transparency problem. pls help.

[marc2050]

Sorry. I must be missing something terribly...
The expected results I thought I should get is as shown in the attached file.
(ignore the checkboard patten in the background. main idea is the transparency, where does it start)

So, this expected result has the transparency starts from the middle of the window and then slowly goes back to the "rainbow" color. But the actual result, after commenting out the code you suggested ends up the opposite.
I really dont get it. What really am I wrong in understanding what I should get?
Thanks once again.