How can I draw text on a TImage and retain Alpha?

There's this...
Pixmap paste with mask although it's not quick for large images. RTT is a possibility.
For the wider than the top stuff can't you...
1) Draw rectangle with, for example, colour 255,0,255
2) Draw the text
3) Grab the area of text.
4) Setmaskcolor 255,0,255
5) Loadimage the text.
6) Draw Scroll
7) Draw Text image.