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---
title: "Drawing Pixels in Plan9"
url: drawing-pixels-in-plan9.html
date: 2023-05-27T17:41:33+02:00
type: note
draft: false
tags: [plan9]
---
I have started exploring Plan9's graphics capabilities. This is a hello world
alternative for drawing that draws a yellow square on a blue background.
More information:
- [draw.h header file](https://github.com/0intro/plan9/blob/main/sys/include/draw.h)
contains all the drawing functions
- [draw man page](https://9fans.github.io/plan9port/man/man3/draw.html)
has a bit more digestable descriptions of the draw functions
- [graphics man page](https://9fans.github.io/plan9port/man/man3/graphics.html)
has a bit more digestable descriptions of the graphics functions
- [all man pages](https://9fans.github.io/plan9port/man/man3/)
can be a valuable resource for learning about the system
```c
// main.c
#include <u.h>
#include <libc.h>
#include <draw.h>
#include <cursor.h>
void
main()
{
ulong co;
Image *im, *bg;
co = 0x0000FFFF;
if (initdraw(nil, nil, argv0) < 0)
{
sysfatal("%s: %r", argv0);
}
im = allocimage(display, Rect(0, 0, 300, 300), RGB24, 0, DYellow);
bg = allocimage(display, Rect(0, 0, 1, 1), RGB24, 1, co);
if (im == nil || bg == nil)
{
sysfatal("not enough memory");
}
draw(screen, screen->r, bg, nil, ZP);
draw(screen, screen->r, im, nil, Pt(-40, -40));
flushimage(display, Refnone);
// Wait 10 seconds before exiting.
sleep(10000);
exits(nil);
}
```
And then compile with `mk` (mkfile below):
```makefile
# mkfile
</$objtype/mkfile
RC=/rc/bin
BIN=/$objtype/bin
MAN=/sys/man
main:
$CC $CFLAGS main.c
$LD $LDFLAGS -o main main.$O
```
And run with `./main`. To exit the program, press `Delete key` (strange but this
is the alternative for Ctrl+C).
*This is **very cool** indeed!*
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