Graphics

Graphics can be done either in an image channel or in the overlay channel which is associated with the display window. The overlay channel is always the highest numbered channel of a display and put on top of any displayed image channel. However, it is not implemented like an image channel. Therefore, only drawing and labeling functions are supported (i.e. you cannot load an image into the overlay channel).
 
All plotting functionality is provided via the family of DRAW commands for different shapes. For writing text you choose a specific character font via a font no.
This number refers to a font name as stored in the ASCII file
MIDASHOME/MIDVERS/systab/bin/x11fonts.dat (Unix syntax).
Three fixed font sizes as well as one dynamic font are supported for writing text. The fonts for the fixed sizes are chosen once via the INITIALIZE/DISPLAY command, the dynamic font can be set with each individual labeling command. ^7.1

The application procedure showfonts.prg lets you view the available fonts, as well as create the ASCII fonts file. The currently available commands associated with the use of the overlay channel are:

SET/OVERLAY - enable the overlay of graphics on top of the image
CLEAR/OVERLAY - disable the overlay
CLEAR/CHANNEL overlay - clear contents of overlay channel
DRAW/... - draw a geometric shape like CIRCLE, RECTANGLE, etc. in the overlay plane
LABEL/DISPLAY - write a string into the overlay channel