dany/libwebp
1
0
Fork 0
mirror of https://github.com/webmproject/libwebp.git synced 2024-12-26 13:48:21 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity

Added HuffmanTreeCode Struct for tree codes.

Browse Source 
To represent tree codes (depth and bits array).

Change-Id: I87650886384dd10d95b16ab808dfd3bb573172bc
This commit is contained in:
Vikas Arora 2012-05-14 13:49:45 +05:30
parent 41d8049451
commit 8b85d01c45
3 changed files with 79 additions and 66 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

119
src/enc/vp8l.c
View File

@ -264,11 +264,9 @@ static int OptimizeHuffmanForRle(int length, int* counts) {
return 1;
}
// TODO(vikasa): Wrap bit_codes and bit_lengths in a Struct.
static int GetHuffBitLengthsAndCodes(
const VP8LHistogramSet* const histogram_image,
int use_color_cache, int* const bit_length_sizes,
uint16_t** const bit_codes, uint8_t** const bit_lengths) {
int use_color_cache, HuffmanTreeCode* const huffman_codes) {
int i, k;
int ok = 1;
int total_length_size = 0;
@ -279,17 +277,18 @@ static int GetHuffBitLengthsAndCodes(
for (i = 0; i < histogram_image_size; ++i) {
VP8LHistogram* const histo = histogram_image->histograms[i];
const int num_literals = VP8LHistogramNumCodes(histo);
const int ix = 5 * i;
k = 0;
bit_length_sizes[5 * i] = num_literals;
huffman_codes[ix].num_symbols = num_literals;
total_length_size += num_literals;
for (k = 1; k < 5; ++k) {
const int val = (k == 4) ? DISTANCE_CODES_MAX : 256;
bit_length_sizes[5 * i + k] = val;
huffman_codes[ix + k].num_symbols = val;
total_length_size += val;
}
}
// Allocate and Set bit_lengths and bit_codes.
// Allocate and Set Huffman codes.
{
uint16_t* codes;
uint8_t* lengths;
@ -303,9 +302,9 @@ static int GetHuffBitLengthsAndCodes(
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 = bit_length_sizes[i];
bit_codes[i] = codes;
bit_lengths[i] = lengths;
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;
}
@ -315,7 +314,7 @@ static int GetHuffBitLengthsAndCodes(
for (i = 0; i < histogram_image_size; ++i) {
const int ix = 5 * i;
VP8LHistogram* const histo = histogram_image->histograms[i];
const int num_literals = bit_length_sizes[ix];
const int num_literals = huffman_codes[ix].num_symbols;
// For each component, optimize histogram for Huffman with RLE compression.
ok = ok && OptimizeHuffmanForRle(num_literals, histo->literal_);
if (!use_color_cache) {
@ -327,29 +326,27 @@ static int GetHuffBitLengthsAndCodes(
}
// Create a Huffman tree (in the form of bit lengths) for each component.
ok = ok && VP8LCreateHuffmanTree(histo->literal_, num_literals, 15,
bit_lengths[ix]);
huffman_codes[ix].code_lengths);
ok = ok && OptimizeHuffmanForRle(256, histo->red_);
ok = ok && VP8LCreateHuffmanTree(histo->red_, 256, 15,
bit_lengths[ix + 1]);
huffman_codes[ix + 1].code_lengths);
ok = ok && OptimizeHuffmanForRle(256, histo->blue_);
ok = ok && VP8LCreateHuffmanTree(histo->blue_, 256, 15,
bit_lengths[ix + 2]);
huffman_codes[ix + 2].code_lengths);
ok = ok && OptimizeHuffmanForRle(256, histo->alpha_);
ok = ok && VP8LCreateHuffmanTree(histo->alpha_, 256, 15,
bit_lengths[ix + 3]);
huffman_codes[ix + 3].code_lengths);
ok = ok && OptimizeHuffmanForRle(DISTANCE_CODES_MAX, histo->distance_);
ok = ok && VP8LCreateHuffmanTree(histo->distance_, DISTANCE_CODES_MAX, 15,
bit_lengths[ix + 4]);
huffman_codes[ix + 4].code_lengths);
// Create the actual bit codes for the bit lengths.
for (k = 0; k < 5; ++k) {
VP8LConvertBitDepthsToSymbols(bit_lengths[ix + k],
bit_length_sizes[ix + k],
bit_codes[ix + k]);
VP8LConvertBitDepthsToSymbols(&huffman_codes[ix + k]);
}
}
@ -358,20 +355,19 @@ static int GetHuffBitLengthsAndCodes(
return ok;
}
static void ClearHuffmanTreeIfOnlyOneSymbol(const int num_symbols,
uint8_t* lengths,
uint16_t* symbols) {
static void ClearHuffmanTreeIfOnlyOneSymbol(
HuffmanTreeCode* const huffman_code) {
int k;
int count = 0;
for (k = 0; k < num_symbols; ++k) {
if (lengths[k] != 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 < num_symbols; ++k) {
lengths[k] = 0;
symbols[k] = 0;
for (k = 0; k < huffman_code->num_symbols; ++k) {
huffman_code->code_lengths[k] = 0;
huffman_code->codes[k] = 0;
}
}
@ -430,6 +426,7 @@ static int StoreFullHuffmanCode(VP8LBitWriter* const bw,
uint8_t code_length_bitdepth[CODE_LENGTH_CODES] = { 0 };
uint16_t code_length_bitdepth_symbols[CODE_LENGTH_CODES] = { 0 };
int num_tokens;
HuffmanTreeCode huffman_code;
HuffmanTreeToken* const tokens =
(HuffmanTreeToken*)malloc(bit_lengths_size * sizeof(*tokens));
if (tokens == NULL) return 0;
@ -449,12 +446,14 @@ static int StoreFullHuffmanCode(VP8LBitWriter* const bw,
goto End;
}
}
VP8LConvertBitDepthsToSymbols(code_length_bitdepth, CODE_LENGTH_CODES,
code_length_bitdepth_symbols);
huffman_code.num_symbols = CODE_LENGTH_CODES;
huffman_code.code_lengths = code_length_bitdepth;
huffman_code.codes = code_length_bitdepth_symbols;
VP8LConvertBitDepthsToSymbols(&huffman_code);
StoreHuffmanTreeOfHuffmanTreeToBitMask(bw, code_length_bitdepth);
ClearHuffmanTreeIfOnlyOneSymbol(CODE_LENGTH_CODES,
code_length_bitdepth,
code_length_bitdepth_symbols);
ClearHuffmanTreeIfOnlyOneSymbol(&huffman_code);
{
int trailing_zero_bits = 0;
int trimmed_length = num_tokens;
@ -534,11 +533,18 @@ static int StoreHuffmanCode(VP8LBitWriter* const bw,
}
}
static void WriteHuffmanCode(VP8LBitWriter* const bw,
const HuffmanTreeCode* const code, int index) {
const int depth = code->code_lengths[index];
const int symbol = code->codes[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,
uint8_t** const bitdepths, uint16_t** const bit_symbols) {
HuffmanTreeCode* const huffman_codes) {
// x and y trace the position in the image.
int x = 0;
int y = 0;
@ -549,18 +555,18 @@ static void StoreImageToBitMask(
const int histogram_ix = histogram_symbols[histo_bits ?
(y >> histo_bits) * histo_xsize +
(x >> histo_bits) : 0];
const int ix = 5 * histogram_ix;
if (PixOrCopyIsCacheIdx(v)) {
const int code = PixOrCopyCacheIdx(v);
const int literal_ix = 256 + kLengthCodes + code;
VP8LWriteBits(bw, bitdepths[5 * histogram_ix][literal_ix],
bit_symbols[5 * histogram_ix][literal_ix]);
WriteHuffmanCode(bw, &huffman_codes[ix], 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]);
VP8LWriteBits(bw, bitdepths[5 * histogram_ix + k][code],
bit_symbols[5 * histogram_ix + k][code]);
WriteHuffmanCode(bw, &huffman_codes[ix + k], code);
}
} else {
int bits, n_bits;
@ -568,14 +574,12 @@ static void StoreImageToBitMask(
int len_ix;
PrefixEncode(v->len, &code, &n_bits, &bits);
len_ix = 256 + code;
VP8LWriteBits(bw, bitdepths[5 * histogram_ix][len_ix],
bit_symbols[5 * histogram_ix][len_ix]);
WriteHuffmanCode(bw, &huffman_codes[ix], len_ix);
VP8LWriteBits(bw, n_bits, bits);
distance = PixOrCopyDistance(v);
PrefixEncode(distance, &code, &n_bits, &bits);
VP8LWriteBits(bw, bitdepths[5 * histogram_ix + 4][code],
bit_symbols[5 * histogram_ix + 4][code]);
WriteHuffmanCode(bw, &huffman_codes[ix + 4], code);
VP8LWriteBits(bw, n_bits, bits);
}
x += PixOrCopyLength(v);
@ -593,9 +597,6 @@ static int EncodeImageInternal(VP8LBitWriter* const bw,
int i;
int ok = 0;
int write_histogram_image;
int* bit_lengths_sizes = NULL;
uint8_t** bit_lengths = NULL;
uint16_t** bit_codes = NULL;
const int use_2d_locality = 1;
const int use_color_cache = (cache_bits > 0);
const int color_cache_size = use_color_cache ? (1 << cache_bits) : 0;
@ -606,6 +607,7 @@ static int EncodeImageInternal(VP8LBitWriter* const bw,
VP8LAllocateHistogramSet(histogram_image_xysize, 0);
int histogram_image_size = 0;
int bit_array_size = 0;
HuffmanTreeCode* huffman_codes = NULL;
VP8LBackwardRefs refs;
uint16_t* const histogram_symbols =
(uint16_t*)malloc(histogram_image_xysize * sizeof(*histogram_symbols));
@ -627,12 +629,11 @@ static int EncodeImageInternal(VP8LBitWriter* const bw,
// Create Huffman bit lengths & codes for each histogram image.
histogram_image_size = histogram_image->size;
bit_array_size = 5 * histogram_image_size;
bit_lengths_sizes = (int*)calloc(bit_array_size, sizeof(*bit_lengths_sizes));
bit_lengths = (uint8_t**)calloc(bit_array_size, sizeof(*bit_lengths));
bit_codes = (uint16_t**)calloc(bit_array_size, sizeof(*bit_codes));
if (bit_lengths_sizes == NULL || bit_lengths == NULL || bit_codes == NULL ||
huffman_codes = (HuffmanTreeCode*)calloc(bit_array_size,
sizeof(*huffman_codes));
if (huffman_codes == NULL ||
!GetHuffBitLengthsAndCodes(histogram_image, use_color_cache,
bit_lengths_sizes, bit_codes, bit_lengths)) {
huffman_codes)) {
goto Error;
}
@ -672,10 +673,13 @@ static int EncodeImageInternal(VP8LBitWriter* const bw,
for (i = 0; i < histogram_image_size; ++i) {
int k;
for (k = 0; k < 5; ++k) {
const uint8_t* const cur_bit_lengths = bit_lengths[5 * i + k];
const int ix = 5 * i + k;
const HuffmanTreeCode* const tree = &huffman_codes[ix];
const uint8_t* const cur_bit_lengths = tree->code_lengths;
const int bit_lengths_size = tree->num_symbols;
// TODO(vikasa): Check why we need this special check for k == 0.
const int cur_bit_lengths_size = (k == 0) ?
256 + kLengthCodes + color_cache_size :
bit_lengths_sizes[5 * i + k];
256 + kLengthCodes + color_cache_size : bit_lengths_size;
if (!StoreHuffmanCode(bw, cur_bit_lengths, cur_bit_lengths_size)) {
goto Error;
}
@ -689,22 +693,21 @@ static int EncodeImageInternal(VP8LBitWriter* const bw,
// Emit no bits if there is only one symbol in the histogram.
// This gives better compression for some images.
for (i = 0; i < 5 * histogram_image_size; ++i) {
ClearHuffmanTreeIfOnlyOneSymbol(bit_lengths_sizes[i], bit_lengths[i],
bit_codes[i]);
ClearHuffmanTreeIfOnlyOneSymbol(&huffman_codes[i]);
}
// Store actual literals.
StoreImageToBitMask(bw, width, histogram_bits, &refs,
histogram_symbols, bit_lengths, bit_codes);
histogram_symbols, huffman_codes);
ok = 1;
Error:
if (!ok) free(histogram_image);
VP8LClearBackwardRefs(&refs);
free(bit_lengths_sizes);
free(bit_lengths);
free(*bit_codes);
free(bit_codes);
if (huffman_codes != NULL) {
free(huffman_codes->codes);
free(huffman_codes);
}
free(histogram_symbols);
return ok;
}

16
src/utils/huffman_encode.c
View File

@ -282,16 +282,19 @@ static uint32_t ReverseBits(int num_bits, uint32_t bits) {
return retval;
}
void VP8LConvertBitDepthsToSymbols(const uint8_t* const depth,
int len,
uint16_t* const bits) {
void VP8LConvertBitDepthsToSymbols(HuffmanTreeCode* const tree) {
// 0 bit-depth means that the symbol does not exist.
int i;
int len;
uint32_t next_code[MAX_BITS];
int depth_count[MAX_BITS] = { 0 };
assert(tree != NULL);
len = tree->num_symbols;
for (i = 0; i < len; ++i) {
assert(depth[i] < MAX_BITS);
++depth_count[depth[i]];
const int code_length = tree->code_lengths[i];
assert(code_length < MAX_BITS);
++depth_count[code_length];
}
depth_count[0] = 0; // ignore unused symbol
next_code[0] = 0;
@ -303,7 +306,8 @@ void VP8LConvertBitDepthsToSymbols(const uint8_t* const depth,
}
}
for (i = 0; i < len; ++i) {
bits[i] = ReverseBits(depth[i], next_code[depth[i]]++);
const int code_length = tree->code_lengths[i];
tree->codes[i] = ReverseBits(code_length, next_code[code_length]++);
}
}

10
src/utils/huffman_encode.h
View File

@ -40,9 +40,15 @@ typedef struct {
int VP8LCreateCompressedHuffmanTree(const uint8_t* const depth, int len,
HuffmanTreeToken* tokens, int max_tokens);
// Struct to represent the tree codes (depth and bits array).
typedef struct {
int num_symbols; // Number of symbols.
uint8_t* code_lengths; // Code lengths of the symbols.
uint16_t* codes; // Symbol Codes.
} HuffmanTreeCode;
// Get the actual bit values for a tree of bit depths.
void VP8LConvertBitDepthsToSymbols(const uint8_t* const depth, int len,
uint16_t* const bits);
void VP8LConvertBitDepthsToSymbols(HuffmanTreeCode* const tree);
#if defined(__cplusplus) || defined(c_plusplus)
}