This simulates a virtual, simplified 9-pin dot matrix ("impact") printer. Currently, this only supports plain text and only CR/LF. I'll add other control characters (like tab) and ESC/P support later.
9-pin dot matrix printers were pretty common in the early personal computing era. For the idealized (i.e. simplified) case, assume that the "top 8" pins are only for printing characters, and the 9th pin is dedicated for underline. I'll count from "zero" so it looks like this:
pin 7
pin 6
pin 5
pin 4
pin 3
pin 2
pin 1
pin 0
pin 9
Let's do some quick math. If we assume 9 pins to print a "line" and leave an extra "pin height" gap between lines, then each line is effectively 10 "pins" high.
For 66 lines on an 11-inch piece of paper (US Letter) that works out to 60 DPI.
If we assume 60 DPI horizontally, then for an 8 1/2 inch paper (US Letter) at 10 CPI, that works out to 5 pins for each character, plus an extra "pin width" gap between each character. So 6 pins total:
012345
7 *****.
6 *****.
5 *****.
4 *****.
3 *****.
2 *****.
1 *****.
0 *****.
9 -----.
x ......
Doing the math, we can figure out how many "pins" or "dots" or "pixels" define a single sheet of US Letter paper:
- 8 1/2 inches x 60 DPI = 510 px wide
- 11 inches x 60 DPI = 660 px tall
That means:
- 640x480 is wide enough, but too "short"
- 800x600 is also wide enough, but still too "short"
- 1024x768 is both wide enough and long enough
The virtual printer generates 510x660 images in 1024x768 that simulate US Letter printed pages. Here is what that looks like:
