Overlays Overview

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An "Overlay Plane" describes graphics or bit-mapped text that is associated with an image or has its own existence within a series. It may also describe a ROI in an Image.

Each "Overlay Plane" is one bit deep (1BPP). Sixteen separate planes may be associated with an image or exist as "Standalone Overlays" in a series.

Overlay pixel data is stored either in "Overlay Data" (60xx, 3000) or embedded in the "Image Pixel Data" (7FE0, 0010).

LEADTOOLS offers a number of functions to manipulate overlays in DICOM datasets.

L_DicomGetOverlayCount can be used to find the number of overlays in the DICOM dataset. Call L_DicomGetOverlayAttributes to retrieve the attributes of an overlay and L_DicomGetOverlayBitmap to retrieve the "Overlay Data" (60xx,3000) for a single-frame overlay or L_DicomGetOverlayBitmapList for a multi-frame one. L_DicomGetOverlayActivationLayer lets you get the activation layer for the overlay.

LEADTOOLS also allows you to insert a new or update an existing overlay. Call L_DicomSetOverlayAttributes to set the attributes of a certain overlay and then call

L_DicomSetOverlayBitmap or L_DicomSetOverlayBitmapList to set its data.

To delete all the elements related to an overlay call L_DicomDeleteOverlay.