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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 yields 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)



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