Combining several Bitmaps

[Frobot]

I am taking several bitmaps and drawing them onto a picturebox with a low opacity so that all of the bitmaps can be seen together as one picture.
My problem is that any time I need to re-draw this "final combined image", I have to put all of the pictures on top of each other again, which is slow when you're dealing with 100+ bitmaps.
How might I be able to draw each bitmap (with opacity) onto a new "final bitmap" rather than onto the picture box so that I can just paste in the final result quickly?

[Frobot]

Figured it out.
Just make a graphics from the final bitmap and draw each individual bitmap onto it using the same color matrix and it still works.

[BioPhysEngr]

Glad you solved your problem. If you're dealing with blending images with transparency you may also be interested in alpha blending; link: http://en.wikipedia.org/wiki/Alpha_compositing