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

[MIRKOSOFT]

Hi!

I'm newbie here and in graphics too.
I'm working with graphics for retro computers.

I have images in 16 color 'near' CGA palette.
I need to recolor it to similar 16 color also 'near' CGA palette.
Reason is simple - rendering tool for transfering images requires exact color to produce single color filled parts - if color doesn't match it uses Floyd Steinberg dithering to create as near as possible color.
But when images with resolution 256x192 are converted to 480x360 is not enough space for dithering and it's high quality loss. Of course there are also typical retro computer color cells - in one color cell 8x1 pixel - so in 8 pixels horizontally - can be 2 colors only. It's for 4-bit colors - one color for low nibble and one color for high nibble = 8 bits = 8 pixels wide.
So, best result I can have by recoloring image from one to 2nd color palette. Both palettes are high similar, so I mean (here's I'm not sure) that there can be created tolerance limit when recoloring...

Qs is nothing more nothing less than: How to recolor images from one to 2nd color palette? I need help 'cause I'm beginner.
I found this forum 'cause on two other forums I got answer: So, why you want to do it?...
So, I hope that anybody helps me.
Thank you all for all.
Miro

[gwpriester]

Welcome to TalkGraphics

I am not sure how this wold be done. We have come so far and 16 color. 32, 64, and 256 color palettes are archaic.

You should be able to disable dithering in a bitmap editing program.

[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.

[Mark321]

Hi!

I'm newbie here and in graphics too.
I'm working with graphics for retro computers.

I have images in 16 color 'near' CGA palette.
I need to recolor it to similar 16 color also 'near' CGA palette.
Reason is simple - rendering tool for transfering images requires exact color to produce single color filled parts - if color doesn't match it uses Floyd Steinberg dithering to create as near as possible color.
But when images with resolution 256x192 are converted to 480x360 is not enough space for dithering and it's high quality loss. Of course there are also typical retro computer color cells - in one color cell 8x1 pixel - so in 8 pixels horizontally - can be 2 colors only. It's for 4-bit colors - one color for low nibble and one color for high nibble = 8 bits = 8 pixels wide.
So, best result I can have by recoloring image from one to 2nd color palette. Both palettes are high similar, so I mean (here's I'm not sure) that there can be created tolerance limit when recoloring...

Qs is nothing more nothing less than: How to recolor images from one to 2nd color palette? I need help 'cause I'm beginner.
I found this forum 'cause on two other forums I got answer: So, why you want to do it?...
So, I hope that anybody helps me.
Thank you all for all.
Miro

Miro,

You are in way over my head but I think I can offer some ideas here. First of all, if you have access to AI, they have a 16 color bitmap tracer that may make the whole process a little easier.
If you will trace it and then "expand" the image, you should be able to "re-color" the artwork without too much trouble. I'm sure you could "re-assign" colors in the palette but I don't know HOW this is done.

Hope this helps...

Mark

[handrawn]

if you have a means to edit the bitmap palette then tracing it is an extra step you don't need; you'd still need to change the colors anyway, and then convert back to bitmap...