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

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
this: changing the range with g'mic makes the files work properly in

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
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.


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