Channel_Boolean

For ex Fusion users  (and everyone else!) who miss the 'Channel Boolean' tool, here's a similar tool in Nuke

1) Choose operation  (copy, multiply, substract....)

2) Choose channels (example if you want channel R from A image to multiply RBGA of B image, select 'red' in scroll down menu

beside the red,green,blue and alpha parameters)

3) If you uncheck the red, green, blue or alpha checkbox, it is the same as selecting 'Do Nothing' in the drop menu in Fusion

4) If you have a MASK input, select the channel (RGBA) you want to use as the MASK

5) The Bypass switch, if activated, will let the B image pass through