DXCompositeUnder function

Composites an alpha premultiplied source sample under a destination sample.

Syntax

DXPMSAMPLE DXCompositeUnder(
  _In_ DXPMSAMPLE Dst,
  _In_ DXPMSAMPLE Src
);

Parameters

• Dst [in]
  A DXPMSAMPLE object that specifies the sample that lies over the source sample.

• Src [in]
  A DXPMSAMPLE object that specifies the sample to be composited under the destination.

Return value

Returns a DXPMSAMPLE structure value resulting from the composite operation.

Remarks

A composite under operation uses the alpha value of the destination sample to combine the colors. To obtain the result, the destination is scaled by alpha, the source is scaled by the inverse of alpha, and the two values are added.

Requirements