[GRASSLIST:4069] Re: vectorizing rasters

[Sandro Klippel]

I do it with r.poly but after to remove small areas with r.reclass.area. 
Although some manual edition was always required.

Em Seg 02 Ago 2004 13:33, você escreveu:
> I have a some scanned maps (black and white, essentially line art) that
> I have imported into a grass53 xy location. I am looking for more
> efficient ways to convert them to vector files than heads up digitizing
> with v.digit.
>
> I have tried r.thin and v.line. However, the resultant map has got lots
> of little dangles that hang off "real" lines. I was going to try using
> v.trim to remove them (my guess is that they are around 2 -3 pixels in
> length), but I'm getting "v.trim command not found", was v.trim removed
> from 53?
>
> That being said, an even bigger problem is all the little 2 to 5 pixel
> line segments the within the enclosed polygons. These are a result of
> trying to vectorize a raster that had bunches of little dots all over
> the place that had nothing to do with the actual line art of the map,
> but were created by the scanner as a representation of paper color.
>
> The main question here is this. Am I wasting my time trying to skip
> over the v.digit step? or would anyone recommend some kind of filtering
> approach first (photoshop or the like) before the maps are even read
> into grass?
>
> Thanks
>
>
> Kirk

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