On Thu, Oct 20, 2011 at 3:08 PM, Andrea Aime
<[email protected]>wrote:
> On Thu, Oct 20, 2011 at 7:18 PM, Gabriel Roldan <[email protected]>
> wrote:
> > Hello raster experts,
> > out of an issue raised in gwc land, I wonder whether we can support semi
> > transparent 8 bit png images (I assume we just don't so far?).
> > A little investigation (as I was trying to reject the proposal of using
> the
> > pngquant external program to achieve this) suggests that what we need is
> to
> > use the NeuQuant quantization algorithm[1], and surprisingly it looks
> like
> > JAI actually supports it:
> > <
> http://download.oracle.com/docs/cd/E17802_01/products/products/java-media/jai/forDevelopers/jai-apidocs/javax/media/jai/operator/ColorQuantizerDescriptor.html
> >
> > So question is has this even been considered, is known to (not)work? and
> if
> > yes, do you think we could add support for it in GeoServer?
>
> It's sometihng that has been in my wish list for a while. The neuquant
> algorithm in
> JAI does not support translucency and it's, afaik, quite slow, so it's
> really useless.
> See here:
>
> http://download.oracle.com/docs/cd/E17802_01/products/products/java-media/jai/forDevelopers/jai-apidocs/javax/media/jai/operator/ColorQuantizerDescriptor.html
> "This operation generates an optimal lookup table (LUT) based on the
> provided 3-band RGB source image by executing a color quantization
> algorithm."
> The op won't work on RGBA images as far as I know.
>
> We can extend the current mediant cut, and I've put eyes on another
> fast C implementation
> that does support translucency that would need to be ported over to
> Java/JAI. but so far
> I haven't had time to work on it. It would require a few days of work
> to do the port and
> test it over the various input types, the pre-cooked palettes and so on.
>
disappointing on the JAI side. Still, the following page[1] points to a java
implementation that claims to support semi transparent: <
http://members.ozemail.com.au/~dekker/NeuQuant.java>
may that be a good starting point?
[1]http://members.ozemail.com.au/~dekker/NEUQUANT.HTML
> Cheers
> Andrea
>
>
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