National Aeronautics and Space Administration

The following actions are defined in the plot area:

• Left-click: plot zooms in by factor of 2 and recenters
• Middle-click: plot recenters at clicked point (Zoom remains same)
• Right-click: plot zooms out by factor of 2 and recenters

• The "Zoom In" button zooms in by factor of 2
• The "Replot" button resets the image to the original zoom of 1
• The "Zoom Out" button zooms out by factor of 2
• The "Zoom:" field below these buttons reflects the current zoom factor

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.

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 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.

In the "Print" window, there are three output options:

• Printer - Writes to pgplot.ps and uses the entered "Print Command:" to send it to the printer
• PS File - Writes to PostScript file entered in "PS File:" field" (Default: pgplot.ps)
• GIF File - Writes to GIF file entered in "GIF File:" field" (Default: pgplot.gif)

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.

• Right-click the cropped image
• From "xv controls" click the "Save" button
• Enter the file name in the "Save file:" field (e.g. pgplot.gif)
• Press "OK"

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 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.

Click "OK" to send a current Netscape browser to the main ximage page. Selecting "Cancel" will close the window with no effect.