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blend OVERLAY mode (Read 1916 times)
mankyd
blend OVERLAY mode
Aug 15th, 2005, 3:24pm  
There seems to be no good/easy way to layer two PImage's together.  I have a dst PImage and I want to put overtop of it a src PImage.  I had to write a custom Overlay() function to do it.  Why not add an OVERLAY mode to PImage's blend() function?

I used the following blend function:

C = A * factor + B * (1 - factor)
where factor is a fraction based on A's alpha level.

Thus, the more transparent A becomes, the more B shows through.  I suppose it would be almost functionally equivalent to PGraphics.image() except that you'd have more control over starting coordinates and widths.
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fry
Re: blend OVERLAY mode
Reply #1 - Aug 17th, 2005, 7:49pm  
it's slated for beta, along with DIFFERENCE, MULTIPLY, SCREEN, HARD_LIGHT and SOFT_LIGHT, but they're just not finished yet.

although this was the function that quasimondo dug up for OVERLAY:
OVERLAY: C = B < 128 ? (2*A*B/255) : 255-2*(255-A)*(255-B)/255
which doesn't appear to be doing the same thing, though perhaps you aren't referring to what's "technically" called overlay.

previous thread on blend modes:
http://processing.org/discourse/yabb/YaBB.cgi?board=Proce55ing_Software;action=display;num=1082056702
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fry
Re: blend OVERLAY mode
Reply #2 - Aug 17th, 2005, 8:07pm  
better yet, since it's on the todo list, i've added it to the bugs db along with more details: http://dev.processing.org/bugs/show_bug.cgi?id=132

so if y'all can follow up there, that would be helpful. i'll just close this thread.
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