javascript - Fastest Gaussian Blur Not Working -

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i not @ javascript , have been trying ivan kuckir's fastest gaussian blur code work no success. when load page, becomes unresponsive have close window somehow. code use follows. doing wrong?

<html> <head> <script src="path_to_gaussianblur.js"></script> </head>  <body> <img id="sourceimage" src="someimage_200px_x_200px.jpg" /> <canvas id="canvas1" width="200" height="200" style="border: 1px solid blue"></canvas> <canvas id="canvas2" width="200" height="200" style="border: 1px solid red"></canvas>  <script>     document.getelementbyid("sourceimage").onload = function () {          var c1 = document.getelementbyid("canvas1");         var c2 = document.getelementbyid("canvas2");          var ctx1 = c1.getcontext("2d");         var ctx2 = c2.getcontext("2d");          var img = document.getelementbyid("sourceimage");          ctx1.drawimage(img, 0, 0);         ctx2.drawimage(img, 0, 0);          var source = ctx1.getimagedata(0, 0, c1.width, c1.height);         var target = ctx2.getimagedata(0, 0, c2.width, c2.height);          (var = 0; < source.data.length; += 4) {             // red chanel             gaussblur_4(source.data[i], target.data[i], c1.width, c1.height, 2);             // green channel             gaussblur_4(source.data[i + 1], target.data[i + 1], c1.width, c1.height, 2);             // blue channel             gaussblur_4(source.data[i + 2], target.data[i + 2], c1.width, c1.height, 2);         }          ctx2.putimagedata(target, 0, 0);     }; </script> </body> </html>

as stated in comments need split rgba array separate channels. can in several ways, here one:

split

var idata = ctx.getimagedata(0, 0, w, h), // assumes ctx/w/h defined     rgba = idata.data,     len = w * h,     rsrc = new uint8array(len),           // source arrays     gsrc = new uint8array(len),     bsrc = new uint8array(len),     asrc = new uint8array(len),     // define target arrays same way above     = 0, offset = 0;  for(; < len; i++) {   rsrc[i] = rgba[offset++];   gsrc[i] = rgba[offset++];   bsrc[i] = rgba[offset++];   asrc[i] = rgba[offset++]; }

now can pass each of arrays blur function using target arrays set in similar manner source arrays, merge result rgba format.

apply

gaussblur_4(rsrc, rtrg, w, h, radius); gaussblur_4(gsrc, gtrg, w, h, radius); gaussblur_4(bsrc, btrg, w, h, radius); gaussblur_4(asrc, atrg, w, h, radius);

additional tip: if you're using images (as in photos) can skip blurring alpha channel there none (or technically, opaque in canvas).

merge

to merge, do:

for(i = 0, offset = 0; < len; i++) {   rgba[offset++] = rtrg[i];   rgba[offset++] = gtrg[i];   rgba[offset++] = btrg[i];   rgba[offset++] = atrg[i]; // or increase offset if skipped alpha }  ctx.putimagedata(idata, 0, 0);

due license conflict on running example can found in fiddle (and here alternative split/merge using 32-bits approach).


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