[Gdal-dev] hatches rendering issues
maplabs at light42.com
Tue Nov 6 11:46:25 EST 2007
On Nov 6, 2007, at 8:11 AM, Frank Warmerdam wrote:
> Eric Lemoine wrote:
>>> It would be helpful to see the results, but generally it is hard to
>>> downsample repeating patterns without odd aliasing effects. The best
>>> is to be very certain that exact factor of 2 downsamplings are done
>>> which case the algorithms should sample the data in a consistent way.
>> Thanks for your response Franck. Would you mind elaborate a bit more
>> on your last sentence?
>> Three screenshots at 1/20000, 1/10000, and 1/5000.
> I've looked at the three images. The 1/5000 is the original, right?
> Is this
> really the *original*? It seems the hatching spacing is not exactly
> and darkness of the hatch is not uniform. So if this is what you are
> from you are basically doomed to relatively poor and inconsistent
> The hatching does not follow on nice power of 2 boundaries, so nearest
> neighbour downsampling will certainly produce inconsistent results
> hatches will be completely missed for instance). Are the 1/10000 and
> 1/20000 samples you provide produced with averaging? With MapServer or
> Basically raster hatching effects put through sampling processes suck,
> and at most you can hope for not-too-bad in my opinion.
people use Gaussian blur and others at that point, y?
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