6.4 Graphics and the Cursor - Saving and Restoring Graphics and Frames
In this exercise, you will save and restore virtual graphics files,
virtual frame files, and GIF files.
Virtual Graphics Files
In these five steps, you will generate a map over a satellite image
and save the map as a virtual graphics file with the VIRT keyword.
Then you'll erase the image and the graphics, locate the saved virtual
graphics file, and restore it with the SHOWVG
command.
- Show frame 1.
- Type: SF 1
- Generate a map over the image and save it as a virtual
graphic assigned to file 9110. You must assign the graphic to a
virtual file at the time you run the graphics command.
- Type: MAP H VIRT=9110
The output is written to virtual graphics file VIRT9110 as well as the
frame.
- List virtual graphic 9110 on your workstation to verify it
was saved.
- Type: DMAP VIRT9110
DMAP VIRT9110
PERM SIZE LAST CHANGED FILENAME DIRECTORY
---- --------- ------------ -------- ---------
-rw- 158992 Oct 26 16:06 VIRT9110 //D/home/user/mcidas/data
158992 bytes in 1 files
- Erase the image and graphics.
- Type: ERASE
- Restore virtual graphic 9110 to frame 1.
- Type: SHOWVG 9110 1
Notice only the graphic was saved not the satellite image.
- Erase the graphic on frame 1.
- Type: ERASE G
Virtual Frame Files
In the next five steps, you will use the SVF
command to save a satellite image and map. Then you'll list the virtual
frame files on your workstation using the LVF
command, and restore a virtual frame file using the
RVF command.
- Display the first GOES-7 4km Vis image centered on Washington DC,
draw a map, and set the loop bounds from 1 to 4.
- Type: IMGDISP GV4.1 1 STA=KDCA;MAP H;LS 1-4
- Save the satellite image and map as a virtual frame file
named SATMAP.
- Type: SVF 1 X SATMAP
Be sure the message "Frames saved in SATMAP.PIX - 1" is displayed
in the text window before continuing.
- List the virtual frame files on your workstation.
- Type: LVF
A list of virtual frame files and corresponding information for
each is displayed in the text window as shown below. Notice
that virtual frame files are saved with the extension .PIX.
PERM SIZE LAST CHANGED FILENAME DIRECTORY
---- --------- ------------ ---------- ---------
-rw- 311272 Oct 26 10:16 SATMAP.PIX /home/user/mcidas/data
311272 bytes in 1 files
- List information about the number of frames, frame size,
graphics, and image levels for the virtual frame file SATMAP.
The frame size and graphic and image levels in the virtual
frame file must be the same as the frame where it is being
restored.
- Type: LVF SATMAP FORM=ALL
PERM SIZE LAST CHANGED FILENAME DIRECTORY
---- --------- ------------ ---------- ---------
-rw- 311272 Oct 26 10:16 SATMAP.PIX /home/user/mcidas/data
311272 bytes in 1 files
file is in new format and contains 1 frame
frame 1 is 480 by 640
LVF: DONE
- Show frame 2 and restore the virtual frame file you saved as
SATMAP.
- Type: SF 2;RVF 2 X SATMAP
- Press: Alt B
- Press: Alt A
The image and graphics are displayed in frame 2. Notice that the
frame's annotation line is saved with the image and may not match
the frame number where the virtual frame file is restored. When
you advance through the frames, use the status line to determine
which frame is displayed.
GIF files
In the following steps, you will load an area into frame 4, draw a
map on it and then save the image as a GIF file.
- Display the first GOES-7 4km Vis image centered on Washington DC
onto frame 4 and draw a map on the image.
- Type: IMGDISP GV4.1 4 STA=KDCA SF=Y;MAP H
- Save frame 4 in GIF format.
- Type: FRMSAVE 4 PICTURE
The default for FRMSAVE is to save the
frame in the GIF format, but you can also specify the FORM keyword to choose to
save it in a PPM, BMP, JPEG or PostScript format.
- List the GIF image PICTURE on your workstation to verify that
it was saved and to where it was saved.
- Type: DMAP PICTURE
Notice that the file was saved with the extension .GIF
- Use your workstation's image viewer (ex: xloadimage, xv, PMJPEG)
to display the GIF file from a terminal window.