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Thread: EGA (enhanced graphics adapter)

  1. #1

    Question EGA (enhanced graphics adapter)

    Hi,

    how do I convert graphics from any kind of colour-deph and format to ega-gif with the ega-palette in the best possible quality ? (perhaps with dithering filter?)
    For generating the Pics I have a PII-333/512/Dos/Win98se/Win2k
    For watching I use a 286/10/EGA and cshow.

    Thx
    Doc

  2. #2

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    Paint Shop Pro 6 can do this (psp602.exe is the shareware version). Choose Windows palette when reducing to 16 colors. Error diffusion dither will probably look the best on photos.

  3. #3

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    Irfanview will do this and almost anything else you want to do. It's very easy to use, small and if you've never used it you really should try it out. Plus it's free for non-commercial use.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  4. #4
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    I think 'best possible quality' is a bit of a problem:
    If you go for 640x350 mode, you can choose any 16 colours from the total palette of 64 colours (2:2:2 bit RGB).
    So you'll need to convert the image in 2 steps:
    1) Find the most suitable 16 colours from the total of 64.
    2) Find the best mapping of the image to these 16 colours (using dithering).

    I guess step 1 would be more of a colour reduction approach, after which you would sort the colours on frequency. Perhaps using median cut or something.
    An interesting problem is whether you would 'merge' two colours that are close together, yet both reasonably frequent.

  5. #5

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    exact! First is the Resolution Problem. Finding 640x350 ART (not Photos) indicates that they are mostly EGA itself.
    That means the most targets are 640x400 or 640x480. Reducing the size means convertig the 16 Color VGA Art or 256 Color VGA-Art to true Color and converting to 640x350. This indicates that the image itself is changed (streched).

    After that the palette must be reduced to the EGA 6Bit palette. And the Colors must be reduced to 16 at the same time. That is the most interesting part, because the are many ways to do that. You described some. What about letting a special filter caclculating patterns in order to simulate more colors. That is a procedure that most Sierra/Lucas Adventures did for their Backgrounds.

    There are only a few real EGA Images in the Inernet available. Mostly they were done/created with EGA. Converting potential Images that have itself not so much colors could be very exciting. Possible target (Amiga/Atari Images with 16/32 Colors, ore some early VGA-Art with 16 or 256 colors.

    Doc

  6. #6

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    ...one more thing

    how do I change the palette to real EGA? all programs that were mentioned do not have the option EGA-Palette.
    Reducing to 16 colors with Irfanview means 16 Colors out of the VGA-Palette with 262.000 Colors.

    Palette/Colors
    8Bit/256 out of 262.000
    6Bit/16 out of 64

    So how do I do this?

    Thx
    Doc

    PS: In a german forum someone told me to due this with a "posterize-effect", but this does not help either because
    I don't know what program and how-to.

  7. #7
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    No matter what tool is used, unless you are willing to do a lot of work, some images will come out of the process looking very strange.

    Posterization is available in Photoshop. I suspect that Irfanview with all of its plugins should do the same. Good chance that it will happen automatically with some other converters. Posterization is just a term for the planned reduction of the number of colors with ranges of colors being replaced with the closest member of smaller result set. Smart dithering would look better on average but sometimes will result in hilariously awful results.

    You don't have to reduce the pixel count. Convert to fewer colors but leave the image size the same. You will only see the top 3/4 of the image and have to scroll to see the bottom. In some cases, that will suffice.

    Have you tried CShow to see if it will display images designed for higher resolution displays? I remember PC Paintbrush would do the adjustments automatically transforming the VGA images I downloaded into EGA equivalents. I know there were other tools that did the same but my EGA system got retired more than a decade ago and I don't have the tools I used to use anymore.

  8. #8
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    You have to take into account that 640x350 may be the same size on screen as 640x480 is on VGA.
    The spacing of the scanlines is just different. So you have to resize in order to get the same aspect ratio on screen, else it will look stretched on EGA.

  9. #9

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    cshow shows not all lines if a 640x400/16 image is displayed on EGA as 640x350/16.
    https://www.flickr.com/photos/948392...7649803051477/

  10. #10

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    the last days I experimented with vga2ega.exe (version 3.0), this old tool has some tuning-options in it,
    but the results did not convice me. if I choose "ordered palette" in Photoshop with 16 colors I get nearly
    the same results.

    Perhaps the easiest way is to choose a "master-pic" and some people try to make a real EGA-GIF 640x350
    out of it and we compare the results?

    "vga2ega" only works directly on diskette, otherwise I get a "out of memory error".

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