Enhancement to Auto Levels on behalf of Emil;
Replacements of the packaged profiles. (see issue 940)
This commit is contained in:
michael
@@ -616,56 +616,169 @@ void ImProcFunctions::colorCurve (LabImage* lold, LabImage* lnew) {
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}
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}
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void ImProcFunctions::getAutoExp (LUTu & histogram, int histcompr, double expcomp, double clip, double& br, int& bl) {
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void ImProcFunctions::getAutoExp (LUTu & histogram, int histcompr, double defgain, double clip, \
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double& expcomp, int& bright, int& contr, int& black, int& hlcompr, int& hlcomprthresh) {
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double sum = 0;
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for (int i=0; i<65536>>histcompr; i++)
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double corr = 1;//pow(2.0, defgain);//defgain may be redundant legacy of superceded code???
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float scale = 65536.0;
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float midgray=0.18445f;//middle gray in linear gamma = 0.18445*65535
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int imax=65536>>histcompr;
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float sum = 0, hisum=0, losum=0;
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float ave = 0, hidev=0, lodev=0;
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//find average luminance
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for (int i=0; i<imax; i++) {
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sum += histogram[i];
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ave += histogram[i] * i;//log((float)(i+1))/log(2.0);
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}
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ave /= (sum);
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// compute clipping points based on the original histograms (linear, without exp comp.)
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int clippable = (int)(sum * clip);
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int clipped = 0;
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int aw = (65536>>histcompr) - 1;
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while (aw>1 && histogram[aw]+clipped <= clippable) {
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clipped += histogram[aw];
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aw--;
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//find median of luminance
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int median=0, count=0;
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while (count<sum/2) {
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median++;
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count += histogram[median];
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}
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// compute std dev on the high and low side of median
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// and octiles of histogram
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float octile[8]={0,0,0,0,0,0,0,0},ospread=0;
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count=0;
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for (int i=0; i<imax; i++) {
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octile[count] += histogram[i];
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if (octile[count]>sum/8) {
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octile[count]=log(1+i)/log(2);
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count = MIN(count+1,7);
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}
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if (i<median) {
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//lodev += SQR(ave-i)*histogram[i];
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lodev += (log(median+1)-log(i+1))*histogram[i];
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losum += histogram[i];
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} else {
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//hidev += SQR(i-ave)*histogram[i];
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hidev += (log(i+1)-log(median+1))*histogram[i];
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hisum += histogram[i];
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}
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}
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lodev = (lodev/(log(2)*losum));
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hidev = (hidev/(log(2)*hisum));
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// compute weighted average separation of octiles
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// for future use in contrast setting
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for (int i=1; i<6; i++) {
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ospread += (octile[i+1]-octile[i])/MAX(0.5,(i>2 ? (octile[i+1]-octile[3]) : (octile[3]-octile[i])));
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}
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ospread /= 5;
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// compute clipping points based on the original histograms (linear, without exp comp.)
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int clipped = 0;
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int rawmax = (imax) - 1;
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while (rawmax>1 && histogram[rawmax]+clipped <= 0) {
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clipped += histogram[rawmax];
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rawmax--;
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}
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//compute clipped white point
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int clippable = (int)(sum * clip);
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clipped = 0;
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int whiteclip = (imax) - 1;
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while (whiteclip>1 && histogram[whiteclip]+clipped <= clippable) {
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clipped += histogram[whiteclip];
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whiteclip--;
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}
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//compute clipped black point
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clipped = 0;
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int shc = 0;
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while (shc<aw-1 && histogram[shc]+clipped <= clippable) {
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while (shc<whiteclip-1 && histogram[shc]+clipped <= clippable) {
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clipped += histogram[shc];
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shc++;
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}
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aw <<= histcompr;
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//rescale to 65535 max
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rawmax <<= histcompr;
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whiteclip <<= histcompr;
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ave = ave*(1<<histcompr);
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median <<= histcompr;
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shc <<= histcompr;
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//prevent division by 0
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if (ave==0) ave=1;
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if (lodev==0) lodev=1;
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double corr = pow(2.0, expcomp);
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//compute exposure compensation as geometric mean of the amount that
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//sets the median at middle gray, and the amount that sets the clipped white point
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//at 65535. Apply a correction factor of median/ave so that high/low key images
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//are treated properly
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float gain = /*corr**/midgray*scale/(median-shc+midgray*shc);
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gain = (median/ave)*sqrt(gain*scale/rawmax);
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black = shc*gain;
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expcomp = log(gain)/log(2.0);//convert to stops
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//now tune hlcompr to bring back rawmax to 65535
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hlcomprthresh = 33;
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float shoulder = ((scale/MAX(1,gain))*(hlcomprthresh/200.0))+0.1;
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//this is a series approximation of the actual formula for comp,
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//which is a transcendental equation
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float comp = (gain*whiteclip/scale - 1)*2*(1-shoulder/scale);
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hlcompr=(int)(100*comp/(MAX(0,expcomp) + 1.0));
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hlcompr = MAX(0,MIN(100,hlcompr));
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//now find brightness if gain didn't bring ave to midgray using
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//the envelope of the actual 'control cage' brightness curve for simplicity
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float midtmp = gain*(median)/scale;
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if (midtmp<0.1) {
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bright = (midgray-midtmp)*15.0/(midtmp);
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} else {
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bright = (midgray-midtmp)*15.0/(0.10833-0.0833*midtmp);
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}
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bright = 0.25*(median/ave)*(hidev/lodev)*MAX(0,bright);
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//compute contrast that spreads the average spacing of octiles
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contr = 50.0*(1.1-ospread);
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contr = MAX(0,MIN(100,contr));
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//diagnostics
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/*printf ("**************** AUTO LEVELS ****************\n");
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printf ("median: %i\n",median);
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printf ("average: %f\n",ave);
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printf ("median/average: %f\n",median/ave);
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printf ("hidev/lodev: %f\n",hidev/lodev);
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printf ("lodev: %f\n",lodev);
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printf ("hidev: %f\n",hidev);
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printf ("octiles: %f %f %f %f %f %f %f\n",octile[0],octile[1],octile[2],octile[3],octile[4],octile[5],octile[6]);
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printf ("ospread= %f\n",ospread);*/
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/*
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// %%%%%%%%%% LEGACY AUTOEXPOSURE CODE %%%%%%%%%%%%%
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// black point selection is based on the linear result (yielding better visual results)
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bl = (int)(shc * corr);
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black = (int)(shc * corr);
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// compute the white point of the exp. compensated gamma corrected image
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double awg = (int)(CurveFactory::gamma2 (aw * corr / 65536.0) * 65536.0);
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double whiteclipg = (int)(CurveFactory::gamma2 (whiteclip * corr / 65536.0) * 65536.0);
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// compute average intensity of the exp compensated, gamma corrected image
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double gavg = 0;
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for (int i=0; i<65536>>histcompr; i++)
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gavg += histogram[i] * CurveFactory::gamma2((int)(corr*(i<<histcompr)<65535 ? corr*(i<<histcompr) : 65535)) / sum;
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if (bl < gavg) {
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int maxaw = (gavg - bl) * 4 / 3 + bl; // dont let aw be such large that the histogram average goes above 3/4
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//double mavg = 65536.0 / (awg-bl) * (gavg - bl);
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if (awg < maxaw)
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awg = maxaw;
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if (black < gavg) {
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int maxwhiteclip = (gavg - black) * 4 / 3 + black; // dont let whiteclip be such large that the histogram average goes above 3/4
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//double mavg = 65536.0 / (whiteclipg-black) * (gavg - black);
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if (whiteclipg < maxwhiteclip)
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whiteclipg = maxwhiteclip;
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}
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awg = CurveFactory::igamma2 ((float)(awg/65535.0)) * 65535.0; //need to inverse gamma transform to get correct exposure compensation parameter
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whiteclipg = CurveFactory::igamma2 ((float)(whiteclipg/65535.0)) * 65535.0; //need to inverse gamma transform to get correct exposure compensation parameter
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bl = (int)((65535*bl)/awg);
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br = log(65535.0 / (awg)) / log(2.0);
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if (br<0.0) br = 0.0;
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if (br>10.0) br=10.0;
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black = (int)((65535*black)/whiteclipg);
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expcomp = log(65535.0 / (whiteclipg)) / log(2.0);
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if (expcomp<0.0) expcomp = 0.0;*/
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if (expcomp>10.0) expcomp=10.0;
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}
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//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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