NAME
ximage - RADIANCE picture display for X window system
SYNOPSIS
ximage [ =geometry ][ -di display ][ -c ncolors ][ -d ][ -b ][ -m ][ -g
gamma ][ -f ][ -e spec ][ -ospec ][ -t intvl ][ -s ] picture ..
DESCRIPTION
Ximage takes one or more RADIANCE picture files and displays them on an
X server. The -c option specifies the number of colors to use (default
fills color table). The -d option turns off color dithering. The -b
option displays the image in black and white (greyscale). The -m
option forces monochrome output. The -g option specifies the exponent
used in gamma correction; the default value is 2.2. The -f option
stores a Pixmap on the server side for faster refresh. This may not
work with large images on some servers. The -o option specifies a
sequence of information to print to the standard output for the ’t’
command (see below). The -t option specifies a minimum interval (in
milliseconds) between successive ray outputs in mouse tracking mode
(right button pressed).
The -e option specifies an exposure compensation in f-stops (powers of
two). Only integer stops are allowed, for efficiency. If the special
word, auto is given instead of a number of stops, then ximage performs
an automatic exposure adjustment similar to pcond(1), compressing the
dynamic range of the image to fit within the dynamic range of the
display. If the special word, human is given instead, then ximage
performs an exposure adjustment similar to pcond with the -s and -c
options, which compensate for human contrast and color sensitivity at
the corresponding scene luminance levels. This option yeilds and
appearance of the scene on the display that closely matches what would
be experienced in the real world.
The -s option tells ximage to display multiple pictures sequentially,
rather than all at once. If no picture is given, input is read from
stdin provided either the -b or -m option is in effect, or the X server
is capable of 24-bit color. However, many of the commands given below
will not work.
COMMANDS
Once a picture is displayed, the user may perform a number of
operations. Some of the 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. Pressing the button and immediately releasing
it defines a single point as the area of interest. A command is a
single character.
q Quit picture. (Also Q or ^D.)
<space> Redraw the area of interest.
^R Redraw the entire image.
<return> Display the radiance averaged over the area of interest. The
maximum of the three (RGB) channels is reported.
l Display the photometrically-weighted 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, as adjusted by the
current exposure setting.
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,
especially when combined with the -b option.
t Print information about the pixel under the cursor according
to the string following the -o command line option. The
valid characters for this option correspond roughly to the
other ximage commands:
o ray origin
d ray direction
v radiance value
l luminance value
p pixel position
The default output is "-ood", which prints the ray origin and
direction. This can be used as input to rtrace(1) to get
additional information about the image (ie. pipe the output
of ximage into rtrace). Pressing the middle mouse button is
equivalent to typing the ’t’ key. Pressing and holding the
right mouse button is equivalent to continuously pressing the
’t’ key.
= 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, as if ximage were
started with the -e auto option. 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, as if ximage were
started with the -e human option. 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 (-f), loading the image
pixmap over to the server side. This command is useful when
network delays are causing slow image refresh, and the user
didn’t notice it until after ximage was started.
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.
X RESOURCES
radiance.gamma the default gamma correction value
ENVIRONMENT
DISPLAY_GAMMA the default gamma correction value
AUTHORS
Greg Ward
Anat Grynberg (Paris)
Philip Thompson (MIT)
SEE ALSO
aedimage(1), normtiff(1), pcond(1), pfilt(1), rpict(1), rtrace(1),
rvu(1), xglaresrc(1), xshowtrace(1)