// 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 <stdio.h>
#include <stdlib.h>
#include "./backward_references.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"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
#define PALETTE_KEY_RIGHT_SHIFT 22 // Key for 1K buffer.
#define MAX_HUFF_IMAGE_SIZE (16 * 1024 * 1024)
#define MAX_COLORS_FOR_GRAPH 64
// -----------------------------------------------------------------------------
// Palette
static int CompareColors(const void* p1, const void* p2) {
const uint32_t a = *(const uint32_t*)p1;
const uint32_t b = *(const uint32_t*)p2;
assert(a != b);
return (a < b) ? -1 : 1;
}
// 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,
uint32_t palette[MAX_PALETTE_SIZE],
int* const palette_size) {
int i, x, y, key;
int num_colors = 0;
uint8_t in_use[MAX_PALETTE_SIZE * 4] = { 0 };
uint32_t colors[MAX_PALETTE_SIZE * 4];
static const uint32_t kHashMul = 0x1e35a7bd;
const uint32_t* argb = pic->argb;
const int width = pic->width;
const int height = pic->height;
uint32_t last_pix = ~argb[0]; // so we're sure that last_pix != argb[0]
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
if (argb[x] == last_pix) {
continue;
}
last_pix = argb[x];
key = (kHashMul * last_pix) >> PALETTE_KEY_RIGHT_SHIFT;
while (1) {
if (!in_use[key]) {
colors[key] = last_pix;
in_use[key] = 1;
++num_colors;
if (num_colors > MAX_PALETTE_SIZE) {
return 0;
}
break;
} else if (colors[key] == last_pix) {
// The color is already there.
break;
} else {
// Some other color sits there.
// Do linear conflict resolution.
++key;
key &= (MAX_PALETTE_SIZE * 4 - 1); // key mask for 1K buffer.
}
}
}
argb += pic->argb_stride;
}
// TODO(skal): could we reuse in_use[] to speed up EncodePalette()?
num_colors = 0;
for (i = 0; i < (int)(sizeof(in_use) / sizeof(in_use[0])); ++i) {
if (in_use[i]) {
palette[num_colors] = colors[i];
++num_colors;
}
}
qsort(palette, num_colors, sizeof(*palette), CompareColors);
*palette_size = num_colors;
return 1;
}
static int AnalyzeEntropy(const uint32_t* argb,
int width, int height, int argb_stride,
double* const nonpredicted_bits,
double* const predicted_bits) {
int x, y;
const uint32_t* last_line = NULL;
uint32_t last_pix = argb[0]; // so we're sure that pix_diff == 0
VP8LHistogram* nonpredicted = NULL;
VP8LHistogram* predicted =
(VP8LHistogram*)malloc(2 * sizeof(*predicted));
if (predicted == NULL) return 0;
nonpredicted = predicted + 1;
VP8LHistogramInit(predicted, 0);
VP8LHistogramInit(nonpredicted, 0);
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
const uint32_t pix = argb[x];
const uint32_t pix_diff = VP8LSubPixels(pix, last_pix);
if (pix_diff == 0) continue;
if (last_line != NULL && pix == last_line[x]) {
continue;
}
last_pix = pix;
{
const PixOrCopy pix_token = PixOrCopyCreateLiteral(pix);
const PixOrCopy pix_diff_token = PixOrCopyCreateLiteral(pix_diff);
VP8LHistogramAddSinglePixOrCopy(nonpredicted, &pix_token);
VP8LHistogramAddSinglePixOrCopy(predicted, &pix_diff_token);
}
}
last_line = argb;
argb += argb_stride;
}
*nonpredicted_bits = VP8LHistogramEstimateBitsBulk(nonpredicted);
*predicted_bits = VP8LHistogramEstimateBitsBulk(predicted);
free(predicted);
return 1;
}
static int VP8LEncAnalyze(VP8LEncoder* const enc, WebPImageHint image_hint) {
const WebPPicture* const pic = enc->pic_;
assert(pic != NULL && pic->argb != NULL);
enc->use_palette_ =
AnalyzeAndCreatePalette(pic, enc->palette_, &enc->palette_size_);
if (image_hint == WEBP_HINT_GRAPH) {
if (enc->use_palette_ && enc->palette_size_ < MAX_COLORS_FOR_GRAPH) {
enc->use_palette_ = 0;
}
}
if (!enc->use_palette_) {
if (image_hint == WEBP_HINT_PHOTO) {
enc->use_predict_ = 1;
enc->use_cross_color_ = 1;
} else {
double non_pred_entropy, pred_entropy;
if (!AnalyzeEntropy(pic->argb, pic->width, pic->height, pic->argb_stride,
&non_pred_entropy, &pred_entropy)) {
return 0;
}
if (pred_entropy < 0.95 * non_pred_entropy) {
enc->use_predict_ = 1;
// TODO(vikasa): Observed some correlation of cross_color transform with
// predict. Need to investigate this further and add separate heuristic
// for setting use_cross_color flag.
enc->use_cross_color_ = 1;
}
}
}
return 1;
}
static int GetHuffBitLengthsAndCodes(
const VP8LHistogramSet* const histogram_image,
HuffmanTreeCode* const huffman_codes) {
int i, k;
int ok = 1;
uint64_t total_length_size = 0;
uint8_t* mem_buf = NULL;
const int histogram_image_size = histogram_image->size;
// 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)
: (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) {
ok = 0;
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;
}
}
// Create Huffman trees.
for (i = 0; ok && (i < histogram_image_size); ++i) {
HuffmanTreeCode* const codes = &huffman_codes[5 * i];
VP8LHistogram* const histo = histogram_image->histograms[i];
ok = ok && VP8LCreateHuffmanTree(histo->literal_, 15, codes + 0);
ok = ok && VP8LCreateHuffmanTree(histo->red_, 15, codes + 1);
ok = ok && VP8LCreateHuffmanTree(histo->blue_, 15, codes + 2);
ok = ok && VP8LCreateHuffmanTree(histo->alpha_, 15, codes + 3);
ok = ok && VP8LCreateHuffmanTree(histo->distance_, 15, codes + 4);
}
End:
if (!ok) {
free(mem_buf);
// If one VP8LCreateHuffmanTree() above fails, we need to clean up behind.
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;
}
}
VP8LWriteBits(bw, 4, codes_to_store - 4);
for (i = 0; i < codes_to_store; ++i) {
VP8LWriteBits(bw, 3, code_length_bitdepth[kStorageOrder[i]]);
}
}
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;
VP8LWriteBits(bw, huffman_code->code_lengths[ix], huffman_code->codes[ix]);
switch (ix) {
case 16:
VP8LWriteBits(bw, 2, extra_bits);
break;
case 17:
VP8LWriteBits(bw, 3, extra_bits);
break;
case 18:
VP8LWriteBits(bw, 7, extra_bits);
break;
}
}
}
static int StoreFullHuffmanCode(VP8LBitWriter* const bw,
const HuffmanTreeCode* const tree) {
int ok = 0;
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;
HuffmanTreeToken* const tokens =
(HuffmanTreeToken*)WebPSafeMalloc((uint64_t)max_tokens, sizeof(*tokens));
if (tokens == NULL) return 0;
huffman_code.num_symbols = CODE_LENGTH_CODES;
huffman_code.code_lengths = code_length_bitdepth;
huffman_code.codes = code_length_bitdepth_symbols;
VP8LWriteBits(bw, 1, 0);
num_tokens = VP8LCreateCompressedHuffmanTree(tree, tokens, max_tokens);
{
int histogram[CODE_LENGTH_CODES] = { 0 };
int i;
for (i = 0; i < num_tokens; ++i) {
++histogram[tokens[i].code];
}
if (!VP8LCreateHuffmanTree(histogram, 7, &huffman_code)) {
goto End;
}
}
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;
VP8LWriteBits(bw, 1, write_trimmed_length);
if (write_trimmed_length) {
const int nbits = VP8LBitsLog2Ceiling(trimmed_length - 1);
const int nbitpairs = (nbits == 0) ? 1 : (nbits + 1) / 2;
VP8LWriteBits(bw, 3, nbitpairs - 1);
assert(trimmed_length >= 2);
VP8LWriteBits(bw, nbitpairs * 2, trimmed_length - 2);
}
StoreHuffmanTreeToBitMask(bw, tokens, length, &huffman_code);
}
ok = 1;
End:
free(tokens);
return ok;
}
static int StoreHuffmanCode(VP8LBitWriter* const bw,
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
VP8LWriteBits(bw, 4, 0x01);
return 1;
} else if (count <= 2 && symbols[0] < kMaxSymbol && symbols[1] < kMaxSymbol) {
VP8LWriteBits(bw, 1, 1); // Small tree marker to encode 1 or 2 symbols.
VP8LWriteBits(bw, 1, count - 1);
if (symbols[0] <= 1) {
VP8LWriteBits(bw, 1, 0); // Code bit for small (1 bit) symbol value.
VP8LWriteBits(bw, 1, symbols[0]);
} else {
VP8LWriteBits(bw, 1, 1);
VP8LWriteBits(bw, 8, symbols[0]);
}
if (count == 2) {
VP8LWriteBits(bw, 8, symbols[1]);
}
return 1;
} else {
return StoreFullHuffmanCode(bw, huffman_code);
}
}
static 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];
VP8LWriteBits(bw, depth, symbol);
}
static void StoreImageToBitMask(
VP8LBitWriter* const bw, int width, int histo_bits,
const VP8LBackwardRefs* const refs,
const uint16_t* histogram_symbols,
const HuffmanTreeCode* const huffman_codes) {
// x and y trace the position in the image.
int x = 0;
int y = 0;
const int histo_xsize = histo_bits ? VP8LSubSampleSize(width, histo_bits) : 1;
int i;
for (i = 0; i < refs->size; ++i) {
const PixOrCopy* const v = &refs->refs[i];
const int histogram_ix = histogram_symbols[histo_bits ?
(y >> histo_bits) * histo_xsize +
(x >> histo_bits) : 0];
const HuffmanTreeCode* const codes = huffman_codes + 5 * histogram_ix;
if (PixOrCopyIsCacheIdx(v)) {
const int code = PixOrCopyCacheIdx(v);
const int literal_ix = 256 + NUM_LENGTH_CODES + code;
WriteHuffmanCode(bw, codes, literal_ix);
} else 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 {
int bits, n_bits;
int code, distance;
PrefixEncode(v->len, &code, &n_bits, &bits);
WriteHuffmanCode(bw, codes, 256 + code);
VP8LWriteBits(bw, n_bits, bits);
distance = PixOrCopyDistance(v);
PrefixEncode(distance, &code, &n_bits, &bits);
WriteHuffmanCode(bw, codes + 4, code);
VP8LWriteBits(bw, n_bits, bits);
}
x += PixOrCopyLength(v);
while (x >= width) {
x -= width;
++y;
}
}
}
// Special case of EncodeImageInternal() for cache-bits=0, histo_bits=31
static int EncodeImageNoHuffman(VP8LBitWriter* const bw,
const uint32_t* const argb,
int width, int height, int quality) {
int i;
int ok = 0;
VP8LBackwardRefs refs;
HuffmanTreeCode huffman_codes[5] = { { 0, NULL, NULL } };
const uint16_t histogram_symbols[1] = { 0 }; // only one tree, one symbol
VP8LHistogramSet* const histogram_image = VP8LAllocateHistogramSet(1, 0);
if (histogram_image == NULL) return 0;
// Calculate backward references from ARGB image.
if (!VP8LGetBackwardReferences(width, height, argb, quality, 0, 1, &refs)) {
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)) {
goto Error;
}
// No color cache, no Huffman image.
VP8LWriteBits(bw, 1, 0);
// Store Huffman codes.
for (i = 0; i < 5; ++i) {
HuffmanTreeCode* const codes = &huffman_codes[i];
if (!StoreHuffmanCode(bw, codes)) {
goto Error;
}
ClearHuffmanTreeIfOnlyOneSymbol(codes);
}
// Store actual literals.
StoreImageToBitMask(bw, width, 0, &refs, histogram_symbols, huffman_codes);
ok = 1;
Error:
free(histogram_image);
VP8LClearBackwardRefs(&refs);
free(huffman_codes[0].codes);
return ok;
}
static int EncodeImageInternal(VP8LBitWriter* const bw,
const uint32_t* const argb,
int width, int height, int quality,
int cache_bits, int histogram_bits) {
int ok = 0;
const int use_2d_locality = 1;
const int use_color_cache = (cache_bits > 0);
const uint32_t histogram_image_xysize =
VP8LSubSampleSize(width, histogram_bits) *
VP8LSubSampleSize(height, histogram_bits);
VP8LHistogramSet* histogram_image =
VP8LAllocateHistogramSet(histogram_image_xysize, 0);
int histogram_image_size = 0;
size_t bit_array_size = 0;
HuffmanTreeCode* huffman_codes = NULL;
VP8LBackwardRefs refs;
uint16_t* const histogram_symbols =
(uint16_t*)WebPSafeMalloc((uint64_t)histogram_image_xysize,
sizeof(*histogram_symbols));
assert(histogram_bits >= MIN_HUFFMAN_BITS);
assert(histogram_bits <= MAX_HUFFMAN_BITS);
if (histogram_image == NULL || histogram_symbols == NULL) {
free(histogram_image);
free(histogram_symbols);
return 0;
}
// Calculate backward references from ARGB image.
if (!VP8LGetBackwardReferences(width, height, argb, quality, cache_bits,
use_2d_locality, &refs)) {
goto Error;
}
// Build histogram image and symbols from backward references.
if (!VP8LGetHistoImageSymbols(width, height, &refs,
quality, histogram_bits, cache_bits,
histogram_image,
histogram_symbols)) {
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));
if (huffman_codes == NULL ||
!GetHuffBitLengthsAndCodes(histogram_image, huffman_codes)) {
goto Error;
}
// Free combined histograms.
free(histogram_image);
histogram_image = NULL;
// Color Cache parameters.
VP8LWriteBits(bw, 1, use_color_cache);
if (use_color_cache) {
VP8LWriteBits(bw, 4, cache_bits);
}
// Huffman image + meta huffman.
{
const int write_histogram_image = (histogram_image_size > 1);
VP8LWriteBits(bw, 1, write_histogram_image);
if (write_histogram_image) {
uint32_t* const histogram_argb =
(uint32_t*)WebPSafeMalloc((uint64_t)histogram_image_xysize,
sizeof(*histogram_argb));
int max_index = 0;
uint32_t i;
if (histogram_argb == NULL) goto Error;
for (i = 0; i < histogram_image_xysize; ++i) {
const int symbol_index = histogram_symbols[i] & 0xffff;
histogram_argb[i] = 0xff000000 | (symbol_index << 8);
if (symbol_index >= max_index) {
max_index = symbol_index + 1;
}
}
histogram_image_size = max_index;
VP8LWriteBits(bw, 3, histogram_bits - 2);
ok = EncodeImageNoHuffman(bw, histogram_argb,
VP8LSubSampleSize(width, histogram_bits),
VP8LSubSampleSize(height, histogram_bits),
quality);
free(histogram_argb);
if (!ok) goto Error;
}
}
// Store Huffman codes.
{
int i;
for (i = 0; i < 5 * histogram_image_size; ++i) {
HuffmanTreeCode* const codes = &huffman_codes[i];
if (!StoreHuffmanCode(bw, codes)) goto Error;
ClearHuffmanTreeIfOnlyOneSymbol(codes);
}
}
// Store actual literals.
StoreImageToBitMask(bw, width, histogram_bits, &refs,
histogram_symbols, huffman_codes);
ok = 1;
Error:
free(histogram_image);
VP8LClearBackwardRefs(&refs);
if (huffman_codes != NULL) {
free(huffman_codes->codes);
free(huffman_codes);
}
free(histogram_symbols);
return ok;
}
// -----------------------------------------------------------------------------
// Transforms
// Check if it would be a good idea to subtract green from red and blue. We
// only impact entropy in red/blue components, don't bother to look at others.
static int EvalAndApplySubtractGreen(VP8LEncoder* const enc,
int width, int height,
VP8LBitWriter* const bw) {
if (!enc->use_palette_) {
int i;
const uint32_t* const argb = enc->argb_;
double bit_cost_before, bit_cost_after;
VP8LHistogram* const histo = (VP8LHistogram*)malloc(sizeof(*histo));
if (histo == NULL) return 0;
VP8LHistogramInit(histo, 1);
for (i = 0; i < width * height; ++i) {
const uint32_t c = argb[i];
++histo->red_[(c >> 16) & 0xff];
++histo->blue_[(c >> 0) & 0xff];
}
bit_cost_before = VP8LHistogramEstimateBits(histo);
VP8LHistogramInit(histo, 1);
for (i = 0; i < width * height; ++i) {
const uint32_t c = argb[i];
const int green = (c >> 8) & 0xff;
++histo->red_[((c >> 16) - green) & 0xff];
++histo->blue_[((c >> 0) - green) & 0xff];
}
bit_cost_after = VP8LHistogramEstimateBits(histo);
free(histo);
// Check if subtracting green yields low entropy.
enc->use_subtract_green_ = (bit_cost_after < bit_cost_before);
if (enc->use_subtract_green_) {
VP8LWriteBits(bw, 1, TRANSFORM_PRESENT);
VP8LWriteBits(bw, 2, SUBTRACT_GREEN);
VP8LSubtractGreenFromBlueAndRed(enc->argb_, width * height);
}
}
return 1;
}
static int ApplyPredictFilter(const VP8LEncoder* const enc,
int width, int height, int quality,
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);
VP8LResidualImage(width, height, pred_bits, enc->argb_, enc->argb_scratch_,
enc->transform_data_);
VP8LWriteBits(bw, 1, TRANSFORM_PRESENT);
VP8LWriteBits(bw, 2, PREDICTOR_TRANSFORM);
assert(pred_bits >= 2);
VP8LWriteBits(bw, 3, pred_bits - 2);
if (!EncodeImageNoHuffman(bw, enc->transform_data_,
transform_width, transform_height, quality)) {
return 0;
}
return 1;
}
static int 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);
const int step = (quality == 0) ? 32 : 8;
VP8LColorSpaceTransform(width, height, ccolor_transform_bits, step,
enc->argb_, enc->transform_data_);
VP8LWriteBits(bw, 1, TRANSFORM_PRESENT);
VP8LWriteBits(bw, 2, CROSS_COLOR_TRANSFORM);
assert(ccolor_transform_bits >= 2);
VP8LWriteBits(bw, 3, ccolor_transform_bits - 2);
if (!EncodeImageNoHuffman(bw, enc->transform_data_,
transform_width, transform_height, quality)) {
return 0;
}
return 1;
}
// -----------------------------------------------------------------------------
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);
VP8LWriteBits(bw, VP8L_IMAGE_SIZE_BITS, width);
VP8LWriteBits(bw, VP8L_IMAGE_SIZE_BITS, height);
return !bw->error_;
}
static int WriteRealAlphaAndVersion(VP8LBitWriter* const bw, int has_alpha) {
VP8LWriteBits(bw, 1, has_alpha);
VP8LWriteBits(bw, VP8L_VERSION_BITS, VP8L_VERSION);
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;
}
// -----------------------------------------------------------------------------
// Allocates the memory for argb (W x H) buffer, 2 rows of context for
// prediction and transform data.
static WebPEncodingError AllocateTransformBuffer(VP8LEncoder* const enc,
int width, int height) {
WebPEncodingError err = VP8_ENC_OK;
const int tile_size = 1 << enc->transform_bits_;
const uint64_t image_size = width * height;
const uint64_t argb_scratch_size = tile_size * width + width;
const uint64_t transform_data_size =
(uint64_t)VP8LSubSampleSize(width, enc->transform_bits_) *
(uint64_t)VP8LSubSampleSize(height, enc->transform_bits_);
const uint64_t total_size =
image_size + argb_scratch_size + transform_data_size;
uint32_t* mem = (uint32_t*)WebPSafeMalloc(total_size, sizeof(*mem));
if (mem == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
enc->argb_ = mem;
mem += image_size;
enc->argb_scratch_ = mem;
mem += argb_scratch_size;
enc->transform_data_ = mem;
enc->current_width_ = width;
Error:
return err;
}
static void ApplyPalette(uint32_t* src, uint32_t* dst,
uint32_t src_stride, uint32_t dst_stride,
const uint32_t* palette, int palette_size,
int width, int height, int xbits, uint8_t* row) {
int i, x, y;
int use_LUT = 1;
for (i = 0; i < palette_size; ++i) {
if ((palette[i] & 0xffff00ffu) != 0) {
use_LUT = 0;
break;
}
}
if (use_LUT) {
int 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;
row[x] = inv_palette[color];
}
VP8LBundleColorMap(row, width, xbits, dst);
src += src_stride;
dst += dst_stride;
}
} else {
// Use 1 pixel cache for ARGB pixels.
uint32_t last_pix = palette[0];
int last_idx = 0;
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
const uint32_t pix = src[x];
if (pix != last_pix) {
for (i = 0; i < palette_size; ++i) {
if (pix == palette[i]) {
last_idx = i;
last_pix = pix;
break;
}
}
}
row[x] = last_idx;
}
VP8LBundleColorMap(row, width, xbits, dst);
src += src_stride;
dst += dst_stride;
}
}
}
// Note: Expects "enc->palette_" to be set properly.
// Also, "enc->palette_" will be modified after this call and should not be used
// later.
static WebPEncodingError EncodePalette(VP8LBitWriter* const bw,
VP8LEncoder* const enc, int quality) {
WebPEncodingError err = VP8_ENC_OK;
int i;
const WebPPicture* const pic = enc->pic_;
uint32_t* src = pic->argb;
uint32_t* dst;
const int width = pic->width;
const int height = pic->height;
uint32_t* const palette = enc->palette_;
const int palette_size = enc->palette_size_;
uint8_t* row = NULL;
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) goto Error;
dst = enc->argb_;
row = WebPSafeMalloc((uint64_t)width, sizeof(*row));
if (row == NULL) return VP8_ENC_ERROR_OUT_OF_MEMORY;
ApplyPalette(src, dst, pic->argb_stride, enc->current_width_,
palette, palette_size, width, height, xbits, row);
// Save palette to bitstream.
VP8LWriteBits(bw, 1, TRANSFORM_PRESENT);
VP8LWriteBits(bw, 2, COLOR_INDEXING_TRANSFORM);
assert(palette_size >= 1);
VP8LWriteBits(bw, 8, palette_size - 1);
for (i = palette_size - 1; i >= 1; --i) {
palette[i] = VP8LSubPixels(palette[i], palette[i - 1]);
}
if (!EncodeImageNoHuffman(bw, palette, palette_size, 1, quality)) {
err = VP8_ENC_ERROR_INVALID_CONFIGURATION;
goto Error;
}
Error:
free(row);
return err;
}
// -----------------------------------------------------------------------------
static int GetHistoBits(int method, int use_palette, int width, int height) {
const uint64_t hist_size = sizeof(VP8LHistogram);
// Make tile size a function of encoding method (Range: 0 to 6).
int histo_bits = (use_palette ? 9 : 7) - method;
while (1) {
const uint64_t huff_image_size = VP8LSubSampleSize(width, histo_bits) *
VP8LSubSampleSize(height, histo_bits) *
hist_size;
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 void FinishEncParams(VP8LEncoder* const enc) {
const WebPConfig* const config = enc->config_;
const WebPPicture* const pic = enc->pic_;
const int method = config->method;
const float quality = config->quality;
const int use_palette = enc->use_palette_;
enc->transform_bits_ = (method < 4) ? 5 : (method > 4) ? 3 : 4;
enc->histo_bits_ = GetHistoBits(method, use_palette, pic->width, pic->height);
enc->cache_bits_ = (quality <= 25.f) ? 0 : 7;
}
// -----------------------------------------------------------------------------
// VP8LEncoder
static VP8LEncoder* VP8LEncoderNew(const WebPConfig* const config,
const WebPPicture* const picture) {
VP8LEncoder* const enc = (VP8LEncoder*)calloc(1, sizeof(*enc));
if (enc == NULL) {
WebPEncodingSetError(picture, VP8_ENC_ERROR_OUT_OF_MEMORY);
return NULL;
}
enc->config_ = config;
enc->pic_ = picture;
return enc;
}
static void VP8LEncoderDelete(VP8LEncoder* enc) {
free(enc->argb_);
free(enc);
}
// -----------------------------------------------------------------------------
// Main call
WebPEncodingError VP8LEncodeStream(const WebPConfig* const config,
const WebPPicture* const picture,
VP8LBitWriter* const bw) {
WebPEncodingError err = VP8_ENC_OK;
const int quality = (int)config->quality;
const int width = picture->width;
const int height = picture->height;
VP8LEncoder* const enc = VP8LEncoderNew(config, picture);
const size_t byte_position = VP8LBitWriterNumBytes(bw);
if (enc == NULL) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
// ---------------------------------------------------------------------------
// Analyze image (entropy, num_palettes etc)
if (!VP8LEncAnalyze(enc, config->image_hint)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
FinishEncParams(enc);
if (enc->use_palette_) {
err = EncodePalette(bw, enc, quality);
if (err != VP8_ENC_OK) goto Error;
// Color cache is disabled for palette.
enc->cache_bits_ = 0;
}
// In case image is not packed.
if (enc->argb_ == NULL) {
int y;
err = AllocateTransformBuffer(enc, width, height);
if (err != VP8_ENC_OK) goto Error;
for (y = 0; y < height; ++y) {
memcpy(enc->argb_ + y * width,
picture->argb + y * picture->argb_stride,
width * sizeof(*enc->argb_));
}
enc->current_width_ = width;
}
// ---------------------------------------------------------------------------
// Apply transforms and write transform data.
if (!EvalAndApplySubtractGreen(enc, enc->current_width_, height, bw)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
if (enc->use_predict_) {
if (!ApplyPredictFilter(enc, enc->current_width_, height, quality, bw)) {
err = VP8_ENC_ERROR_INVALID_CONFIGURATION;
goto Error;
}
}
if (enc->use_cross_color_) {
if (!ApplyCrossColorFilter(enc, enc->current_width_, height, quality, bw)) {
err = VP8_ENC_ERROR_INVALID_CONFIGURATION;
goto Error;
}
}
VP8LWriteBits(bw, 1, !TRANSFORM_PRESENT); // No more transforms.
// ---------------------------------------------------------------------------
// Estimate the color cache size.
if (enc->cache_bits_ > 0) {
if (!VP8LCalculateEstimateForCacheSize(enc->argb_, enc->current_width_,
height, &enc->cache_bits_)) {
err = VP8_ENC_ERROR_INVALID_CONFIGURATION;
goto Error;
}
}
// ---------------------------------------------------------------------------
// Encode and write the transformed image.
if (!EncodeImageInternal(bw, enc->argb_, enc->current_width_, height,
quality, enc->cache_bits_, enc->histo_bits_)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
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);
}
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;
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;
if (!VP8LBitWriterInit(&bw, (width * height) >> 1)) {
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);
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;
VP8LBitWriterDestroy(&bw);
if (err != VP8_ENC_OK) {
WebPEncodingSetError(picture, err);
return 0;
}
return 1;
}
//------------------------------------------------------------------------------
#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"
#endif