home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Amiga Tools 2
/
Amiga Tools 2.iso
/
grafik
/
bildanzeiger
/
jpegaga
/
doc
/
jpegaga.doc
< prev
next >
Wrap
Text File
|
1995-03-09
|
11KB
|
317 lines
jpegAGA 1.1 by Günther Röhrich
******************************
jpegAGA is, at this time, the highest quality JPEG viewer (if a map-file for
that picture is available) To use it you need the AGA chipset, a 68020 or
higher processor and OS 3.0 or higher. This program uses the HAM8-mode, gray-
scale display will use 256-color-mode.
If a precomputed colormap (a file with the ending .map) is available then
the picture will be displayed in a much higher quality compared to other
viewers.
With the supplied shell script you can create such map-files for all your
pictures. These files will only be 198 bytes long.
If a map-file is not available then you will get a lower quality display. For
grayscale display this file is not needed.
The advantages of jpegAGA:
- very high quality (better than any other viewer)
- complete source is available
- best compatibility to all JPEG pictures because the unmodified JPEG source
from the Independent JPEG group is used for decoding
- high speed gained by using the GNU C compiler and the 24-bit-RGB to HAM8 con-
verter written directly in assembly language
- support for grayscale JPEG's and for showing color pictures in grayscale
format
This program and the supplied source is Public Domain, you can do what you want
with it. For the JPEG-source please read the file README.
I have to thank the following persons/groups:
The Independent JPEG Group (jpeg-info@uunet.uu.net):
for the source to decode/encode the JPEG picture format
Free Software Foundation, Inc. and all contributors for the GNU C compiler
and related tools
***********************************************************************
Now let's go on with the real documentation:
Installation
************
Copy the programs from the bin directory anywhere into your shell's search
path. The file name extensions are showing for what processors they are com-
piled. After installation you should remove these extensions.
Extension 000: 68000 and 68010 processors, runs on all others too
Extension 020: 68020 or higher processors
All programs are compiled with GNU C 2.5.8 and need therefore the file
ixemul.library in the LIBS: directory.
For using the shell script CreateMap you have to assign JPEGTMP: to a directory
on your hard disk with enough free space. (e.g. assign JPEGTMP: HD:T) The pro-
grams djpeg and cjpeg will eventually need this directory too.
The best solution is to add this command to the user-startup file.
The shell script CreateMap should be copied to the S: directory. It assumes that
the programs djpeg and ppm2AGA are available (with exactly these names) in the
shell's search path and the JPEGTMP: directory exists.
Invoking jpegAGA:
jpegAGA inputfile options
Inputfile
*********
The name of the JPEG-file that should be read. If the picture is in grayscale
format it will be shown on a 256 colors screen without extensive computations.
Unfortunately there are also grayscale pictures encoded in color mode. You
should use the -GRAY option for such pictures.
When showing the picture in color mode the map-file for this picture will be
used if it is available. The map-file must have the same name as the picture
with the additional ending .map. To support the PC-filesystem it will also
accept a name that has the extension replaced by ".map".
If a map-file is found this will be notified in the console window.
Examples for file names:
picture file: picture.jpeg map-file: picture.jpeg.map or picture.map
pic1.jpg map-file: pic1.jpg.map or pic1.map
jpegAGA will also try to find the map-file in the directory pointed to by
the environment variable MAPDIR. (new in version 1.1)
Options
*******
All options are case-insensitive. If they are not set then internal default
values will be used.
-GRAY
Display picture in grayscale mode.
-BS
Use block-smoothing. You should set this option when the image has been
encoded at a very low quality setting. Without this option you can see multi-
ple blocks with a nearly constant color in the picture. When this option is
set the borders of these blocks will be smoothed.
You should use this option only for such cases.
-VGA
The picture will always use the VGA screenmode (also called 'multiscan') for
display. Use this option when you know that the picture was intended for
displaying on a PC or other machines with square screen resolution.
(this is the case for most JPEG-pictures)
NOTE: With 'square' I don't mean that the screen has the same number of pixels
in horizontal and vertical direction. (e.g. 1024x1024)
I mean that a square composed of e.g. 100x100 pixels will be shown as a
square on the screen. Because a usual picture tube has a ratio of 4 to 3
the screen's resolution must be a multiple of that. (e.g. 640x480 because
640 4
--- = - )
480 3
-SUPER72 (new in version 1.1)
This option will only be accepted if you also set the -VGA option. The SUPER72
screen mode will be used for very large pictures. You have to modify the SUPER72
monitor driver in most of the cases (e.g. with the program "moned") if you want
to get a square resolution in that mode.
There is also a JPEG decompression program included. It converts JPEG
pictures to the ppm format. (It is also needed for creating the map-files.)
To use it enter:
djpeg inputfile outputfile
In some cases djpeg will try to store temporary files to JPEGTMP:, you
have then to assign this directory to somewhere on your hard disk.
(for example assign JPEGTMP: HD:T)
For more informations read the included documentation.
With the program cjpeg you can create your own JPEG files.
Creating the map-files
**********************
These files are needed for showing color picture with best possible quality.
Normally, they are created by the shell-script CreateMap.
Usage:
CreateMap picturefile
After succesfull completion a map-file with the correct name will be created.
(On PC-filesystems too) You can process several pictures with a single invo-
cation. The command
SPat CreateMap pictures/#?.jpg
will create, for example, a map-file for all pictures with the extension .jpg
in the directory pictures.
If it is not possible to store the map-file at the same location as the picture
itself then it will be stored in the directory pointed to by the environment
variable MAPDIR. jpegAGA 1.1 will then also try to find the map-file in that
place. You can set the environment variable e.g. with the command:
setenv MAPDIR HD:tempdir
If you reset your machine the variable will get lost. To prevent this you can
use the command:
copy ENV:MAPDIR ENVARC:
Now you can also show pictures from a CD-ROM with best possible quality.
If problems occur please check the following:
- Have you installed everything as it is described in the section
"Installation" ?
The files djpeg and ppm2AGA are needed under these names in the search path.
ixemul.library must exist in the LIBS: directory an the shell-script itself
must be in the S: directory.
attention: - ppm2AGA must have version 1.4 or higher
- use djpeg from this distribution only
- Have you assigned the directory JPEGTMP: correctly ?
- Has the hard disk partion enough free space ?
- Is enough memory available ?
If not you can reduce memory usage by using the -M0 option with the shell
script. (See the documentation for ppm2AGA for more.)
example: CreateMap pic.jpg -M0 or SPat CreateMap #?.jpg -M0
- Is the disk, on which the JPEG-picture is stored, write enabled and does it
has enough free space ?
- Have you set the environment variable MAPDIR correctly ? You can check this
with the command: getenv MAPDIR
You can interrupt the shell-script at any time by pressing CTRL-C. In this case
all temporary files in the directory JPEGTMP: will be removed automatically.
The picture screen
******************
You can move it around with the mouse. It also has an invisible, but full
functional drag bar and depth gadget.
Pressing the right mouse button will close the screen.
If you have additional questions, suggestions for enhancements, bug reports,
Mungwall/Enforcer hits, etc. then please contact me. It would also be nice
if you would send me a corrected version of this manual. (and for ppm2AGA too)
History
*******
1.0 - 4-June-1994
- first public release
1.1 - 5-October-1994
- added the option -SUPER72
- the picture screen no longer flashes when closing it and the delay is much
smaller now
- map-files will also be searched in the directory pointed to by the MAPDIR
environment variable
- if a map-file is not found the user will get informed that he should
create one
- file/path names of any length are now accepted
Announcement
************
The actual version of this program does not offer very much. My spare time
is very limited because I am now studying Electrical Engineering at the Uni-
versity Stuttgart. Therefore I am searching for other developers to cooperate
with me and beta-testers for testing purposes. If you want to join in then
please contact me. I will then create a detailed description of the source.
To recompile ppm2AGA you need the newiff package from Commodore.
V37 is available on Fish-disk 705, V39 on the "3.1 Amiga Developer Update"
disks and on Aminet.
Next I intend to write a PhotoCD viewer/converter with the picture quality
of jpegAGA/ppm2AGA. This will be a free program too and I will also release
the complete source. If you are interested in such a program it would be very
nice if you would lend me some PhotoCD's for testing purposes. You will get
them back together with my viewer/converter as soon as it will be working. If
you give them to me as a present I will be even more happy. Your name will then
be mentioned in the documentation and I will also send you the program.
To contact me write to:
electronic mail: normal mail:
**************** ************
Guenther@studbox.uni-stuttgart.de Günther Röhrich
(Internet EMAIL) Lerchenbergstr. 4
73733 Esslingen
Germany
If you don't get an answer to a EMAIL within 3 weeks then try it again
with normal mail.
In the document "Info.Developer" you can read how to get other developer
material, especially the "3.1 Amiga Developer Update".
NOTE: Commodore does not exist any more, I don't know if it is still possible
to get developer materials there. Try to contact the German company
Hirsch & Wolf oHG.