Peter Lubbers - Pro HTML 5 Programming

}
}
CHAPTER 8 ■ USING THE HTML5 WEB WORKERS API
"width" : e.data.width,
"height" : e.data.height,
"startX" : e.data.startX
});
sendStatus("Finished blur on data in range: " +
e.data.startX + "-" + (e.data.width+e.data.startX));
break;
default:
sendStatus("Worker got message: " + e.data);
addEventListener("message", messageHandler, true);
Listing 8-9. Content of the file blur.js
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;
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