Quote from: Piotr on October 06, 2015, 06:18:42 am

Quote from: Ai on October 05, 2015, 12:06:16 pm

Then concerns like "it's recommended that palette size is a power of two." are completely irrelevant.

If you would like to expand CPC palette out to 32 colors, why not? You seem to like that idea.

But there is no compelling performance reason to do so. Most existing quantization routines* support any size of palette, not just powers of two; and, because of this, using palette sizes that are powers of two does not improve the speed at all. This is because the code was not written using that optimization.

* for example, the ones in ImageMagick, GIMP, and GMIC.

I am going to keep all 24-bit color in arts, and not quantizing them. These concerns become relevant if you think of older machines like CGA or ZX Spectrum, not the newer ones like VGA or Windows.

.. Do you mean that you want to write quantization code that runs natively on retro platforms like Spectrum, using 24bit images as input? That seems strange and probably not what you meant, but I can't think of any other way to understand what you mean.

(BTW, CGA, VGA and Windows are not machines.  PC is a machine. CGA and VGA (and EGA) were video cards for PC. Windows is a family of operating system that runs on PCs)

... Do you even have a complete working system for this website, yet? Or, at least, profiling data for some working quantization code?

If you did, making it faster might be relevant.

Quote

I wish there was a web site where you can make and share palettes from 2 to 256/65536 colors (including a possibility to use png images containing all the colors in palette), uncompressed image formats (modes) to fit in some graphics memory size (for example 320x200 16 colors fits in 32KB), an adapter containing multiple of them and possibility to make images fitting these modes. Then the purpose of "best palette" is making images/game screenshots for this site. Then this thread could serve as place in which users could choose one of these suggestions.

Okay.  This is good, this is more definite.

In that case, it seems to me that you indeed are not really looking for a 'best' palette, but rather, want a collection of different 'good' ones. For example, Arne's 16color and 32color palettes seem like they would fit into your idea here, and so does the EGA 64color palette and even the CPC 27color palette. Correct me if I'm wrong about any of those.

A second point I wanted to raise is: I'm aware that support for palettes larger than 256colors is much rarer than palettes <=256colors. Have you looked into what software can perform the necessary adaptation?

I also wanted to ask if you have tried GrafX2's RGB restriction option?  It seems relevant to your broad goal of exploring these restricted palettes.