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vp8l_enc.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 ([email protected])
//
#include <assert.h>
#include <stdlib.h>
#include "src/dsp/lossless.h"
#include "src/dsp/lossless_common.h"
#include "src/enc/backward_references_enc.h"
#include "src/enc/histogram_enc.h"
#include "src/enc/vp8i_enc.h"
#include "src/enc/vp8li_enc.h"
#include "src/utils/bit_writer_utils.h"
#include "src/utils/huffman_encode_utils.h"
#include "src/utils/palette.h"
#include "src/utils/utils.h"
#include "src/webp/encode.h"
#include "src/webp/format_constants.h"
// Maximum number of histogram images (sub-blocks).
#define MAX_HUFF_IMAGE_SIZE 2600
#define MAX_HUFFMAN_BITS (MIN_HUFFMAN_BITS + (1 << NUM_HUFFMAN_BITS) - 1)
// Empirical value for which it becomes too computationally expensive to
// compute the best predictor image.
#define MAX_PREDICTOR_IMAGE_SIZE (1 << 14)
// -----------------------------------------------------------------------------
// Palette
// These five modes are evaluated and their respective entropy is computed.
typedef enum {
kDirect = 0,
kSpatial = 1,
kSubGreen = 2,
kSpatialSubGreen = 3,
kPalette = 4,
kPaletteAndSpatial = 5,
kNumEntropyIx = 6
} 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* const r, uint32_t* const b) {
const int green = (int)p >> 8; // The upper bits are masked away later.
++r[(((int)p >> 16) - green) & 0xff];
++b[(((int)p >> 0) - green) & 0xff];
}
static void AddSingle(uint32_t p,
uint32_t* const a, uint32_t* const r,
uint32_t* const g, uint32_t* const b) {
++a[(p >> 24) & 0xff];
++r[(p >> 16) & 0xff];
++g[(p >> 8) & 0xff];
++b[(p >> 0) & 0xff];
}
static WEBP_INLINE uint32_t HashPix(uint32_t pix) {
// Note that masking with 0xffffffffu is for preventing an
// 'unsigned int overflow' warning. Doesn't impact the compiled code.
return ((((uint64_t)pix + (pix >> 19)) * 0x39c5fba7ull) & 0xffffffffu) >> 24;
}
static int AnalyzeEntropy(const uint32_t* argb,
int width, int height, int argb_stride,
int use_palette,
int palette_size, int transform_bits,
EntropyIx* const min_entropy_ix,
int* const red_and_blue_always_zero) {
// Allocate histogram set with cache_bits = 0.
uint32_t* histo;
if (use_palette && palette_size <= 16) {
// In the case of small palettes, we pack 2, 4 or 8 pixels together. In
// practice, small palettes are better than any other transform.
*min_entropy_ix = kPalette;
*red_and_blue_always_zero = 1;
return 1;
}
histo = (uint32_t*)WebPSafeCalloc(kHistoTotal, sizeof(*histo) * 256);
if (histo != NULL) {
int i, x, y;
const uint32_t* prev_row = NULL;
const uint32_t* curr_row = argb;
uint32_t pix_prev = argb[0]; // Skip the first pixel.
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
const uint32_t pix = curr_row[x];
const uint32_t pix_diff = VP8LSubPixels(pix, pix_prev);
pix_prev = pix;
if ((pix_diff == 0) || (prev_row != NULL && pix == prev_row[x])) {
continue;
}
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 uint32_t hash = HashPix(pix);
++histo[kHistoPalette * 256 + hash];
}
}
prev_row = curr_row;
curr_row += argb_stride;
}
{
uint64_t entropy_comp[kHistoTotal];
uint64_t entropy[kNumEntropyIx];
int k;
int 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);
}
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];
entropy[kPalette] = entropy_comp[kHistoPalette];
// When including transforms, there is an overhead in bits from
// storing them. This overhead is small but matters for small images.
// For spatial, there are 14 transformations.
entropy[kSpatial] += (uint64_t)VP8LSubSampleSize(width, transform_bits) *
VP8LSubSampleSize(height, transform_bits) *
VP8LFastLog2(14);
// For color transforms: 24 as only 3 channels are considered in a
// ColorTransformElement.
entropy[kSpatialSubGreen] +=
(uint64_t)VP8LSubSampleSize(width, transform_bits) *
VP8LSubSampleSize(height, transform_bits) * VP8LFastLog2(24);
// For palettes, add the cost of storing the palette.
// We empirically estimate the cost of a compressed entry as 8 bits.
// The palette is differential-coded when compressed hence a much
// lower cost than sizeof(uint32_t)*8.
entropy[kPalette] += (palette_size * 8ull) << LOG_2_PRECISION_BITS;
*min_entropy_ix = kDirect;
for (k = kDirect + 1; k <= last_mode_to_analyze; ++k) {
if (entropy[*min_entropy_ix] > entropy[k]) {
*min_entropy_ix = (EntropyIx)k;
}
}
assert((int)*min_entropy_ix <= last_mode_to_analyze);
*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;
}
}
// Clamp histogram and transform bits.
static int ClampBits(int width, int height, int bits, int min_bits,
int max_bits, int image_size_max) {
int image_size;
bits = (bits < min_bits) ? min_bits : (bits > max_bits) ? max_bits : bits;
image_size = VP8LSubSampleSize(width, bits) * VP8LSubSampleSize(height, bits);
while (bits < max_bits && image_size > image_size_max) {
++bits;
image_size =
VP8LSubSampleSize(width, bits) * VP8LSubSampleSize(height, bits);
}
// In case the bits reduce the image too much, choose the smallest value
// setting the histogram image size to 1.
while (bits > min_bits && image_size == 1) {
image_size = VP8LSubSampleSize(width, bits - 1) *
VP8LSubSampleSize(height, bits - 1);
if (image_size != 1) break;
--bits;
}
return bits;
}
static int GetHistoBits(int method, int use_palette, int width, int height) {
// Make tile size a function of encoding method (Range: 0 to 6).
const int histo_bits = (use_palette ? 9 : 7) - method;
return ClampBits(width, height, histo_bits, MIN_HUFFMAN_BITS,
MAX_HUFFMAN_BITS, MAX_HUFF_IMAGE_SIZE);
}
static int GetTransformBits(int method, int histo_bits) {
const int max_transform_bits = (method < 4) ? 6 : (method > 4) ? 4 : 5;
const int res =
(histo_bits > max_transform_bits) ? max_transform_bits : histo_bits;
assert(res <= MAX_TRANSFORM_BITS);
return res;
}
// Set of parameters to be used in each iteration of the cruncher.
#define CRUNCH_SUBCONFIGS_MAX 2
typedef struct {
int lz77_;
int do_no_cache_;
} CrunchSubConfig;
typedef struct {
int entropy_idx_;
PaletteSorting palette_sorting_type_;
CrunchSubConfig sub_configs_[CRUNCH_SUBCONFIGS_MAX];
int sub_configs_size_;
} CrunchConfig;
// +2 because we add a palette sorting configuration for kPalette and
// kPaletteAndSpatial.
#define CRUNCH_CONFIGS_MAX (kNumEntropyIx + 2 * kPaletteSortingNum)
static int EncoderAnalyze(VP8LEncoder* const enc,
CrunchConfig crunch_configs[CRUNCH_CONFIGS_MAX],
int* const crunch_configs_size,
int* const red_and_blue_always_zero) {
const WebPPicture* const pic = enc->pic_;
const int width = pic->width;
const int height = pic->height;
const WebPConfig* const config = enc->config_;
const int method = config->method;
const int low_effort = (config->method == 0);
int i;
int use_palette, transform_bits;
int n_lz77s;
// If set to 0, analyze the cache with the computed cache value. If 1, also
// analyze with no-cache.
int do_no_cache = 0;
assert(pic != NULL && pic->argb != NULL);
// Check whether a palette is possible.
enc->palette_size_ = GetColorPalette(pic, enc->palette_sorted_);
use_palette = (enc->palette_size_ <= MAX_PALETTE_SIZE);
if (!use_palette) {
enc->palette_size_ = 0;
}
// Empirical bit sizes.
enc->histo_bits_ = GetHistoBits(method, use_palette,
pic->width, pic->height);
transform_bits = GetTransformBits(method, enc->histo_bits_);
enc->predictor_transform_bits_ = transform_bits;
enc->cross_color_transform_bits_ = transform_bits;
if (low_effort) {
// AnalyzeEntropy is somewhat slow.
crunch_configs[0].entropy_idx_ = use_palette ? kPalette : kSpatialSubGreen;
crunch_configs[0].palette_sorting_type_ =
use_palette ? kSortedDefault : kUnusedPalette;
n_lz77s = 1;
*crunch_configs_size = 1;
} else {
EntropyIx min_entropy_ix;
// Try out multiple LZ77 on images with few colors.
n_lz77s = (enc->palette_size_ > 0 && enc->palette_size_ <= 16) ? 2 : 1;
if (!AnalyzeEntropy(pic->argb, width, height, pic->argb_stride, use_palette,
enc->palette_size_, transform_bits, &min_entropy_ix,
red_and_blue_always_zero)) {
return 0;
}
if (method == 6 && config->quality == 100) {
do_no_cache = 1;
// Go brute force on all transforms.
*crunch_configs_size = 0;
for (i = 0; i < kNumEntropyIx; ++i) {
// We can only apply kPalette or kPaletteAndSpatial if we can indeed use
// a palette.
if ((i != kPalette && i != kPaletteAndSpatial) || use_palette) {
assert(*crunch_configs_size < CRUNCH_CONFIGS_MAX);
if (use_palette && (i == kPalette || i == kPaletteAndSpatial)) {
int sorting_method;
for (sorting_method = 0; sorting_method < kPaletteSortingNum;
++sorting_method) {
const PaletteSorting typed_sorting_method =
(PaletteSorting)sorting_method;
// TODO(vrabaud) kSortedDefault should be tested. It is omitted
// for now for backward compatibility.
if (typed_sorting_method == kUnusedPalette ||
typed_sorting_method == kSortedDefault) {
continue;
}
crunch_configs[(*crunch_configs_size)].entropy_idx_ = i;
crunch_configs[(*crunch_configs_size)].palette_sorting_type_ =
typed_sorting_method;
++*crunch_configs_size;
}
} else {
crunch_configs[(*crunch_configs_size)].entropy_idx_ = i;
crunch_configs[(*crunch_configs_size)].palette_sorting_type_ =
kUnusedPalette;
++*crunch_configs_size;
}
}
}
} else {
// Only choose the guessed best transform.
*crunch_configs_size = 1;
crunch_configs[0].entropy_idx_ = min_entropy_ix;
crunch_configs[0].palette_sorting_type_ =
use_palette ? kMinimizeDelta : kUnusedPalette;
if (config->quality >= 75 && method == 5) {
// Test with and without color cache.
do_no_cache = 1;
// If we have a palette, also check in combination with spatial.
if (min_entropy_ix == kPalette) {
*crunch_configs_size = 2;
crunch_configs[1].entropy_idx_ = kPaletteAndSpatial;
crunch_configs[1].palette_sorting_type_ = kMinimizeDelta;
}
}
}
}
// Fill in the different LZ77s.
assert(n_lz77s <= CRUNCH_SUBCONFIGS_MAX);
for (i = 0; i < *crunch_configs_size; ++i) {
int j;
for (j = 0; j < n_lz77s; ++j) {
assert(j < CRUNCH_SUBCONFIGS_MAX);
crunch_configs[i].sub_configs_[j].lz77_ =
(j == 0) ? kLZ77Standard | kLZ77RLE : kLZ77Box;
crunch_configs[i].sub_configs_[j].do_no_cache_ = do_no_cache;
}
crunch_configs[i].sub_configs_size_ = n_lz77s;
}
return 1;
}
static int EncoderInit(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;
// we round the block size up, so we're guaranteed to have
// at most MAX_REFS_BLOCK_PER_IMAGE blocks used:
const int refs_block_size = (pix_cnt - 1) / MAX_REFS_BLOCK_PER_IMAGE + 1;
int i;
if (!VP8LHashChainInit(&enc->hash_chain_, pix_cnt)) return 0;
for (i = 0; i < 4; ++i) VP8LBackwardRefsInit(&enc->refs_[i], 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];
assert(histo != NULL);
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) {
if (trimmed_length == 2) {
VP8LPutBits(bw, 0, 3 + 2); // nbitpairs=1, trimmed_length=2
} else {
const int nbits = BitsLog2Floor(trimmed_length - 2);
const int nbitpairs = nbits / 2 + 1;
assert(trimmed_length > 2);
assert(nbitpairs - 1 < 8);
VP8LPutBits(bw, nbitpairs - 1, 3);
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 int StoreImageToBitMask(VP8LBitWriter* const bw, int width,
int histo_bits,
const VP8LBackwardRefs* const refs,
const uint32_t* histogram_symbols,
const HuffmanTreeCode* const huffman_codes,
const WebPPicture* const pic) {
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] >> 8) & 0xffff;
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)] >>
8) &
0xffff;
codes = huffman_codes + 5 * histogram_ix;
}
if (PixOrCopyIsLiteral(v)) {
static const uint8_t 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.
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);
}
if (bw->error_) {
return WebPEncodingSetError(pic, VP8_ENC_ERROR_OUT_OF_MEMORY);
}
return 1;
}
// Special case of EncodeImageInternal() for cache-bits=0, histo_bits=31.
// pic and percent are for progress.
static int EncodeImageNoHuffman(VP8LBitWriter* const bw,
const uint32_t* const argb,
VP8LHashChain* const hash_chain,
VP8LBackwardRefs* const refs_array, int width,
int height, int quality, int low_effort,
const WebPPicture* const pic, int percent_range,
int* const percent) {
int i;
int max_tokens = 0;
VP8LBackwardRefs* refs;
HuffmanTreeToken* tokens = NULL;
HuffmanTreeCode huffman_codes[5] = {{0, NULL, NULL}};
const uint32_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) {
WebPEncodingSetError(pic, VP8_ENC_ERROR_OUT_OF_MEMORY);
goto Error;
}
// Calculate backward references from ARGB image.
if (!VP8LHashChainFill(hash_chain, quality, argb, width, height, low_effort,
pic, percent_range / 2, percent)) {
goto Error;
}
if (!VP8LGetBackwardReferences(width, height, argb, quality, /*low_effort=*/0,
kLZ77Standard | kLZ77RLE, cache_bits,
/*do_no_cache=*/0, hash_chain, refs_array,
&cache_bits, pic,
percent_range - percent_range / 2, percent)) {
goto Error;
}
refs = &refs_array[0];
histogram_image = VP8LAllocateHistogramSet(1, cache_bits);
if (histogram_image == NULL) {
WebPEncodingSetError(pic, VP8_ENC_ERROR_OUT_OF_MEMORY);
goto Error;
}
VP8LHistogramSetClear(histogram_image);
// 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)) {
WebPEncodingSetError(pic, 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) {
WebPEncodingSetError(pic, 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.
if (!StoreImageToBitMask(bw, width, 0, refs, histogram_symbols, huffman_codes,
pic)) {
goto Error;
}
Error:
WebPSafeFree(tokens);
WebPSafeFree(huff_tree);
VP8LFreeHistogramSet(histogram_image);
WebPSafeFree(huffman_codes[0].codes);
return (pic->error_code == VP8_ENC_OK);
}
// pic and percent are for progress.
static int EncodeImageInternal(
VP8LBitWriter* const bw, const uint32_t* const argb,
VP8LHashChain* const hash_chain, VP8LBackwardRefs refs_array[4], int width,
int height, int quality, int low_effort, const CrunchConfig* const config,
int* cache_bits, int histogram_bits_in, size_t init_byte_position,
int* const hdr_size, int* const data_size, const WebPPicture* const pic,
int percent_range, int* const percent) {
const uint32_t histogram_image_xysize =
VP8LSubSampleSize(width, histogram_bits_in) *
VP8LSubSampleSize(height, histogram_bits_in);
int remaining_percent = percent_range;
int percent_start = *percent;
VP8LHistogramSet* histogram_image = NULL;
VP8LHistogram* tmp_histo = NULL;
uint32_t i, histogram_image_size = 0;
size_t bit_array_size = 0;
HuffmanTree* const huff_tree = (HuffmanTree*)WebPSafeMalloc(
3ULL * CODE_LENGTH_CODES, sizeof(*huff_tree));
HuffmanTreeToken* tokens = NULL;
HuffmanTreeCode* huffman_codes = NULL;
uint32_t* const histogram_argb = (uint32_t*)WebPSafeMalloc(
histogram_image_xysize, sizeof(*histogram_argb));
int sub_configs_idx;
int cache_bits_init, write_histogram_image;
VP8LBitWriter bw_init = *bw, bw_best;
int hdr_size_tmp;
VP8LHashChain hash_chain_histogram; // histogram image hash chain
size_t bw_size_best = ~(size_t)0;
assert(histogram_bits_in >= MIN_HUFFMAN_BITS);
assert(histogram_bits_in <= MAX_HUFFMAN_BITS);
assert(hdr_size != NULL);
assert(data_size != NULL);
memset(&hash_chain_histogram, 0, sizeof(hash_chain_histogram));
if (!VP8LBitWriterInit(&bw_best, 0)) {
WebPEncodingSetError(pic, VP8_ENC_ERROR_OUT_OF_MEMORY);
goto Error;
}
// Make sure we can allocate the different objects.
if (huff_tree == NULL || histogram_argb == NULL ||
!VP8LHashChainInit(&hash_chain_histogram, histogram_image_xysize)) {
WebPEncodingSetError(pic, VP8_ENC_ERROR_OUT_OF_MEMORY);
goto Error;
}
percent_range = remaining_percent / 5;
if (!VP8LHashChainFill(hash_chain, quality, argb, width, height,
low_effort, pic, percent_range, percent)) {
goto Error;
}
percent_start += percent_range;
remaining_percent -= percent_range;
// If the value is different from zero, it has been set during the palette
// analysis.
cache_bits_init = (*cache_bits == 0) ? MAX_COLOR_CACHE_BITS : *cache_bits;
// If several iterations will happen, clone into bw_best.
if ((config->sub_configs_size_ > 1 || config->sub_configs_[0].do_no_cache_) &&
!VP8LBitWriterClone(bw, &bw_best)) {
WebPEncodingSetError(pic, VP8_ENC_ERROR_OUT_OF_MEMORY);
goto Error;
}
for (sub_configs_idx = 0; sub_configs_idx < config->sub_configs_size_;
++sub_configs_idx) {
const CrunchSubConfig* const sub_config =
&config->sub_configs_[sub_configs_idx];
int cache_bits_best, i_cache;
int i_remaining_percent = remaining_percent / config->sub_configs_size_;
int i_percent_range = i_remaining_percent / 4;
i_remaining_percent -= i_percent_range;
if (!VP8LGetBackwardReferences(
width, height, argb, quality, low_effort, sub_config->lz77_,
cache_bits_init, sub_config->do_no_cache_, hash_chain,
&refs_array[0], &cache_bits_best, pic, i_percent_range, percent)) {
goto Error;
}
for (i_cache = 0; i_cache < (sub_config->do_no_cache_ ? 2 : 1); ++i_cache) {
const int cache_bits_tmp = (i_cache == 0) ? cache_bits_best : 0;
int histogram_bits = histogram_bits_in;
// Speed-up: no need to study the no-cache case if it was already studied
// in i_cache == 0.
if (i_cache == 1 && cache_bits_best == 0) break;
// Reset the bit writer for this iteration.
VP8LBitWriterReset(&bw_init, bw);
// Build histogram image and symbols from backward references.
histogram_image =
VP8LAllocateHistogramSet(histogram_image_xysize, cache_bits_tmp);
tmp_histo = VP8LAllocateHistogram(cache_bits_tmp);
if (histogram_image == NULL || tmp_histo == NULL) {
WebPEncodingSetError(pic, VP8_ENC_ERROR_OUT_OF_MEMORY);
goto Error;
}
i_percent_range = i_remaining_percent / 3;
i_remaining_percent -= i_percent_range;
if (!VP8LGetHistoImageSymbols(
width, height, &refs_array[i_cache], quality, low_effort,
histogram_bits, cache_bits_tmp, histogram_image, tmp_histo,
histogram_argb, pic, i_percent_range, percent)) {
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)) {
WebPEncodingSetError(pic, VP8_ENC_ERROR_OUT_OF_MEMORY);
goto Error;
}
// Free combined histograms.
VP8LFreeHistogramSet(histogram_image);
histogram_image = NULL;
// Free scratch histograms.
VP8LFreeHistogram(tmp_histo);
tmp_histo = NULL;
// Color Cache parameters.
if (cache_bits_tmp > 0) {
VP8LPutBits(bw, 1, 1);
VP8LPutBits(bw, cache_bits_tmp, 4);
} else {
VP8LPutBits(bw, 0, 1);
}
// Huffman image + meta huffman.
histogram_image_size = 0;
for (i = 0; i < histogram_image_xysize; ++i) {
if (histogram_argb[i] >= histogram_image_size) {
histogram_image_size = histogram_argb[i] + 1;
}
histogram_argb[i] <<= 8;
}
write_histogram_image = (histogram_image_size > 1);
VP8LPutBits(bw, write_histogram_image, 1);
if (write_histogram_image) {
VP8LOptimizeSampling(histogram_argb, width, height, histogram_bits_in,
MAX_HUFFMAN_BITS, &histogram_bits);
VP8LPutBits(bw, histogram_bits - 2, 3);
i_percent_range = i_remaining_percent / 2;
i_remaining_percent -= i_percent_range;
if (!EncodeImageNoHuffman(
bw, histogram_argb, &hash_chain_histogram, &refs_array[2],
VP8LSubSampleSize(width, histogram_bits),