Combine Multiple Masks

Common operations for merging masks from multiple sources.

Union (logical OR)

Combine regions from any of the masks:

combined = mask1 | mask2

# Or for many masks:
combined = RLEMask.union([mask1, mask2, mask3, mask4])

Intersection (logical AND)

Keep only regions present in all masks:

overlap = mask1 & mask2

# Or for many masks:
overlap = RLEMask.intersection([mask1, mask2, mask3])

Difference (subtract)

Remove one mask’s region from another:

# Pixels in mask1 but not in mask2
difference = mask1 - mask2

XOR (exclusive or)

Pixels in exactly one mask, not both:

xor = mask1 ^ mask2

Layer compositing

When stacking objects front-to-back, compute visible portions:

# Objects sorted back-to-front (furthest first)
occluder = RLEMask.zeros(shape)

for obj in reversed(objects):
    # What's visible = instance minus everything in front
    obj.visible_mask = obj.instance_mask - occluder
    occluder = occluder | obj.instance_mask