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  1. #1
    Join Date
    Jun 2017
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    Default How to recolor 16 color image to other 16 color palette?

    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

  2. #2
    Join Date
    Aug 2000
    Location
    Placitas, New Mexico, USA
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    37,374

    Default Re: How to recolor 16 color image to other 16 color palette?

    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.
    Gary W. Priester
    Mr. Moderator Emeritus Dude
    , Sir

    gwpriester.com | Custom-Stereograms.com | eyeTricks on Facebook






  3. #3
    Join Date
    Jun 2017
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    19

    Default Re: How to recolor 16 color image to other 16 color palette?

    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

  4. #4

    Default Re: How to recolor 16 color image to other 16 color palette?

    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.

  5. #5
    Join Date
    Feb 2007
    Location
    UK
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    16,854

    Default Re: How to recolor 16 color image to other 16 color palette?

    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]
    -------------------------------
    The trouble with political jokes is... they get elected

  6. #6

    Default Re: How to recolor 16 color image to other 16 color palette?

    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.


    Click image for larger version. 

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    Last edited by theinonen; 05 June 2017 at 12:37 PM.

  7. #7
    Join Date
    Jun 2017
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    19

    Default Re: How to recolor 16 color image to other 16 color palette?

    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

  8. #8
    Join Date
    Feb 2007
    Location
    UK
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    16,854

    Default Re: How to recolor 16 color image to other 16 color palette?

    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
    -------------------------------
    The trouble with political jokes is... they get elected

  9. #9
    Join Date
    Jun 2017
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    19

    Default Re: How to recolor 16 color image to other 16 color palette?

    Ok, I'm very thankful.

    Source palette:
    Click image for larger version. 

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    Target palette:
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    Example:
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    Original image:
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    Converted image:
    Click image for larger version. 

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    Miro

  10. #10
    Join Date
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    Location
    UK
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    16,854

    Default Re: How to recolor 16 color image to other 16 color palette?

    you want the original image recolored with the target palette?
    -------------------------------
    The trouble with political jokes is... they get elected

 

 

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