Avoid roi_in over-expanding

[jenshannoschwalm]

Due to imprecisions or ceil functions we might set roi_in size to be larger than what we provide via piece->buf_in.width/height.
Relevant for modules that do scaling in the pipe like demosaic or finalscale.

Fixes #15876

We might want to do all these "safety checks" not in the module's code but in pixelpipe while we do all the modify roi_in calls, as this PR is meant for 4.6 and 4.8 branch just this fix.

While being here it doesn't hurt to fix some comments too.

[gi-man]

I tested the PR on windows 11 and it works as when using the 0/1080 values.

The issue with 1/1080 is still happening. I will start a new Issue for it. Basically the scale is being calculated as a very small number (close to zero), so the resulting image is too small.

    22.2689 [dt_imageio_export] [export] imgid 1, 4936x3296 --> 1x0 (scale 0.000203). upscale=no, hq=yes
    22.2689 pixelpipe starting CL      [export]                                (   0/   0)    1x   0 scale=0.0002 --> (   0/   0)    1x   0 scale=0.0002 device=0 (nvidiacudanvidiageforcertx3060)

[jenshannoschwalm]

so the resulting image is too small.

Yes, that's an UI issue for me. We should always restrict exported image sizes to something meaningful.

[gi-man]

I was thinking of using the range limit in the field, but 0 is a valid number. I'm thinking it is not a significant issue. I will just leave it alone.

[jenshannoschwalm]

Latest squash-force-pushed commit ensures a minimal size to be processed to avoid crashing and finish the export pipe.
@TurboGit ready for review ...

[TurboGit]

@jenshannoschwalm : If I read this correctly we now do not allow to export a picture smaller than 16 x 16. Right?

[jenshannoschwalm]

Yes. It is not a bad restriction - at least i think so. Also it doesn't make sense for most algos. Let me know if you don't agree.

[TurboGit]

Yes. It is not a bad restriction

I fully agree, just to be sure I'm understanding the code properly.

[TurboGit]

Thanks, merged in master and darktable-4.6.x branch.

[jenshannoschwalm]

Release note for 4.6 and 4.6

Fix spurious crashes while exporting to some output sizes