How to get the alpha channel data information?

[_Prabudass_]

How to get the alpha channel data information. Sometimes alpha channel also contains data(information). So i need to know wheather the alpha channel contains data or not through scripting. Could you please advice me.

[Michael_L_Hale]

All channels contain data. You can tell if an alpha channel is black, white, or greyscale by the histogram.

For example if activeDocument.channels.getByName('myAlpha').histogram[0] == the number of pixels in the doc the alpha is all black. use histogram[255] to test for white.