Atari ST color palette - Revision history

Foxtrot: Added category

2023-01-11T17:18:08Z

Added category

Tekkno at 15:12, 7 August 2018

2018-08-07T15:12:51Z

Jsummers: /* Format details */

2017-05-05T13:20:10Z

‎Format details

Jsummers at 16:54, 2 February 2016

2016-02-02T16:54:33Z

Jsummers: Created page with "{{FormatInfo |formattype=electronic |subcat=Graphics |subcat2=Atari graphics formats }} The Atari ST computer supports 3 bits per color channel, giving (2^3)^3 = 512 different..."

2016-01-24T23:06:15Z

Created page with "{{FormatInfo |formattype=electronic |subcat=Graphics |subcat2=Atari graphics formats }} The Atari ST computer supports 3 bits per color channel, giving (2^3)^3 = 512 different..."

New page

{{FormatInfo
|formattype=electronic
|subcat=Graphics
|subcat2=Atari graphics formats
}}
The Atari ST computer supports 3 bits per color channel, giving (2^3)^3 = 512 different colors. In the standard video modes, no more than 16 different colors can be displayed at the same time, and a color palette is used to define the available colors.

== Format details ==
In a number of Atari graphics formats, the palette is stored in a format with 16 bits per palette entry, only 9 of which are significant:
xx xx xx xx xx R2 R1 R0 xx G2 G1 G0 xx B2 B1 B0

The Atari "STE" models increased the color depth from 3 to 4 bits per color channel, thus supporting (2^4)^3 = 4096 different colors. For compatibility reasons, its palettes have the least significant bit in the position one might otherwise expect to be used for the ''most'' significant bit:
xx xx xx xx R0 R3 R2 R1 G0 G3 G2 G1 B0 B3 B2 B1

Some Atari image files use these Atari STE 12-bit palettes, usually with no external indication that they do so. Trying to detect and interpret such palettes is a good idea, as grayscale (and grayscale-ish) images can be significantly improved by the extra color depth. (Unfortunately, it seems that some non-STE files contain garbage in the unused bits, instead of zeroes. So, autodetecting STE palettes may not be possible to do in a completely reliable way.)

== Sample files ==
=== Images with 12-bit palettes ===
* [http://cd.textfiles.com/suzybatari2/picmanip/pic_r2z/sty_demo/pictures/bwlady.pc1 bwlady.pc1]
* [http://cd.textfiles.com/suzybatari2/picmanip/pic_r2z/ss_img_1/clinton.img clinton.img]
=== Other ===
* [http://cd.textfiles.com/suzybatari2/picmanip/pic_r2z/scanner/images/bilboule.pi1 bilboule.pi1] - Example of a file that appears to have garbage in the unused palette bits

== Related formats ==
Formats that use this style of palette (12-bit palettes are not necessarily allowed for all of these formats):
* [[DEGAS image]]
* [[Tiny Stuff]]
* [[NEOchrome]]
* At least one of the color [[GEM Raster]] formats

== Software ==
Software known to support 12-bit STE-style palettes:
* [[RECOIL]]
* [http://entropymine.com/deark/ Deark]

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	Some Atari image files use these Atari STE 12-bit palettes, usually with no external indication that they do so. Trying to detect and interpret such palettes is a good idea, as grayscale (and grayscale-ish) images can be significantly improved by the extra color depth. (Unfortunately, it seems that some non-STE files contain garbage (or private data) in the unused bits, instead of zeroes. So, autodetecting STE palettes may not be possible to do in a completely reliable way.)		Some Atari image files use these Atari STE 12-bit palettes, usually with no external indication that they do so. Trying to detect and interpret such palettes is a good idea, as grayscale (and grayscale-ish) images can be significantly improved by the extra color depth. (Unfortunately, it seems that some non-STE files contain garbage (or private data) in the unused bits, instead of zeroes. So, autodetecting STE palettes may not be possible to do in a completely reliable way.)
		+
		+	=== Spectrum 512 Enhanced palettes ===
		+	For completeness, we mention the obscure [[Spectrum 512 formats\|Spectrum 512]] "Enhanced" format, which extends the palette even further, to 5 bits per color channel:
		+	R0 G0 B0 xx R1 R4 R3 R2 G1 G4 G3 G2 B1 B4 B3 B2

	=== Bi-level images ===		=== Bi-level images ===

@@ Line 36: / Line 36: @@
 * [[NEOchrome]]
 * At least one of the color [[GEM Raster]] formats
 == Software ==
@@ Line 41: / Line 44: @@
 * [[RECOIL]]
 * {{Deark}}

@@ Line 10: / Line 10: @@
   xx xx xx xx xx R2 R1 R0  xx G2 G1 G0 xx B2 B1 B0
 The Atari "STE" models increased the color depth from 3 to 4 bits per color channel, thus supporting (2^4)^3 = 4096 different colors. For compatibility reasons, its palettes have the least significant bit in the position one might otherwise expect to be used for the ''most'' significant bit:
   xx xx xx xx R0 R3 R2 R1  G0 G3 G2 G1 B0 B3 B2 B1
-Some Atari image files use these Atari STE 12-bit palettes, usually with no external indication that they do so. Trying to detect and interpret such palettes is a good idea, as grayscale (and grayscale-ish) images can be significantly improved by the extra color depth. (Unfortunately, it seems that some non-STE files contain garbage in the unused bits, instead of zeroes. So, autodetecting STE palettes may not be possible to do in a completely reliable way.)
+Some Atari image files use these Atari STE 12-bit palettes, usually with no external indication that they do so. Trying to detect and interpret such palettes is a good idea, as grayscale (and grayscale-ish) images can be significantly improved by the extra color depth. (Unfortunately, it seems that some non-STE files contain garbage (or private data) in the unused bits, instead of zeroes. So, autodetecting STE palettes may not be possible to do in a completely reliable way.)
 == Sample files ==
@@ Line 20: / Line 24: @@
 * [http://cd.textfiles.com/suzybatari2/picmanip/pic_r2z/ss_img_1/clinton.img clinton.img]
 === Other ===
-* [http://cd.textfiles.com/suzybatari2/picmanip/pic_r2z/scanner/images/bilboule.pi1 bilboule.pi1] - Example of a file that appears to have garbage in the unused palette bits
+* [http://cd.textfiles.com/suzybatari2/picmanip/pic_r2z/scanner/images/bilboule.pi1 bilboule.pi1] - Example of a file in which the extra palette bits are not zero
 == Related formats ==
@@ Line 32: / Line 36: @@
 Software known to support 12-bit STE-style palettes:
 * [[RECOIL]]
-* [http://entropymine.com/deark/ Deark]
+* {{Deark}}