x80) ? 8 : 16;
}
if (bd != 0x00) {
sign_found |= (bd < 0x80) ? 64 : 128;
}
predict = palette[i];
}
return (sign_found & (sign_found << 1)) != 0; // two consequent signs.
}
// -----------------------------------------------------------------------------
// Palette
// If number of colors in the image is less than or equal to MAX_PALETTE_SIZE,
// creates a palette and returns true, else returns false.
static int AnalyzeAndCreatePalette(const WebPPicture* const pic,
int low_effort,
uint32_t palette[MAX_PALETTE_SIZE],
int* const palette_size) {
const int num_colors = WebPGetColorPalette(pic, palette);
if (num_colors > MAX_PALETTE_SIZE) return 0;
*palette_size = num_colors;
qsort(palette, num_colors, sizeof(*palette), PaletteCompareColorsForQsort);
if (!low_effort && PaletteHasNonMonotonousDeltas(palette, num_colors)) {
GreedyMinimizeDeltas(palette, num_colors);
}
return 1;
}
// These five modes are evaluated and their respective entropy is computed.
typedef enum {
kDirect = 0,
kSpatial = 1,
kSubGreen = 2,
kSpatialSubGreen = 3,
kPalette = 4,
kNumEntropyIx = 5
} EntropyIx;
typedef enum {
kHistoAlpha = 0,
kHistoAlphaPred,
kHistoGreen,
kHistoGreenPred,
kHistoRed,
kHistoRedPred,
kHistoBlue,
kHistoBluePred,
kHistoRedSubGreen,
kHistoRedPredSubGreen,
kHistoBlueSubGreen,
kHistoBluePredSubGreen,
kHistoPalette,
kHistoTotal // Must be last.
} HistoIx;
static void AddSingleSubGreen(uint32_t p, uint32_t* r, uint32_t* b) {
const uint32_t green = p >> 8; // The upper bits are masked away later.
++r[((p >> 16) - green) & 0xff];
++b[(p - green) & 0xff];
}
static void AddSingle(uint32_t p,
uint32_t* a, uint32_t* r, uint32_t* g, uint32_t* b) {
++a[p >> 24];
++r[(p >> 16) & 0xff];
++g[(p >> 8) & 0xff];
++b[(p & 0xff)];
}
static int AnalyzeEntropy(const uint32_t* argb,
int width, int height, int argb_stride,
int use_palette,
EntropyIx* const min_entropy_ix,
int* const red_and_blue_always_zero) {
// Allocate histogram set with cache_bits = 0.
uint32_t* const histo =
(uint32_t*)WebPSafeCalloc(kHistoTotal, sizeof(*histo) * 256);
if (histo != NULL) {
int i, x, y;
const uint32_t* prev_row = argb;
const uint32_t* curr_row = argb + argb_stride;
for (y = 1; y < height; ++y) {
uint32_t prev_pix = curr_row[0];
for (x = 1; x < width; ++x) {
const uint32_t pix = curr_row[x];
const uint32_t pix_diff = VP8LSubPixels(pix, prev_pix);
if ((pix_diff == 0) || (pix == prev_row[x])) continue;
prev_pix = pix;
AddSingle(pix,
&histo[kHistoAlpha * 256],
&histo[kHistoRed * 256],
&histo[kHistoGreen * 256],
&histo[kHistoBlue * 256]);
AddSingle(pix_diff,
&histo[kHistoAlphaPred * 256],
&histo[kHistoRedPred * 256],
&histo[kHistoGreenPred * 256],
&histo[kHistoBluePred * 256]);
AddSingleSubGreen(pix,
&histo[kHistoRedSubGreen * 256],
&histo[kHistoBlueSubGreen * 256]);
AddSingleSubGreen(pix_diff,
&histo[kHistoRedPredSubGreen * 256],
&histo[kHistoBluePredSubGreen * 256]);
{
// Approximate the palette by the entropy of the multiplicative hash.
const int hash = ((pix + (pix >> 19)) * 0x39c5fba7) >> 24;
++histo[kHistoPalette * 256 + (hash & 0xff)];
}
}
prev_row = curr_row;
curr_row += argb_stride;
}
{
double entropy_comp[kHistoTotal];
double entropy[kNumEntropyIx];
EntropyIx k;
EntropyIx last_mode_to_analyze =
use_palette ? kPalette : kSpatialSubGreen;
int j;
// Let's add one zero to the predicted histograms. The zeros are removed
// too efficiently by the pix_diff == 0 comparison, at least one of the
// zeros is likely to exist.
++histo[kHistoRedPredSubGreen * 256];
++histo[kHistoBluePredSubGreen * 256];
++histo[kHistoRedPred * 256];
++histo[kHistoGreenPred * 256];
++histo[kHistoBluePred * 256];
++histo[kHistoAlphaPred * 256];
for (j = 0; j < kHistoTotal; ++j) {
entropy_comp[j] = VP8LBitsEntropy(&histo[j * 256], 256, NULL);
}
entropy[kDirect] = entropy_comp[kHistoAlpha] +
entropy_comp[kHistoRed] +
entropy_comp[kHistoGreen] +
entropy_comp[kHistoBlue];
entropy[kSpatial] = entropy_comp[kHistoAlphaPred] +
entropy_comp[kHistoRedPred] +
entropy_comp[kHistoGreenPred] +
entropy_comp[kHistoBluePred];
entropy[kSubGreen] = entropy_comp[kHistoAlpha] +
entropy_comp[kHistoRedSubGreen] +
entropy_comp[kHistoGreen] +
entropy_comp[kHistoBlueSubGreen];
entropy[kSpatialSubGreen] = entropy_comp[kHistoAlphaPred] +
entropy_comp[kHistoRedPredSubGreen] +
entropy_comp[kHistoGreenPred] +
entropy_comp[kHistoBluePredSubGreen];
// Palette mode seems more efficient in a breakeven case. Bias with 1.0.
entropy[kPalette] = entropy_comp[kHistoPalette] - 1.0;
*min_entropy_ix = kDirect;
for (k = kDirect + 1; k <= last_mode_to_analyze; ++k) {
if (entropy[*min_entropy_ix] > entropy[k]) {
*min_entropy_ix = k;
}
}
*red_and_blue_always_zero = 1;
// Let's check if the histogram of the chosen entropy mode has
// non-zero red and blue values. If all are zero, we can later skip
// the cross color optimization.
{
static const uint8_t kHistoPairs[5][2] = {
{ kHistoRed, kHistoBlue },
{ kHistoRedPred, kHistoBluePred },
{ kHistoRedSubGreen, kHistoBlueSubGreen },
{ kHistoRedPredSubGreen, kHistoBluePredSubGreen },
{ kHistoRed, kHistoBlue }
};
const uint32_t* const red_histo =
&histo[256 * kHistoPairs[*min_entropy_ix][0]];
const uint32_t* const blue_histo =
&histo[256 * kHistoPairs[*min_entropy_ix][1]];
for (i = 1; i < 256; ++i) {
if ((red_histo[i] | blue_histo[i]) != 0) {
*red_and_blue_always_zero = 0;
break;
}
}
}
}
WebPSafeFree(histo);
return 1;
} else {
return 0;
}
}
static int GetHistoBits(int method, int use_palette, int width, int height) {
// Make tile size a function of encoding method (Range: 0 to 6).
int histo_bits = (use_palette ? 9 : 7) - method;
while (1) {
const int huff_image_size = VP8LSubSampleSize(width, histo_bits) *
VP8LSubSampleSize(height, histo_bits);
if (huff_image_size <= MAX_HUFF_IMAGE_SIZE) break;
++histo_bits;
}
return (histo_bits < MIN_HUFFMAN_BITS) ? MIN_HUFFMAN_BITS :
(histo_bits > MAX_HUFFMAN_BITS) ? MAX_HUFFMAN_BITS : histo_bits;
}
static int GetTransformBits(int method, int histo_bits) {
const int max_transform_bits = (method < 4) ? 6 : (method > 4) ? 4 : 5;
return (histo_bits > max_transform_bits) ? max_transform_bits : histo_bits;
}
static int AnalyzeAndInit(VP8LEncoder* const enc) {
const WebPPicture* const pic = enc->pic_;
const int width = pic->width;
const int height = pic->height;
const int pix_cnt = width * height;
const WebPConfig* const config = enc->config_;
const int method = config->method;
const int low_effort = (config->method == 0);
// we round the block size up, so we're guaranteed to have
// at max MAX_REFS_BLOCK_PER_IMAGE blocks used:
int refs_block_size = (pix_cnt - 1) / MAX_REFS_BLOCK_PER_IMAGE + 1;
assert(pic != NULL && pic->argb != NULL);
enc->use_cross_color_ = 0;
enc->use_predict_ = 0;
enc->use_subtract_green_ = 0;
enc->use_palette_ =
AnalyzeAndCreatePalette(pic, low_effort,
enc->palette_, &enc->palette_size_);
// TODO(jyrki): replace the decision to be based on an actual estimate
// of entropy, or even spatial variance of entropy.
enc->histo_bits_ = GetHistoBits(method, enc->use_palette_,
pic->width, pic->height);
enc->transform_bits_ = GetTransformBits(method, enc->histo_bits_);
if (low_effort) {
// AnalyzeEntropy is somewhat slow.
enc->use_predict_ = !enc->use_palette_;
enc->use_subtract_green_ = !enc->use_palette_;
enc->use_cross_color_ = 0;
} else {
int red_and_blue_always_zero;
EntropyIx min_entropy_ix;
if (!AnalyzeEntropy(pic->argb, width, height, pic->argb_stride,
enc->use_palette_, &min_entropy_ix,
&red_and_blue_always_zero)) {
return 0;
}
enc->use_palette_ = (min_entropy_ix == kPalette);
enc->use_subtract_green_ =
(min_entropy_ix == kSubGreen) || (min_entropy_ix == kSpatialSubGreen);
enc->use_predict_ =
(min_entropy_ix == kSpatial) || (min_entropy_ix == kSpatialSubGreen);
enc->use_cross_color_ = red_and_blue_always_zero ? 0 : enc->use_predict_;
}
if (!VP8LHashChainInit(&enc->hash_chain_, pix_cnt)) return 0;
// palette-friendly input typically uses less literals
// -> reduce block size a bit
if (enc->use_palette_) refs_block_size /= 2;
VP8LBackwardRefsInit(&enc->refs_[0], refs_block_size);
VP8LBackwardRefsInit(&enc->refs_[1], refs_block_size);
return 1;
}
// Returns false in case of memory error.
static int GetHuffBitLengthsAndCodes(
const VP8LHistogramSet* const histogram_image,
HuffmanTreeCode* const huffman_codes) {
int i, k;
int ok = 0;
uint64_t total_length_size = 0;
uint8_t* mem_buf = NULL;
const int histogram_image_size = histogram_image->size;
int max_num_symbols = 0;
uint8_t* buf_rle = NULL;
HuffmanTree* huff_tree = NULL;
// Iterate over all histograms and get the aggregate number of codes used.
for (i = 0; i < histogram_image_size; ++i) {
const VP8LHistogram* const histo = histogram_image->histograms[i];
HuffmanTreeCode* const codes = &huffman_codes[5 * i];
for (k = 0; k < 5; ++k) {
const int num_symbols =
(k == 0) ? VP8LHistogramNumCodes(histo->palette_code_bits_) :
(k == 4) ? NUM_DISTANCE_CODES : 256;
codes[k].num_symbols = num_symbols;
total_length_size += num_symbols;
}
}
// Allocate and Set Huffman codes.
{
uint16_t* codes;
uint8_t* lengths;
mem_buf = (uint8_t*)WebPSafeCalloc(total_length_size,
sizeof(*lengths) + sizeof(*codes));
if (mem_buf == NULL) goto End;
codes = (uint16_t*)mem_buf;
lengths = (uint8_t*)&codes[total_length_size];
for (i = 0; i < 5 * histogram_image_size; ++i) {
const int bit_length = huffman_codes[i].num_symbols;
huffman_codes[i].codes = codes;
huffman_codes[i].code_lengths = lengths;
codes += bit_length;
lengths += bit_length;
if (max_num_symbols < bit_length) {
max_num_symbols = bit_length;
}
}
}
buf_rle = (uint8_t*)WebPSafeMalloc(1ULL, max_num_symbols);
huff_tree = (HuffmanTree*)WebPSafeMalloc(3ULL * max_num_symbols,
sizeof(*huff_tree));
if (buf_rle == NULL || huff_tree == NULL) goto End;
// Create Huffman trees.
for (i = 0; i < histogram_image_size; ++i) {
HuffmanTreeCode* const codes = &huffman_codes[5 * i];
VP8LHistogram* const histo = histogram_image->histograms[i];
VP8LCreateHuffmanTree(histo->literal_, 15, buf_rle, huff_tree, codes + 0);
VP8LCreateHuffmanTree(histo->red_, 15, buf_rle, huff_tree, codes + 1);
VP8LCreateHuffmanTree(histo->blue_, 15, buf_rle, huff_tree, codes + 2);
VP8LCreateHuffmanTree(histo->alpha_, 15, buf_rle, huff_tree, codes + 3);
VP8LCreateHuffmanTree(histo->distance_, 15, buf_rle, huff_tree, codes + 4);
}
ok = 1;
End:
WebPSafeFree(huff_tree);
WebPSafeFree(buf_rle);
if (!ok) {
WebPSafeFree(mem_buf);
memset(huffman_codes, 0, 5 * histogram_image_size * sizeof(*huffman_codes));
}
return ok;
}
static void StoreHuffmanTreeOfHuffmanTreeToBitMask(
VP8LBitWriter* const bw, const uint8_t* code_length_bitdepth) {
// RFC 1951 will calm you down if you are worried about this funny sequence.
// This sequence is tuned from that, but more weighted for lower symbol count,
// and more spiking histograms.
static const uint8_t kStorageOrder[CODE_LENGTH_CODES] = {
17, 18, 0, 1, 2, 3, 4, 5, 16, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
};
int i;
// Throw away trailing zeros:
int codes_to_store = CODE_LENGTH_CODES;
for (; codes_to_store > 4; --codes_to_store) {
if (code_length_bitdepth[kStorageOrder[codes_to_store - 1]] != 0) {
break;
}
}
VP8LPutBits(bw, codes_to_store - 4, 4);
for (i = 0; i < codes_to_store; ++i) {
VP8LPutBits(bw, code_length_bitdepth[kStorageOrder[i]], 3);
}
}
static void ClearHuffmanTreeIfOnlyOneSymbol(
HuffmanTreeCode* const huffman_code) {
int k;
int count = 0;
for (k = 0; k < huffman_code->num_symbols; ++k) {
if (huffman_code->code_lengths[k] != 0) {
++count;
if (count > 1) return;
}
}
for (k = 0; k < huffman_code->num_symbols; ++k) {
huffman_code->code_lengths[k] = 0;
huffman_code->codes[k] = 0;
}
}
static void StoreHuffmanTreeToBitMask(
VP8LBitWriter* const bw,
const HuffmanTreeToken* const tokens, const int num_tokens,
const HuffmanTreeCode* const huffman_code) {
int i;
for (i = 0; i < num_tokens; ++i) {
const int ix = tokens[i].code;
const int extra_bits = tokens[i].extra_bits;
VP8LPutBits(bw, huffman_code->codes[ix], huffman_code->code_lengths[ix]);
switch (ix) {
case 16:
VP8LPutBits(bw, extra_bits, 2);
break;
case 17:
VP8LPutBits(bw, extra_bits, 3);
break;
case 18:
VP8LPutBits(bw, extra_bits, 7);
break;
}
}
}
// 'huff_tree' and 'tokens' are pre-alloacted buffers.
static void StoreFullHuffmanCode(VP8LBitWriter* const bw,
HuffmanTree* const huff_tree,
HuffmanTreeToken* const tokens,
const HuffmanTreeCode* const tree) {
uint8_t code_length_bitdepth[CODE_LENGTH_CODES] = { 0 };
uint16_t code_length_bitdepth_symbols[CODE_LENGTH_CODES] = { 0 };
const int max_tokens = tree->num_symbols;
int num_tokens;
HuffmanTreeCode huffman_code;
huffman_code.num_symbols = CODE_LENGTH_CODES;
huffman_code.code_lengths = code_length_bitdepth;
huffman_code.codes = code_length_bitdepth_symbols;
VP8LPutBits(bw, 0, 1);
num_tokens = VP8LCreateCompressedHuffmanTree(tree, tokens, max_tokens);
{
uint32_t histogram[CODE_LENGTH_CODES] = { 0 };
uint8_t buf_rle[CODE_LENGTH_CODES] = { 0 };
int i;
for (i = 0; i < num_tokens; ++i) {
++histogram[tokens[i].code];
}
VP8LCreateHuffmanTree(histogram, 7, buf_rle, huff_tree, &huffman_code);
}
StoreHuffmanTreeOfHuffmanTreeToBitMask(bw, code_length_bitdepth);
ClearHuffmanTreeIfOnlyOneSymbol(&huffman_code);
{
int trailing_zero_bits = 0;
int trimmed_length = num_tokens;
int write_trimmed_length;
int length;
int i = num_tokens;
while (i-- > 0) {
const int ix = tokens[i].code;
if (ix == 0 || ix == 17 || ix == 18) {
--trimmed_length; // discount trailing zeros
trailing_zero_bits += code_length_bitdepth[ix];
if (ix == 17) {
trailing_zero_bits += 3;
} else if (ix == 18) {
trailing_zero_bits += 7;
}
} else {
break;
}
}
write_trimmed_length = (trimmed_length > 1 && trailing_zero_bits > 12);
length = write_trimmed_length ? trimmed_length : num_tokens;
VP8LPutBits(bw, write_trimmed_length, 1);
if (write_trimmed_length) {
const int nbits = VP8LBitsLog2Ceiling(trimmed_length - 1);
const int nbitpairs = (nbits == 0) ? 1 : (nbits + 1) / 2;
VP8LPutBits(bw, nbitpairs - 1, 3);
assert(trimmed_length >= 2);
VP8LPutBits(bw, trimmed_length - 2, nbitpairs * 2);
}
StoreHuffmanTreeToBitMask(bw, tokens, length, &huffman_code);
}
}
// 'huff_tree' and 'tokens' are pre-alloacted buffers.
static void StoreHuffmanCode(VP8LBitWriter* const bw,
HuffmanTree* const huff_tree,
HuffmanTreeToken* const tokens,
const HuffmanTreeCode* const huffman_code) {
int i;
int count = 0;
int symbols[2] = { 0, 0 };
const int kMaxBits = 8;
const int kMaxSymbol = 1 << kMaxBits;
// Check whether it's a small tree.
for (i = 0; i < huffman_code->num_symbols && count < 3; ++i) {
if (huffman_code->code_lengths[i] != 0) {
if (count < 2) symbols[count] = i;
++count;
}
}
if (count == 0) { // emit minimal tree for empty cases
// bits: small tree marker: 1, count-1: 0, large 8-bit code: 0, code: 0
VP8LPutBits(bw, 0x01, 4);
} else if (count <= 2 && symbols[0] < kMaxSymbol && symbols[1] < kMaxSymbol) {
VP8LPutBits(bw, 1, 1); // Small tree marker to encode 1 or 2 symbols.
VP8LPutBits(bw, count - 1, 1);
if (symbols[0] <= 1) {
VP8LPutBits(bw, 0, 1); // Code bit for small (1 bit) symbol value.
VP8LPutBits(bw, symbols[0], 1);
} else {
VP8LPutBits(bw, 1, 1);
VP8LPutBits(bw, symbols[0], 8);
}
if (count == 2) {
VP8LPutBits(bw, symbols[1], 8);
}
} else {
StoreFullHuffmanCode(bw, huff_tree, tokens, huffman_code);
}
}
static WEBP_INLINE void WriteHuffmanCode(VP8LBitWriter* const bw,
const HuffmanTreeCode* const code,
int code_index) {
const int depth = code->code_lengths[code_index];
const int symbol = code->codes[code_index];
VP8LPutBits(bw, symbol, depth);
}
static WEBP_INLINE void WriteHuffmanCodeWithExtraBits(
VP8LBitWriter* const bw,
const HuffmanTreeCode* const code,
int code_index,
int bits,
int n_bits) {
const int depth = code->code_lengths[code_index];
const int symbol = code->codes[code_index];
VP8LPutBits(bw, (bits << depth) | symbol, depth + n_bits);
}
static WebPEncodingError StoreImageToBitMask(
VP8LBitWriter* const bw, int width, int histo_bits,
VP8LBackwardRefs* const refs,
const uint16_t* histogram_symbols,
const HuffmanTreeCode* const huffman_codes) {
const int histo_xsize = histo_bits ? VP8LSubSampleSize(width, histo_bits) : 1;
const int tile_mask = (histo_bits == 0) ? 0 : -(1 << histo_bits);
// x and y trace the position in the image.
int x = 0;
int y = 0;
int tile_x = x & tile_mask;
int tile_y = y & tile_mask;
int histogram_ix = histogram_symbols[0];
const HuffmanTreeCode* codes = huffman_codes + 5 * histogram_ix;
VP8LRefsCursor c = VP8LRefsCursorInit(refs);
while (VP8LRefsCursorOk(&c)) {
const PixOrCopy* const v = c.cur_pos;
if ((tile_x != (x & tile_mask)) || (tile_y != (y & tile_mask))) {
tile_x = x & tile_mask;
tile_y = y & tile_mask;
histogram_ix = histogram_symbols[(y >> histo_bits) * histo_xsize +
(x >> histo_bits)];
codes = huffman_codes + 5 * histogram_ix;
}
if (PixOrCopyIsLiteral(v)) {
static const int order[] = { 1, 2, 0, 3 };
int k;
for (k = 0; k < 4; ++k) {
const int code = PixOrCopyLiteral(v, order[k]);
WriteHuffmanCode(bw, codes + k, code);
}
} else if (PixOrCopyIsCacheIdx(v)) {
const int code = PixOrCopyCacheIdx(v);
const int literal_ix = 256 + NUM_LENGTH_CODES + code;
WriteHuffmanCode(bw, codes, literal_ix);
} else {
int bits, n_bits;
int code;
const int distance = PixOrCopyDistance(v);
VP8LPrefixEncode(v->len, &code, &n_bits, &bits);
WriteHuffmanCodeWithExtraBits(bw, codes, 256 + code, bits, n_bits);
// Don't write the distance with the extra bits code since
// the distance can be up to 18 bits of extra bits, and the prefix
// 15 bits, totaling to 33, and our PutBits only supports up to 32 bits.
// TODO(jyrki): optimize this further.
VP8LPrefixEncode(distance, &code, &n_bits, &bits);
WriteHuffmanCode(bw, codes + 4, code);
VP8LPutBits(bw, bits, n_bits);
}
x += PixOrCopyLength(v);
while (x >= width) {
x -= width;
++y;
}
VP8LRefsCursorNext(&c);
}
return bw->error_ ? VP8_ENC_ERROR_OUT_OF_MEMORY : VP8_ENC_OK;
}
// Special case of EncodeImageInternal() for cache-bits=0, histo_bits=31
static WebPEncodingError EncodeImageNoHuffman(VP8LBitWriter* const bw,
const uint32_t* const argb,
VP8LHashChain* const hash_chain,
VP8LBackwardRefs refs_array[2],
int width, int height,
int quality) {
int i;
int max_tokens = 0;
WebPEncodingError err = VP8_ENC_OK;
VP8LBackwardRefs* refs;
HuffmanTreeToken* tokens = NULL;
HuffmanTreeCode huffman_codes[5] = { { 0, NULL, NULL } };
const uint16_t histogram_symbols[1] = { 0 }; // only one tree, one symbol
int cache_bits = 0;
VP8LHistogramSet* histogram_image = NULL;
HuffmanTree* const huff_tree = (HuffmanTree*)WebPSafeMalloc(
3ULL * CODE_LENGTH_CODES, sizeof(*huff_tree));
if (huff_tree == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
// Calculate backward references from ARGB image.
if (VP8LHashChainFill(hash_chain, quality, argb, width, height) == 0) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
refs = VP8LGetBackwardReferences(width, height, argb, quality, 0, &cache_bits,
hash_chain, refs_array);
if (refs == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
histogram_image = VP8LAllocateHistogramSet(1, cache_bits);
if (histogram_image == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
// Build histogram image and symbols from backward references.
VP8LHistogramStoreRefs(refs, histogram_image->histograms[0]);
// Create Huffman bit lengths and codes for each histogram image.
assert(histogram_image->size == 1);
if (!GetHuffBitLengthsAndCodes(histogram_image, huffman_codes)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
// No color cache, no Huffman image.
VP8LPutBits(bw, 0, 1);
// Find maximum number of symbols for the huffman tree-set.
for (i = 0; i < 5; ++i) {
HuffmanTreeCode* const codes = &huffman_codes[i];
if (max_tokens < codes->num_symbols) {
max_tokens = codes->num_symbols;
}
}
tokens = (HuffmanTreeToken*)WebPSafeMalloc(max_tokens, sizeof(*tokens));
if (tokens == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
// Store Huffman codes.
for (i = 0; i < 5; ++i) {
HuffmanTreeCode* const codes = &huffman_codes[i];
StoreHuffmanCode(bw, huff_tree, tokens, codes);
ClearHuffmanTreeIfOnlyOneSymbol(codes);
}
// Store actual literals.
err = StoreImageToBitMask(bw, width, 0, refs, histogram_symbols,
huffman_codes);
Error:
WebPSafeFree(tokens);
WebPSafeFree(huff_tree);
VP8LFreeHistogramSet(histogram_image);
WebPSafeFree(huffman_codes[0].codes);
return err;
}
static WebPEncodingError EncodeImageInternal(VP8LBitWriter* const bw,
const uint32_t* const argb,
VP8LHashChain* const hash_chain,
VP8LBackwardRefs refs_array[2],
int width, int height, int quality,
int low_effort,
int use_cache, int* cache_bits,
int histogram_bits,
size_t init_byte_position,
int* const hdr_size,
int* const data_size) {
WebPEncodingError err = VP8_ENC_OK;
const uint32_t histogram_image_xysize =
VP8LSubSampleSize(width, histogram_bits) *
VP8LSubSampleSize(height, histogram_bits);
VP8LHistogramSet* histogram_image = NULL;
VP8LHistogramSet* tmp_histos = NULL;
int histogram_image_size = 0;
size_t bit_array_size = 0;
HuffmanTree* huff_tree = NULL;
HuffmanTreeToken* tokens = NULL;
HuffmanTreeCode* huffman_codes = NULL;
VP8LBackwardRefs refs;
VP8LBackwardRefs* best_refs;
uint16_t* const histogram_symbols =
(uint16_t*)WebPSafeMalloc(histogram_image_xysize,
sizeof(*histogram_symbols));
assert(histogram_bits >= MIN_HUFFMAN_BITS);
assert(histogram_bits <= MAX_HUFFMAN_BITS);
assert(hdr_size != NULL);
assert(data_size != NULL);
VP8LBackwardRefsInit(&refs, refs_array[0].block_size_);
if (histogram_symbols == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
*cache_bits = use_cache ? MAX_COLOR_CACHE_BITS : 0;
// 'best_refs' is the reference to the best backward refs and points to one
// of refs_array[0] or refs_array[1].
// Calculate backward references from ARGB image.
if (VP8LHashChainFill(hash_chain, quality, argb, width, height) == 0) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
best_refs = VP8LGetBackwardReferences(width, height, argb, quality,
low_effort, cache_bits, hash_chain,
refs_array);
if (best_refs == NULL || !VP8LBackwardRefsCopy(best_refs, &refs)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
histogram_image =
VP8LAllocateHistogramSet(histogram_image_xysize, *cache_bits);
tmp_histos = VP8LAllocateHistogramSet(2, *cache_bits);
if (histogram_image == NULL || tmp_histos == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
// Build histogram image and symbols from backward references.
if (!VP8LGetHistoImageSymbols(width, height, &refs, quality, low_effort,
histogram_bits, *cache_bits, histogram_image,
tmp_histos, histogram_symbols)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
// Create Huffman bit lengths and codes for each histogram image.
histogram_image_size = histogram_image->size;
bit_array_size = 5 * histogram_image_size;
huffman_codes = (HuffmanTreeCode*)WebPSafeCalloc(bit_array_size,
sizeof(*huffman_codes));
// Note: some histogram_image entries may point to tmp_histos[], so the latter
// need to outlive the following call to GetHuffBitLengthsAndCodes().
if (huffman_codes == NULL ||
!GetHuffBitLengthsAndCodes(histogram_image, huffman_codes)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
// Free combined histograms.
VP8LFreeHistogramSet(histogram_image);
histogram_image = NULL;
// Free scratch histograms.
VP8LFreeHistogramSet(tmp_histos);
tmp_histos = NULL;
// Color Cache parameters.
if (*cache_bits > 0) {
VP8LPutBits(bw, 1, 1);
VP8LPutBits(bw, *cache_bits, 4);
} else {
VP8LPutBits(bw, 0, 1);
}
// Huffman image + meta huffman.
{
const int write_histogram_image = (histogram_image_size > 1);
VP8LPutBits(bw, write_histogram_image, 1);
if (write_histogram_image) {
uint32_t* const histogram_argb =
(uint32_t*)WebPSafeMalloc(histogram_image_xysize,
sizeof(*histogram_argb));
int max_index = 0;
uint32_t i;
if (histogram_argb == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
for (i = 0; i < histogram_image_xysize; ++i) {
const int symbol_index = histogram_symbols[i] & 0xffff;
histogram_argb[i] = (symbol_index << 8);
if (symbol_index >= max_index) {
max_index = symbol_index + 1;
}
}
histogram_image_size = max_index;
VP8LPutBits(bw, histogram_bits - 2, 3);
err = EncodeImageNoHuffman(bw, histogram_argb, hash_chain, refs_array,
VP8LSubSampleSize(width, histogram_bits),
VP8LSubSampleSize(height, histogram_bits),
quality);
WebPSafeFree(histogram_argb);
if (err != VP8_ENC_OK) goto Error;
}
}
// Store Huffman codes.
{
int i;
int max_tokens = 0;
huff_tree = (HuffmanTree*)WebPSafeMalloc(3ULL * CODE_LENGTH_CODES,
sizeof(*huff_tree));
if (huff_tree == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
// Find maximum number of symbols for the huffman tree-set.
for (i = 0; i < 5 * histogram_image_size; ++i) {
HuffmanTreeCode* const codes = &huffman_codes[i];
if (max_tokens < codes->num_symbols) {
max_tokens = codes->num_symbols;
}
}
tokens = (HuffmanTreeToken*)WebPSafeMalloc(max_tokens,
sizeof(*tokens));
if (tokens == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
for (i = 0; i < 5 * histogram_image_size; ++i) {
HuffmanTreeCode* const codes = &huffman_codes[i];
StoreHuffmanCode(bw, huff_tree, tokens, codes);
ClearHuffmanTreeIfOnlyOneSymbol(codes);
}
}
*hdr_size = (int)(VP8LBitWriterNumBytes(bw) - init_byte_position);
// Store actual literals.
err = StoreImageToBitMask(bw, width, histogram_bits, &refs,
histogram_symbols, huffman_codes);
*data_size =
(int)(VP8LBitWriterNumBytes(bw) - init_byte_position - *hdr_size);
Error:
WebPSafeFree(tokens);
WebPSafeFree(huff_tree);
VP8LFreeHistogramSet(histogram_image);
VP8LFreeHistogramSet(tmp_histos);
VP8LBackwardRefsClear(&refs);
if (huffman_codes != NULL) {
WebPSafeFree(huffman_codes->codes);
WebPSafeFree(huffman_codes);
}
WebPSafeFree(histogram_symbols);
return err;
}
// -----------------------------------------------------------------------------
// Transforms
static void ApplySubtractGreen(VP8LEncoder* const enc, int width, int height,
VP8LBitWriter* const bw) {
VP8LPutBits(bw, TRANSFORM_PRESENT, 1);
VP8LPutBits(bw, SUBTRACT_GREEN, 2);
VP8LSubtractGreenFromBlueAndRed(enc->argb_, width * height);
}
static WebPEncodingError ApplyPredictFilter(const VP8LEncoder* const enc,
int width, int height,
int quality, int low_effort,
int used_subtract_green,
VP8LBitWriter* const bw) {
const int pred_bits = enc->transform_bits_;
const int transform_width = VP8LSubSampleSize(width, pred_bits);
const int transform_height = VP8LSubSampleSize(height, pred_bits);
// we disable near-lossless quantization if palette is used.
const int near_lossless_strength = enc->use_palette_ ? 100
: enc->config_->near_lossless;
VP8LResidualImage(width, height, pred_bits, low_effort, enc->argb_,
enc->argb_scratch_, enc->transform_data_,
near_lossless_strength, enc->config_->exact,
used_subtract_green);
VP8LPutBits(bw, TRANSFORM_PRESENT, 1);
VP8LPutBits(bw, PREDICTOR_TRANSFORM, 2);
assert(pred_bits >= 2);
VP8LPutBits(bw, pred_bits - 2, 3);
return EncodeImageNoHuffman(bw, enc->transform_data_,
(VP8LHashChain*)&enc->hash_chain_,
(VP8LBackwardRefs*)enc->refs_, // cast const away
transform_width, transform_height,
quality);
}
static WebPEncodingError ApplyCrossColorFilter(const VP8LEncoder* const enc,
int width, int height,
int quality,
VP8LBitWriter* const bw) {
const int ccolor_transform_bits = enc->transform_bits_;
const int transform_width = VP8LSubSampleSize(width, ccolor_transform_bits);
const int transform_height = VP8LSubSampleSize(height, ccolor_transform_bits);
VP8LColorSpaceTransform(width, height, ccolor_transform_bits, quality,
enc->argb_, enc->transform_data_);
VP8LPutBits(bw, TRANSFORM_PRESENT, 1);
VP8LPutBits(bw, CROSS_COLOR_TRANSFORM, 2);
assert(ccolor_transform_bits >= 2);
VP8LPutBits(bw, ccolor_transform_bits - 2, 3);
return EncodeImageNoHuffman(bw, enc->transform_data_,
(VP8LHashChain*)&enc->hash_chain_,
(VP8LBackwardRefs*)enc->refs_, // cast const away
transform_width, transform_height,
quality);
}
// -----------------------------------------------------------------------------
static WebPEncodingError WriteRiffHeader(const WebPPicture* const pic,
size_t riff_size, size_t vp8l_size) {
uint8_t riff[RIFF_HEADER_SIZE + CHUNK_HEADER_SIZE + VP8L_SIGNATURE_SIZE] = {
'R', 'I', 'F', 'F', 0, 0, 0, 0, 'W', 'E', 'B', 'P',
'V', 'P', '8', 'L', 0, 0, 0, 0, VP8L_MAGIC_BYTE,
};
PutLE32(riff + TAG_SIZE, (uint32_t)riff_size);
PutLE32(riff + RIFF_HEADER_SIZE + TAG_SIZE, (uint32_t)vp8l_size);
if (!pic->writer(riff, sizeof(riff), pic)) {
return VP8_ENC_ERROR_BAD_WRITE;
}
return VP8_ENC_OK;
}
static int WriteImageSize(const WebPPicture* const pic,
VP8LBitWriter* const bw) {
const int width = pic->width - 1;
const int height = pic->height - 1;
assert(width < WEBP_MAX_DIMENSION && height < WEBP_MAX_DIMENSION);
VP8LPutBits(bw, width, VP8L_IMAGE_SIZE_BITS);
VP8LPutBits(bw, height, VP8L_IMAGE_SIZE_BITS);
return !bw->error_;
}
static int WriteRealAlphaAndVersion(VP8LBitWriter* const bw, int has_alpha) {
VP8LPutBits(bw, has_alpha, 1);
VP8LPutBits(bw, VP8L_VERSION, VP8L_VERSION_BITS);
return !bw->error_;
}
static WebPEncodingError WriteImage(const WebPPicture* const pic,
VP8LBitWriter* const bw,
size_t* const coded_size) {
WebPEncodingError err = VP8_ENC_OK;
const uint8_t* const webpll_data = VP8LBitWriterFinish(bw);
const size_t webpll_size = VP8LBitWriterNumBytes(bw);
const size_t vp8l_size = VP8L_SIGNATURE_SIZE + webpll_size;
const size_t pad = vp8l_size & 1;
const size_t riff_size = TAG_SIZE + CHUNK_HEADER_SIZE + vp8l_size + pad;
err = WriteRiffHeader(pic, riff_size, vp8l_size);
if (err != VP8_ENC_OK) goto Error;
if (!pic->writer(webpll_data, webpll_size, pic)) {
err = VP8_ENC_ERROR_BAD_WRITE;
goto Error;
}
if (pad) {
const uint8_t pad_byte[1] = { 0 };
if (!pic->writer(pad_byte, 1, pic)) {
err = VP8_ENC_ERROR_BAD_WRITE;
goto Error;
}
}
*coded_size = CHUNK_HEADER_SIZE + riff_size;
return VP8_ENC_OK;
Error:
return err;
}
// -----------------------------------------------------------------------------
static void ClearTransformBuffer(VP8LEncoder* const enc) {
WebPSafeFree(enc->transform_mem_);
enc->transform_mem_ = NULL;
enc->transform_mem_size_ = 0;
}
// Allocates the memory for argb (W x H) buffer, 2 rows of context for
// prediction and transform data.
// Flags influencing the memory allocated:
// enc->transform_bits_
// enc->use_predict_, enc->use_cross_color_
static WebPEncodingError AllocateTransformBuffer(VP8LEncoder* const enc,
int width, int height) {
WebPEncodingError err = VP8_ENC_OK;
const uint64_t image_size = width * height;
// VP8LResidualImage needs room for 2 scanlines of uint32 pixels with an extra
// pixel in each, plus 2 regular scanlines of bytes.
// TODO(skal): Clean up by using arithmetic in bytes instead of words.
const uint64_t argb_scratch_size =
enc->use_predict_
? (width + 1) * 2 +
(width * 2 + sizeof(uint32_t) - 1) / sizeof(uint32_t)
: 0;
const uint64_t transform_data_size =
(enc->use_predict_ || enc->use_cross_color_)
? VP8LSubSampleSize(width, enc->transform_bits_) *
VP8LSubSampleSize(height, enc->transform_bits_)
: 0;
const uint64_t max_alignment_in_words =
(WEBP_ALIGN_CST + sizeof(uint32_t) - 1) / sizeof(uint32_t);
const uint64_t mem_size =
image_size + max_alignment_in_words +
argb_scratch_size + max_alignment_in_words +
transform_data_size;
uint32_t* mem = enc->transform_mem_;
if (mem == NULL || mem_size > enc->transform_mem_size_) {
ClearTransformBuffer(enc);
mem = (uint32_t*)WebPSafeMalloc(mem_size, sizeof(*mem));
if (mem == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
enc->transform_mem_ = mem;
enc->transform_mem_size_ = (size_t)mem_size;
}
enc->argb_ = mem;
mem = (uint32_t*)WEBP_ALIGN(mem + image_size);
enc->argb_scratch_ = mem;
mem = (uint32_t*)WEBP_ALIGN(mem + argb_scratch_size);
enc->transform_data_ = mem;
enc->current_width_ = width;
Error:
return err;
}
static WebPEncodingError MakeInputImageCopy(VP8LEncoder* const enc) {
WebPEncodingError err = VP8_ENC_OK;
const WebPPicture* const picture = enc->pic_;
const int width = picture->width;
const int height = picture->height;
int y;
err = AllocateTransformBuffer(enc, width, height);
if (err != VP8_ENC_OK) return err;
for (y = 0; y < height; ++y) {
memcpy(enc->argb_ + y * width,
picture->argb + y * picture->argb_stride,
width * sizeof(*enc->argb_));
}
assert(enc->current_width_ == width);
return VP8_ENC_OK;
}
// -----------------------------------------------------------------------------
static int SearchColor(const uint32_t sorted[], uint32_t color, int hi) {
int low = 0;
if (sorted[low] == color) return low; // loop invariant: sorted[low] != color
while (1) {
const int mid = (low + hi) >> 1;
if (sorted[mid] == color) {
return mid;
} else if (sorted[mid] < color) {
low = mid;
} else {
hi = mid;
}
}
}
// Sort palette in increasing order and prepare an inverse mapping array.
static void PrepareMapToPalette(const uint32_t palette[], int num_colors,
uint32_t sorted[], int idx_map[]) {
int i;
memcpy(sorted, palette, num_colors * sizeof(*sorted));
qsort(sorted, num_colors, sizeof(*sorted), PaletteCompareColorsForQsort);
for (i = 0; i < num_colors; ++i) {
idx_map[SearchColor(sorted, palette[i], num_colors)] = i;
}
}
static void MapToPalette(const uint32_t sorted_palette[], int num_colors,
uint32_t* const last_pix, int* const last_idx,
const int idx_map[],
const uint32_t* src, uint8_t* dst, int width) {
int x;
int prev_idx = *last_idx;
uint32_t prev_pix = *last_pix;
for (x = 0; x < width; ++x) {
const uint32_t pix = src[x];
if (pix != prev_pix) {
prev_idx = idx_map[SearchColor(sorted_palette, pix, num_colors)];
prev_pix = pix;
}
dst[x] = prev_idx;
}
*last_idx = prev_idx;
*last_pix = prev_pix;
}
// Remap argb values in src[] to packed palettes entries in dst[]
// using 'row' as a temporary buffer of size 'width'.
// We assume that all src[] values have a corresponding entry in the palette.
// Note: src[] can be the same as dst[]
static WebPEncodingError ApplyPalette(const uint32_t* src, uint32_t src_stride,
uint32_t* dst, uint32_t dst_stride,
const uint32_t* palette, int palette_size,
int width, int height, int xbits) {
// TODO(skal): this tmp buffer is not needed if VP8LBundleColorMap() can be
// made to work in-place.
uint8_t* const tmp_row = (uint8_t*)WebPSafeMalloc(width, sizeof(*tmp_row));
int i, x, y;
int use_LUT = 1;
if (tmp_row == NULL) return VP8_ENC_ERROR_OUT_OF_MEMORY;
for (i = 0; i < palette_size; ++i) {
if ((palette[i] & 0xffff00ffu) != 0) {
use_LUT = 0;
break;
}
}
if (use_LUT) {
uint8_t inv_palette[MAX_PALETTE_SIZE] = { 0 };
for (i = 0; i < palette_size; ++i) {
const int color = (palette[i] >> 8) & 0xff;
inv_palette[color] = i;
}
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
const int color = (src[x] >> 8) & 0xff;
tmp_row[x] = inv_palette[color];
}
VP8LBundleColorMap(tmp_row, width, xbits, dst);
src += src_stride;
dst += dst_stride;
}
} else {
// Use 1 pixel cache for ARGB pixels.
uint32_t last_pix;
int last_idx;
uint32_t sorted[MAX_PALETTE_SIZE];
int idx_map[MAX_PALETTE_SIZE];
PrepareMapToPalette(palette, palette_size, sorted, idx_map);
last_pix = palette[0];
last_idx = 0;
for (y = 0; y < height; ++y) {
MapToPalette(sorted, palette_size, &last_pix, &last_idx,
idx_map, src, tmp_row, width);
VP8LBundleColorMap(tmp_row, width, xbits, dst);
src += src_stride;
dst += dst_stride;
}
}
WebPSafeFree(tmp_row);
return VP8_ENC_OK;
}
// Note: Expects "enc->palette_" to be set properly.
static WebPEncodingError MapImageFromPalette(VP8LEncoder* const enc,
int in_place) {
WebPEncodingError err = VP8_ENC_OK;
const WebPPicture* const pic = enc->pic_;
const int width = pic->width;
const int height = pic->height;
const uint32_t* const palette = enc->palette_;
const uint32_t* src = in_place ? enc->argb_ : pic->argb;
const int src_stride = in_place ? enc->current_width_ : pic->argb_stride;
const int palette_size = enc->palette_size_;
int xbits;
// Replace each input pixel by corresponding palette index.
// This is done line by line.
if (palette_size <= 4) {
xbits = (palette_size <= 2) ? 3 : 2;
} else {
xbits = (palette_size <= 16) ? 1 : 0;
}
err = AllocateTransformBuffer(enc, VP8LSubSampleSize(width, xbits), height);
if (err != VP8_ENC_OK) return err;
err = ApplyPalette(src, src_stride,
enc->argb_, enc->current_width_,
palette, palette_size, width, height, xbits);
return err;
}
// Save palette_[] to bitstream.
static WebPEncodingError EncodePalette(VP8LBitWriter* const bw,
VP8LEncoder* const enc) {
int i;
uint32_t tmp_palette[MAX_PALETTE_SIZE];
const int palette_size = enc->palette_size_;
const uint32_t* const palette = enc->palette_;
VP8LPutBits(bw, TRANSFORM_PRESENT, 1);
VP8LPutBits(bw, COLOR_INDEXING_TRANSFORM, 2);
assert(palette_size >= 1 && palette_size <= MAX_PALETTE_SIZE);
VP8LPutBits(bw, palette_size - 1, 8);
for (i = palette_size - 1; i >= 1; --i) {
tmp_palette[i] = VP8LSubPixels(palette[i], palette[i - 1]);
}
tmp_palette[0] = palette[0];
return EncodeImageNoHuffman(bw, tmp_palette, &enc->hash_chain_, enc->refs_,
palette_size, 1, 20 /* quality */);
}
#ifdef WEBP_EXPERIMENTAL_FEATURES
static WebPEncodingError EncodeDeltaPalettePredictorImage(
VP8LBitWriter* const bw, VP8LEncoder* const enc, int quality) {
const WebPPicture* const pic = enc->pic_;
const int width = pic->width;
const int height = pic->height;
const int pred_bits = 5;
const int transform_width = VP8LSubSampleSize(width, pred_bits);
const int transform_height = VP8LSubSampleSize(height, pred_bits);
const int pred = 7; // default is Predictor7 (Top/Left Average)
const int tiles_per_row = VP8LSubSampleSize(width, pred_bits);
const int tiles_per_col = VP8LSubSampleSize(height, pred_bits);
uint32_t* predictors;
int tile_x, tile_y;
WebPEncodingError err = VP8_ENC_OK;
predictors = (uint32_t*)WebPSafeMalloc(tiles_per_col * tiles_per_row,
sizeof(*predictors));
if (predictors == NULL) return VP8_ENC_ERROR_OUT_OF_MEMORY;
for (tile_y = 0; tile_y < tiles_per_col; ++tile_y) {
for (tile_x = 0; tile_x < tiles_per_row; ++tile_x) {
predictors[tile_y * tiles_per_row + tile_x] = 0xff000000u | (pred << 8);
}
}
VP8LPutBits(bw, TRANSFORM_PRESENT, 1);
VP8LPutBits(bw, PREDICTOR_TRANSFORM, 2);
VP8LPutBits(bw, pred_bits - 2, 3);
err = EncodeImageNoHuffman(bw, predictors, &enc->hash_chain_,
(VP8LBackwardRefs*)enc->refs_, // cast const away
transform_width, transform_height,
quality);
WebPSafeFree(predictors);
return err;
}
#endif // WEBP_EXPERIMENTAL_FEATURES
// -----------------------------------------------------------------------------
// VP8LEncoder
static VP8LEncoder* VP8LEncoderNew(const WebPConfig* const config,
const WebPPicture* const picture) {
VP8LEncoder* const enc = (VP8LEncoder*)WebPSafeCalloc(1ULL, sizeof(*enc));
if (enc == NULL) {
WebPEncodingSetError(picture, VP8_ENC_ERROR_OUT_OF_MEMORY);
return NULL;
}
enc->config_ = config;
enc->pic_ = picture;
VP8LEncDspInit();
return enc;
}
static void VP8LEncoderDelete(VP8LEncoder* enc) {
if (enc != NULL) {
VP8LHashChainClear(&enc->hash_chain_);
VP8LBackwardRefsClear(&enc->refs_[0]);
VP8LBackwardRefsClear(&enc->refs_[1]);
ClearTransformBuffer(enc);
WebPSafeFree(enc);
}
}
// -----------------------------------------------------------------------------
// Main call
WebPEncodingError VP8LEncodeStream(const WebPConfig* const config,
const WebPPicture* const picture,
VP8LBitWriter* const bw, int use_cache) {
WebPEncodingError err = VP8_ENC_OK;
const int quality = (int)config->quality;
const int low_effort = (config->method == 0);
const int width = picture->width;
const int height = picture->height;
VP8LEncoder* const enc = VP8LEncoderNew(config, picture);
const size_t byte_position = VP8LBitWriterNumBytes(bw);
int use_near_lossless = 0;
int hdr_size = 0;
int data_size = 0;
int use_delta_palettization = 0;
if (enc == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
// ---------------------------------------------------------------------------
// Analyze image (entropy, num_palettes etc)
if (!AnalyzeAndInit(enc)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
// Apply near-lossless preprocessing.
use_near_lossless =
(config->near_lossless < 100) && !enc->use_palette_ && !enc->use_predict_;
if (use_near_lossless) {
if (!VP8ApplyNearLossless(width, height, picture->argb,
config->near_lossless)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
}
#ifdef WEBP_EXPERIMENTAL_FEATURES
if (config->delta_palettization) {
enc->use_predict_ = 1;
enc->use_cross_color_ = 0;
enc->use_subtract_green_ = 0;
enc->use_palette_ = 1;
err = MakeInputImageCopy(enc);
if (err != VP8_ENC_OK) goto Error;
err = WebPSearchOptimalDeltaPalette(enc);
if (err != VP8_ENC_OK) goto Error;
if (enc->use_palette_) {
err = AllocateTransformBuffer(enc, width, height);
if (err != VP8_ENC_OK) goto Error;
err = EncodeDeltaPalettePredictorImage(bw, enc, quality);
if (err != VP8_ENC_OK) goto Error;
use_delta_palettization = 1;
}
}
#endif // WEBP_EXPERIMENTAL_FEATURES
// Encode palette
if (enc->use_palette_) {
err = EncodePalette(bw, enc);
if (err != VP8_ENC_OK) goto Error;
err = MapImageFromPalette(enc, use_delta_palettization);
if (err != VP8_ENC_OK) goto Error;
}
if (!use_delta_palettization) {
// In case image is not packed.
if (enc->argb_ == NULL) {
err = MakeInputImageCopy(enc);
if (err != VP8_ENC_OK) goto Error;
}
// -------------------------------------------------------------------------
// Apply transforms and write transform data.
if (enc->use_subtract_green_) {
ApplySubtractGreen(enc, enc->current_width_, height, bw);
}
if (enc->use_predict_) {
err = ApplyPredictFilter(enc, enc->current_width_, height, quality,
low_effort, enc->use_subtract_green_, bw);
if (err != VP8_ENC_OK) goto Error;
}
if (enc->use_cross_color_) {
err = ApplyCrossColorFilter(enc, enc->current_width_,
height, quality, bw);
if (err != VP8_ENC_OK) goto Error;
}
}
VP8LPutBits(bw, !TRANSFORM_PRESENT, 1); // No more transforms.
// ---------------------------------------------------------------------------
// Encode and write the transformed image.
err = EncodeImageInternal(bw, enc->argb_, &enc->hash_chain_, enc->refs_,
enc->current_width_, height, quality, low_effort,
use_cache, &enc->cache_bits_, enc->histo_bits_,
byte_position, &hdr_size, &data_size);
if (err != VP8_ENC_OK) goto Error;
if (picture->stats != NULL) {
WebPAuxStats* const stats = picture->stats;
stats->lossless_features = 0;
if (enc->use_predict_) stats->lossless_features |= 1;
if (enc->use_cross_color_) stats->lossless_features |= 2;
if (enc->use_subtract_green_) stats->lossless_features |= 4;
if (enc->use_palette_) stats->lossless_features |= 8;
stats->histogram_bits = enc->histo_bits_;
stats->transform_bits = enc->transform_bits_;
stats->cache_bits = enc->cache_bits_;
stats->palette_size = enc->palette_size_;
stats->lossless_size = (int)(VP8LBitWriterNumBytes(bw) - byte_position);
stats->lossless_hdr_size = hdr_size;
stats->lossless_data_size = data_size;
}
Error:
VP8LEncoderDelete(enc);
return err;
}
int VP8LEncodeImage(const WebPConfig* const config,
const WebPPicture* const picture) {
int width, height;
int has_alpha;
size_t coded_size;
int percent = 0;
int initial_size;
WebPEncodingError err = VP8_ENC_OK;
VP8LBitWriter bw;
if (picture == NULL) return 0;
if (config == NULL || picture->argb == NULL) {
err = VP8_ENC_ERROR_NULL_PARAMETER;
WebPEncodingSetError(picture, err);
return 0;
}
width = picture->width;
height = picture->height;
// Initialize BitWriter with size corresponding to 16 bpp to photo images and
// 8 bpp for graphical images.
initial_size = (config->image_hint == WEBP_HINT_GRAPH) ?
width * height : width * height * 2;
if (!VP8LBitWriterInit(&bw, initial_size)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
if (!WebPReportProgress(picture, 1, &percent)) {
UserAbort:
err = VP8_ENC_ERROR_USER_ABORT;
goto Error;
}
// Reset stats (for pure lossless coding)
if (picture->stats != NULL) {
WebPAuxStats* const stats = picture->stats;
memset(stats, 0, sizeof(*stats));
stats->PSNR[0] = 99.f;
stats->PSNR[1] = 99.f;
stats->PSNR[2] = 99.f;
stats->PSNR[3] = 99.f;
stats->PSNR[4] = 99.f;
}
// Write image size.
if (!WriteImageSize(picture, &bw)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
has_alpha = WebPPictureHasTransparency(picture);
// Write the non-trivial Alpha flag and lossless version.
if (!WriteRealAlphaAndVersion(&bw, has_alpha)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
if (!WebPReportProgress(picture, 5, &percent)) goto UserAbort;
// Encode main image stream.
err = VP8LEncodeStream(config, picture, &bw, 1 /*use_cache*/);
if (err != VP8_ENC_OK) goto Error;
// TODO(skal): have a fine-grained progress report in VP8LEncodeStream().
if (!WebPReportProgress(picture, 90, &percent)) goto UserAbort;
// Finish the RIFF chunk.
err = WriteImage(picture, &bw, &coded_size);
if (err != VP8_ENC_OK) goto Error;
if (!WebPReportProgress(picture, 100, &percent)) goto UserAbort;
// Save size.
if (picture->stats != NULL) {
picture->stats->coded_size += (int)coded_size;
picture->stats->lossless_size = (int)coded_size;
}
if (picture->extra_info != NULL) {
const int mb_w = (width + 15) >> 4;
const int mb_h = (height + 15) >> 4;
memset(picture->extra_info, 0, mb_w * mb_h * sizeof(*picture->extra_info));
}
Error:
if (bw.error_) err = VP8_ENC_ERROR_OUT_OF_MEMORY;
VP8LBitWriterWipeOut(&bw);
if (err != VP8_ENC_OK) {
WebPEncodingSetError(picture, err);
return 0;
}
return 1;
}
//------------------------------------------------------------------------------
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