Dr. Halo PIC

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File Format
Name Dr. Halo PIC
Extension(s) .pic
Released 1984

Dr. Halo (including Dr. Halo Plus and Dr. Genius) is a line of raster image editing software for DOS, developed by Media Cybernetics.

Its main native file format is .PIC. Sometimes, a PIC file has a companion .PAL file. This article is about PIC format, and the software in general. There are separate articles for some formats:

PIC format does not seem to be as well known as CUT. A reference to "Dr. Halo format" most likely means CUT, not PIC.



PIC is highly "device dependent". A PIC file contains identifiers for the relevant graphics hardware and mode, and a compressed copy of raw video memory.

Some editions of Dr. Halo support several dozen video cards, each with a handful of graphics modes, so supporting the entire format would be quite difficult. But it is realistic to support files that use the standard CGA/EGA/VGA modes.

Format details

[Some of this information is based on reverse engineering, and may be incorrect. Written for the fileformats.archiveteam.org wiki.]

A PIC file consists of a header segment, followed by the compressed image data. Byte order is little-endian.

Header structure

Offset Length Description
0 2 "AH" signature
2 2 Software version code?
4 2 Unused?
6 1 File type? Always 0x02.
7 1 Board ID? Known values:
Value Description Implied header size
0x01 CGA 16
0x07 Hercules 10
0x15 EGA (4-plane modes) 12
0x3c VGA (1-plane modes) 16
0x47 VGA (4-plane modes) 12
8 2 Unknown
10 2 Graphics mode. This field is not always present.

Some of the known modes are listed below.

Board ID Mode Description
0x01 0x00 320x200 4-color
0x01 0x01 640x200 2-color
0x07 n/a 720x348 2-color
0x15 0x02 320x200 16-color
0x15 0x03 640x200 16-color
0x15 0x04 640x350 16-color
0x15 0x05 640x800 16-color
0x3c 0x00 320x200 4-color
0x3c 0x01 640x200 2-color
0x3c 0x02 640x480 2-color
0x3c 0x03 320x200 256-color
0x47 0x04 320x200 16-color
0x47 0x05 640x200 16-color
0x47 0x06 640x350 16-color
0x47 0x07 640x480 16-color

For 4-color CGA-like modes:

Offset Length Description
12 1 0x10 bit: One of the palette selector bits.

Low 4 bits: Color of palette entry 0, from the standard 16-color PC/CGA palette.

13 1 Unknown
14 1 0x01 bit: One of the palette selector bits.
15 1 Unknown

Compression scheme

Compression is byte-oriented. The "next multiple of 512 bytes" instructions refer to the absolute file position.

To decompress, read a byte (N), follow the instructions below, repeat.

Code byte (N) Instructions
N = 0 End of plane. If there are more planes, seek to the next multiple of 512 bytes.
1 ≤ N ≤ 127 Emit the next N bytes literally.
N = 128 End of block: Seek to the next multiple of 512 bytes.
N ≥ 129 Emit the next byte N−128 times.


PIC files start with ASCII "AH", and the byte at offset 6 is 0x02.


Sample files


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