This is a simple narrative description of the blending application included with the Lumen library as a demo.

The blending demo accepts two command-line parameter, which are the names of two image files in any format Lumen supports. The Crate.bmp and Glass.bmp images were added to support this demo, but any two images will work, though maybe not be as pretty. You invoke blending by typing its name followed by the two image names, like bin/blending data/Crate.bmp data/Glass.dmp. When run, blending creates a window with the two images "blended" in it, starting with the default parameters. The images are offset; the overlapping area is where they are blended together.

The window should have a black background with the blended images overlapping. With the default parameters, one or both of the images might not be immediately visible, but they're there. Terminate the app by pressing the Escape key, or by closing the window.

While it is running, you can cycle through the various blending equations (add, subtract, reverse subtract, min, max) by pressing the "e" key. You can cycle through the source and destination factors (zero, one, color, source alpha, and many more--consult the OpenGL documentation for the glBlendFunc routine) by pressing the "s" key to cycle source, and the "d" key to cycle the destination. The app prints out a summary of the parameters it is using onto the terminal where it was started. This can be a useful tool for quickly seeing what two images will look like when blended with a given set of parameters.

The blending demo uses the single-handler Lumen.Events.Animate.Receive_Events call for its event loop. It doesn't do animation, though it does use double buffering. Ask the author why, because I don't know!

Last Updated: 14 Dec 2011 09:32:32