COAL_IMAGE is a medium level routine to perform the scaling,
alignment, and roll two images so they are co-aligned. Some sample calls are:
IDL> data_out = coal_image(data, index_or_corn, out_corn, out_siz)
IDL> data_out = coal_image(data, index, out_corn, out_siz, index_out=index_out)
IDL> data_out = coal_image(img1, corner1, corner2, out_siz, mag=pix1/pix2)
where the first parameter is the image which is to be changed so that
it is co-aligned with another image. The second parameter can be
an SXT index or the pixel address of the lower left corner relative to
the sun center for the input image. The pixel address
is in units of the input image pixel size. The third parameter is where
you want to shift the image to, it is a two element array of the lower corner
value (relative to sun center) for the output array in output pixel units.
out_siz is the output size of the image, mag is the
magnification factor required to convert the image to the same scale as
the other image. The optional input angle=angle is available to
correct for a roll difference between the two images.