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POApplying Edge Filter on Video using Canvas in HTML5 but getting lag in video. Is there any better way that i don't get lag?
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9636577
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2012-03-09T15:26:37.140
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2012-05-18T09:49:50.433
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<p>I am using HTML5 Canvas and applying Edge Filter by pixel manipulation. But I am getting lag in the video. Is there any better way to achieve video with edge filter without any lag in video?</p> <p>Following is the JavaScript I am using with canvas and HTML 5 to apply the effect:-</p> <pre><code> function sobel (px) { px = greyScale(px); var vertical = convoluteFloat32(px, [-1, -2, -1, 0, 0, 0, 1, 2, 1], false); var horizontal = convoluteFloat32(px, [-1, 0, 1, -2, 0, 2, -1, 0, 1], false); var id = createImageData(vertical.width, vertical.height); for (var i = 0; i < id.data.length; i += 4) { var v = Math.abs(vertical.data[i]); id.data[i] = v; var h = Math.abs(horizontal.data[i]); id.data[i + 1] = h id.data[i + 2] = (v + h) / 4; id.data[i + 3] = 255; } return id; } function convoluteFloat32 (pixels, weights, opaque) { var side = Math.round(Math.sqrt(weights.length)); var halfSide = Math.floor(side / 2); var src = pixels.data; var sw = pixels.width; var sh = pixels.height; var w = sw; var h = sh; var output = { width: w, height: h, data: new Float32Array(w * h * 4) }; var dst = output.data; var alphaFac = opaque ? 1 : 0; for (var y = 0; y < h; y++) { for (var x = 0; x < w; x++) { var sy = y; var sx = x; var dstOff = (y * w + x) * 4; var r = 0, g = 0, b = 0, a = 0; for (var cy = 0; cy < side; cy++) { for (var cx = 0; cx < side; cx++) { var scy = Math.min(sh - 1, Math.max(0, sy + cy - halfSide)); var scx = Math.min(sw - 1, Math.max(0, sx + cx - halfSide)); var srcOff = (scy * sw + scx) * 4; var wt = weights[cy * side + cx]; r += src[srcOff] * wt; g += src[srcOff + 1] * wt; b += src[srcOff + 2] * wt; a += src[srcOff + 3] * wt; } } dst[dstOff] = r; dst[dstOff + 1] = g; dst[dstOff + 2] = b; dst[dstOff + 3] = a + alphaFac * (255 - a); } } return output; } function draw() { // First, draw it into the backing canvas backcontext.drawImage(video, 0, 0, video.width, video.height); // Grab the pixel data from the backing canvas var idata = backcontext.getImageData(0, 0, video.width, video.height); idata = sobel(idata); context.putImageData(idata, 0, 0); // Start over! setTimeout(draw, 50); } </code></pre>
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<javascript><html5><image-processing><canvas>
Title
Applying Edge Filter on Video using Canvas in HTML5 but getting lag in video. Is there any better way that i don't get lag?
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1. USBalraj Singh
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