Hi David ;),

> This is a normal phenomenon when moving to higher bitdepths.
> Unless you're talking about 16 bits in total, and not 16 bits per
> channel, in which case I'd be a bit mystified...

Yes, i meant 16 bits per channel ;)

> Floyd-Steinberg dithering is basically a way to approximate more 
> colors with a smaller palette... it does not actually do anything
> like what you are expecting (as you have noticed).

Yup, i already noticed that. Maybe i'm wrong, so please correct me, but
the Floyd-Steinberg is implemented by the gimp, and the dithering in
gdk_pixbuf (the paramater XlibRgbDither to functions like gdk_pixbuf_draw)
are different things, isn't it?

> Have you tried blurring the image with a radius of 0.5 or 1.5
> pixels? This sometimes works quite well.

I've tried it without success. The bands are too visible to be removed
with a blur filter...

> > Programs like gqview, an image viewer, use the dither
> > algorithms bundled with gdx_pixbuf in gtk2, and they work perfectly with
> > the same images. Why cannot the gimp do the same quality dithering if
> > it's using the same library?
> Oh, I see what you mean, I think - you're talking about the
> rendering of the data, you don't actually want to change the
> underlying data, you want it to look better. Is that right?

Yes, i want it to look better, and have the option to save the dithered
image ;). Gqview does a dithering pass on the image, and the image looks
great. I looked in the sources and saw that it doesn't implements any
dithering algorithm, it just uses the underlying gdk_pixbuf dithering

> If that's the case, then I'm afraid the answer is that I don't
> know. I thought we used a GdkPixbuf, so if we don't I'm stumped
> :)

I know that the Gimp is using GdkPixbuf, that's why i'm asking
why it doesn't do a better dithering ;)


David Gómez

"The question of whether computers can think is just like the question of
 whether submarines can swim." -- Edsger W. Dijkstra
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