DICOM PS3.17 2018a - Explanatory Information

XXX.5 Compositing and the Use of Weighting Transfer Functions
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## XXX.5 Compositing and the Use of Weighting Transfer Functions

The RGB Compositor described in Section FF.2.3.3.2 “Internal Structure of RGB and RGBA Compositor Components” in PS3.4 utilizes two weighting transfer functions of Alpha-1 and Alpha-2 to control the Compositor Function, allowing compositing functions that would not be possible if each weighting factor were based only on that input's Alpha value. These weighting transfer functions are implemented as Weighting Look-Up Tables (LUTs). Several examples of the use of these Weighting LUTs are described in this section. The format of the examples is in the form of a graph whose horizontal axis is the Alpha-1 input value and whose vertical axis is the Alpha-2 input value. The Weight output value is represented as a gray level, where 0.0=black and 1.0=white.

Section XXX.3 references these different weighting function styles from real clinical use cases.

### XXX.5.1 Fixed Proportional Compositing

In this example, a fixed proportion (in this case 2/3) of RGB-1 is added to a fixed proportion (in this case 1/3) of RGB-2. Note that the weighting factors are independent of Alpha values in this case:

Figure XXX.5-1. Weighting LUTs for Fixed Proportional Composting

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XXX.4.3 Ad Hoc Display Layout | Home | XXX.5.2 Partially Transparent A Over B Compositing

DICOM PS3.17 2018a - Explanatory Information