STOS packed screen
(Created page with "{{FormatInfo |formattype=electronic |subcat=Graphics |subcat2=Atari graphics formats |extensions={{ext|pac}}, {{ext|mbk}}, others }} '''STOS packed screen''' is an Atari raste...") |
Revision as of 23:57, 24 June 2024
STOS packed screen is an Atari raster graphics format. It is one of the "bank" formats used in STOS memory bank (MBK). This article explains some of the formats related to packed screen, some of which are also covered in other articles.
Contents |
Discussion
A packed screen can appear in an MBK container file, and maybe in other STOS formats. Or it can appear in a file by itself that starts with bytes 06 07 19 63.
Independent of the container format, there are at least six different image formats. Unfortunately, there is not always a good way to tell which format a given image uses. The filename extension can help, but isn't always good enough.
Format details
Internally, packed screen format is very similar to AMOS Picture Bank, just with different rules for how many planes there can be, etc. The compression is a kind of RLE, applied twice.
Formats
| Format | Res. code | Planes | Colors | Remarks |
|---|---|---|---|---|
| Standard low res. | 0 | 4 | 16 | |
| Standard medium res. | 1 | 2 | 4 | Same as Picture Packer PP2. |
| Standard high res. | 2 | 1 | 2 | |
| Picture Packer PP1 | 1 | 2 | 16 | Refer to Picture Packer. |
| Picture Packer PP3 | 1 | 2 | 2 | Refer to Picture Packer. |
| "DAJ" 4-plane | 0 | 4 | 4 | Used by a viewer for the ST+ (ST Plus) Atari diskmagazine. |
The "resolution code", which implies the number of planes, is stored in the file. The number of colors is not.
Identification
An MBK file containing a packed screen starts with "Lionpoubnk", has a nonzero number (4-byte big endian) at offset 10, has byte (hex) 81 at offset 14, and bytes 06 07 19 63 at offset 18. The signature at offset 18 is not sufficient by itself, because it also matches STOS character set files.
A raw packed screen file starts with bytes 06 07 19 63. Following that is 00 00, or 00 01, or 00 02.
Specifications
- Atari Forum Wiki: STOS.MBK, section named "Banktype $81, data, magic $06071963, packed screen"
Sample files
(TODO)
