Re: [Gimp-developer] high bit depth tiff issues

[Michael Natterer <mitch gimp org>]

On Thu, 2017-04-27 at 23:07 -0700, Casey Connor wrote:
> ...and a final follow-up, just so people don't need to spend any time
> on 
> this: changing the range with g'mic makes the files work properly in
> GIMP:
>
> gmic 16bit_input.tif -/ 65535 -o 32bit_float_output.tif
>
> (that scales the output to the [0,1] range.)
>
> So that seems like the logical way to handle this, unless gimp wanted
> to 
> handle large ranges automatically or something. (Apparently the CCE 
> edition is already doing that to some extent.)

Hi Casey,

thanks for investigating this issue. GIMP should load all
these files just fine. I think support for 16/32 bit float
TIFF was added without checking what range the values
would have.

GIMP completely ignores TIFFTAG_{MAX,MIN}SAMPLEVALUE, and
according to the spec they should default to 

2**(BitsPerSample) - 1

which is just the scaling factor of 65535 you encountered.

However not for 32 bit files, but judging from your command
line above I assume you meant 16 bit, or both gmic and gimp
are broken, who knows :)

Can you please file a bug and attach the sample files?

The fix should be trivial, but I need some files to test.

Regards,
Mitch