From Newsgroup: comp.sys.tandy

Atreyu

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From Newsgroup: comp.sys.tandy

Just wandered in here myself, actually - had a hankering to putter
around with 8086 assembly recently and have set myself to the task of developing a reasonably performant blitter for TGA 320x200x16 mode.
Still in progress at the moment, but I may as well share it here once
I've got something worth demonstrating :)

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From Newsgroup: comp.sys.tandy

On 16 Jul 25 13:39:22, John Ames said the following to All:

Just wandered in here myself, actually - had a hankering to putter
around with 8086 assembly recently and have set myself to the task
of
developing a reasonably performant blitter for TGA 320x200x16 mode.
Still in progress at the moment, but I may as well share it here
once
I've got something worth demonstrating :)

What about the rare 640x200x16 mode? I think only Deskmate uses that
one?

Atreyu

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From Newsgroup: comp.sys.tandy

On Thu, 17 Jul 2025 09:05:59
NOSPAM.sysop@darkrealms.ca (Atreyu) wrote:

What about the rare 640x200x16 mode? I think only Deskmate uses that
one?

There were a few games that used it, some of them basically doubling up
the pixels as an ordered-dither approximation of VGA/MCGA 320x200x256
mode (there are, IIRC, 136 unique combinations of 16-color pixel pairs,
not accounting for order, so it's reasonable enough if you squint just
right.)

I do have an RL and can try it, but I'm targeting the more common mode
first. Shouldn't be difficult to modify once I have it functional. (You
could actually do a simpler, more performant version if you *did* treat
it as functionally 320x200, since your "pixels" would be whole bytes,
but I'm not gonna bother with that.)

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From Newsgroup: comp.sys.tandy

On Thu, 17 Jul 2025 08:19:32 -0700
John Ames <commodorejohn@gmail.com> wrote:

(there are, IIRC, 136 unique combinations of 16-color pixel pairs,

(Though, thinking about it, there are probably fewer than 136 "average"
colors that these'd work out to. Should look into this sometime.)

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From Newsgroup: comp.sys.tandy

On Thu, 17 Jul 2025 09:09:37 -0700
John Ames <commodorejohn@gmail.com> wrote:

(there are, IIRC, 136 unique combinations of 16-color pixel pairs,

(Though, thinking about it, there are probably fewer than 136
"average" colors that these'd work out to. Should look into this
sometime.)

Well, I got curious and looked into this a bit. Using the semi-canonical
RGBI reference colors:

(element value) = (color bit * 170) + (intensity bit * 85)

with the special case for color 6 (dark yellow/brown) where green
intensity is halved, and the color-averaging function:

(average) = sqrt(((a * a) + (b * b)) / 2)

I identified 122 unique "composite" colors. For cases where multiple
color pairs yield the same "composite" RGB value, the lowest-contrast
pairing has been preferred, and the subjectively brighter color is
kept in the left pixel to minimize luma "noise." The table, sorted by approximate luminance:

Byte RGB
0x00 #000000
0x10 #000078
0x11 #0000AA
0x40 #780000
0x41 #780078
0x44 #AA0000
0x51 #7800AA
0x80 #3C3C3C
0x54 #AA0078
0x81 #3C3C86
0x55 #AA00AA
0x20 #007800
0x60 #783C00
0x90 #3C3CB4
0x91 #3C3CD9
0x48 #863C3C
0x21 #007878
0x61 #783C78
0x88 #555555
0x64 #AA3C00
0x31 #0078AA
0x58 #863C86
0x49 #863CB4
0xC0 #B43C3C
0x68 #86553C
0x98 #5555BE
0x65 #AA3C78
0x22 #00AA00
0x59 #863CD9
0x66 #AA5500
0x28 #3C863C
0xC1 #B43C86
0x99 #5555FF
0x24 #787800
0xC4 #D93C3C
0xD0 #B43CB4
0x69 #8655B4
0x38 #3C8686
0x32 #00AA78
0xD1 #B43CD9
0x26 #788600
0xC5 #D93C86
0xC8 #BE5555
0x29 #3C86B4
0x33 #00AAAA
0x25 #787878
0xD4 #D93CB4
0x39 #3C86D9
0xC6 #D9553C
0xD5 #D93CD9
0x35 #7878AA
0x36 #788678
0xC9 #BE55BE
0xA0 #3CB43C
0x78 #868686
0x74 #AA7878
0xD6 #D955B4
0xD9 #BE55FF
0xCC #FF5555
0xA1 #3CB486
0xC2 #B4863C
0x75 #AA78AA
0x76 #AA8678
0x79 #8686D9
0xB0 #3CB4B4
0xA8 #55BE55
0xC3 #B48686
0xDC #FF55BE
0xB1 #3CB4D9
0x72 #78AA78
0xA2 #3CD93C
0xA4 #86B43C
0xD2 #B486B4
0x73 #78AAAA
0xDD #FF55FF
0xD3 #B486D9
0xA6 #86BE3C
0xA9 #55BEBE
0x7C #D98686
0xA3 #3CD986
0xA5 #86B486
0xB2 #3CD9B4
0xB9 #55BEFF
0xB4 #86B4B4
0xE0 #B4B43C
0x7D #D986D9
0x77 #AAAAAA
0xB3 #3CD9D9
0xB5 #86B4D9
0xB6 #86BEB4
0xE1 #B4B486
0xE4 #D9B43C
0xAC #BEBE55
0xF0 #B4B4B4
0xA7 #86D986
0xE6 #D9BE3C
0xF1 #B4B4D9
0xAA #55FF55
0xE5 #D9B486
0xE2 #B4D93C
0xAD #BEBEBE
0xF4 #D9B4B4
0xB7 #86D9D9
0xF5 #D9B4D9
0xE3 #B4D986
0xBA #55FFBE
0xF6 #D9BEB4
0xBD #BEBEFF
0xEC #FFBE55
0xF2 #B4D9B4
0xBB #55FFFF
0xF3 #B4D9D9
0xE7 #D9D986
0xED #FFBEBE
0xEA #BEFF55
0xFD #FFBEFF
0xF7 #D9D9D9
0xEB #BEFFBE
0xFB #BEFFFF
0xEE #FFFF55
0xFE #FFFFBE
0xFF #FFFFFF

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From Newsgroup: comp.sys.tandy

Atreyu <NOSPAM.sysop@darkrealms.ca> wrote:

Atreyu

The Thin Man.



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