[mapserver-users] Removing collars on raster images

[Espen Isaksen]

Ok, thanks for taking you time answering these questions. I am testing
this out now as I am writing this e-mail :-)

Espen

2009/8/14 Rahkonen Jukka <Jukka.Rahkonen at mmmtike.fi>:
> Hi,
>
> I have not played with either lately. At least one difference is that gdal_merge.py can't warp images. Gdalwarp has also lots of more options.  Long time ago I used modified gdal_merge.py first for creating a virtual raster file (.VRT) which I used later as input file for gdalwarp. Now there seems to be a separate tool for this purpose, gdalbuildvrt. Is even seems to acceps Mapserver tileindex files as input. I guess that if you'll select to make rectangular images with no nodata areas then the work chain would include (gdaltindex) - gdalbuildvrt - gdalwarp.
>
> -Jukka Rahkonen-
>
> Espen Isaksen wrote
>
>
>> Yes, that is a solution that will probably work. Do you know
>> the difference between gdal_merge.py and gdalwarp?
>>
>> Espen
>>
>>
>>
>> 2009/8/14 Rahkonen Jukka <Jukka.Rahkonen at mmmtike.fi>:
>> > Hi,
>> >
>> > Not a very clever solution is to get rid of the collards
>> forever. However, it works for sure. Select a rectangular
>> grid in preferred output projection and mosaic and compress
>> the original images to suit that grid with gdalwarp by using
>> -te option. Then there will be no black borders to make
>> transparent any longer. It does not mean much extra work if
>> you have to compress the images in any case, but it does make
>> updating image layer a bit more complicated if you will
>> receice new images from scattered places every now and then.
>> >
>> > -Jukka Rahkonen-
>> >
>> >
>> >> -----Alkuperäinen viesti-----
>> >> Lähettäjä: mapserver-users-bounces at lists.osgeo.org
>> >> [mailto:mapserver-users-bounces at lists.osgeo.org] Puolesta Espen
>> >> Isaksen
>> >> Lähetetty: 14. elokuuta 2009 12:00
>> >> Vastaanottaja: mapserver-users at lists.osgeo.org
>> >> Aihe: [mapserver-users] Removing collars on raster images
>> >>
>> >> Hi!
>> >>
>> >> This question has been asked in different ways before, but the
>> >> threads do not seem to give me the answers I need.
>> >>
>> >> We have lots of TB of images with black collars(borders). We would
>> >> like to try out using Mapserver for serving these images,
>> but we need
>> >> to have the black collars transparent.
>> >> That is fine in Mapserver as long at you use regular Tiff.
>> >> However, because of the many TB of data we need to
>> compress this data
>> >> and preferably tiff with jpeg compression.
>> >>
>> >> However, this compression creates edges between the collar and the
>> >> image where the image does not get transparent.
>> >>
>> >> I am struggling to find a solution to this problem. Is
>> ideas on how
>> >> we can avoid this problem? Is it for example possible to set a
>> >> transparency mask in the Tiff image which can be used by Mapserver?
>> >> Another solution would be if Mapserver could support
>> setting an area
>> >> in an image transparent based on a polygon file.
>> >>
>> >> Any help is appreciated.
>> >>
>> >> Espen
>> >> _______________________________________________
>> >> mapserver-users mailing list
>> >> mapserver-users at lists.osgeo.org
>> >> http://lists.osgeo.org/mailman/listinfo/mapserver-users
>> >>
>> >
>>
>