Optimized RGB and RGBA Compositing

[Shane_W_]

Is there anything in the IPP that will accomplish using the Alpha channel of RGBA image to overlay the RGB components onto an RGB image or to a new image?  I've taken a look at the ippiAlphaComp() functions, but they do not seem to allow mixing of C4R and C3R.

Basically looking for this:

SourceB = RGB image

SourceO = RGBA image

SourceB = (SourceO x SourceO) + (SourceB x (255 - SourceO))
SourceB = (SourceO x SourceO) + (SourceB x (255 - SourceO))
SourceB = (SourceO x SourceO) + (SourceB x (255 - SourceO))

[Igor_A_Intel]

Hi Shane,

yes, mixing in this case doesn't work. Possible way is to convert C3 image to AC4 (ippiCopy_8u_C3AC4R), fill A channel with "1" and then use ippAlphaOver function that applies aA*A+(1-aA)*aB*B formula. I guess it will be too expensive from the performance point of view and it's better to use the simple loop in your code.

regards, Igor

[Shane_W_]

I ended up asking a similar question on stackoverflow, here is the link that will hopefully aid someone else.

http://stackoverflow.com/questions/22018826/implement-a-near-real-time-cpu-capability-like-glalphafuncgl-greater-with-rgb