How to convert graphics to color per point - how to convert graphics to the "EGA" ATM Turbo mode.

How to convert graphics to color per point
 by Alone Coder

There was a question about how to convert graphics to "EGA" mode
ATM Turbo. 

If you just need a photo with dithering:

1. In Photoshop, adjust the brightness/contrast/color to make it more palatable.

2. Convert ~30 colors to an adaptive palette. But we don’t use
this palette. On the contrary, we try to fix it manually. 

3. Each color is manually matched to ATM colors (i.e. with
components 0/85/170/255 - according to measurementsLVDthere should be 
0/93/162/255, but I'm not sure what the authors of ATM Turbo wanted 
these values; however, the difference is insignificant). If there is 
options, where to round - we make a couple of color options (all 
equally there will be many matching ones in the palette). 

4. Let's see how many different colors we got (apply
convert to RGB, select the “exact” palette). If less than 16, then 
adding color options. If there are more, then we remove rare ones 
shades (if they can be conveyed using shading by others 
flowers). 

5. Apply the palette. Dithering can be adjusted from 30%up to 100%.

6. Convert again to RGB.

7. Convert to an “exact” palette - already exactly 16 colors.

8. Save as 4-bit BMP.

During the palette selection process, you can periodically save the palette,
apply, cancel the result...

Hippiman offers the following option:

──────────────────────────────── ───────────────────────────────┐ 
It is necessary to smoothly reduce the number of colors in the image to
minimal. It is best to do this in several steps.

First, you need to experimentally convert the image
to an adaptive palette without much loss of quality. Usually this
about 60-70 colors.

Next you need to “merge together” similar colors, if possible
fitting them to the ATM palette. We try to get rid of small
areas of rare occurrencecolors.

Then we convert to RGB and repeat the procedure several times until
there will be about 30 colors left.
───────────────────────── ─────────────────── ───────────────────┘ 

If you need to convert hand-drawn graphics (as in Nedodemo 2), then
fuss more. You need to manually go through several options
sequences of colors instead of each color transition
original palette. Sometimes you have to sacrifice
one or another color (merge it with the neighboring one). If you need 50%
shading, then first we convert the image to ~30 colors with
components 0/42/85/128/170/212/255, then we look for the ATM
a palette with which you can shade the desired colors, and
then we manually convert each color field into shading (all
together it is impossible - clear 50% shading does not work). I didn't find
faster way than copying the selected color
fields to another document (initially white), setting
3-color palette (white plus two colors, between which
fits exactly as specified) and conversion with diamond shading. Then
copy back what happened to the original document.

Converting to paletteDDp (RХGЧB4) is easier - just convert to
adaptive palette and save. When cuttingleast significant bits
There won't be much difference in color. In which case it is possible in the process
conversion to adaptive palette manually round components
colors, then apply the palette.

SoftwareDiHalt Visitors for batch conversion of BMP to
packed memory dumps are posted here:
http://alonecoder.nedopc.com/zx/convega.rar

By the way, there is a special program fromTmK that converts
in two flickering screens, color per point. But she doesn't know how to pick
palette

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