Image presentation consistency is achieved by the DICOM Presentation State standard. This describes and communicates the presentation information (zoom, rotate, shutters, annotations etc.) that are applied to the image.
Presentation States are defined for both grayscale and color.
The Presentation State includes the zoom factor, its specific window width and level value, displayed overlays, masks and shutters and the image orientation parameters.
All the presentation information, applied by a technologist to an image at a workstation, can be preserved in the DICOM Presentation Object and sent with the image to other workstations to preserve the same appearance. These objects can be stored on an archive and retrieved later using the regular storage services. These objects are similar to image objects. The headers are similar; but instead of having pixel data in the body, there is just information on the image manipulations to be applied.From an implementation perspective, the following steps should be applied in a specific order and this is known as the pixel presentation pipeline.
The steps are:
- Shutter Transformation – apply shutters to the image
- Image Annotation – add notes that is image related
- Spatial Transformation – apply operations such as flip, rotate, zoom and pan
- Display Area Annotation – add text that is independent from spatial transformation.