Re: Tiff with signed samples

On 8/18/20 6:58 AM, Bob Friesenhahn wrote:
> The 2GB download size seems somewhat prohibitive to easily test with.
Not quite as bad as their 11 GB version!

> GM's -operator command can be useful such as using the logical And 
> operator, as well as the LShift, RShift, and Multiply operators to try 
> to convert the data into useful unsigned values.

Hmm, so what I'm wanting to do is for each pixel value v, make v = (v >> 
8) | (v << 8)
Samples are 16 bit grayscale, and gm quantum depth is 16.
I'm assuming there's no shift-and-wraparound operator.
If I read the docs right, -operator is a single thing done, the original 
value is forgotten, so something like that formula wouldn't be possible 
in a command line single call?

> Software such as GDAL may be better suited for dealing with these images.
exiftool shows tags with "gdal" in it, probably that's what nasa used 
for it I guess! Might be overkill for my current purposes. I have a gimp 
workaround that seems to be ok (on a scaled down file with -filter Point).

Slightly different question but part of my goal, can gm create normal 
maps from heightmaps? Usually gimp or krita do fine for this, but are 
crashing with this image for some unknown reason.

Thanks,
-Tom