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Another bug fix.

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In the previous commit, we simply accomodated for alpha errors when compressing single color partitions. In fact, the issue was a bit more greivous: we weren't computing the proper error term at all! This fixed that function so that we emphasize the error metrics induced by *squaring* the error in each channel and then returning that as a measurement of the acceptability of using a single color compression for that partition.
This commit is contained in:
Pavel Krajcevski 2013-04-08 16:44:15 -04:00
parent ff18e8f33e
commit d23125e14c
1 changed files with 14 additions and 7 deletions
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21
BPTCEncoder/src/BC7Compressor.cpp
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@ -346,14 +346,14 @@ double BC7CompressionMode::CompressSingleColor(const RGBAVector &p, RGBAVector &
const uint32 pixel = p.ToPixel();
uint32 bestDist = 0xFF;
float bestError = FLT_MAX;
bestPbitCombo = -1;
for(int pbi = 0; pbi < GetNumPbitCombos(); pbi++) {
const int *pbitCombo = GetPBitCombo(pbi);
uint32 dist = 0x0;
uint32 dist[4] = { 0x0, 0x0, 0x0, 0x0 };
uint32 bestValI[kNumColorChannels] = { 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF };
uint32 bestValJ[kNumColorChannels] = { 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF };
@ -365,7 +365,7 @@ double BC7CompressionMode::CompressSingleColor(const RGBAVector &p, RGBAVector &
// If we don't handle this channel, then it must be the full value (alpha)
if(nBits == 0) {
bestValI[ci] = bestValJ[ci] = 0xFF;
dist = std::max(dist, (uint32)((uint8)0xFF - val));
dist[ci] = std::max(dist[ci], (uint32)((uint8)0xFF - val));
continue;
}
@ -417,11 +417,18 @@ double BC7CompressionMode::CompressSingleColor(const RGBAVector &p, RGBAVector &
}
}
dist = std::max(bestChannelDist, dist);
dist[ci] = std::max(bestChannelDist, dist[ci]);
}
if(dist < bestDist) {
bestDist = dist;
const float *errorWeights = BC7C::GetErrorMetric();
float error = 0.0;
for(int i = 0; i < kNumColorChannels; i++) {
float e = float(dist[i]) * errorWeights[i];
error += e * e;
}
if(error < bestError) {
bestError = error;
bestPbitCombo = pbi;
for(uint32 ci = 0; ci < kNumColorChannels; ci++) {
@ -431,7 +438,7 @@ double BC7CompressionMode::CompressSingleColor(const RGBAVector &p, RGBAVector &
}
}
return bestDist;
return bestError;
}
// Fast random number generator. See more information at