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PMView Pro Forums _ PMView - General Discussion _ Color/Shade Reducing - missing feature?

Posted by: Andreas Kieser Aug 10 2003, 09:37 AM

It makes a big difference in size in indexed color formats how many colors a picture has. One can see this when switching from 8 to 4 bit (or 2). PMView sometimes reduces the number of colors according to internal tables (it says 6-bit for example).

But: I didn't ever get the hang of willingly reducing the number of colors - say: from 254 or such to say 137 which may preserve an acceptable quality but reduces the needed size to a minimum.

It is doable: one might edit the colors within the palette editor to equal values - PMView will correct the numbers after loading the palette again.

I think that this process could be "automized" and the "quantizing" of colors could be done by algorithms that might well be implemented in the code.

I know that christmas hasn't come yet but .... ;-)))

Regards,

Andreas

Posted by: Peter Aug 11 2003, 04:37 AM

This feature already exists:

Select "Color->Convert to->256 colors" from the menu bar.
Use the "Number of colors" spinbutton to select the number of colors you want (from 2-256).

Thanks,

Posted by: andreask Aug 11 2003, 03:07 PM

Thanks, you're right - I've missed it.

I've made a quick test - a (big) grayscale image with 245 shades. When I try to set up 129 shades the result is 64 shades. (In fact not a bad result, the picture quality is acceptable).

Is this a foreseeable effect? How does it work?

A little lengthy explanation why I did ask: I was forced to Win lately (notebook..) and with this kind of problems I'm still used to Embellish. There's a nice implementation of (visible) color reducing in Embellish: when saving (as) two representations of the picture are shown within a seperate frame and one can fiddle around with save options and see the difference visually and the data related to it (say estimated size etc.).

One can't have it all ...

Regards,

Andreas

Posted by: Peter Aug 14 2003, 07:43 AM

This is because the color reduction algorithm uses only 6 bits per color (instead of 8).

Usually this is good enough. I have planned to add a full 8-bit reduction, but because noone has requested it (yet), it is not high priority...

Thanks,