Masks

The mask annotation renderer keeps compressed RLE masks semantic in detection frames. BaseMaskStyle controls the visible fill, global opacity, outline, and render mode while the browser package privately prepares efficient artifacts.

Add the mask renderer

session.setPresentation({
  renderers: [
    annotationRenderers.mask({
      style: new BaseMaskStyle({
        fillAlpha: 1,
        opacity: 0.72,
        stroke: { alpha: 1, width: 2 },
      }),
    }),
  ],
});
Copy

opacity applies to the complete mask layer and can be updated cheaply. fillAlpha is part of prepared fill styling and remains separate so an outline can stay opaque.

See Detections And Rendering for the semantic-mask and prepared-artifact boundary.