DTF Glossary
Colour knockout
A colour knockout removes or makes transparent pixels selected by colour criteria so a background or unwanted region does not print. It is distinct from alpha-threshold cleanup, which selects by opacity, and from white-underbase choke, which erodes a production mask. Tolerance and edge handling determine what the knockout preserves.
In practice
Colour similarity is not design intent. A broad tolerance can remove wanted highlights, antialiasing, or repeated colours elsewhere; a narrow one can leave a fringe. Compare the result over contrasting backgrounds and against the approved source.
Make a colour knockout in the source artwork editor, compare it with the approval and export a transparent PNG. In NestSheet, check the resulting physical size, alpha boundary and white coverage before preparing the sheet.