[mapserver-users] Removing collars on raster images

[Rahkonen Jukka]

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
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