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function inRange(i, width, height) { return ((i>=0) && (i < width*height*4)); } function averageNeighbors(imageData, width, height, i) { var v = imageData[i]; // cardinal directions var north = inRange(i-width*4, width, height) ? imageData[i-width*4] : v; var south = inRange(i+width*4, width, height) ? imageData[i+width*4] : v; var west = inRange(i-4, width, height) ? imageData[i-4] : v; var east = inRange(i+4, width, height) ? imageData[i+4] : v; // diagonal neighbors var ne = inRange(i-width*4+4, width, height) ? imageData[i-width*4+4] : v; var nw = inRange(i-width*4-4, width, height) ? imageData[i-width*4-4] : v; var se = inRange(i+width*4+4, width, height) ? imageData[i+width*4+4] : v; var sw = inRange(i+width*4-4, width, height) ? imageData[i+width*4-4] : v; // average var newVal = Math.floor((north + south + east + west + se + sw + ne + nw + v)/9); if (isNaN(newVal)) { sendStatus("bad value " + i + " for height " + height); throw new Error("NaN"); } return newVal; } function boxBlur(imageData, width, height) { var data = []; var val = 0; for (var i=0; i<width*height*4; i++) { val = averageNeighbors(imageData, width, height, i); data[i] = val; } return data; }