You can gain performance by using the typed array's .set method:
Unfortunately, IE still uses the CanvasPixelArray instead of the new html specification (Uint8ClampedArray). IE's imageData.data doesn't yet have the .set method.
But you can still use .set indirectly using a conversion array:
// create a typed array to pipe data through
// (used to be able to do .set later)
buffer = new ArrayBuffer(imgData.data.length);
converterArray=new Uint8Array(buffer);
// In repaint
imgData.data = converterArray.set(MEMU8.subarray(0,siz));