[Ubuntu] imagemagick & gdal ?

[Heikki Julkunen]

Duh

What tool should I use to show relevant tiff-info, and I'll post that info on the gdal-dev list instead.

On Apr 21, 2012, at 8:25 AM, Frank Warmerdam wrote:

> On 12-04-21 07:32 AM, Heikki Julkunen wrote:
>> First, thanks all for a great set of tools!
>> 
>> Anyway, I've seen this mentioned in a post elsewhere, but there was no reply.
>> I'm not sure who to 'blame', gdal or imagemagick, but it seems like the alpha channel
>> embedded by imagemagick is NOT compatible with gdal. The transparency is NOT used.
>> (since imagemagick has no clue about geo-data after image processing I use geotifcp to add that).
>> 
>> Example: gdalinfo bad-example.tif
>> <<geo meta removed>>
>> Band 1 Block=10020x1 Type=Byte, ColorInterp=Red
>> Band 2 Block=10020x1 Type=Byte, ColorInterp=Green
>> Band 3 Block=10020x1 Type=Byte, ColorInterp=Blue
>> Band 4 Block=10020x1 Type=Byte, ColorInterp=Undefined
>> 
>> A working file looks like this:
>> gdalinfo good-example.tif
>> <<geo meta removed>>
>> Band 1 Block=10020x1 Type=Byte, ColorInterp=Red
>>   Mask Flags: PER_DATASET ALPHA
>> Band 2 Block=10020x1 Type=Byte, ColorInterp=Green
>>   Mask Flags: PER_DATASET ALPHA
>> Band 3 Block=10020x1 Type=Byte, ColorInterp=Blue
>>   Mask Flags: PER_DATASET ALPHA
>> Band 4 Block=10020x1 Type=Byte, ColorInterp=Alpha
>> 
>> I.e, it seems like the alpha from imagemagick is global but gdal expects a per dataset alpha ?
> 
> Heikki,
> 
> This would likely be better pursued on the gdal-dev mailing list, but it
> is not possible to evaluate without seeing the tiffinfo report for the
> file in question.  It may be an "associated" vs. "unassociated" alpha
> problem.
> 
> Best regards,
> -- 
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
> light and sound - activate the windows | http://home.gdal.org/warmerda
> and watch the world go round - Rush    | Geospatial Software Developer
> 
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