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fix VP8LHistogramNumCodes to handle the case palette_code_bits == 0

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-> lot of simplifications ensue and we should be able to get rid of
 ClearHuffmanTreeIfOnlyOneSymbol() too, in a subsequent patch.

Change-Id: Ic4c51d05e4b1970e37f94ffd85fae6a02e4a6422
This commit is contained in:
Pascal Massimino 2012-05-14 01:23:58 -07:00
parent b5551d2e1d
commit 9c7a3cf5e7
2 changed files with 50 additions and 74 deletions
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3
src/enc/histogram.h
View File

@ -118,7 +118,8 @@ static WEBP_INLINE void VP8LHistogramRemove(VP8LHistogram* const p,
}
static WEBP_INLINE int VP8LHistogramNumCodes(const VP8LHistogram* const p) {
return 256 + kLengthCodes + (1 << p->palette_code_bits_);
return 256 + kLengthCodes +
((p->palette_code_bits_ > 0) ? (1 << p->palette_code_bits_) : 0);
}
void VP8LConvertPopulationCountTableToBitEstimates(

121
src/enc/vp8l.c
View File

@ -266,7 +266,7 @@ static int OptimizeHuffmanForRle(int length, int* counts) {
static int GetHuffBitLengthsAndCodes(
const VP8LHistogramSet* const histogram_image,
int use_color_cache, HuffmanTreeCode* const huffman_codes) {
HuffmanTreeCode* const huffman_codes) {
int i, k;
int ok = 1;
int total_length_size = 0;
@ -275,16 +275,14 @@ static int GetHuffBitLengthsAndCodes(
// Iterate over all histograms and get the aggregate number of codes used.
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;
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;
huffman_codes[ix + k].num_symbols = val;
total_length_size += val;
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) ? DISTANCE_CODES_MAX
: 256;
codes[k].num_symbols = num_symbols;
total_length_size += num_symbols;
}
}
@ -312,41 +310,35 @@ static int GetHuffBitLengthsAndCodes(
// Create Huffman trees.
for (i = 0; i < histogram_image_size; ++i) {
const int ix = 5 * i;
HuffmanTreeCode* const codes = &huffman_codes[5 * i];
VP8LHistogram* const histo = histogram_image->histograms[i];
const int num_literals = huffman_codes[ix].num_symbols;
// For each component, optimize histogram for Huffman with RLE compression.
const int num_literals = codes[0].num_symbols;
// For each component, optimize histogram for Huffman with RLE compression,
// and create a Huffman tree (in the form of bit lengths) for each.
ok = ok && OptimizeHuffmanForRle(num_literals, histo->literal_);
if (!use_color_cache) {
// Implies that palette_bits == 0,
// and so number of palette entries = (1 << 0) = 1.
// Optimization might have smeared population count in this single
// palette entry, so zero it out.
histo->literal_[256 + kLengthCodes] = 0;
}
// Create a Huffman tree (in the form of bit lengths) for each component.
ok = ok && VP8LCreateHuffmanTree(histo->literal_, num_literals, 15,
huffman_codes[ix].code_lengths);
codes[0].code_lengths);
ok = ok && OptimizeHuffmanForRle(256, histo->red_);
ok = ok && VP8LCreateHuffmanTree(histo->red_, 256, 15,
huffman_codes[ix + 1].code_lengths);
codes[1].code_lengths);
ok = ok && OptimizeHuffmanForRle(256, histo->blue_);
ok = ok && VP8LCreateHuffmanTree(histo->blue_, 256, 15,
huffman_codes[ix + 2].code_lengths);
codes[2].code_lengths);
ok = ok && OptimizeHuffmanForRle(256, histo->alpha_);
ok = ok && VP8LCreateHuffmanTree(histo->alpha_, 256, 15,
huffman_codes[ix + 3].code_lengths);
codes[3].code_lengths);
ok = ok && OptimizeHuffmanForRle(DISTANCE_CODES_MAX, histo->distance_);
ok = ok && VP8LCreateHuffmanTree(histo->distance_, DISTANCE_CODES_MAX, 15,
huffman_codes[ix + 4].code_lengths);
codes[4].code_lengths);
// Create the actual bit codes for the bit lengths.
// TODO(vikasa): merge with each VP8LCreateHuffmanTree() ?
for (k = 0; k < 5; ++k) {
VP8LConvertBitDepthsToSymbols(&huffman_codes[ix + k]);
VP8LConvertBitDepthsToSymbols(codes + k);
}
}
@ -355,22 +347,6 @@ static int GetHuffBitLengthsAndCodes(
return ok;
}
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 StoreHuffmanTreeOfHuffmanTreeToBitMask(
VP8LBitWriter* const bw, const uint8_t* code_length_bitdepth) {
// RFC 1951 will calm you down if you are worried about this funny sequence.
@ -393,6 +369,22 @@ static void StoreHuffmanTreeOfHuffmanTreeToBitMask(
}
}
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,
@ -555,31 +547,29 @@ 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;
const HuffmanTreeCode* const codes = huffman_codes + 5 * histogram_ix;
if (PixOrCopyIsCacheIdx(v)) {
const int code = PixOrCopyCacheIdx(v);
const int literal_ix = 256 + kLengthCodes + code;
WriteHuffmanCode(bw, &huffman_codes[ix], literal_ix);
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, &huffman_codes[ix + k], code);
WriteHuffmanCode(bw, codes + k, code);
}
} else {
int bits, n_bits;
int code, distance;
int len_ix;
PrefixEncode(v->len, &code, &n_bits, &bits);
len_ix = 256 + code;
WriteHuffmanCode(bw, &huffman_codes[ix], len_ix);
WriteHuffmanCode(bw, codes, 256 + code);
VP8LWriteBits(bw, n_bits, bits);
distance = PixOrCopyDistance(v);
PrefixEncode(distance, &code, &n_bits, &bits);
WriteHuffmanCode(bw, &huffman_codes[ix + 4], code);
WriteHuffmanCode(bw, codes + 4, code);
VP8LWriteBits(bw, n_bits, bits);
}
x += PixOrCopyLength(v);
@ -599,7 +589,6 @@ static int EncodeImageInternal(VP8LBitWriter* const bw,
int write_histogram_image;
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;
const int histogram_image_xysize =
VP8LSubSampleSize(width, histogram_bits) *
VP8LSubSampleSize(height, histogram_bits);
@ -632,8 +621,7 @@ static int EncodeImageInternal(VP8LBitWriter* const bw,
huffman_codes = (HuffmanTreeCode*)calloc(bit_array_size,
sizeof(*huffman_codes));
if (huffman_codes == NULL ||
!GetHuffBitLengthsAndCodes(histogram_image, use_color_cache,
huffman_codes)) {
!GetHuffBitLengthsAndCodes(histogram_image, huffman_codes)) {
goto Error;
}
@ -670,31 +658,18 @@ static int EncodeImageInternal(VP8LBitWriter* const bw,
}
// Store Huffman codes.
for (i = 0; i < histogram_image_size; ++i) {
int k;
for (k = 0; k < 5; ++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_size;
if (!StoreHuffmanCode(bw, cur_bit_lengths, cur_bit_lengths_size)) {
goto Error;
}
for (i = 0; i < 5 * histogram_image_size; ++i) {
const HuffmanTreeCode* const codes = &huffman_codes[i];
if (!StoreHuffmanCode(bw, codes->code_lengths, codes->num_symbols)) {
goto Error;
}
ClearHuffmanTreeIfOnlyOneSymbol(&huffman_codes[i]);
}
// Free combined histograms.
free(histogram_image);
histogram_image = NULL;
// 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(&huffman_codes[i]);
}
// Store actual literals.
StoreImageToBitMask(bw, width, histogram_bits, &refs,
histogram_symbols, huffman_codes);