Syntax:

oldAlpha = setFigTransparency(hFig, alpha, fadeDuration, blockingFlag)

Description:
setFigTransparency sets the figure hFig's transparency value. The entire figure window, including all internal menus, toolbars and components, is made transparent according to the alpha value.

oldAlpha = setFigTransparency(...) returns the old transparency value of the specified figure, prior to its modification.

This submission is based on an original idea implemented by Malcolm Lidierth in his MUtilities submission: http://www.mathworks.com/matlabcentral/fileexchange/28326-mutilities

Input parameters: (all parameters are optional)

hFig (default=gcf) - Handle(s) of the modified figure(s). If component handle(s) is/are specified, the containing figure(s) will be inferred and used.

alpha (default=0.5) - Transparency value, between 0.0 (=fully transparent) and 1.0 (=fully opaque). Note that all Matlab figure windows are created opaque. alpha<0 indicates that alpha value should not be modified.

fadeDuration (default=0) - Number of seconds for fade-in/fade-out effect. Note: default value of 0 means immediately (no fading)

blockingFlag - (default=true) Whether or not the function should wait for the fade-in/fade-out effect to complete before returning

Examples:
oldAlpha = setFigTransparency(hFig,-1); % get hFig's current alpha
oldAlpha = setFigTransparency(hFig); % set hFig's alpha to 0.5 (semi-transparent)
oldAlpha = setFigTransparency(hFig,0.7); % set hFig's alpha to 0.7
oldAlpha = setFigTransparency([hFig1,hFig2],0.7); % set transparency for several figures
oldAlpha = setFigTransparency(hFig,0.3,1.5,false); % non-blocking fade over 1.5 secs

Bugs and suggestions:
Please send to Yair Altman (altmany at gmail dot com)

Warning:
This code heavily relies on undocumented and unsupported Matlab functionality. It works on Matlab 7.9 (R2009b) and higher, but use at your own risk!