If inverse is selected, a deconvolution is performed, that is division of the FFTs. The output matrix is twice the size of the input matrix. 2D auto and cross correlation Cross correlation performs on two input matricies of the same size . It is like convolution, but operates on the conjugates of the second matrix. The output matrix is twice the size of the input matrix.
Threshold is a method applied to a greyscale image to translate it into a boolean bitmap.
OIPI supports global and local threshold. When you select global threshold, the Thresh parameter is a percentage used to determine whether or not the target pel should be true. The entire image is searched to discover its range, and any given pixel is then compared to the treshold value after adjusted for range. When you select local threshold, the local arithmetic mean around some point is calculated given distance M to yield an adaptive, local threshold T. T is then modified using the Thresh parameter. The OIP bi-cubic spline command is not intended to interpolate single points.