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Analyze Images on Unix
This functionality is available as a menu item of
as a button with the process list. It starts the program
"ximage(1)", which is used to display a Radiance format
picture and analyze it to a certain degree.
Note that this program is not capable of storing any analysis
results to disk. You will have to some of the various
Radiance command line tools included with Rayfront
if you want your analysis results to become persistent
on a unix system. Please refer to the manual pages included
on the instllation CD-ROM.
Once the image is displayed, and the window has the
focus, there are a number of commands available.
A command is a single character typed at the keyboard,
which will immediately trigger the requested operation.
Some operations make use of an area of interest,
defined by pressing the left mouse button and dragging
the cursor over a section of the image, before executing
the command. Pressing the button and immediately releasing it
defines a single point as the area of interest.
- q
Quit ximage (also Q or <ctrl>-D).
- <space>
Redraw the area of interest.
- <ctrl>-R
Redraw the entire image.
- <return>
Quit ximage (also Q or <ctrl>-D).
- l
Display the luminance value in the area of
interest. This assumes that the image was correctly
computed in terms of luminance.
- c
Display the color in the area of interest.
- p
Display the x and y location of the cursor.
- i
Identify identical pixels by assigning a random
color at the cursor position. This is useful
for displaying contours.
- t
Print information about the pixel under the cursor
to standard output. This command is only useful when
ximage is run seperately from Rayfront.
Please refer to the ximage(1)
man page for more detail.
- =
Adjust the exposure to the area of interest. A
crude adjustment is made immediately, and the
number of stops is printed while the colors are
resampled. After a few seconds to a minute, the
final image is redisplayed. If the area of
interest is already within 1/2 stop of the
ideal, no adjustment is made.
- @
Same as '="'" command, only the exposure is
adjusted to provide roughly the same visibility
for the selected region on screen as a viewer
would experience in the actual space. Like the
'l' command, this adjustment assumes that the
image has been correctly computed in terms of
luminance. (See also the 'h' command, below.)
- a
Perform automatic exposure compensation. If
a rectangular area has been selected, the pixels
in this region will be emphasized in the histogram,
offering this area exposure preference.
(Each pixel within the rectangle will be
weighted as 21 outside pixels.)
- h
Perform human expsoure compensation. See
the 'a' command above regarding pixel weighting.
- 0
Reset the origin to the upper left corner of the
image. This command is used to restore the
original image position after using the shift or
control key with the mouse to relocate the image
within the frame (see below).
- f
Switch on the fast redraw option, loading
the image pixmap over to the server side. This
command is useful when network delays are caus
ing slow image refresh.
- F
Switch off the fast redraw option. This frees
up some memory on the server, as well as the
color table for other windows.
In addition to the commands listed above, the control or
shift key may be held while the cursor is dragged to reposition
the image within the window.
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