javascript - Faulty Logic in this image color equalization algorithm -

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somewhere in code, seem doing wrong , cannot tell part going awry. i've printed console values i'm getting various arrays , seems match up. when run equalization function (a la wikipedia-histogram equalization) output image close total black. trying interpret this guy's php javascript test stuff out , figured did decent job. i'm not expert.

the pertinent parts: 

        function imageloaded(ev) {             element = document.getelementbyid("canvas1");             c = element.getcontext("2d");              im = ev.target; // image              // read width , height of canvas             width = element.width;             height = element.height;              // stamp image on left of canvas:             c.drawimage(im, 0, 0);             // canvas pixel data             imagedata = c.getimagedata(0, 0, width, height);              w2 = width / 2;             var reds = new array();             var greens = new array();             var blues = new array();              var freqr = new array();             var freqg = new array();             var freqb = new array();              if (imagedata){                  buildhistograms(reds, greens,blues);                  buildfrequencies(reds, greens, blues, freqr, freqg, freqb);              }              var alpha = 255/(w2*height);               // run through image             (y = 0; y < height; y++) {                 inpos = y * width * 4; // *4 4 ints per pixel                 outpos = inpos + w2 * 4;                 (x = 0; x < w2; x++) {                       //reads pixel data(of img c)to each channel of rgb                     r = imagedata.data[inpos++];                       g = imagedata.data[inpos++];                     b = imagedata.data[inpos++];                     = imagedata.data[inpos++];                       //using histogram eqalization formula:                      adjr = freqr[r]*alpha;                     adjg = freqg[g]*alpha;                     adjb = freqb[b]*alpha;                //assigns pixel data of output image                     imagedata.data[outpos++] = adjr;                     imagedata.data[outpos++] = adjg;                     imagedata.data[outpos++] = adjb;                     imagedata.data[outpos++] = a;                 }             }             // put pixel data on canvas             c.putimagedata(imagedata, 0,0);          }          im = new image();         im.onload = imageloaded;         im.src = "lenna.png";             function buildhistograms(reds,greens,blues){             //run through image building histogram                   (y=0; y < height; y++){                 inpos = y * width *4;                 (x=0; x < w2; x++){                 rd = imagedata.data[inpos++];                      g = imagedata.data[inpos++];                     b = imagedata.data[inpos++];                     = imagedata.data[inpos++];                     // add counts our histogram arrays each color.                     reds.push(rd);                     greens.push(g);                     blues.push(b);                 }             }              // sort them keys order             reds.sort(function(a,b){return a-b});             greens.sort(function(a,b){return a-b});             blues.sort(function(a,b){return a-b});           }          function buildfrequencies(reds, greens, blues, freqr, freqg, freqb){         // build frequency charts colors: takes reds greens blues buildhistograms , places them on top of each other accordingly             for(i=0; i<=255; i++){                 sumr=0;                 sumg=0;                 sumb=0;                  for(j=0; j<= i; j++){                     if (reds[j]){sumr+=reds[j];}                     if (greens[j]){sumg+=greens[j];}                     if (blues[j]){sumb+=blues[j];}                 }                  freqr[i] = sumr;                 freqg[i] = sumg;                 freqb[i] = sumb;              }         }

any appreciated, thanks.

looks build frequencies section wrong. modified in way:

var len = reds.length;               (j=0; j < len; j++) {                     var rcurrval = reds[j];                     var gcurrval = greens[j];                     var bcurrval = blues[j];                     if (freqr.hasownproperty(rcurrval)) {                         freqr[rcurrval] += 1;                     }   else {                        freqr[rcurrval] = 1;                     }                      if (freqg.hasownproperty(gcurrval)) {                         freqg[gcurrval] += 1;                     }   else {                        freqg[gcurrval] = 1;                     }                     if (freqb.hasownproperty(bcurrval)) {                         freqb[bcurrval] += 1;                     }   else {                        freqb[bcurrval] = 1;                     }             }               (i=0; i<255; i++){                    if ($.inarray(i,reds)===-1){freqr[i]=0;}                 if ($.inarray(i,greens)=== -1){freqg[i]=0;}                 if ($.inarray(i,blues)=== -1){freqb[i]=0;}                  if (i>0){                     freqr[i]+=freqr[i-1];                     freqg[i]+=freqg[i-1];                     freqb[i]+=freqb[i-1];                  }             }

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