[Qgis-user] map collars

[John C. Tull]

Although, this approach can be problematic if white is important for  
properly displaying the map information. E.g., USGS topographic maps  
use a white background for the map and a white collar. My solution was  
to hand select the collar in Gimp, make it a unique color (magenta or  
something), then apply the transparency to that color. This is not fun  
if you have many maps to work with.

John

On Mar 18, 2009, at 4:17 AM, Paolo Cavallini wrote:

> Chris h ha scritto:
>
>> No apology necessary. Map collars are the white borders around maps  
>> that are
>> typically distributed from governmental sources in raster format.  
>> In order to
>> stitch or glue charts together you need to remove the collars.  
>> (white area)
>
> Oh, that can be easy: for displaying purposes, just set the white  
> value
> to null, in the raster properties dialogue. If you want to permanently
> set the white to NULL, you can use gdal for this.
> All the best.
> -- 
> Paolo Cavallini: http://www.faunalia.it/pc
> _______________________________________________
> Qgis-user mailing list
> Qgis-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-user