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Chapter 6 ....continued
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The Zoom function button is used to enlarge any part of an image drawn in the display window. Once selected, the button label changes to Zoom out, despite the fact that there is a separate Zoom out button listed below this button. Pressing this will result in an unzoom of the enlarged area.
6.4.13
The Zoom button
Example 15 The user needs to zoom in on a section of an element network.
Display the .elm file Press the Zoom button in the menu window The mouse cursor changes to a cross-hair
Move the mouse cursor to the display window. Position the centroid of the cross-hair cursor on the upper left-hand corner of the section you wish to zoom in on, then press any mouse key Keeping the mouse key depressed, drag the cursor to the lower right-hand corner of the section you wish to zoom in on, then release the mouse button An expanding box appears in the display window as the cursor is dragged from the upper left position to the bottom right position. When the mouse button is released, the display window is refreshed with an enlarged view of the area within the box
The Zoom out function button is used to cancel any enlargements of screen images initiated using the Zoom button. It has the same effect as pressing the Zoom button twice.
6.4.14
The Zoom out button
The Digitise function button is used to digitise lines and polygons in the display window and write these to a file for use in ancillary Topog programs. Multiple lines or polygons can be saved in any one file and several files can be generated in any one digitise session. Saved polygons are written to a file called basename.dat.[a-z]. If a .dat.a file exists within the operative directory, the program will write to a .dat.b file. The program continues to automatically update the file name extension as more polygon files are created. It is advisable to rename the .dat files.with more meaningful names, to allow easier user recognition.
6.4.15
The Digitise button
Example 16 The user wants to digitise two polygons on the screen which will be used for denoting the distribution of catchment soil type.
Press the Digitise button in the menu window In the upper left-hand corner of the information area appears a block of diagnostic information. This includes the name of the file to which the digitised data will be written (eg; basename.dat.a). The polygon number and the name of the file that will contain the digitised polygons are also displayed in the information area. The mouse cursor turns to a cross-hair
Move the cursor to the display window and press the mouse at each point used to define a polygon. No data is created until you release the mouse button, so if you keep the button depressed you can experiment on the position of the polygon line; just let go of the mouse button when the line position looks right. A red line will be drawn between each defined point in the polygon. After two points in the polygon are chosen, the label on Digitise button changes to read New Poly. Clicking this button once instructs the program that you wish to digitise another polygon for inclusion in the same file. Clicking it twice will result in all data digitised thus far being saved to file.
Press the New Poly button to begin digitising a second polygon for inclusion in the same file The number of the new polygon (ie: Polygon #2) is displayed in the information area and the New Poly button label changes to read Save
After you have finished digitising the second polygon, press the Save button The polygon data is written to file and the program exits from Digitise mode
The Colours function button is used to change the colours and style of lines and points mapped in the display window. Once the button is pressed it changes to Style mode that allows line thicknesses and point symbols to be changed.
6.4.16
The Colours button
Example 17 The user wishes to change the colour and style of saddle data points (ie: a .sad file) mapped in the display window.
Press the Colours button in the menu window A list of all attributes and files currently mapped in the display window is listed in the selection area
Select the "Saddles" option from the selection area A colour palette appears in the information area of the menu window and the function button label changes to read Style
Select the desired colour from the palette by clicking on that colour The colour of the saddles is changed in the display window
Press the Style button in the menu window A symbol palette appears in the information area of the menu window. If a line type file had been selected then a lines palette would have appeared instead
Select the desired symbol from the palette by clicking on that symbol The symbol used to represent the saddles is changed in the display window
The Dump function button is used to capture screen images for output to a colour printer. When the button is pressed, all information in the display window is written to two files:
6.4.17
The Dump button
Dump_File an xwindows dump (xwd) format file Dump_File.ps a postscript format file Most modern printers can process the second file.
Example 18 The user wants to dump the screen image in the display window.
Press the Dump button in the menu window One beep sounds at the start of the dump, two beeps sound when the dump is finished. The image in the display window is written to files Dump_File and Dump_File.ps.
The QUIT button is used to terminate a session with Topog_Display.
6.4.18
The Quit button
6.5 |
Some hints on using Topog_Display |
Display window screen images dumped using the Dump function button can be reviewed by using the xwud command. This is a command line operation that must be invoked outside of program Topog_Display.
6.5.1
Reviewing a dumped file
The image stored in Dump_File will be drawn in the display window. Alternatively, the file Dump_File.ps can be viewed using the common UNIX program, "Ghostscript".
To invoke the xwud command, type: $ xwud < Dump_File
If you do not want to sacrifice a process window, Topog_Display can be run in background mode by typing:
6.5.2
Operating Topog_Display in background mode
at the program startup stage. By doing this, you can toggle back to the parent window and execute command line functions.
To run Topog_Display in background mode, type: $ _display &
The size, location, colour and style of the display window and menu window in Topog_Display can be customised by modifying the .Xdefaults file. See Appendix D for further details.
6.5.3
Customising the size and appearance of your windows
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