[gdal-dev] GSoC GDAL2Tiles: Opacity for Google Maps Overlay, Embedded Google Earth, Tile generation

Vincent Schut schut at sarvision.nl
Tue Aug 12 03:42:55 EDT 2008

Hi Ivan, Klokan,

Lucena, Ivan wrote:
> Hi Klokan,
> Would you mind if I extend your message tread a little bit?
> The GDAL2Tiles is a great tool and it just getting better, congratulation.
> But I have some end-user complain that they don't like to see the pixel blended when you get very close to then. Those folks really want to see the big square blocks of their images classification on top of Google Earth images. That is not your fault of course. That is a nice feature on GE, a anti-aliasing rendering technique that probably attend the general public. I have spoken with Google about that but it didn't resonate. 
> As far as I can remember (from OpenGL project that I worked in the past) this problem could be easily solved with just a parameter change on the texture-surface-rendering definition. I may be wrong.
> My question is, do you know if there is any way to change that behavior on GE? 
> Doesn't look like you can change that option through the API as a plugin, does it? Or maybe there is something you can do on the KML.
> By the way, does any one have ever received that request from users?
> Best regards,
> Ivan
<big snip>

It does resonate here :)
I have been publishing deforestation maps with GE (using a home-brewn
gdal-python script), and had the same complaints. I don't want my
classes to mix. An area is either forest, or non-forest, or deforested,
and nothing in between. O how nice it is to force your own will upon
reality :-)
The way I 'solved' this was by adding subsampled tiles, which
effectively prevent GE to start antialiasing to soon. So my highest
resolution tiles are in fact higher resolution than the real full
resolution. This of course is just a workaround and just works if the
user does not zoom in too much, but in my experience it improved the
users' feeling a lot.

I must say I am very interested in a better way to force GE to not
antialias raster overlays.

Vincent Schut.

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