You cannot use AutoCAD Raster Design toolset commands that apply to an entire image if REM objects are associated with the image. Such commands include Despeckle, Mirror, Invert, Histogram, and Crop. Commands that operate on a sub-region of an image are allowed only if the bounding box of the edit operation does not overlap any REM objects.
When you create REM objects in an image, you must finish all REM edits and merge, convert, or remove all REM objects before you can do any raster editing.
If you attempt to perform a non-REM edit that overlaps a REM object, the AutoCAD Raster Design toolset Edit Status dialog box is displayed. Clear the REM objects or merge the objects into the image before editing the entire image.