Mask

What is it for?

• Keep only the needed part of an image
• Use a black-and-white mask to define visible areas
• Perform the opposite operation from Erase By Mask

Overview

The most basic mask-compositing node, cutting out an image with a black-and-white mask. Remember one rule—white remains, black becomes transparent—and you can apply it to circular icons, shape cutouts, and partial visibility.

Usage tips

• Masks usually come from three sources: shape_generate, where a white shape is already a mask; threshold, which extracts a condition from an image; and path_mask, which uses a path shape.
• Gray produces partial transparency. You can create a soft mask with a 1px gray edge, though binary black and white is the standard for pixel art.
• To cut out and then composite over another image, this node plus blend works in two steps, while blend_by_mask does it in one.

How to think about it

• White: remains
• Black: disappears
• Gray: remains at half opacity

Turn invert on to reverse the behavior.

Difference from Erase By Mask

• Mask
  • Keeps white areas
• Erase By Mask
  • Erases white areas

Use Mask to show only the mask shape.
Use Erase By Mask to cut a hole in the mask shape.

Technical details

By default, mask-image luminance is used as alpha: white areas remain, while black areas become transparent.
Turn alpha_enabled on to use mask-image alpha instead of luminance. Both invert and alpha_enabled can be promoted to input pins for shared or animated control.

Examples

1. Apply a circular mask to a character image to make a round icon.
2. Keep only the visible area defined by PathMask.
3. Turn invert on to hide only white areas.

Common pitfalls

• Everything disappeared / remained: the mask is pure black / pure white. Preview the mask, and remember that a color image is interpreted by luminance.
• Mask alpha has no effect: luminance is used by default. Turn alpha_enabled ON.
• Different dimensions cause misalignment: source and mask should normally match. Fit the mask with canvas_resize.

Related nodes

• erase_by_mask — the opposite direction, erasing white areas
• blend_by_mask — composite two images through a mask
• threshold / path_mask / shape_generate — mask sources
• mask_boolean — AND/OR/difference between masks