I am in the process of compositing a number of solid color images, using masks which extend to the each edge.
The process entails using multiple numbers of these masks and multiple images. During the process, I have to subtract portions of each mask, using the freehand subtract tool. When doing this subtraction, I have to subtract portions which abut the edges.
As a quick example, I generate a mask that is only white in each corner and black in the rest of the space, so four white sections which extend right up to the image edge. I composite two images using this mask. I then composite this image with another, and subtract three of the white corner areas, leaving a single white area. To do this, I draw a subtraction boundary around the three areas I wish to eliminate and to do this I start the cursor inside the image, then extend the cursor off the page (but the white subtraction line can be seen moving along the image edge) as I encircle the three areas. After the three areas are encircled along the four edges, I cut back into the image to join the subtraction area.
I do this mask subtraction process a number of times during multiple composites (for the most recent image, I had to do this over 30 times).
However, I have found that this results in a (fine, like one or two pixel width) line along the upper and lower edges, where I drew the freehand subtraction outside the image edges. Visually, I can't determine if this occurs along the two side edges. As the images are all solid color, this line is quite visible and is the same color as the previous image, as if the subtraction area did not fully encapsulate the edge(s) where I went off-image.
How do I prevent this line from occurring? I could either clone over the line or crop the image, both of which I don't wish to do.
Marv
Subtract Mask
Moderator: jsachs