[gdal-dev] 16 bit / px / band TIFFs unreadable by ImageMagick, others

[Frank Warmerdam]

Nissim Chudnoff wrote:
> Frank,
> 
>> 1) It's tiled.  Some programs still don't support tiled tiff files.
> 
> These are supported by IM, GS and IV, so I don't think it's a problem,
> same with INTERLEAVE=band or pixel.
> 
>> 2) It's 16bit.  Lots of programs don't support 16bit tiff files.
> I can't vouch for GeoServer/GeoTools, but IrfanView and ImageMagick have
> no problems with the 16 bit/band RGB or grayscale images in the libtiff
> test suite, so I'm not sure this is what's wrong.
> 
>> 3) It uses only a fraction of the 16bit dynamic range.  Lots of programs
>>    that *can* read 16bit assume the image is full dynamic range (values
>>    from 0 to 65535 so your image in the 0 to 1000 range (roughly) will
> end
>>    up getting shown as black and slightly off black.
> 
> That's just it -- that image isn't just black/off black. If you use
> "gdal_translate -scale -ot Byte" to produce an 8-bit version of it, you'll
> see land features, river and ocean (in many pretty colors, not just
> grayscale), and the file opens Ok in all the various software.
> 
> Obviously I can just go ahead and use the 8-bit images for our
> application, but I was curious if anyone knew more about this, if it was a
> bug/feature, gotten it to work, etc.

Nissim,

It is not a bug.  It is just a disconnect in purposes and approaches
in two different imaging fields.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org