Units ; Scaling ; Transformation - Page 158

2001/10/02 

CHAPTER 4 HP-GL/2 - 10 

5. 

THE HP-GL GRAPHICS WINDOW 

5.1. 

Units 

When you first enter graphics mode, the prevailing coordinate system has its origin in the bottom left hand 
corner of the graphics window and has x- and y -units of 1/1016".  Using the SC command you can divide the 
axes into more convenient units.  The size of the graphics window remains unaltered. 

5.2. 

The Scaling Points P1 and P2 

Many instructions use two refere nce scaling points ,  P1 and P2.  Initially these are in the bottom left and top 
right hand corners of the graphics window respectively.  You can alter the position of these points relative to 
the graphics window,  or relative to one another, by using the IP or IR commands. 

5.3. 

Scaling 

You can easily scale images up or down by increasing or decreasing the distance between P1 and P2.  You 
can do this both with existing images that are to be imported and with images that are generated by a s tring of 
HP-GL and HP-GL/2 commands, identical commands can be used to create the same image in different sizes. 

5.4. 

Transformation 

You can transform images horizontally or vertically by changing the relative positions of P1 and P2.  You can 
do this both with existing images that are to be imported and with images that are generated by a string of HP-
GL/2 commands.