[mapserver-users] [mapserver-dev] Maps for 16 bit displays

[thomas bonfort]

Ian,
I don't believe it is currently possible to render 16bit images.
However, I'm pretty certain PNG does not support 565 encoding, and
couldn't find any reference as to whether jpeg can either. Unless you
are accessing the image bytes directly from the mapserver library
(which I suspect you are not, it is not a public api/structure), I
would investigate in reducing from 32 to 16 bits directly on the
device at image loading time.

If you absolutely need 565 encoded output, I suspect the code can be
worked on on the vector side with AGG to produce that, but it will not
be a trivial task. Concerning raster rendering, this would also be a
non trivial task.

regards,
thomas

On Fri, Jun 1, 2012 at 11:27 PM, Ian Walberg <ian.walberg at airborne.aero> wrote:
> Hello folks,
>
> We need to render maps for a system which has a 16 bit colour (yes I am
> English) depth.
>
> Currently we render the images at 24 bit (888) and they look fabulous.
>
> However when they are rendered on the target hardware they are crudely
> reduced to (565) and this causes some horrible artefacts and banding.
> Our best guess is that the lower bits are just being discarded.
>
> So now we understand the problem the question is what we can do to
> generate the map images with a reduce RGB range so that they are
> displayed correctly.
>
> Having a look at the various options we cannot see anything between 256
> colour and 24 bit colour which would help.
>
> Anyone have any good ideas?
>
> Thanks
>
> Ian
>
>
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