03/13/2003
15-462 Graphics I
38
Image Compositing
•Compositing
operation
–Source:
s = [sr sg sb sa]
–Destination:
d = [dr dg db
da]
–b
= [br bg bb
ba] source blending factors
–c
= [cr cg cb
ca] destination blending factors
–d’
= [brsr + crdr bgsg + cgdg
bbsb + cbdb basa + cada]
•Overlay
n images with equal weight
–Set a-value for each pixel in each image to
1/n
–Source
blending factor is “a”
–Destination
blending factor is “1”