Merge / Viewer / Writer Node issue with Operation Modes

[magdesign]

When using a Merge node to Merge two color Solids with the Under Operation, I would expect following result:

The Viewer (with activated checkerboard) shows me this result:

The Writer output results in an empty .png:

Test Scene to reproduce (rename it to : Merge_testscene.ntp):
Merge_testscene.log

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Natron 2.3.15 Snapshot, Version 2bf9f84
Ubuntu Linux

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[magdesign]

Example2:

Using a Merge node with Operation Divide to divide a SeNoise with a Solid color,
the viewer shows me following (as expected):

The Writer result is an empty .png:

Testscene to reproduce (rename it to: Merge_Divide.ntp):
Merge_Divide.log

[devernay]

If you want inputs to Merge to have an alpha component (which will be set to 1), you should check the A (alpha) checkboxes in the merge inputs, and you'll get what you want. Alpha is off by default when connecting RGB inputs. There are good reasons to make it on by defaults, and equally good reasons to make it off by default. One has to be careful when merging images that don't have an alpha channel.
It's the same with the second graph: my guess is that you really want a solid noise (alpha=1), and it's not the case here. When you divide your solid color, you should make sure to create the alpha channel for it (check "A"(lpha) checkbox for the A input). Than way you will get alpha=1 on the output, instead of alpha=0 here (please check in the viewer, use the checkerboard or press the A key). A PNG with alpha=0 is transparent.

[devernay]

another solution to avoid that is to set the output components of the solid nodes to "RGBA", which will set alpha=1