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EGA (enhanced graphics adapter)

dr.zeissler said:
If I have to correct the aspect ratio in order to get sqares then I will have to do
some converting that will easily cost a lot of quality of the converted image.
Click to expand...

There is no good way to fix this because EGA high-res pixel art was composed for its native aspect ratio. Most conversions will ruin the image. It is usually best to just display 640x350 pictures as-is.

If you want to try fixing the aspect ratio anyway, use nearest neighbor (point) resizing to (640*3)x(350*4) or 1920x1400 which will convert to square pixels while retaining the crisp nature of pixel art. You can then resize smaller if you like using a smoother algorithm like lanczos or bicubic. But this is only for displaying on the web.
 
The aspect ratio is a bit of a problem while watching the cut-out-images on the real machine :(
With some images it is quite obvious that there is something wrong with the proportions. If I resize the source-material I need to go for true color and that makes them look good, but this produces "antialiasing" which causes a lot of problems when reducing to 6Bit color! the image is not crisp anymore, there are details lost and that is not my intention.

the question is, are there better ways to get a real good EGA Image out of low-color VGA 640x400/640x480 source-material.

Doc
 
there are some real 640x200 images in the source material, so there are three different aspects.

Source 640x400
Source 640x480
Source 640x200

Yesterday I tested some ways to correct the aspect for the EGA Monitor. I changed the Monitor itself a bit.

I think I will only change a view of the pics, because mostly you don't recognize the false aspect.
It is harder to deal with the quality issues, then with the false aspect ratio.

Doc
 
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Why don't you post one of the pics you're working with so we can see what this is all about. Just u/l one original. Don't post it on the forum directly as the board's software will manipulate it before we get a look at it. Post it on a host site with a link.
 
Goals

1. Display them with the correct aspect on the real machine (EGA Monitor 640x350). If that's not possible without seeing quality issues then the cut out version will be the one to display on the real machine.
2. Make an EGA-Hires Slideshow (perhaps with music and scrolling text)
3. Questions about this:
- Is a starfield in EGA-Hires possible
- Is a stutterfree scroller in EGA-Hires possible
- Can the gfx-file scrolled in (stutterfree)
- Does the FPU do any job for it, or is it not accessible/useable?

I am currently searching the web for pascal-source file, because I ha euro-pascal here on my 286.

Doc
 
Based on the images uploaded, you will not be able to adjust them to maintain aspect ratio and look similar to the original. For example, ALTAIR6.GIF will probably wind up looking like a checkerboard as all the star pixels combine into lines. So many pixel width elements are just guaranteed to defeat virtually any automatic conversion program.

2) Making a EGA HiRes slideshow is doable but you should strive for EGA original images or post a note saying that the images are inspired by Warhol transforming the errors in conversion into an artistic statement.

3) Starfield: Have seen that before
Stutterfree: very difficult but I have seen it before
FPU: Probably won't provide any help in converting or displaying graphics
 
no dithering, therefore good good quality. vga16 colors mostly not ega16 colors.
try cd2 from the 400. i do not get the text uncorrupted if i correct the aspect ratio to get the cd round again on an ega monitor.
 
Maybe post a set of images: original and what you get when you convert. It may just be what you want is nearly impossible and the conversions you get are close to the best that can be made automatically. Hand revising would be necessary to fix the flaws of the conversion.
 
dr.zeissler said:
1. Display them with the correct aspect on the real machine (EGA Monitor 640x350). If that's not possible without seeing quality issues then the cut out version will be the one to display on the real machine.
2. Make an EGA-Hires Slideshow (perhaps with music and scrolling text)
3. Questions about this:
- Is a starfield in EGA-Hires possible
- Is a stutterfree scroller in EGA-Hires possible
- Can the gfx-file scrolled in (stutterfree)
- Does the FPU do any job for it, or is it not accessible/useable?
Click to expand...

1. You know this is already impossible, so just display them 1:1 and either crop, center, or scroll them. 640x200x16 works on EGA. Search compuserve GIF archives from the 1980s, there were hundreds of nice 640x350 pictures floating around BBSes at that time.

3. Yes, Yes, Yes, FPU is not used. But I'm not going to code it for you. The slideshow programs I linked to previously may do this correctly.
 
Don't laugh...I got the "Turbo Pascal 7.0" Compendium here and searched for demofiles(.pas) for "starfield" and "scroller"
Though the programmers-guide book looks very interesting, but I think that I will not understand it... but I'll checkout if I get it somewhere.

btw. I never saw any demos/intros/scroller/starfields in Hires-EGA. perhaps there are currently none, but the idea is great :)
 
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May not be demos but a variety of Windows 3.0 screen savers and hDC's tiny game Rocks provided smooth scrolling and starfields with HiRes EGA (10 MHz 286). If it can be done with Windows overhead, doing it with DOS should be possible.
 
krebizfan said:
May not be demos but a variety of Windows 3.0 screen savers and hDC's tiny game Rocks provided smooth scrolling and starfields with HiRes EGA (10 MHz 286). If it can be done with Windows overhead, doing it with DOS should be possible.
Click to expand...

I suppose they just bypassed Windows completely then. The Windows graphics API has no support for smooth scrolling. In fact, I don't think even DirectDraw had support for scrolling. You'd just do it 'bruteforce' by blitting your whole screenbuffer.
So I suppose they just set up a fullscreen EGA environment and banged the hardware directly, just like in DOS. Because a 286 with EGA wouldn't be fast enough for anything bruteforce.
 
To get into the material, I first read this one: http://www.minuszerodegrees.net/oa/OA - IBM Enhanced Graphics Adapter.pdf
Then I have an Assembler-Book for "8086/8088/80186/80286" an the TurboPascal7-Book and I have someone who studies "IT".
But this guy told me weeks ago, that they do "java" etc. but that is not what I call "assembler-programming" but as you know, I have no clue.
 
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Michael Abrash had a series of articles regarding fast graphics on EGA printed in Programmer's Journal in 1987 and 1988 though the later parts started switching over to a focus on VGA. Good enough that a couple of game developers used the techniques presented there. Several erstwhile online libraries have copies of it which should be easy to find with a search.
 
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