.MSK File Extension

Layer mask created by Paint Shop Pro (PSP), an image-editing program; stores the height, width, resolution, and the mask, which is stored as a grayscale image; used to cover parts of an image, or to create fading effects.

MSK files store shades of gray that define the varying degrees of the image mask. Where the mask is black, the underlying image is not visible. Masks can be built in Paint Shop Pro using preset shapes and sizes.

NOTE: PaintShop Photo Pro, the successor to Paint Shop Pro, does not support MSK files.