Transparent Image on Background

Allows to merge a background with a transparent foreground without using alphadata.

This quite simple function (immerge.m, as in "image merge") allows to display two images, one on each other, the one in the foreground being transparent (transparency weighted).

Creates an image 'out'.
'out' has 'bg' as background, and 'fg' (transparent, weighted by 'coef') above 'bg'.
Useful when one cannot use OpenGL as renderer, but still wants to have transparency!
'out', 'bg', and 'fg' are RGB images.

merged = immerged(bg, fg, coef)
- bg matrix of type double or uint8
- fg matrix of type double or uint8
- coef is a scalar between 0 and 1, or a matrix of such scalars, same (r,c) size as 'fg' and 'bg' (similar to AlphaData).

Suggestions for future development:
- allow to have 'coef' referring to the AlphaMap
- allow 'coef' to take values between 1 and 64.

The function comes with a short demo script.