HDR filtering

Hi

I am interested in writing a filter for dealing specifically with hdr 
images. I downloaded
cinepaint-0.22-0_rc4.tar.gz and built it on Fedora Core 6 and modified 
the unsharp plugin to get my feet wet. I am medical imaging researcher 
during the day.

I do get an image but I realize that I do not understand how a plugin 
like unsharp deals with different image types. All of the data pointer 
are of the type
guchar  *cur_col;
guchar  *dest_col;
guchar  *cur_row;

 I am puzzled as to how this code works for all of the data types 
supported in cinepaint. In C, I would have expected the need to cast 
data pointers to unsigned short or float etc and yet this just seems to 
work magically for all images. In C++, I would have expected to see 
templates or function overloading.  There is no reference to colour at 
all in this code either so does it just get called on each colour 
channels or I am working in a colour different representation and 
dealing with intensity?

I hope that you will not find these questions too naive but I mostly 
work with greyscale images in my world.

Regards

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