Overlays

An Overlay Plane describes graphics or bit-mapped text that is associated with an Image. It may also describe a Region of Interest in an Image. Each Overlay Plane is one bit deep. Sixteen separate Overlay Planes may be associated with an Image. Overlay data is stored in Overlay Data (60xx,3000).

Use the ImGearDICOM.LoadOverlay method to load graphic overlays from a DICOM DataSet to ART annotations. Use the ImGearDICOM.SaveOverlay to save ART annotations into a DICOM DataSet as overlay data.

DICOM overlays are monochrome images (see DICOM specification PS 3.3 - 2008, C.9.2 Overlay plane module) - pixels from overlay data with a zero value (i.e., black) will not be displayed; pixels with a non-zero value will be displayed.

Upon saving of ART annotations, all non-black pixels of annotations will be saved as overlay data. As a result, a text annotation that has a non-null or non-black fill color will be displayed as a square. To save the text only as an overlay, it is necessary to set the fill color of the annotation to null or black.