Fusion – Multiply color with alpha on import to fix rough edges

Software:
Fusion 9

When importing transparent graphic files, depending on the way the file was saved, you may encounter rough white edges at the transparency border.
In this case the image colors must be multiplied with the Alpha channel values.

In the Import tab of the Loader node,
Check Post Multiply by Alpha.

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Note:
You can use a Matte > Matte Control node to further refine the edges.

Example image from:
www.mrcutout.com