[Freeciv-Dev] Re: [FreeCiv-Cvs] jdorje: Replace XPM files in misc/ and trident/ with...

[Vasco Alexandre Da Silva Costa <vasc@xxxxxxxxxxxxxx>]

On Wed, 6 Nov 2002, Jason Dorje Short wrote:

> Vasco Alexandre Da Silva Costa wrote:
> > On Wed, 6 Nov 2002, Jason Dorje Short wrote:
>
> >>We still need to convert the isotrident files to PNGs.  Since these will
> >>never (in the forseeable future) be used with the XAW client, we don't
> >>need to make them paletted PNGs.  So I could just run 'convert' over
> >>them.  Or is there a better conversion mechanism?
> >
> >
> > It is still a good idea to make them paletted PNGs because:
> > a) the tiles use less than 256 colours.
> > b) paletted PNGs are much smaller.
> >
> > You may either use the GIMP or a tool like pngquant on a regular 24-bit
> > PNG to achieve this.
>
> Are there any disadvantages to useing a paletted PNG?  Are they slower
> to load, for instance?

They should not be slower to load. The only disadvantage is you have less
colours available at once :)

> pngquant does not always give good results.  For instance, "pngquant 256
> nuke.png" gives me a nuke with a black (not transparent) background.  I
> don't know why.
>
> What is the process to do the conversion with the GIMP?  I can have it
> "generate an optimal palette" with 256 colors.  Should there still be no
> dithering?  What does dithering mean, in this context?

Yes. I suggest no dithering. Dithering is only helpful in case the picture
has more than 256 colours. But it will add noise to the images.
If isotrident uses more than 256 colors it is better not to distort the
images by reducing the colour space. In that case I guess 24-bits is a
better choice.

You can see the diferences between several types of dithering here:
http://www.cs.princeton.edu/courses/archive/fall99/cs426/lectures/dither/sld022.htm

---
Vasco Alexandre da Silva Costa @ Instituto Superior Tecnico, Lisboa