Overlays Overview
(Medical only) 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 provides functionality to manipulate overlays in DICOM. The GetOverlayCount method gets or sets the number of overlays in the DICOM Data Set. The attributes of an overlay can be obtained using the following methods/properties:
The OverlayAttributes property is a pointer to an ILEADOverlayAttributes object that contains a number of properties, which can be set by the user. These attributes are broken into two categories:
Display properties
These properties specify how an overlay gets painted:
BitPosition property (ILEADOverlayAttributes)
Color property (ILEADOverlayAttributes)
OriginX property (ILEADOverlayAttributes)
OriginY property (ILEADOverlayAttributes)
DICOM-related properties
These properties are DICOM specific and are based on the "Overlay Plane Module Attributes" defined in PS 3.3 of the DICOM standard:
ActivationLayer property (ILEADOverlayAttributes)
BitsAllocated property (ILEADOverlayAttributes)
Columns property (ILEADOverlayAttributes)
Description property (ILEADOverlayAttributes)
Flags property (ILEADOverlayAttributes)
ImageFrameOrigin property (ILEADOverlayAttributes)
Label property (ILEADOverlayAttributes)
NumberFramesInOverlay property (ILEADOverlayAttributes)
ROIArea property (ILEADOverlayAttributes)
ROIMean property (ILEADOverlayAttributes)
ROIStandardDeviation property (ILEADOverlayAttributes)
Rows property (ILEADOverlayAttributes)
Subtype property (ILEADOverlayAttributes)
Type property (ILEADOverlayAttributes)
Use the GetOverlayBitmap method to retrieve the "Overlay Data" (60xx,3000) for a single-frame overlay.
The UpdateOverlayBits method updates the overlay bitmap pixels with the bits from the corresponding bitplane of the main bitmap, or it updates the main bitmap’s bitplane with the data from the overlay bitmap.
LEADTOOLS also allows you to insert a new or update an existing overlay. Use the SetOverlayAttributes method to set the attributes of a certain overlay and then use the SetOverlayBitmap method to set its data.