[Gdal-dev] hatches rendering issues

[Eric Lemoine]

On 11/5/07, Frank Warmerdam <warmerdam at pobox.com> wrote:
> Eric Lemoine wrote:
> > Hello
> >
> > (Resending this since it didn't make it due to too big attachments)
>
> Eric,
>
> The list is configure with a fairly restrictive limit on email size.
> I'd suggest pointing to images on a web server you own or demonstrating
> the issue with very small swatches.
>
> > The result isn't satisfying as the horizontal hatches aren't equally
> > spaced as they should be for the scales 1/20000 and 1/10000. It is a
> > lot better for 1/5000, although some lines seem bolder than others.
> >
> > (In my previous email, I attached some png images to illustrate the
> > problem, but my email didn't make it to the list because of these
> > attachments).
> >
> > I've used several other combinations. For example, I tried to use "nearest"
> > both with Gdal and MapServer. The results are very very bad.
> >
> > Do you have suggestions?
>
> 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 in
> 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?

<http://dev.camptocamp.com/grandlyon_plu/problem_images/>

Three screenshots at 1/20000, 1/10000, and 1/5000.

Cheers,

--
Eric