There are a number of APIs available for the Raspberry Pi that can make use of the computers GPU. These include OpenMAX, Open GL ES(1 and 2) and OpenVG. The raspberrypi/firmware repository has short examples for these and other APIs. They can be found in /opt/vc/src/hello_pi/ on the Raspbian 'wheezy' image. Among these examples is a program called hello_dispmanx. It is a very small example of the Dispmanx windowing system. Apart from this:-
https://github.com/raspberrypi/firmware/tree/master/opt/vc/src/hello_pi/hello_dispmanx
example, there is very little documentation available for this API. There are snippets of information on the Raspberry Pi forum, but I have not found a single place with detailed information on DispmanX. Hopefully these programs can be used as a starting point for anyone wanting to make use of DispmanX.
The programs demonstrate layers with the following types: 4BPP (4 bit indexed), 8BPP (8 bit indexed), RGB565 (16 bit), RGB888 (24 bit), RGBA16 (16 bit with transparency) and RGBA32 (32 bit with transparency)
This test pattern should be familiar to anyone who has used the Raspberry Pi. It is the same four colour square displayed when the Raspberry Pi boots.
Displays a triangle in a layer with red, green and blue gradients starting at each corner respectively. Blends to grey in the center. Demonstrates changing size of source and destination rectangles.
Conway's game of life. Demonstrates double buffering.
The program raspiworms uses a single 16 or 32 bit RGBA layer to display a number of coloured worms on the screen of the Raspberry Pi.
Load a png image file and display it as a Dispmanx layer.
Loads a sprite (png) image file and displays it as an animation.
Demonstrates a seamless background image that can be scolled in any direction. As well as animated sprites.
The famous (in the 1990s) Mandelbrot set.
An animation of a 'radar sweep' using 16 bit (rgb) palette animation.
An animation of a 'radar sweep' using 32 bit (rgba) palette animation.
An example of using an offscreen display to resize an image.
Code that may be common to some of the demonstration programs is in this folder.
If you type make in the top level directory, the make file will build all the different programs in this repository. Each program has its own make file, so you can build them individually if you wish.
You will need to install libpng before you build the program. On Raspbian
sudo apt-get install libpng12-dev