ios - meaning of R, S, Da in kCGBlendMode values -


i'm having trouble grasping meaning of r = 0, r = s, r = s*da, defined in kcgblendmode values such kcgblendmodeclear, kcgblendmodecopy, kcgblendmodesourcein. so, these symbols refer?

r=0 means result color 0, meaning cleared.

r=s means result color same source color

r=s*da means result source color times alpha value of destination

if take @ documentation , scroll down see meaning listed:

the blend mode constants introduced in os x v10.5 represent porter-duff blend modes (a little explanation how work). symbols in equations these blend modes are:

  • r premultiplied result
  • s source color, , includes alpha
  • d destination color, , includes alpha
  • ra, sa, , da alpha components of r, s, , d

if furthermore take @ setting blend modes can see of blend modes applied , result may like.


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