Could specify it in device coordinates ...
BUT, suppose we want to run program on several
hardware platforms or graphic devices.
Two common conventions for DCS:
- Origin in the lower left corner,
with x to the right and y
upward.
- Origin in the top left corner,
with x to the right and y
downward.
Many different resolutions for graphics display devices:
- Workstations commonly have 1280 1024 frame buffers.
- A PostScript page is 612 792 points, but
2550 3300 pixels at 300dpi.
- And so on ...
Aspect ratios may vary ...