McIDAS Learning Guide
Version 2006

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Graphics and the Cursor - Basic Concepts

Graphics

Graphics are lines and text that can be drawn on frames. Examples of graphics include: A frame can have several different graphics. For example, you can have a map and a temperature contour over a satellite image. By default, McIDAS graphics in McIDAS are independent from the displayed image in a frame. You can remove the graphics in a frame without erasing the underlying image.

Graphics Parameters

You can modify graphics colors using the GU command. Line width, dash and gap lengths, and the color of gaps in dashed lines can also be changed with the GD command.

Multiple colors are particularly useful for creating graphics displays with several overlays. The graphics commands assign colors through the use of levels. Each level is assigned one color. For example, by default, level 1 is magenta. The assigned colors are not fixed and you can assign different colors to the levels.

When the color of a level changes, all the graphics already drawn in that level are changed on the current frame.

By default, McIDAS-X has 35 predefined colors and 16 graphics color levels. Therefore, only the maximum number of color levels can be used at one time. However, you can change the color assigned to each level.

The following tables show the default color levels:

 LEVEL   COLOR         BLUE  GREEN  RED                                 
 -----  ----------     ----  -----  ---                                  
    0   BLACK             0      0    0   (Graphic background)          
    1   MAGENTA         255      0  255                                 
    2   CYAN            255    255    0                                 
    3   YELLOW            0    255  255                                  
    4   GREEN             0    255    0                                  
    5   RED               0      0  255                                 
    6   BLUE            255      0    0                                  
    7   WHITE           255    255  255                                
    8   GRAY            127    127  127                              
    9   GOLD              0    187  255                                  
   10   PINK            127    127  255                                 
   11   AQUAMARINE      147    219  112                                 
   12   ORCHID          219    112  219                                  
   13   NAVY            115      0    0                                   
   14   SKY             255    163    0                                
   15   BEIGE           127    171  255                                  
   16   PURPLE          127      0  127

Most McIDAS graphics commands are displayed with a default color level, but you can usually specify a different color level using a parameter or keyword.

Although McIDAS has predefined graphics colors, you can create custom colors using the GU command and specify intensities for each of the primary colors. The intensities range from 0 to 255; 0 is the darkest shade of the color and 255 is the brightest. The predefined colors and their intensities of blue, green and red are listed below. You can save new colors to a file called a graphics table which you can restore to an individual frame or a range of frames.

McIDAS has the following predefined colors:

Color Blue Green Red   Color Blue Green Red   Color Blue Green Red
 
 
Aquamarine 147 219 112   Grey 127 127 127   Red 255 0 0
Avocado 35 131 67   Green 0 255 0   Salmon 66 66 111
Beige 127 171 255   Khaki 95 159 159   Sienna 35 107 142
Black 0 0 0   Lemon 67 255 227   Sky 255 0 0
Blue 255 0 0   Magenta 255 0 255   Tan 112 147 219
Brown 35 35 127   Maroon 105 35 142   Thistle 216 191 216
Coral 80 127 255   Navy 115 0 0   Turquoise 234 234 173
Cyan 255 255 0   Orange 0 127 255   Violet 203 127 255
Firebrick 35 35 142   Orchid 219 112 219   Yellow 0 255 255
Gold 0 187 255   Pink 127 127 255   Wheat 191 216 216
Goldenrod 112 219 219   Plum 234 173 234   White 255 255 255
Gray 127 127 127   Purple 127 0 127

Drawing Maps

You can draw maps on frames containing nothing, an image and/or a graphic. To draw a map over a satellite image, the satellite image must be navigated; all real-time satellite images are navigated.

Virtual Graphics and Virtual Frame files

Graphics can be saved in eight formats:

Virtual graphics files contain only graphics. Virtual graphics are saved when they are created with the VIRT keyword. VIRT is a global keyword you can use with any graphics command.

The VIRT keyword assigns a number to the virtual graphics file for identification when restoring it with the SHOWVG command. For example, VIRT=1 writes the virtual graphic to file VIRT0001. Each workstation can have up to 9999 virtual graphics.

Virtual frame files save the entire contents of the frame, unlike virtual graphics files which save only the graphics. The RVF command restores the image, graphic, frame directory, navigation, image enhancement and graphics table that were present when the frame was saved with the SVF command.

The GIF, JPG, PPM, BMP, and PostScript formats save only the pixel brightness values. These formats are useful for displaying McIDAS images on workstations not running McIDAS.

Cursor

There are 4 cursor shapes:

To change the cursor size, shape and color, use the CUR command. The size is designated by height and width and should be defined in odd numbers. If you enter even numbers, they are rounded up to odd numbers. For example, if you specify a 20 by 20 pixel cursor, the cursor will be 21 by 21 pixels. The maximum size for a cursor in McIDAS-X is display dependent; the default is 31 by 31 pixels.

Use the PC command to place the cursor at specific positions, and the E command to list the coordinates at the cursor center.

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