C.10.7 Graphic Layer Module
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### C.10.7 Graphic Layer Module

This Module defines the characteristics of the layers in which overlays, graphic and text may be rendered.

Layers group together graphics that are related. It is recommended that a layer be displayed such that it may be distinguished from other layers that have a different value for Graphic Layer Order (0070,0062).

### Note

The transparency, opacity, and any other interaction (such as exclusive or) with underlying layers or image data are not specified and are at the discretion of the implementation.

Table C.10-7. Graphic Layer Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Graphic Layer Sequence | (0070,0060) | 1 | A sequence of Items each of which represents a single layer in which overlays, curves, graphics or text may be rendered. One or more Items shall be included in this sequence. An Item is required for each layer referenced from the Graphic Annotation Module or the Overlay Activation Module.
>Graphic Layer | (0070,0002) | 1 | A string that identifies the layer. ### Note This identifier may be used by other Attributes within the same presentation state instance to reference this layer. There is no requirement for the same identifiers to be used in different presentation states, and there is no mechanism for referencing layers in other presentation states. That is, a UID is not required.
>Graphic Layer Order | (0070,0062) | 1 | An integer indicating the order in which it is recommended that the layer be rendered, if the display is capable of distinguishing. Lower numbered layers are to be rendered first.
>Graphic Layer Recommended Display Grayscale Value | (0070,0066) | 3 | A default single gray unsigned value in which it is recommended that the layer be rendered on a monochrome display. The units are specified in P-Values from a minimum of 0000H (black) up to a maximum of FFFFH (white). ### Note The maximum P-Value for this Attribute may be different from the maximum P-Value from the output of the Presentation LUT, which may be less than 16 bits in depth.
>Graphic Layer Recommended Display CIELab Value | (0070,0401) | 3 | A default color triplet value in which it is recommended that the layer be rendered on a color display. The units are specified in PCS-Values, and the value is encoded as CIELab. See Section C.10.7.1.1.
>Graphic Layer Description | (0070,0068) | 3 | A free text description of the contents of this layer.

### Note

Graphic Layer Recommended Display RGB Value (0070,0067) was previously used in this Module, but has been retired and its function replaced by Graphic Layer Recommended Display CIELab Value (0070,0401). See PS3.3-2004.

#### C.10.7.1 Graphic Layer Module Attributes

##### C.10.7.1.1 Encoding of CIELab Values

Attributes such as Graphic Layer Recommended Display CIELab Value (0070,0401) consist of three unsigned short values:

- An L value linearly scaled to 16 bits, such that 0x0000 corresponds to an L of 0.0, and 0xFFFF corresponds to an L of 100.0.

- An a* then a b* value, each linearly scaled to 16 bits and offset to an unsigned range, such that 0x0000 corresponds to an a* or b* of -128.0, 0x8080 corresponds to an a* or b* of 0.0 and 0xFFFF corresponds to an a* or b* of 127.0

### Note

This is the same form of encoding as used for the PCS in ICC Profiles.

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