GIMP-299 screen layer blend mode results depend on linear vs nonlinear "precision"
Here are two test files, one saved in GIMP-2.10 and one in GIMP-2.99. They are supposed to be "the same" as both are at "nonlinear" precision and both have the same ICC profile from disk assigned, which is a version of ClayRGB with the sRGB TRC. I don't know if these two versions look the same/have the same channel values regardless of which version of GIMP opens which file. But for purposes of this bug report open each one in the designated version of GIMP:
Both versions are at perceptual precision. Open each with the designated version of GIMP, and each version looks the same.
But change the precision to linear precision in each version, and the GIMP-2.99 version gets darker. Here's a screenshot after changing the precision to "linear" in both versions of GIMP:
To make the version in GIMP-2.99 look the same as the version in GIMP-2.10, right-click on the top "screen layer blend" layer and select "Perceptual" instead of "Auto".
Is this intended behavior, that the results of "screen" depend on the choice between linear and nonlinear precision? If it is, then this seems like the wrong coding decision, as it puts blend modes back to the state of GIMP-2.9.5-ish, where changing the precision was the way to change the results of blend modes. Or is this a bug, perhaps an unintended side effect of the space invasion?
At first I thought this difference in behavior might be because the image was in a non-sRGB color space. But convert both files, each in its designated version of GIMP, to built-in sRGB, and results are the same - in GIMP-2.10 screen produces the same results regardless of precision (unless the user opts to change the blend space from auto to linear), but in GIMP-2.99 screen produces different results before and after changing the precision.