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⚡ Optimize AdjustHistogramApplyFunction with precomputed LUT #7

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⚡ Optimize AdjustHistogramApplyFunction with precomputed LUT #7

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61 changes: 32 additions & 29 deletions app/src/main/java/net/sourceforge/opencamera/JavaImageFunctions.java
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Original file line number Diff line number Diff line change
Expand Up @@ -2308,24 +2308,27 @@ static class AdjustHistogramApplyFunction implements JavaImageProcessing.ApplyFu
private final int n_tiles;
private final int width;
private final int height;
private final int [] c_histogram;
private final int [] equal_value_lut; // look up table for performance

AdjustHistogramApplyFunction(float hdr_alpha, int n_tiles, int width, int height, int [] c_histogram) {
this.hdr_alpha = hdr_alpha;
this.n_tiles = n_tiles;
this.width = width;
this.height = height;
this.c_histogram = c_histogram;
}

private int getEqualValue(int histogram_offset, int value) {
int cdf_v = c_histogram[histogram_offset+value];
int cdf_0 = c_histogram[histogram_offset];
int n_pixels = c_histogram[histogram_offset+255];
float num = (float)(cdf_v - cdf_0);
float den = (float)(n_pixels - cdf_0);
int equal_value = (int)( 255.0f * (num/den) ); // value that we should choose to fully equalise the histogram
return equal_value;
this.equal_value_lut = new int[n_tiles*n_tiles*256];
for(int i=0;i<n_tiles*n_tiles;i++) {
int histogram_offset = 256*i;
int cdf_0 = c_histogram[histogram_offset];
int n_pixels = c_histogram[histogram_offset+255];
float den = (float)(n_pixels - cdf_0);
for(int value=0;value<256;value++) {
int cdf_v = c_histogram[histogram_offset+value];
float num = (float)(cdf_v - cdf_0);
int equal_value = (int)( 255.0f * (num/den) ); // value that we should choose to fully equalise the histogram
this.equal_value_lut[histogram_offset+value] = equal_value;
}
}
}

@Override
Expand Down Expand Up @@ -2369,10 +2372,10 @@ public void apply(JavaImageProcessing.CachedBitmap output, int thread_index, int
int histogram_offset10 = 256*((ix+1)*n_tiles+iy);
int histogram_offset01 = 256*(ix*n_tiles+iy+1);
int histogram_offset11 = 256*((ix+1)*n_tiles+iy+1);
int equal_value00 = getEqualValue(histogram_offset00, value);
int equal_value10 = getEqualValue(histogram_offset10, value);
int equal_value01 = getEqualValue(histogram_offset01, value);
int equal_value11 = getEqualValue(histogram_offset11, value);
int equal_value00 = equal_value_lut[histogram_offset00+value];
int equal_value10 = equal_value_lut[histogram_offset10+value];
int equal_value01 = equal_value_lut[histogram_offset01+value];
int equal_value11 = equal_value_lut[histogram_offset11+value];
float alpha = tx - ix;
float beta = ty - iy;

Expand All @@ -2384,25 +2387,25 @@ else if( ix >= 0 && ix < n_tiles-1 ) {
int this_y = (iy<0) ? iy+1 : iy;
int histogram_offset0 = 256*(ix*n_tiles+this_y);
int histogram_offset1 = 256*((ix+1)*n_tiles+this_y);
int equal_value0 = getEqualValue(histogram_offset0, value);
int equal_value1 = getEqualValue(histogram_offset1, value);
int equal_value0 = equal_value_lut[histogram_offset0+value];
int equal_value1 = equal_value_lut[histogram_offset1+value];
float alpha = tx - ix;
equal_value = (int)((1.0f-alpha)*equal_value0 + alpha*equal_value1);
}
else if( iy >= 0 && iy < n_tiles-1 ) {
int this_x = (ix<0) ? ix+1 : ix;
int histogram_offset0 = 256*(this_x*n_tiles+iy);
int histogram_offset1 = 256*(this_x*n_tiles+iy+1);
int equal_value0 = getEqualValue(histogram_offset0, value);
int equal_value1 = getEqualValue(histogram_offset1, value);
int equal_value0 = equal_value_lut[histogram_offset0+value];
int equal_value1 = equal_value_lut[histogram_offset1+value];
float beta = ty - iy;
equal_value = (int)((1.0f-beta)*equal_value0 + beta*equal_value1);
}
else {
int this_x = (ix<0) ? ix+1 : ix;
int this_y = (iy<0) ? iy+1 : iy;
int histogram_offset = 256*(this_x*n_tiles+this_y);
equal_value = getEqualValue(histogram_offset, value);
equal_value = equal_value_lut[histogram_offset+value];
}

int new_value = (int)( (1.0f-hdr_alpha) * value + hdr_alpha * equal_value );
Expand Down Expand Up @@ -2460,10 +2463,10 @@ public void apply(JavaImageProcessing.CachedBitmap output, int thread_index, byt
int histogram_offset10 = 256*((ix+1)*n_tiles+iy);
int histogram_offset01 = 256*(ix*n_tiles+iy+1);
int histogram_offset11 = 256*((ix+1)*n_tiles+iy+1);
int equal_value00 = getEqualValue(histogram_offset00, value);
int equal_value10 = getEqualValue(histogram_offset10, value);
int equal_value01 = getEqualValue(histogram_offset01, value);
int equal_value11 = getEqualValue(histogram_offset11, value);
int equal_value00 = equal_value_lut[histogram_offset00+value];
int equal_value10 = equal_value_lut[histogram_offset10+value];
int equal_value01 = equal_value_lut[histogram_offset01+value];
int equal_value11 = equal_value_lut[histogram_offset11+value];
float alpha = tx - ix;
float beta = ty - iy;

Expand All @@ -2475,25 +2478,25 @@ else if( ix >= 0 && ix < n_tiles-1 ) {
int this_y = (iy<0) ? iy+1 : iy;
int histogram_offset0 = 256*(ix*n_tiles+this_y);
int histogram_offset1 = 256*((ix+1)*n_tiles+this_y);
int equal_value0 = getEqualValue(histogram_offset0, value);
int equal_value1 = getEqualValue(histogram_offset1, value);
int equal_value0 = equal_value_lut[histogram_offset0+value];
int equal_value1 = equal_value_lut[histogram_offset1+value];
float alpha = tx - ix;
equal_value = (int)((1.0f-alpha)*equal_value0 + alpha*equal_value1);
}
else if( iy >= 0 && iy < n_tiles-1 ) {
int this_x = (ix<0) ? ix+1 : ix;
int histogram_offset0 = 256*(this_x*n_tiles+iy);
int histogram_offset1 = 256*(this_x*n_tiles+iy+1);
int equal_value0 = getEqualValue(histogram_offset0, value);
int equal_value1 = getEqualValue(histogram_offset1, value);
int equal_value0 = equal_value_lut[histogram_offset0+value];
int equal_value1 = equal_value_lut[histogram_offset1+value];
float beta = ty - iy;
equal_value = (int)((1.0f-beta)*equal_value0 + beta*equal_value1);
}
else {
int this_x = (ix<0) ? ix+1 : ix;
int this_y = (iy<0) ? iy+1 : iy;
int histogram_offset = 256*(this_x*n_tiles+this_y);
equal_value = getEqualValue(histogram_offset, value);
equal_value = equal_value_lut[histogram_offset+value];
}

int new_value = (int)( (1.0f-hdr_alpha) * value + hdr_alpha * equal_value );
Expand Down