There is a bounty of cheap color LCD displays these days. Driving them requires some direct bit twiddling to do basic things like draw lines or circles or characters on them. The simple graphics library has a collection of these functions which are generally useful and not too heavyweight.
As an LCD driver where you can create a non-complex UI the following capabilities are provided:
- Write text to the screen in a large or small font, scale the font as desired but increasing the size of pixels.
- Text rotation of 0, 90, 180, and 270 degrees supported.
- Draw filled or open triangles, with colinear edges that correctly rasterize. So if you're building a pattern out of triangles it will look correct.
- Draw filled or open circles by specifying center and radius.
- Draw rectangles with square or rounded corners, either filled or open.
- Rotate the display so that the code can treat it as if it were correctly oriented, even if the LCD was wired up in an inconvenient orientation.
- Mirror the display so if your graphics are viewed through a mirror as they are on a "heads up" type display they appear correct to the viewer.
- Minimal porting, the code is portable so you just supply your own
draw_pixel(int, int, uint16_t)function which works in LCD display co-ordinates, pre-mapping based on orientation for you, and pre-clipped so the pixel writer doesn't get passed invalid X or Y values. - A set of basic tests that use ASCII as their color pallete so you can experiment on a machine without display hardware.