DICOM PS3.3 2020b - Information Object Definitions

C.7.6.23 Enhanced Palette Color Lookup Table Module (Current)
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#### C.7.6.23 Enhanced Palette Color Lookup Table Module

Table C.7.6.23-1 specifies the Attributes that define data flow through the Enhanced Blending and Display Pipeline. See Section C.7.6.23.1 for an overview of the Enhanced Blending and Display Pipeline.

Table C.7.6.23-1. Enhanced Palette Color Lookup Table Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Data Frame Assignment Sequence | (0028,1401) | 1 | Sequence of Items each assigning frames of one particular value of Data Type (0018,9808) to a data path in the Enhanced Blending and Display Pipeline. One, two, or three Items shall be included in this Sequence.
>Data Type | (0018,9808) | 1 | Identification of the data type of frames using this data path assignment.
>Data Path Assignment | (0028,1402) | 1 | The data path to use for this data type in the Enhanced Blending and Display Pipeline. Enumerated Values: PRIMARY_PVALUES PRIMARY_SINGLE SECONDARY_SINGLE SECONDARY_HIGH SECONDARY_LOW See Section C.7.6.23.2 for usage.
>Bits Mapped to Color Lookup Table | (0028,1403) | 3 | The number of most significant bits of each value of Pixel Data (7FE0,0010) from this frame contributing to the Palette Color Lookup Table input. If absent, Bits Stored (0028,0101) bits of each value of Pixel Data (7FE0,0010) from this frame contributes to the Palette Color Lookup Table input. See Section C.7.6.23.3 for usage.
>Include Table C.11-2b “VOI LUT Macro Attributes” |
Blending LUT 1 Sequence | (0028,1404) | 1C | Specification of the weight of the primary path input to the Blending Operation, i.e., the value that is referred to as "Weight 1" in the Enhanced Blending and Display Pipeline. Only a single Item shall be included in this Sequence. Required if there are one or more Items of the Data Path Assignment Sequence (0028,1402) other than PRIMARY_PVALUES.
>Blending LUT 1 Transfer Function | (0028,1405) | 1 | Specifies the algorithm used to determine the output value of Blending LUT 1. Enumerated Values: CONSTANT ALPHA_1 ALPHA_2 TABLE See Section C.7.6.23.4 for details.
>Blending Weight Constant | (0028,1406) | 1C | Constant value of the Weight input to blending operation. Shall be from 0.0 to 1.0, inclusive. Required if Blending LUT 1 Transfer Function (0028,1405) is CONSTANT.
>Blending Lookup Table Descriptor | (0028,1407) | 1C | Specifies the format of Blending Lookup Table Data (0028,1408) in this Sequence Item. The second value (first stored pixel value mapped) shall be zero. See Section C.7.6.23.5 for further explanation. Required if Blending LUT 1 Transfer Function (0028,1405) is TABLE.
>Blending Lookup Table Data | (0028,1408) | 1C | Contains the Blending Lookup Table values for this Weight input to the Blending Operation. Required if Blending LUT 1 Transfer Function (0028,1405) is TABLE.
Blending LUT 2 Sequence | (0028,140C) | 1C | Specification of the weight of the secondary path input to the Blending Operation, i.e., the value that is referred to as "Weight 2" in the Enhanced Blending and Display Pipeline. Only a single Item shall be included in this Sequence. Required if there are one or more Items of the Data Path Assignment Sequence (0028,1402) other than PRIMARY_PVALUES.
>Blending LUT 2 Transfer Function | (0028,140D) | 1 | Specifies the algorithm used to determine the output value of Blending LUT 2. Enumerated Values: CONSTANT ONE_MINUS ALPHA_1 ALPHA_2 TABLE See Section C.7.6.23.4 for details.
>Blending Weight Constant | (0028,1406) | 1C | Constant value of the Weight input to blending operation. Shall be from 0.0 to 1.0, inclusive. Required if Blending LUT 2 Transfer Function (0028,140D) is CONSTANT.
>Blending Lookup Table Descriptor | (0028,1407) | 1C | Specifies the format of Blending Lookup Table Data (0028,1408) in this Sequence Item. The second value (first stored pixel value mapped) shall be zero. See Section C.7.6.23.5 for further explanation. Required if Blending LUT 2 Transfer Function (0028,140D) is TABLE.
>Blending Lookup Table Data | (0028,1408) | 1C | Contains the Blending Lookup Table values for this Weight input to the Blending operation. Required if Blending LUT 2 Transfer Function (0028,140D) is TABLE.
Enhanced Palette Color Lookup Table Sequence | (0028,140B) | 1C | This Sequence contains the Palette Color Lookup Table. One or two Items shall be included in this Sequence. Required if Data Path Assignment (0028,1402) is present with a value other than PRIMARY_PVALUES.
>Data Path ID | (0028,140E) | 1 | Identifier of the data path in which this Palette Color Lookup Table is used. Enumerated Values: PRIMARY SECONDARY Each Item shall have a distinct value of Data Path ID.
>RGB LUT Transfer Function | (0028,140F) | 1 | Specifies the mapping that takes place between the input value and RGB input to the Blending Operation. Enumerated Values: EQUAL_RGB Output is R=G=B=input value TABLE Output is RGB LUT values
>Alpha LUT Transfer Function | (0028,1410) | 1 | Specifies the transformation that is used to create the Alpha input to the Blending LUTs. ### Note Depending on the values of Blending LUT 1 Transfer Function (0028,1405) and Blending LUT 2 Transfer Function (0028,140D) the Alpha LUT value may be ignored. It is recommended that IDENTITY be used if this is the case. Enumerated Values: NONE IDENTITY TABLE
>Red Palette Color Lookup Table Descriptor | (0028,1101) | 1C | Specifies the format of the Red Palette Color Lookup Table Data (0028,1201). The second value (first stored pixel value mapped) shall be zero. Required if RGB LUT Transfer Function (0028,140F) is TABLE.
>Green Palette Color Lookup Table Descriptor | (0028,1102) | 1C | Specifies the format of the Green Palette Color Lookup Table Data (0028,1202). The second value (first stored pixel value mapped) shall be zero. Required if RGB LUT Transfer Function (0028,140F) is TABLE.
>Blue Palette Color Lookup Table Descriptor | (0028,1103) | 1C | Specifies the format of the Blue Palette Color Lookup Table Data (0028,1203). The second value (first stored pixel value mapped) shall be zero. Required if RGB LUT Transfer Function (0028,140F) is TABLE.
>Alpha Palette Color Lookup Table Descriptor | (0028,1104) | 1C | Specifies the format of the Alpha Palette Color Lookup Table Data. The second value (first stored pixel value mapped) shall be zero. Required if Alpha LUT Transfer Function (0028,1410) is TABLE.
>Red Palette Color Lookup Table Data | (0028,1201) | 1C | Red Palette Color Lookup Table Data. Required if RGB LUT Transfer Function (0028,140F) is TABLE.
>Green Palette Color Lookup Table Data | (0028,1202) | 1C | Green Palette Color Lookup Table Data. Required if RGB LUT Transfer Function (0028,140F) is TABLE.
>Blue Palette Color Lookup Table Data | (0028,1203) | 1C | Blue Palette Color Lookup Table Data. Required if RGB LUT Transfer Function (0028,140F) is TABLE.
>Alpha Palette Color Lookup Table Data | (0028,1204) | 1C | Alpha LUT contains the blending values for the data frames. Required if Alpha LUT Transfer Function (0028,1410) is TABLE.
ICC Profile | (0028,2000) | 1C | An ICC Profile encoding the transformation of device-dependent color stored pixel values into PCS-Values. See Section C.11.15.1.1 When present, defines the color space of the output of the Enhanced Blending and Display Pipeline. Required if Data Path Assignment (0028,1402) is present and there exists any value other than PRIMARY_PVALUES.
Color Space | (0028,2002) | 3 | A label that identifies the well-known color space of the image. Shall be consistent with any ICC Profile (0028,2000) that is also present. See Section C.11.15.1.2.

##### C.7.6.23.1 Description of the Enhanced Blending and Display Pipeline

The Enhanced Blending and Display Pipeline describes a scheme for blending of data frames of different Data Types and a color/grayscale mapping for display recommended by the provider of this information. There are no requirements upon an receiving application to utilize this recommendation in the processing and display of the referenced image.

The blending transformation model in Figure C.7.6.23-1 applies for mapping images derived from one, two, or three data frames with the same image position and orientation but of different values of Data Type (0018,9808) to grayscale P-Values or color PCS-values for presentation. These inputs to the pipeline are frames of pixel values obtained from Pixel Data (7FE0,0010) and structured as described by Attributes of the Image Pixel Module. Co-located pixels from each data frame are processed through the Pipeline, resulting in one output sample at that location.

The model utilizes up to two data paths called the Primary and the Secondary data paths. Each input data frame may be initially processed by a Modality LUT and a VOI LUT. If not explicitly specified, the Modality LUT and VOI LUT are assumed to be identity transformations. The Primary path may be used alone to obtain only grayscale transformation without blending. In this case, the Primary data path input after going through the Modality LUT and VOI LUT is mapped through a Presentation LUT to obtain device independent grayscale values (P-Values) for presentation.

Either Primary or Secondary paths alone or both paths together may be used to obtain color transformation with blending. Up to one data frame input in the Primary data path and up to two data frames input in the Secondary data path are allowed for this blending transformation. These frames may be mapped to color using one-input or two-input palette color lookup tables depending on the number of data frames input to the data path. Alternatively if a path has one data frame, values may be converted to RGB (where R=G=B) before blending, if pseudo-color presentation of this data path is not desired. RGB values from Primary and Secondary data paths are combined via a "Blending Operation" in which the RGB color components are multiplied by a corresponding blending weight function (Weight 1 and Weight 2, respectively), and for each color component the two products are added together to produce the blended output value of that component. All inputs to the Blending Operation are normalized to the range 0.0 to 1.0, inclusive, even if they are fixed integer values that had been the entries in a lookup table.

Each of the Weight inputs to the blending operation is the output of a corresponding Blending LUT Transfer Function, which is selectable as either a constant or a derivation of the data frame values as described in Section C.7.6.23.4.

The RGB output from the Blending Operation is clamped to limit each color component (R, G, and B) to fall within the range 0.0 to 1.0, inclusive. The clamping function simply sets the value of any color component to 1.0 if the output from the Blending operation for that component exceeds 1.0. The RGB output of the clamping function is made available for use in rendering and slicing algorithms. Further, the output of the clamping function is transformed by the Profile Connection Space Transformation to device independent color values (PCS-values) for presentation.

If the input data frame values are representative of real world data, then they can be mapped to the real world values and units using the Real World Value Mapping Macro.

### Note

Annex QQ “Enhanced US Data Type Blending Examples (Informative)” in PS3.17 describes a number of examples of the Enhanced Blending and Display Pipeline with specific Attribute values for each example that invoke particular data flows through the pipeline.

Figure C.7.6.23-1. Enhanced Blending and Display Pipeline

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DICOM PS3.3 2020b - Information Object Definitions