Overlay Data Attribute
| Tag | (60xx,3000) |
|---|---|
| Type | Required (1) |
| Keyword | OverlayData |
| Value Multiplicity | 1 |
| Value Representation | OB or OW |
Overlay pixel data.
The order of pixels encoded for each overlay is left to right, top to bottom, i.e., the upper left pixel is encoded first followed by the remainder of the first row, followed by the first pixel of the 2nd row, then the remainder of the 2nd row and so on.
Overlay data shall be contained in this Attribute.
See Section C.9.2.1.1 for further explanation.
Section C.9.2.1.1
C.9.2.1.1 Overlay Type
There are two specific types of overlays. The type is specified in this Attribute.
A Region of Interest (ROI) is a specific use of an Overlay. The overlay bits corresponding to all the pixels included in the ROI shall be set to 1. All other bits are set to 0. This is used to specify an area of the image of particular interest.
A Graphics overlay may express reference marks, graphic annotation, or bit mapped text, etc. A Graphics overlay may be used to mark the boundary of a ROI. If this is the case and the ROI statistical parameters are used, they will only refer to the pixels under the boundaries, not those in the included regions.
The overlay bits corresponding to all the pixels included in the Graphics shall be set to 1. All other bits are set to 0.