Date: Tue, 8 Sep 2015 10:21:58 -0300 From: "Joao S. O. Bueno"
To: Richard
Cc: "gimp-user-list@gnome.org"
Subject: Re: [Gimp-user] GIMP's "EGA" default palette Message-ID:

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On 7 September 2015 at 03:22, Richard wrote:

Are we talking EGA as in https://en.wikipedia.org/wiki/Enhanced_Graphics_Adapter ? Or am I missing something important? What is this palette, anyway?

Yes.
So, as the name says, it has the 16 colors taht were hardcoded in the firmware for those adapters. That is not useful for anything today, but for having 16 highly distinguished colors - and there is the historical fun aspect of it,as you found out.

Date: Tue, 8 Sep 2015 20:18:38 -0700 From: Richard
To: "Joao S. O. Bueno"
Cc: "gimp-user-list@gnome.org"
Subject: Re: [Gimp-user] GIMP's "EGA" default palette Message-ID:
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Thanks. I have never heard that before (and so far am unable to find any citations about it).

Now at the same time, clearly this is not the set of 16 colors by which EGA is most commonly known. Shouldn't we have a palette for that? ;)

I missed some postings, but I have documentation about EGA cards.

The colors were from a palette of 64 colors, with each bit corresponding to a separate wire. Low-intensity colors have a high

https://en.wikipedia.org/wiki/List_of_monochrome_and_RGB_palettes#6-bit_RGB

The 16 default CGA colors were mapped to the values 00 01 02 03 04 05 14 07 38 39 3a 3b 3c 3d 3e 3f (everything like CGA, where only one high intensity bit was available, except for brown, because 0x06 looked bad on some screens)

The VGA cards will emulate these 64 colors by having default 6-bit color values in their 256 color registers. The high bit corresponds to 0x15, the low bit to 0x2a, giving a total of 0x3f (white). For 8 bits, I'll use 0x55 and 0xAA for a corresponding appearance. E.g. the brown (0x14) is green (0x10->#005500) + dark red (0x40->#aa0000) -> #aa5500.

EGA Color 8-bit 0x20 = dark red, #550000
0x10 = dark green #005500
0x08 = dark blue #000055
(0x38 = dark gray, emulates the CGA intensity bit) 0x04 = bright red #aa0000
0x02 = bright green #00aa00
0x01 = bright blue #0000aa

--- The VGA 256-color-default-palette is yet something different, available on http://objectmix.com/graphics/383737-vga-palette.html (to convert to 8 bit, left-shift by 2 and add the lower 2 bits)

HTH