N.2.3 Common Spatial and Annotation Transformations
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### N.2.3 Common Spatial and Annotation Transformations

Figure N.2-2. Common Spatial and Annotation Transformation Model

The common spatial and annotation transformations apply to any device-independent values, whether they be grayscale P-Values or color PCS-Values, for any type of presentation state.

The values with which to render annotations are encoded as device-independent values, either as grayscale P-Values or as color PCS-Values. In the case of PCS-Values, CIELab values are encoded, and defined by reference to a D50 illuminant.

Grayscale presentation states may specify annotations in color for rendering on a color output device.

The mechanism for mapping grayscale P-Values and color PCS-values to the same display is implementation-dependent and not defined by the standard.

#### N.2.3.1 Shutter

The Shutter transformation provides the ability to exclude the perimeter outside a region of an image. A gray level may be specified to replace the area under the shutter.

One form of this transformation uses the Display Shutter Module as used in the X-Ray Angiography Image Storage SOP Class, though it may be applied to any Image Storage SOP Instance, including single frame images.

Another form uses a bit-mapped overlay to indicate arbitrary areas of the image that should be excluded from display by replacement with a specified gray level, as described in the Bitmap Display Shutter Module.

### Note

1. Since annotations follow the shutter operation in the pipeline, annotations in shuttered regions are not obscured and are visible.

2. Any shutter present in the referenced image object is ignored (i.e., not applied).

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