Contents of the OS2GIF.DOC file
OS2GIF Version 1.0
OS/2 NON PM GIF Display
for EGA and VGA
James C. Huebsch
August 5, 1989
NOTICE: GIF and 'Graphics Interchange Format' are trademarks of
CompuServe, Incorporated. an H&R Block Company.
OS2GIF V1.0 User Guide Page 1
OS2GIF is a NON PM OS/2 application to display GIF files on EGA or VGA
video systems.The 256 color GIF files will require a VGA adapter for an
enjoyable picture. OS2GIF supports a virtual screen larger than the physical
video screen which allows panning over the image.
The executable program OS2GIF is hereby placed into the public domain.
It is "freeware" not "shareware". No payment of any kind is requested. If
you like the program, you may send comments or suggestions for enhancements.
If you find errors (bugs) you may also report them, but there is no commitment
on my part to fix them or to provide future enhancements. If no one else
provides a better program for OS/2 GIF viewing I intend to enhance and
continue distribution of this one.
The OS/2 Video Environment, Now and the Future
Currently OS/2 Presentation Manager Version 1.1 does not effectively
support the 256 color mode of the VGA, this limits PM to a dithered image
display. Since many GIF files are in 256 colors, the loss of the full beauty
of the colors is significant. However OS2GIF performs direct I/O to the video
adapter with OS/2 Ring 2 I/O code, providing full functionality of the video
systems under OS/2.
Also, currently OS/2 PM has performance disadvantages for image display.
It is expected that these shortcomings may be addressed in future versions of
OS/2, but until they are OS2GIF will not use PM.
As video board vendors provide OS/2 PM display drivers for their boards, I
expect the SuperVGA (640 x 480 x 256, 800 x 600 x 256) and better resolutions
to become common for OS/2. When IBM enters the SuperVGA market it will become
a standard for video systems.
The only video hardware I have available is IBM EGA and IBM VGA. Due to
this limitation I may not be able to support the SuperVGA boards. However IBM
compatible boards should work with OS2GIF in standard EGA or VGA modes. As I
gain access to additional video boards I will strive to support them in
OS2GIF. As OS/2 PM becomes a usable environment I hope to provide a PM
version of OS2GIF.
The first version of OS2GIF (version 1.0) is written in the C language
with assembler routines for the Ring 2 I/O video control. It does not have
the best performance during image display, but future versions should provide
more optimization using assembler code. I expect a two to threefold
OS2GIF V1.0 User Guide Page 2
INSTALLATION AND STARTING
To install OS2GIF, simply copy the OS2GIF.EXE module into a directory which
is in the "PATH=" list in CONFIG.SYS. OS2GIF is a NON PM, protected mode
application; it does not execute under DOS or in the DOS compatibility
Since OS2GIF requires I/O previledge, you must insure your CONFIG.SYS
contains a "IOPL=YES" statement. Optionaly you could list the OS2GIF program
name on the IOPL statement. For example, "IOPL=OS2GIF". See your OS/2
documentation for the CONFIG.SYS "IOPL" statement.
The OS/2 command line may be used to start OS2GIF. OS2GIF is easy to use
and has a help function available by pressing the F1 key.
OS2GIF should execute in the foreground and it will lock the video display
during image drawing. This means that no other processes may "pop up" onto
the video display during OS2GIF image drawing.Currently OS/2 limits this
locking to a 30 second maximum. If after this time the display is disrupted,
you must return to the selection menu and reselect the GIF file to redraw it.
The command line may provide several options as described below:
OS2GIF [filemask] [...] [/G] [/Q] [/L]
The filemask is one or more standard file names with wildcards.
For example: *.* or *.GIF (the GIF is assumed if not specifed)
Also for the first filemask a drive and path may be specified.
For example, " OS2GIF D:\JAMES\PICS *.PIC *.IMG", specifies
all the "*.GIF" and "*.PIC" and "*.IMG" files in "D:\JAMES\PICS"
directory. The default filemask of: *.GIF (current drive and
directory) is used if none is specified.
/L will bypass the OS/2 Screen Locking. This is used primarily
for debugging, but may be used anytime locking is inconvient.
/G will display the GIF file information on the select menu.
Without the "/G", a normal directory listing will appear for
the selection menu. With "/G", the GIF screen size and colors
will be read from each GIF file and appear with the file name
in the selection menu.
/Q will provide a 'quiet' mode without beeps.
The OS2GIF full screen selection menu will display after reading the
files specifed by the filemask.
OS2GIF V1.0 User Guide Page 3
When OS2GIF starts it will read the directory entries for the specified
filemask and display them in a full screen selection menu. You may use the
highlighted line as a cursor and position it with the up/down arrows, the
left/right arrows, the PageUp/PageDown keys, and the Home/End keys.
When you have highlighted the GIF file you wish to view, press ENTER.
The GIF image will be displayed in the best fit of screen size, colors, and
your video adapter. CNTL-ENTER may be used to select a file, then prompt you
to select the video display mode for the file.
You may also key the name of the GIF file directly into the data entry
field at the bottom of the screen, and press ENTER (or CNTL-ENTER) for
The following keys may be used to control OS2GIF while the selection menu
ESC = Exit from Menu Screen back to OS2.
Up/Down/Left/Right = Move the highlight cursor for file selection.
PgUp/PgDn = Scroll directory list by pages.
ENTER = Select file for display.
CNTL-ENTER = Select file for display and prompt for video mode.
F1 = Online Help Function.
F2 = Rebuild Directory List using new file mask if any.
F10 = Toggle GIF Screen data display/Directory data.
Normal ASCII keys may be used to enter a file name.
The F10 key may be used with the F2 key to rebuild the selection display
with the GIF Screen information rather than the normal directory list.
If a new filemask is entered in the data entry field, F2 may be pressed
to use it for the selection menu. This mask may include a drive and path.
When the CNTL-ENTER selection is made, a menu of video modes will be shown.
Simply press the number key for the video mode desired to display the GIF file.
OS2GIF V1.0 User Guide Page 4
GIF IMAGE DISPLAY
After selection of a GIF file, the video screen will be set to the video
mode for the image and the drawing will begin.During the image drawing, the
CNTL-C and CNTL-BREAK keys may be used to cancel the drawing. These are the
normal OS/2 interrupt keys.
The 256 color GIF files will require a VGA adapter for a useful display.
GIF files with screen sizes larger than the adapter are supported. A
virtual screen is used by OS2GIF. For the 16 color mode, the virtual screen
exists in the video adapter's 256K of memory and the largest supported virtual
screen size is 640 x 800. For the 256 color modes, the virtual screen exists
in OS/2 memory, and the largest supported virtual screen size is limited by
OS/2's dynamic memory availability which should be larger than most GIF file
When GIF file is drawn with an image larger than the physical screen,
a beep will be heard at the begining and the end of the drawing process,
unless the "/Q" quiet mode is specified. The first beep lets you know panning
will be available for the image. The second beep lets you know when you may
begin the panning.
The virtual screen may be panned with the Up/Down/Left/Right arrows, the
Home/End keys, the PageUp/PageDown keys, the CNTL-left/CNTL-right keys, and
the CNTL-PgUp/CNTL-PgDn keys.
After viewing the image, you may return to the selection menu by pressing
the ESC key.