Compute pixel vignetting across the image sensor array vignetting = pixelVignetting(ISA,OI) PURPOSE: Calculate the correction factor for the irradiance of off-axis pixels due to pixel vignetting. The routine calculates the vignetting at 100 samples from the image center to the periphery along the X-axis. THese values are interpolated and then circularly symmetric function across the rest of the array. Calculating every pixel takes a long time, and this function is invariably smooth. Copyright ImagEval Consultants, LLC, 2003.