Created
April 23, 2013 15:12
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| /* Histogram exponential equalization when alpha = 0.011 */ | |
| float exponential_histogram(unsigned char* inbuf, unsigned char* outbuf, int height, int width){ | |
| double g_min=255; | |
| double g_max=0; | |
| double* histogram = new double[256]; | |
| /* histogram array */ | |
| double* cdf = new double[256]; /*Pf(f) values [cumulative distribution function]*/ | |
| double* out = new double[height*width]; | |
| int start = GetTickCount(); | |
| for(int i=0;i<256;i++) | |
| histogram[i] = 0.0; | |
| /*Counting histogram values 0..255 */ | |
| double d = 1.0/double(height*width); | |
| for(int i=0;i<height;i++){ | |
| for(int j=0;j<width;j++) | |
| { | |
| if(inbuf[i*width+j]<g_min) g_min = inbuf[i*width+j]; | |
| if(inbuf[i*width+j]>g_max) g_max = inbuf[i*width+j]; | |
| histogram[inbuf[i*width+j]]+=d; | |
| } | |
| } | |
| cdf[0]=histogram[0]; | |
| for(int i=1;i<256;i++) | |
| cdf[i]=(cdf[i-1]+histogram[i]); /*Pf(f) cumsuming*/ | |
| double max=-999,min=999,alpha=0.011; | |
| for(int i=0;i<height;i++){ | |
| for(int j=0;j<width;j++){ | |
| out[i*width+j] = g_min - (1.0/alpha)*log(1.1 - cdf[inbuf[i*width+j]]); | |
| if(out[i*width+j] > max) max=out[i*width+j]; | |
| if(out[i*width+j] < min) min=out[i*width+j]; | |
| } | |
| } | |
| /* double array to unsigned char */ | |
| for(int i=0;i<height;i++){ | |
| for(int j=0;j<width;j++){ | |
| outbuf[i*width+j]=(unsigned char)(out[i*width+j]-min)/(max - min) * 255; | |
| } | |
| } | |
| return (float)(GetTickCount() - start); | |
| } |
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