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histogram: fix bin calculation

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It could overflow if min==max

Change-Id: I11580328712879fe310e3d9c8c5e10835c4faf86
also: collect GetHistoBinIndex() variant into a single function
This commit is contained in:
Pascal Massimino 2016-06-08 13:38:00 +02:00
parent 5f8f998d0e
commit 96c3d62496
1 changed files with 21 additions and 26 deletions
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47
src/enc/histogram.c
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@ -386,29 +386,27 @@ static void UpdateHistogramCost(VP8LHistogram* const h) {
}
static int GetBinIdForEntropy(double min, double max, double val) {
const double range = max - min + 1e-6;
const double delta = val - min;
return (int)(NUM_PARTITIONS * delta / range);
const double range = max - min;
if (range > 0.) {
const double delta = val - min;
return (int)((NUM_PARTITIONS - 1e-6) * delta / range);
} else {
return 0;
}
}
static int GetHistoBinIndexLowEffort(
const VP8LHistogram* const h, const DominantCostRange* const c) {
const int bin_id = GetBinIdForEntropy(c->literal_min_, c->literal_max_,
h->literal_cost_);
static int GetHistoBinIndex(const VP8LHistogram* const h,
const DominantCostRange* const c, int low_effort) {
int bin_id = GetBinIdForEntropy(c->literal_min_, c->literal_max_,
h->literal_cost_);
assert(bin_id < NUM_PARTITIONS);
return bin_id;
}
static int GetHistoBinIndex(
const VP8LHistogram* const h, const DominantCostRange* const c) {
const int bin_id =
GetBinIdForEntropy(c->blue_min_, c->blue_max_, h->blue_cost_) +
NUM_PARTITIONS * GetBinIdForEntropy(c->red_min_, c->red_max_,
h->red_cost_) +
NUM_PARTITIONS * NUM_PARTITIONS * GetBinIdForEntropy(c->literal_min_,
c->literal_max_,
h->literal_cost_);
assert(bin_id < BIN_SIZE);
if (!low_effort) {
bin_id = bin_id * NUM_PARTITIONS
+ GetBinIdForEntropy(c->red_min_, c->red_max_, h->red_cost_);
bin_id = bin_id * NUM_PARTITIONS
+ GetBinIdForEntropy(c->blue_min_, c->blue_max_, h->blue_cost_);
assert(bin_id < BIN_SIZE);
}
return bin_id;
}
@ -469,16 +467,13 @@ static void HistogramAnalyzeEntropyBin(VP8LHistogramSet* const image_histo,
// bin-hash histograms on three of the dominant (literal, red and blue)
// symbol costs.
for (i = 0; i < histo_size; ++i) {
int num_histos;
VP8LHistogram* const histo = histograms[i];
const int16_t bin_id = low_effort ?
(int16_t)GetHistoBinIndexLowEffort(histo, &cost_range) :
(int16_t)GetHistoBinIndex(histo, &cost_range);
const VP8LHistogram* const histo = histograms[i];
const int bin_id = GetHistoBinIndex(histo, &cost_range, low_effort);
const int bin_offset = bin_id * bin_depth;
// bin_map[n][0] for every bin 'n' maintains the counter for the number of
// histograms in that bin.
// Get and increment the num_histos in that bin.
num_histos = ++bin_map[bin_offset];
const int num_histos = ++bin_map[bin_offset];
assert(bin_offset + num_histos < bin_depth * BIN_SIZE);
// Add histogram i'th index at num_histos (last) position in the bin_map.
bin_map[bin_offset + num_histos] = i;