Initial data commit

Task/Image-convolution/JavaScript/image-convolution.js

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+// Image imageIn, Array kernel, function (Error error, Image imageOut)
+// precondition: Image is loaded
+// returns loaded Image to asynchronous callback function
+function convolve(imageIn, kernel, callback) {
+    var dim = Math.sqrt(kernel.length),
+        pad = Math.floor(dim / 2);
+
+    if (dim % 2 !== 1) {
+        return callback(new RangeError("Invalid kernel dimension"), null);
+    }
+
+    var w = imageIn.width,
+        h = imageIn.height,
+        can = document.createElement('canvas'),
+        cw,
+        ch,
+        ctx,
+        imgIn, imgOut,
+        datIn, datOut;
+
+    can.width = cw = w + pad * 2; // add padding
+    can.height = ch = h + pad * 2; // add padding
+
+    ctx = can.getContext('2d');
+    ctx.fillStyle = '#000'; // fill with opaque black
+    ctx.fillRect(0, 0, cw, ch);
+    ctx.drawImage(imageIn, pad, pad);
+
+    imgIn = ctx.getImageData(0, 0, cw, ch);
+    datIn = imgIn.data;
+
+    imgOut = ctx.createImageData(w, h);
+    datOut = imgOut.data;
+
+    var row, col, pix, i, dx, dy, r, g, b;
+
+    for (row = pad; row <= h; row++) {
+        for (col = pad; col <= w; col++) {
+            r = g = b = 0;
+
+            for (dx = -pad; dx <= pad; dx++) {
+                for (dy = -pad; dy <= pad; dy++) {
+                    i = (dy + pad) * dim + (dx + pad); // kernel index
+                    pix = 4 * ((row + dy) * cw + (col + dx)); // image index
+                    r += datIn[pix++] * kernel[i];
+                    g += datIn[pix++] * kernel[i];
+                    b += datIn[pix  ] * kernel[i];
+                }
+            }
+
+            pix = 4 * ((row - pad) * w + (col - pad)); // destination index
+            datOut[pix++] = (r + .5) ^ 0;
+            datOut[pix++] = (g + .5) ^ 0;
+            datOut[pix++] = (b + .5) ^ 0;
+            datOut[pix  ] = 255; // we want opaque image
+        }
+    }
+
+    // reuse canvas
+    can.width = w;
+    can.height = h;
+
+    ctx.putImageData(imgOut, 0, 0);
+
+    var imageOut = new Image();
+
+    imageOut.addEventListener('load', function () {
+        callback(null, imageOut);
+    });
+
+    imageOut.addEventListener('error', function (error) {
+        callback(error, null);
+    });
+
+    imageOut.src = can.toDataURL('image/png');
+}