[XM, XN, XO, and XP are optional register parameters, such
that 10 <= M,N,O,P <= 99. On completion of the operation,
XM contains the picture maximum, XN its minimum, XO its
average, and XP its standard deviation.
However, only if the image statistics have already been
determined in a previous operation and have been recorded
in the file header are the values are placed in the
registers: XM,XN,XO,XP.
.INPUT FILE: PIC001
[Enter name of image file to be analyzed. If this is a
whole stack then results are reported for all of the
images in the stack]