Odd alpha behavior during (supposedly) pixel-aligned cut-and-paste

[Casey Muratori]

I am encountering a weird bug when trying to cut-and-paste pixel-aligned rectangular regions from one image to another in Affinity Photo 1.8.3.  This bug seems to be present in at least all 1.8.x versions that I had, so it is not specific to 1.8.3.  Whether it goes back further than the 1.8 branch is anyone's guess.

If I open two images, one completely blank (literally nothing, so rgba all 0) and the other an RGB image with no alpha, then use the rectangle select tool to select a rectangular region in the RGB image, CTRL-C to copy, switch to the blank image, then CTRL-V to paste, I get weird partial alpha at the edges of the selection in the paste.  These appear to be because of sub-pixel alignment, but I copied a pixel-aligned region and pasted pixel-aligned as well... and in fact, I have the "whole pixel" alignment enabled the whole time, so it shouldn't be possible for me to be off-pixel alignment unless I'm misunderstanding the intended behavior of that feature.

If I then turn off whole pixel alignment and slide the pasted region slowly, I can manage to get it back into alignment and the partial transparency resolves itself mostly (although it still may be slightly wrong).

What is going on here?  Is this some sort of bug with whole-pixel alignment that nobody noticed?  Or am I doing something weird?

Thanks,

- Casey

[Gabe]

Hi @Casey Muratori,

Sorry for the delayed reply. 

Can you attach a document with the pasted image that's not aligned properly and a screen recording of your workflow? I can't replicate this here. 

[Casey Muratori]

I normally only use Affinity Photo on my main Windows machine, but I installed it on another Windows machine here that has recording software on it so I could try to record the video you requested.  In so doing, I stumbled upon what the issue actually is!  It is not related to the document or the workflow, actually - it is related to the monitor setup. I installed it on a third Windows machine just to verify, and the pattern seems to hold:

When using Affinity Photo on machines with a single monitor, pixel alignment works as expected.  It is only when I use Affinity Photo on a machine with multiple monitors that this problem occurs.  It may also be the case that the monitors must have different resolutions, but I do not have any machine with two identical monitors so I am unable to test that.

Is it possible that the pixel-snapping code is actually not snapping properly when multiple monitors are involved? Perhaps if the monitors have different DPIs as well?

Are you able to reproduce this there now?  You do not need to do anything special at all, you can just:

1. Install Affinity Photo on a machine with two monitors that have substantially different resolutions (say, one is 1920x1200 and one is 3840x2160).
2. Create a new document (say, QFHD).
3. Hit the PRT SCR key to capture the desktop.
4. Select "New From Clipboard" from the file menu to create a second document with the image.
5. Pixel-exactly select a rectangular shape using the rectangle select tool (say, the Affinity logo button in the upper left).
6. "Copy Flattened" to copy the rectangle.
7. Switch back to the empty QFHD document.
8. "Paste" to paste the Affinity logo.

The pasted rectangle should be obviously off-pixel alignment (the edges will be blurred, and the marquee doesn't line up with the document pixels).  I believe I can now definitely say this is a bug, because it happens on a completely clean install of the latest Affinity Photo download right out of the gate, no preference changes necessary, no prior usage of the software necessary, no particular files necessary, etc.

- Casey

[Gabe]

Thanks. I managed to replicate it, and while looking into it it's not even dual-screen related. It's zoom related. If you zoom in past 100%, that's when it happens. Issue logged. 

[Casey Muratori]

Cool. I feel like this should presumably be a high-priority item, since this means people are generally getting blurry images all the time and might not even realize it?

Thanks,

- Casey

[Casey Muratori]

Did this end up getting fixed?

- Casey

[Gabe]

I'm afraid no. Sorry

 

[Casey Muratori]

That is the ultimate sadness :(

- Casey

[Affinity Info Bot]

The issue "Pasting pixel selection is not on whole pixels" (REF: AF-4886) has been fixed by the developers in the latest beta build (2.6.0.3058). The fix is planned for inclusion in the next customer release.
Customer beta builds are announced here and you can participate by following these instructions.
If you still experience this problem once you are using that build version (or later) please reply to this thread including @Affinity Info Bot to notify us.