This function overlays a logical mask on top of an image (with user-defined color and opacity) and creates a flattened image without an alpha channel. The resulting output can be treated as another image data. Interactive explorations, such as zooming, panning, and data tips, are faster, because the image does not contain an alpha channel.
flattenMaskOverlay(img, mask, opacity, color);
See the published example for more information.
Fixed alphaLevel bug and example bug.