Op 20-3-2012 14:17, Josiah Bryan schreef: > > So it all boils down to this: > Is there any way to force QPainter (or, heck, just do it on a raw > OpenGL surface and skip QPainter/QImage all together) to blend things > where 50% opacity + 50% opacity = 100% opacity in the resultant image? > > Or, as some might say, am I just waayyyy off base here? Perhaps the > mere mention of this idea is causing Porter and/or Duff to want to > smack me with a stick...I don't know. Any thoughts? I *think* what you need to do, is this:
* Express the progress of your face as a value between 0 and 1. Let's call this p * Create a transparent image with the right size. This will be image F (foreground) * Render image A with 1-p opacity into F * For each pixel in B, add the values for that pixel B*p to the corresponding pixel in F * Render F over your background image, at 100% opacity. The result should be that a pixel i,j in F contains 255, 0, 0 at all times if both images A and B contain that value at i, j. However, I think the fourth step will be slow, but I don't thing there is a standard composition mode that does what you want by default. I'm not 100% sure how to deal with alpha channels in A and B though, if they are not just 0 or 255. André _______________________________________________ Interest mailing list [email protected] http://lists.qt-project.org/mailman/listinfo/interest
