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Code cleanup for VP8LGetHistoImageSymbols.

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Fix comments and few nits.
Change-Id: I8fa25ed523f12c6a7bfe125f0e4d638466ba4304
This commit is contained in:
Vikas Arora 2014-05-08 14:13:07 -07:00
parent 5fe628d35d
commit b0757db7c6
1 changed files with 95 additions and 100 deletions
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195
src/enc/histogram.c
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@ -423,10 +423,10 @@ static int GetHistoBinIndex(
// Construct the histograms from backward references. // Construct the histograms from backward references.
static void HistogramBuild( static void HistogramBuild(
int xsize, int histo_bits, const VP8LBackwardRefs* const backward_refs, int xsize, int histo_bits, const VP8LBackwardRefs* const backward_refs,
VP8LHistogramSet* const init_histo) { VP8LHistogramSet* const image_histo) {
int x = 0, y = 0; int x = 0, y = 0;
const int histo_xsize = VP8LSubSampleSize(xsize, histo_bits); const int histo_xsize = VP8LSubSampleSize(xsize, histo_bits);
VP8LHistogram** const histograms = init_histo->histograms; VP8LHistogram** const histograms = image_histo->histograms;
VP8LRefsCursor c = VP8LRefsCursorInit(backward_refs); VP8LRefsCursor c = VP8LRefsCursorInit(backward_refs);
assert(histo_bits > 0); assert(histo_bits > 0);
// Construct the Histo from a given backward references. // Construct the Histo from a given backward references.
@ -443,38 +443,35 @@ static void HistogramBuild(
} }
} }
// Compute the histogram aggregate bit_cost. // Copies the histograms and computes its bit_cost.
static void HistogramAnalyze( static void HistogramCopyAndAnalyze(
VP8LHistogramSet* const init_histo, VP8LHistogramSet* const histo_image) { VP8LHistogramSet* const orig_histo, VP8LHistogramSet* const image_histo) {
int i; int i;
const int histo_size = init_histo->size; const int histo_size = orig_histo->size;
VP8LHistogram** const histograms = init_histo->histograms; VP8LHistogram** const orig_histograms = orig_histo->histograms;
VP8LHistogram** const histograms = image_histo->histograms;
for (i = 0; i < histo_size; ++i) { for (i = 0; i < histo_size; ++i) {
VP8LHistogram* const histo = histograms[i]; VP8LHistogram* const histo = orig_histograms[i];
histo->bit_cost_ = VP8LHistogramEstimateBits(histo); UpdateHistogramCost(histo);
// Copy histograms from init_histo[] to histo_image[]. // Copy histograms from orig_histo[] to image_histo[].
HistogramCopy(histo, histo_image->histograms[i]); HistogramCopy(histo, histograms[i]);
} }
} }
// Partition Histograms to different entropy bins for three dominant (literal, // Partition histograms to different entropy bins for three dominant (literal,
// red and blue) symbol costs and compute the histogram aggregate bit_cost. // red and blue) symbol costs and compute the histogram aggregate bit_cost.
static void HistogramAnalyzeBin( static void HistogramAnalyzeEntropyBin(
VP8LHistogramSet* const init_histo, VP8LHistogramSet* const histo_image, VP8LHistogramSet* const image_histo, int16_t* const bin_map) {
int16_t* const bin_map) {
int i; int i;
const int histo_size = init_histo->size; VP8LHistogram** const histograms = image_histo->histograms;
VP8LHistogram** const histograms = init_histo->histograms; const int histo_size = image_histo->size;
const int bin_depth = init_histo->size + 1; const int bin_depth = histo_size + 1;
DominantCostRange cost_range; DominantCostRange cost_range;
DominantCostRangeInit(&cost_range); DominantCostRangeInit(&cost_range);
// Analyze the dominant (literal, red and blue) entropy costs. // Analyze the dominant (literal, red and blue) entropy costs.
for (i = 0; i < histo_size; ++i) { for (i = 0; i < histo_size; ++i) {
VP8LHistogram* const histo = histograms[i]; VP8LHistogram* const histo = histograms[i];
UpdateHistogramCost(histo);
// Copy histograms from init_histo[] to histo_image[].
HistogramCopy(histo, histo_image->histograms[i]);
UpdateDominantCostRange(histo, &cost_range); UpdateDominantCostRange(histo, &cost_range);
} }
@ -499,39 +496,38 @@ static void HistogramAnalyzeBin(
// head and moving the ones that have been merged to other histograms towards // head and moving the ones that have been merged to other histograms towards
// the end. // the end.
// TODO(vikasa): Evaluate if this method can be avoided by altering the code // TODO(vikasa): Evaluate if this method can be avoided by altering the code
// logic of HistogramCombineBin main loop. // logic of HistogramCombineEntropyBin main loop.
static void HistogramCompactBins(VP8LHistogramSet* const histo_image) { static void HistogramCompactBins(VP8LHistogramSet* const image_histo) {
int start = 0; int start = 0;
int end = histo_image->size - 1; int end = image_histo->size - 1;
VP8LHistogram** const histograms = image_histo->histograms;
while (start < end) { while (start < end) {
while (start <= end && while (start <= end && histograms[start] != NULL &&
histo_image->histograms[start] != NULL && histograms[start]->bit_cost_ != 0.) {
histo_image->histograms[start]->bit_cost_ != 0.) {
++start; ++start;
} }
while (start <= end && while (start <= end && histograms[end]->bit_cost_ == 0.) {
histo_image->histograms[end]->bit_cost_ == 0.) { histograms[end] = NULL;
histo_image->histograms[end] = NULL;
--end; --end;
} }
if (start < end) { if (start < end) {
assert(histo_image->histograms[start] != NULL); assert(histograms[start] != NULL);
assert(histo_image->histograms[end] != NULL); assert(histograms[end] != NULL);
HistogramCopy(histo_image->histograms[end], HistogramCopy(histograms[end], histograms[start]);
histo_image->histograms[start]); histograms[end] = NULL;
histo_image->histograms[end] = NULL;
--end; --end;
} }
} }
histo_image->size = end + 1; image_histo->size = end + 1;
} }
static void HistogramCombineBin(VP8LHistogramSet* const histo_image, static void HistogramCombineEntropyBin(VP8LHistogramSet* const image_histo,
VP8LHistogram* const histos, int bin_depth, VP8LHistogram* const histos,
double combine_cost_factor, int16_t* const bin_map, int bin_depth,
int16_t* const bin_map) { double combine_cost_factor) {
int bin_id; int bin_id;
VP8LHistogram* cur_combo = histos; VP8LHistogram* cur_combo = histos;
VP8LHistogram** const histograms = image_histo->histograms;
for (bin_id = 0; bin_id < BIN_SIZE; ++bin_id) { for (bin_id = 0; bin_id < BIN_SIZE; ++bin_id) {
const int bin_offset = bin_id * bin_depth; const int bin_offset = bin_id * bin_depth;
@ -540,21 +536,20 @@ static void HistogramCombineBin(VP8LHistogramSet* const histo_image,
int n; int n;
for (n = 2; n <= num_histos; ++n) { for (n = 2; n <= num_histos; ++n) {
const int idx2 = bin_map[bin_offset + n]; const int idx2 = bin_map[bin_offset + n];
const double bit_cost_idx2 = histo_image->histograms[idx2]->bit_cost_; const double bit_cost_idx2 = histograms[idx2]->bit_cost_;
if (bit_cost_idx2 > 0.) { if (bit_cost_idx2 > 0.) {
const double bit_cost_thresh = -bit_cost_idx2 * combine_cost_factor; const double bit_cost_thresh = -bit_cost_idx2 * combine_cost_factor;
const double curr_cost_diff = const double curr_cost_diff =
HistogramAddEval(histo_image->histograms[idx1], HistogramAddEval(histograms[idx1], histograms[idx2],
histo_image->histograms[idx2],
cur_combo, bit_cost_thresh); cur_combo, bit_cost_thresh);
if (curr_cost_diff < bit_cost_thresh) { if (curr_cost_diff < bit_cost_thresh) {
HistogramCopy(cur_combo, histo_image->histograms[idx1]); HistogramCopy(cur_combo, histograms[idx1]);
histo_image->histograms[idx2]->bit_cost_ = 0.; histograms[idx2]->bit_cost_ = 0.;
} }
} }
} }
} }
HistogramCompactBins(histo_image); HistogramCompactBins(image_histo);
} }
static uint32_t MyRand(uint32_t *seed) { static uint32_t MyRand(uint32_t *seed) {
@ -565,45 +560,45 @@ static uint32_t MyRand(uint32_t *seed) {
return *seed; return *seed;
} }
static void HistogramCombine(VP8LHistogramSet* const histo_image, static void HistogramCombine(VP8LHistogramSet* const image_histo,
VP8LHistogramSet* const histos, int quality) { VP8LHistogramSet* const histos, int quality) {
int iter; int iter;
uint32_t seed = 0; uint32_t seed = 0;
int tries_with_no_success = 0; int tries_with_no_success = 0;
int histo_image_size = histo_image->size; int image_histo_size = image_histo->size;
const int iter_mult = (quality < 25) ? 2 : 2 + (quality - 25) / 8; const int iter_mult = (quality < 25) ? 2 : 2 + (quality - 25) / 8;
const int outer_iters = histo_image_size * iter_mult; const int outer_iters = image_histo_size * iter_mult;
const int num_pairs = histo_image_size / 2; const int num_pairs = image_histo_size / 2;
const int num_tries_no_success = outer_iters / 2; const int num_tries_no_success = outer_iters / 2;
const int min_cluster_size = 2; const int min_cluster_size = 2;
VP8LHistogram** const histograms = image_histo->histograms;
VP8LHistogram* cur_combo = histos->histograms[0]; // trial histogram VP8LHistogram* cur_combo = histos->histograms[0]; // trial histogram
VP8LHistogram* best_combo = histos->histograms[1]; // best histogram so far VP8LHistogram* best_combo = histos->histograms[1]; // best histogram so far
// Collapse similar histograms in 'histo_image'. // Collapse similar histograms in 'image_histo'.
for (iter = 0; for (iter = 0;
iter < outer_iters && histo_image_size >= min_cluster_size; iter < outer_iters && image_histo_size >= min_cluster_size;
++iter) { ++iter) {
double best_cost_diff = 0.; double best_cost_diff = 0.;
int best_idx1 = -1, best_idx2 = 1; int best_idx1 = -1, best_idx2 = 1;
int j; int j;
const int num_tries = const int num_tries =
(num_pairs < histo_image_size) ? num_pairs : histo_image_size; (num_pairs < image_histo_size) ? num_pairs : image_histo_size;
seed += iter; seed += iter;
for (j = 0; j < num_tries; ++j) { for (j = 0; j < num_tries; ++j) {
double curr_cost_diff; double curr_cost_diff;
// Choose two histograms at random and try to combine them. // Choose two histograms at random and try to combine them.
const uint32_t idx1 = MyRand(&seed) % histo_image_size; const uint32_t idx1 = MyRand(&seed) % image_histo_size;
const uint32_t tmp = (j & 7) + 1; const uint32_t tmp = (j & 7) + 1;
const uint32_t diff = const uint32_t diff =
(tmp < 3) ? tmp : MyRand(&seed) % (histo_image_size - 1); (tmp < 3) ? tmp : MyRand(&seed) % (image_histo_size - 1);
const uint32_t idx2 = (idx1 + diff + 1) % histo_image_size; const uint32_t idx2 = (idx1 + diff + 1) % image_histo_size;
if (idx1 == idx2) { if (idx1 == idx2) {
continue; continue;
} }
// Calculate cost reduction on combining. // Calculate cost reduction on combining.
curr_cost_diff = HistogramAddEval(histo_image->histograms[idx1], curr_cost_diff = HistogramAddEval(histograms[idx1], histograms[idx2],
histo_image->histograms[idx2],
cur_combo, best_cost_diff); cur_combo, best_cost_diff);
if (curr_cost_diff < best_cost_diff) { // found a better pair? if (curr_cost_diff < best_cost_diff) { // found a better pair?
{ // swap cur/best combo histograms { // swap cur/best combo histograms
@ -618,13 +613,12 @@ static void HistogramCombine(VP8LHistogramSet* const histo_image,
} }
if (best_idx1 >= 0) { if (best_idx1 >= 0) {
HistogramCopy(best_combo, histo_image->histograms[best_idx1]); HistogramCopy(best_combo, histograms[best_idx1]);
// swap best_idx2 slot with last one (which is now unused) // swap best_idx2 slot with last one (which is now unused)
--histo_image_size; --image_histo_size;
if (best_idx2 != histo_image_size) { if (best_idx2 != image_histo_size) {
HistogramCopy(histo_image->histograms[histo_image_size], HistogramCopy(histograms[image_histo_size], histograms[best_idx2]);
histo_image->histograms[best_idx2]); histograms[image_histo_size] = NULL;
histo_image->histograms[histo_image_size] = NULL;
} }
tries_with_no_success = 0; tries_with_no_success = 0;
} }
@ -632,7 +626,7 @@ static void HistogramCombine(VP8LHistogramSet* const histo_image,
break; break;
} }
} }
histo_image->size = histo_image_size; image_histo->size = image_histo_size;
} }
// ----------------------------------------------------------------------------- // -----------------------------------------------------------------------------
@ -640,19 +634,20 @@ static void HistogramCombine(VP8LHistogramSet* const histo_image,
// Find the best 'out' histogram for each of the 'in' histograms. // Find the best 'out' histogram for each of the 'in' histograms.
// Note: we assume that out[]->bit_cost_ is already up-to-date. // Note: we assume that out[]->bit_cost_ is already up-to-date.
static void HistogramRemap(const VP8LHistogramSet* const init_histo, static void HistogramRemap(const VP8LHistogramSet* const orig_histo,
const VP8LHistogramSet* const histo_image, const VP8LHistogramSet* const image_histo,
uint16_t* const symbols) { uint16_t* const symbols) {
int i; int i;
for (i = 0; i < init_histo->size; ++i) { VP8LHistogram** const orig_histograms = orig_histo->histograms;
VP8LHistogram** const histograms = image_histo->histograms;
for (i = 0; i < orig_histo->size; ++i) {
int best_out = 0; int best_out = 0;
double best_bits = HistogramAddThresh(histo_image->histograms[0], double best_bits =
init_histo->histograms[i], MAX_COST); HistogramAddThresh(histograms[0], orig_histograms[i], MAX_COST);
int k; int k;
for (k = 1; k < histo_image->size; ++k) { for (k = 1; k < image_histo->size; ++k) {
const double cur_bits = HistogramAddThresh(histo_image->histograms[k], const double cur_bits =
init_histo->histograms[i], HistogramAddThresh(histograms[k], orig_histograms[i], best_bits);
best_bits);
if (cur_bits < best_bits) { if (cur_bits < best_bits) {
best_bits = cur_bits; best_bits = cur_bits;
best_out = k; best_out = k;
@ -662,14 +657,13 @@ static void HistogramRemap(const VP8LHistogramSet* const init_histo,
} }
// Recompute each out based on raw and symbols. // Recompute each out based on raw and symbols.
for (i = 0; i < histo_image->size; ++i) { for (i = 0; i < image_histo->size; ++i) {
HistogramClear(histo_image->histograms[i]); HistogramClear(histograms[i]);
} }
for (i = 0; i < init_histo->size; ++i) { for (i = 0; i < orig_histo->size; ++i) {
VP8LHistogramAdd(init_histo->histograms[i], const int idx = symbols[i];
histo_image->histograms[symbols[i]], VP8LHistogramAdd(orig_histograms[i], histograms[idx], histograms[idx]);
histo_image->histograms[symbols[i]]);
} }
} }
@ -685,62 +679,63 @@ static double GetCombineCostFactor(int histo_size, int quality) {
int VP8LGetHistoImageSymbols(int xsize, int ysize, int VP8LGetHistoImageSymbols(int xsize, int ysize,
const VP8LBackwardRefs* const refs, const VP8LBackwardRefs* const refs,
int quality, int histo_bits, int cache_bits, int quality, int histo_bits, int cache_bits,
VP8LHistogramSet* const histo_image, VP8LHistogramSet* const image_histo,
uint16_t* const histogram_symbols) { uint16_t* const histogram_symbols) {
int ok = 0; int ok = 0;
const int histo_xsize = histo_bits ? VP8LSubSampleSize(xsize, histo_bits) : 1; const int histo_xsize = histo_bits ? VP8LSubSampleSize(xsize, histo_bits) : 1;
const int histo_ysize = histo_bits ? VP8LSubSampleSize(ysize, histo_bits) : 1; const int histo_ysize = histo_bits ? VP8LSubSampleSize(ysize, histo_bits) : 1;
const int histo_image_raw_size = histo_xsize * histo_ysize; const int image_histo_raw_size = histo_xsize * histo_ysize;
// The bin_map for every bin follows following semantics: // The bin_map for every bin follows following semantics:
// bin_map[n][0] = num_histo; // The number of histograms in that bin. // bin_map[n][0] = num_histo; // The number of histograms in that bin.
// bin_map[n][1] = index of first histogram in that bin; // bin_map[n][1] = index of first histogram in that bin;
// bin_map[n][num_histo] = index of last histogram in that bin; // bin_map[n][num_histo] = index of last histogram in that bin;
// bin_map[n][num_histo + 1] ... bin_map[n][bin_depth - 1] = un-used indices. // bin_map[n][num_histo + 1] ... bin_map[n][bin_depth - 1] = un-used indices.
const int bin_depth = histo_image_raw_size + 1; const int bin_depth = image_histo_raw_size + 1;
int16_t* bin_map = NULL; int16_t* bin_map = NULL;
VP8LHistogramSet* const histos = VP8LAllocateHistogramSet(2, cache_bits); VP8LHistogramSet* const histos = VP8LAllocateHistogramSet(2, cache_bits);
VP8LHistogramSet* const init_histo = VP8LHistogramSet* const orig_histo =
VP8LAllocateHistogramSet(histo_image_raw_size, cache_bits); VP8LAllocateHistogramSet(image_histo_raw_size, cache_bits);
if (init_histo == NULL || histos == NULL) { if (orig_histo == NULL || histos == NULL) {
goto Error; goto Error;
} }
// Don't attempt linear bin-partition heuristic for: // Don't attempt linear bin-partition heuristic for:
// Histograms of small sizes, as bin_map will be very sparse and; // histograms of small sizes, as bin_map will be very sparse and;
// Higher qualities (> 90), to preserve the compression gains at those // Higher qualities (> 90), to preserve the compression gains at those
// quality settings. // quality settings.
if (init_histo->size > 2 * BIN_SIZE && quality < 90) { if (orig_histo->size > 2 * BIN_SIZE && quality < 90) {
const int bin_map_size = bin_depth * BIN_SIZE; const int bin_map_size = bin_depth * BIN_SIZE;
bin_map = (int16_t*)WebPSafeCalloc(bin_map_size, sizeof(*bin_map)); bin_map = (int16_t*)WebPSafeCalloc(bin_map_size, sizeof(*bin_map));
if (bin_map == NULL) goto Error; if (bin_map == NULL) goto Error;
} }
// Construct the histogram from backward references. // Construct the histograms from backward references.
HistogramBuild(xsize, histo_bits, refs, init_histo); HistogramBuild(xsize, histo_bits, refs, orig_histo);
// Copies the histograms and computes its bit_cost.
HistogramCopyAndAnalyze(orig_histo, image_histo);
if (bin_map != NULL) { if (bin_map != NULL) {
const double combine_cost_factor = const double combine_cost_factor =
GetCombineCostFactor(histo_image_raw_size, quality); GetCombineCostFactor(image_histo_raw_size, quality);
HistogramAnalyzeBin(init_histo, histo_image, bin_map); HistogramAnalyzeEntropyBin(orig_histo, bin_map);
HistogramCombineBin(histo_image, histos->histograms[0], // Collapse histograms with similar entropy.
bin_depth, combine_cost_factor, bin_map); HistogramCombineEntropyBin(image_histo, histos->histograms[0],
} else { bin_map, bin_depth, combine_cost_factor);
HistogramAnalyze(init_histo, histo_image);
} }
// Collapse similar histograms. // Collapse similar histograms by random histogram-pair compares.
HistogramCombine(histo_image, histos, quality); HistogramCombine(image_histo, histos, quality);
// Find the optimal map from original histograms to the final ones. // Find the optimal map from original histograms to the final ones.
HistogramRemap(init_histo, histo_image, histogram_symbols); HistogramRemap(orig_histo, image_histo, histogram_symbols);
ok = 1; ok = 1;
Error: Error:
WebPSafeFree(bin_map); WebPSafeFree(bin_map);
VP8LFreeHistogramSet(init_histo); VP8LFreeHistogramSet(orig_histo);
VP8LFreeHistogramSet(histos); VP8LFreeHistogramSet(histos);
return ok; return ok;
} }