GEMVEC.TXT
Remove Frame
GEM VDI description excerpted from:
ST Picture Formats
------------------
Edited by:
David Baggett
Internet:
[email protected]
(Please report errors or additions.)
Copyright (C) 1988 -- 1995 by David M. Baggett
Non-profit redistribution of this document is permitted, provided
the document is not modified in any way.
Reproduction of this document in whole or in part for commercial
purposes is expressly forbidden without the prior written consent
of David M. Baggett.
The information presented here is not guaranteed to be correct.
The editor and contributors will in no event be liable for direct,
indirect, incidental, or consequential damages resulting from the
use of the information in this document.
This document is the product of many hours of volunteer work by a
large number of people. Please respect this -- do not violate the
distribution policy.
CONTRIBUTORS
Steve Belczyk Phil Blanchfield Marcel Boom Jason Blochowiak
John Brochu** David Brooks Daniel Deimert Martyn Dryden
Neil Forsyth Stefan Hoehn Gerfried Klein G. "Maddog" Knauss
Ken MacLeod Shamus McBride Jim McCabe Lars Michael
Darek Mihocka David Mumper George Nassas Jim Omura
Chris Ridd George Seto Joe Smith Greg Wageman
Roland Waldi* Gerry Wheeler
Introductory Information
------------------------
word = 2 bytes
long = 4 bytes
palette = Hardware color palette, stored as 16 words. First word is
color register zero (background), last word is color register
15. Each word has the form:
Bit: (MSB) 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 (LSB)
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
0 0 0 0 0 R2 R1 R0 0 G2 G1 G0 0 B2 B1 B0
R2 = MSB of red intensity
R0 = LSB of red intensity
G2 = MSB of green intensity
G0 = LSB of green intensity
B2 = MSB of blue intensity
B0 = LSB of blue intensity
Intensity ranges from 0 (color not present) to 7 (highest
intensity).
Example: { red = 7, green = 3, blue = 5 } -> 0735 (hex)
Caveat: It is wise to mask off the upper four bits of each
palette entry, since a few programs store special
information there (e.g., Art Studio).
<GEM Metafile> *.GEM
Marcel Boom <[email protected]> recently sent me this
format description. I have reproduced it here, largely unchanged.
The file consists out of a header and the data records. The header has
the following format:
word mf_header: should be -1, which indicates a metafile
word mf_hlength: The length of the header part (usually 24 words)
word mf_version: Version number (usually 101)
word mf_ndcrcfl: 0: NDC coordinates, 2: Raster coordinates
word mf_extends1: Optional, minimal used x coordinate
word mf_extends2: Optional, minimal used y coordinate
word mf_extends3: Optional, maximal used x coordinate
word mf_extends4: Optional, maximal used y coordinate
word mf_width: Optional, page width in 0.1 mm
word mf_height: Optional, page height in 0.1 mm
word mf_coords1: Optional, coordinate system param 1
word mf_coords2: Optional, coordinate system param 2
word mf_coords3: Optional, coordinate system param 3
word mf_coords4: Optional, coordinate system param 4
word mf_imgflag: 0: No images, 1 contains bit images
word mf_reserved1: reserved.
.
.
word mf_reserved9: reserved.
After the header follows the data records of the following format:
word 0: VDI command number
word 1: n: Number of parameters for ptsin array
word 2: m: Number of parameters for intin array
word 3: Subopcode
word 4 to 4+n: ptsin array
word 4+n to 4+n+m: intin array
A VDI command number of -1 signals the end of file.
VDI command numbers:
5: Escape functions:
Subopcode:
1: Inquire addressable character cells
2: Exit alpha mode
3: Enter alpha mode
20: Form advance
21: Output window
22: Clear display list
23: Output bit image file
98: Update metafile extents
99: Write metafile item
100: Change GEM VDI filename
6: Polyline
7: Polymarker
8: Text
9: Filled area
11: GDP:
subopcode:
1: Bar
2: Arc
3: Pie
4: Circle
5: Ellipse
6: Elliptical arc
7: Elliptical Pie
8: Rounded rectangle
9: Filled rounded rectangle
10: Jutified graphic text
12: Set character height, absolute mode
13: Set character baseline vector
14: Set color representation
15: Set polyline linetype
16: Set polyline line width
17: Set polyline color index
18: Set polymarker type
19: Set polymarker height
20: Set polymarker color index
21: Set text face
22: Set graphic text color index
23: Set fill interior style
24: Set fill style index
25: Set fill color index
26: Inquire color representation
32: Set writing mode
35: Inquire current polyline attributes
36: Inquire current polymarker attributes
37: Inquire current fill area attributes
38: Inquire current graphic text attributes
39: Set graphic text allignment
102: Extended inquire function
103: Countour fill
104: Set fill perimeter visibility
106: Set graphic text special effects
107: Set character cell height, points mode
108: Set polyline end styles
112: Set user defines fill pattern
113: Set user defined line style pattern
114: Fill rectangle
117: Inquire character cell width
129: Set clipping rectangle
131: Inquire current face information
The meaning of the arrays can be found in the several GEM programming books.
NOTE: The word qualifier is not the Motorola word, but the Intel word,
so high and low byte are swapped!
<STAD> *.PAC (high resolution only)
4 bytes "pM86" (vertically packed) or "pM85" (horizontally packed)
1 byte id byte
1 byte pack byte (most frequently occuring byte in bitmap)
1 byte "special" byte
-------
7 bytes total for header
? bytes data
The data is encoded as follows. For each byte x in the data section:
x = id byte Read one more byte, n. Use pack byte
n + 1 times.
x = "special" byte Read two more bytes, d, and n (in order).
Use byte d n times.
otherwise Use byte x literally.
<Imagic Film/Picture> *.IC1 (low resolution)
*.IC2 (medium resolution)
*.IC3 (high resolution)
4 bytes "IMDC"
1 word resolution (0 = low res, 1 = medium res, 2 = high res)
16 words palette
1 word date (GEMDOS format)
1 word time (GEMDOS format)
8 bytes name of base picture file (for delta compression), or zeroes
1 word length of data (?)
1 long registration number
8 bytes reserved
1 byte compressed? (0 = no, 1 = yes)
If compressed {
1 byte delta-compressed? (-1 = no, > -1 = yes)
1 byte ?
1 byte escape byte
}
-------
65 bytes total for header (68 bytes if compressed)
? bytes data
Compressed data may be either stand-alone or delta-compressed (relative
to the base picture named in the header). Delta compression involves
storing only how the picture differs from the base picture (i.e., only
portions of the screen that have changed are stored). This is used to
to encode animated sequences efficiently.
Compressed data, stand-alone:
For each byte x in the data section:
x = escape byte Read one more byte, n. (n is unsigned).
If n >= 2, use the next byte n times.
If n = 1, keep reading bytes until a
byte k not equal to 1 is encountered.
Then read the next byte d.
If the number of 1 bytes encountered is o,
use d (256 * o + k) times. I.e.,
if (n == 1) {
o = 0;
while (n == 1) {
o++;
n = next byte;
}
k = n;
d = next byte;
Use d (256 * o + k) times.
}
else {
d = next byte;
Use d (n) times.
}
x != escape byte Use x literally.
Compressed data, delta compressed:
For each byte x in the data section:
x = escape byte Read one more byte, n. (n is unsigned).
If n >= 3, use the next byte n times.
If n = 1, do the same as for n = 1 in
stand-alone compression (above).
If n = 2, then set n = next byte.
If n = 0, end of picture.
If n >= 2, take n bytes from base
picture.
If n = 1, do the same as for n = 1
in stand-alone compression (above),
but take (256 * o + k) bytes from
base picture.
x != escape byte Use x literally.
* Roland Waldi contributed extensive information on the following formats:
GEM, IMG, Doodle, STAD, Imagic Film/Picture, Art Director, IFF
** John Brochu, ST picture formats guru, provided sage advice and many
corrections to the following formats:
NeoChrome, DEGAS Elite Compressed, Spectrum 512 Compressed,
GEM Bit Image, IFF, MacPaint
Version of...........Sun Oct 30 12:40:13 EST 1994
(Last change: Extended GEM .IMG format updated)
