Alpha Compositing and shyts

Uh, if you're trying to alpha-compose using over:

Code:

double alpha1 = a1/255.,
           alpha2 = a2/255. * (1 - alpha1);
    newImage[offset + j*4 + 3] = (byte)(a1 * alpha1 + a2 * alpha2);
    newImage[offset + j*4] = (byte)(r1 * alpha1 + r2 * alpha2);
    newImage[offset + j*4 + 1] = (byte)(g1 * alpha1 + g2 * alpha2);
    newImage[offset + j*4 + 2] = (byte)(b1 * alpha1 + b2 * alpha2);