How to recolor 16 color image to other 16 color palette?

[MIRKOSOFT]

Problem with dithering is that I'm not program creator and don't have sources...
I know that low count color palettes are archaic, but look back ~30 years and you will see what were 16 colors...

Miro

[sculptex]

First step would be to create CGA pallette colours and add them to pallette.
Then xara should still have ability to export to 16 colour gif or whatever. Its not a bitmap editor though so its not suitable for editing bitmaps.

[handrawn]

I'm not clear on what you are doing - neither 256 x 192 nor 480 x 360 are standard CGA resolutions, but other resolutions were used

are you emulating CGA graphics on a modern computer?

I have no idea what a 'near' CGA palette is - details of the IBM CGA standard are outlined here: http://cs.mcgill.ca/~rwest/wikispeed...cs_Adapter.htm

if you are emulating then you can use a bitmap editor [eg photoshop in index color mode] to change the palette - but depending on the program you may not be able to save/export this below 256 colours, in which case as sculptex said, you can import, then export that way from xara [but you can't edit the bitmap palette in xara just reduce it down]

[theinonen]

What kind of images are the original images and did you draw those with palette limitations in mind, or converting existing images?

Reducing palette to 16 freely selected colours is easy but when working with fixed palette you really need dithering to have decent results, as without different shades of colour it must be done by dithering. When you have nice 16 colour image with optimum palette and then just swap the palette to CGA one, your image will be rainbow coloured mess if there is any shading.


Even with just CGA colour palette without any other limitations, I would actually decrease colour depth to 2bit, or even 1 bit and after that convert back to 4bit and swap the palette. For dithering when decreasing the colour depth can experiment with FS or ordered and then pick one that gives more suitable image, then use no dithering when converting image back to 4bit colour for the full CGA palette.

[MIRKOSOFT]

Ok, here's explain:
Source image is ZX Spectrum bitmap. ZXS has 15 color palette (black has only one level). Colors are very similar to CGA colors (I mean full 16 color palette). I need not to emulate CGA.
These sources I need to convert to Commodore 128 VDC color palette - again very similar colors like CGA. For best results I need to match exact color - it removes dithering.
You can now see that in 15 and 16 color palettes is dithering not required - I need convert one palette to second - I need not similar colors, I need exact match to avoid dithering.
I'm creating ZX Spectrum emulator for Commodore 128. So, when is anything emulated it needs to look like original - and dithering looks different to original.
If you will need I upload palettes.
Miro

[handrawn]

it sounds like you should be able to do that in a bitmap editor that handles index tables - if you want to post up the palettes and a source image I can run it through photoshop to test for you

[MIRKOSOFT]

Ok, I'm very thankful.

Source palette:

Target palette:

Example:

Original image:

Converted image:


Miro