Tcl/Tk Device (/xtk)
Color Capability
Device Size
Plot Area
Coordinate Info
Zoom
Viewport Switching
Color Table
Adjustment
Missing Data
"File" Menu
"Edit" Menu
"Help" Menu
The recommended interactive device for XIMAGE 4.0 and beyond is the /xtk device. This device provides zoom, recenter, and color adjustment capabilities through a GUI interface.
By default, 100 colors are allocated to the /xtk device,
however, this may be changed through the global Tcl variable,
xtkcols, up to a maximum of 255. If you wish to use the maximum
number of colors available every time you run ximage (for
example, your display is capable of 16-bit or higher), edit your
~/.ximagerc file to contain the line: set xtkcols 255.
This variable may also be set while executing ximage, however,
if the /xtk device is already in use, the setting will not
take effect until it is closed and plotted to again.
Ximage reserves color indices 0-15 as
default colors which remain
unchanged regardless of the current color table. Indices from
16 up to the color capability of the device are available for
image display. The number of color levels is determined by
the number of levels set with the levels/num= command
(16 by default). The number of colors used in image plotting
is one more than the number of levels, hence the maximum number
of levels that may be used with the /xtk device is 238 (i.e.
levels/num=238), although levels divisible by 4 are
recommended, such 16, 64, 216, etc. as the scale command
is better suited for such values.
By default, the size of the plot area in the /xtk device is
760x576, however, the width may be changed through global Tcl
variable, xtkwid, and the height may be changed through
xtkhgt.
It is best to preserve the same aspect ratio when changing
sizes, otherwise some viewport settings will have unwanted
spacing. If the /xtk device is already in use, size changes
will not take effect until it is closed and plotted to again.
The plot area is where the images, contours, etc appear in the
/xtk device. The size of the plot area is fixed, however, if the
window's size is adjusted smaller, the visible portion of the
plot decreases. The scroll bars may be used to adjust which
portion of the plot area is visible.
The following actions are defined in the plot area:
Mousing over the plot area updates coordinate information,
including sky (RA/Dec), galactic, detector and image
coordinates as well as the value of the pixel at that location.
To perform plot zooming without changing the center, use
the Zoom buttons.
When viewports are defined (e.g. viewport 3x2 for the
pictured example), all
actions, such as displaying coordinate information and zooming,
apply to the current image, which is the last plotted image
by default. The current viewport, however, may be changed by
using the viewport selector:
A box is drawn representing each plotted viewport, numbered for the order
defined in the viewport file. The viewport highlighted in
blue is the current viewport, to which mouseover coordinates,
zooming, etc. apply.
The current viewport may be changed by clicking inside the
viewport as it is represented in the viewport selector.
Note: the position where the next viewport will be displayed is
not affected by the viewport selector.
Use the sliders to adjust the color table that is currently
being displayed. Clicking the left button on either side
of a slider, increments the value by the smallest division
in that direction. Left-clicking and holding allows you to
drag the slider to the desired value, while interim values
are plotted. Middle-clicking on any value makes the slider
jump to that position without plotting the effects of any
interim values.
The "Brightness" slider adjusts the brightness of
displayed color table. The default is 0.5 with available
values ranging from 0.0 to 1.0. If a scale is
displayed, the colors will appear to shift to the right as
brightness decreases, and the colors will shift to the left
as brightness increases.
The "Contrast" slider adjusts the contrast of
displayed color table. The default is 1.0 with available
values ranging from 0.0 to 4.0. If a scale is
displayed, the colors will appear to compress for higher
contrast values (bright spots get brighter and dark spots get
darker) and spread out for lower contrast values.
The "Reset" button returns the brightness to the
default value of 0.5, and the contrast to the default value
of 1.0.
Note: depending on the color capability of
your display, the adjustment of color tables will have
a slightly different behavior.
For 8-bit PseudoColor displays, all color adjustments will
be virtually instantaneous, as you drag the slider. For
more color-capable TrueColor displays, changing the colors
requires a redraw, so there is a slight delay between changes.
It is not recommended that you drag the slider in this case,
but rather jump to a specific contrast or brightness setting
by clicking the middle button on the desired value.
The /xtk device is unique from all other devices as it can zoom
images and contours already displayed, while retaining labels,
boxes, etc. that are on the image. The device is actually
keeping track of everything as it is plotted. Image maps,
however, are usually quite large, so all that is remembered is
the mapid (e.g. MAP1, EXMAP1). When a displayed map is freed, moved,
or another map is read into its place, the /xtk device cannot perform any
action which requires access to the original map, such as
retrieving mouseover coordinate information and zooming. If you
attempt to perform such an action, an error will be displayed:
"Original map data is unavailable". In special cases where
some maps are available and some are not, a warning is presented:
The safest option is "Cancel" which leaves the plot untouched.
If you are sure you wish to redraw the image, however, "OK" will go ahead and
plot all the images that are still available, omitting those that are
not. Note: if you are using multiple viewports the order will also
change to fill in where the missing images were. In general, the "OK"
option is not recommended. To avoid this situation, ensure that all
the image maps you wish to plot on one screen are loaded in the
available slots (MAP1-9).
Note that there is a special feature implemented in ximage which
attempts to improve the missing data situation. When an image map
is copied with the map copy command, a linkage between the
two maps is created, which recognizes them as exact duplicates. If
a map that has been plotted is overwritten or modified through a
command such as smooth, further replots that need the original
map will be able to refer to an unaltered copy if one exists in
any other map slot.
The "File" menu contains two options for recording the plot area,
"Print..." and "Screen Grab..." The Print option switches to
a PostScript or GIF device and redraws everything.
In the "Print" window, there are three output options:
By default the output file is drawn using "Color" as the plot area
of the /xtk device is in color, however, when printing to paper
white on black color tables are not optimal. Clicking on the
"Greyscale" option switches to the invgray color table,
and temporarily changes the /xtk device to that color table for
a preview.
Press the "Print" button to initiate writing to a file and
printing, if applicable. Note: the /xtk device will not
be able to update until the operation is complete. To exit
the "Print" window without doing anything, press "Cancel"
If, however, all data is not available for items in the
plotted area, the "Print..." option will be unable to reproduce
the plot as it appears. In this case, the "Screen Grab..."
option is recommended.
There are two methods for performing the screen grab, "xv" and
"ImageMagick convert". The default, "xv", raises the /xtk device
and uses xv to crop the plot area. You must save the image from
xv or it will be lost.
The "ImageMagick convert" method requires ImageMagick to be installed,
however, it is much more automatic than the "xv" method. When this
method is selected the "Image file:" field becomes available for
editing. The filename entered in this field, which is pgplot.gif
by default, determines the type of the converted file by its extension.
GIFs are recommended. The uncropped grab, pgplot.xwd, is deleted
automatically after the output file is written.
The "File" menu also contains a "Close" option which closes the /xtk
device. This is equivalent to using the close_pg_window command.
The "Edit" menu contains quick access to a couple commonly used
ximage commands, grid, which overlays a grid of sky coordinates
on the image, and scale, which plots a legend representing the
values assigned to each color in the image.
The difference is that "Show Grid" and "Show Scale" are checkboxes which
allow these annotations to the plots to be turned on and off
without redisplaying the image.
Selecting "Ximage" from the "Help" menu is a simple way to connect
to the latest online help for ximage, provided Netscape is running.
Click "OK" to send a current Netscape browser to the main ximage
page. Selecting "Cancel" will close the window with no effect.
Color Capability
Device Size
Plot Area
Note, if an interactive command is executed, such as
centroid/cursor, these actions are suspended until the
command is finished requesting mouse input.
Coordinate Info
Zoom
Viewport Switching
Color Table Adjustment
Missing Data
"File" Menu
The orientation of the output file defaults to "Landscape" as
this matches the aspect ratio of the plot area. The
"Portrait" orientation inverts the width and height of the plot area.
Combining the "Portrait" mode with multiple viewports may cause
unwanted spacing to appear between the viewports.
The uncropped grab, pgplot.xwd, will remain in your directory unless
removed manually.
"Edit" Menu
"Help" Menu
Please send reports of errors to :
xanprob@athena.gsfc.nasa.gov
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Last modified: Wednesday, 29-Mar-2006 14:44:33 EST