Export bug: white box in picture

[Christian S.]

I have an Affinity Photo file where a white box shows up in the exported picture that is not visible in Affinity Photo 1.7.3.

I've tried numerous things to get rid of this:

• Merge all layers to one pixel layer, export while only this is visible
• Crop the picture a little bit
• Use different formats (PNG, PSD) instead of PDF
• Use different algorithms (bilinear vs. my preferred Lanzcos). With bilinear the box is only a small spot of 1px, but still there.
• Use red background color on export, but the box is always white. So it doesn't seem to be an issue with a transparent pixel in the image. 
• Use different color spaces (sRGB, AdobeRGB), has no effect
• Copy the pixel layer into a new document (no white box), then export (white box appears)
• Change resize on export (I want 1200px at the long edge), but regardless of output size original or smaller, only the absolute size of the white box changes, e. g. 1x2px instead of 6x7px with 1200px export.

The white box is always at the same place in the picture.

It would be helpful to know if this a known issue and how I can possibly avoid this.

[Gabe]

Hi @Christian S.,

Can you attach the project file in question, please?

[Christian S.]

Sure.

Note that the effect is biggest when using Lanzcos interpolation and a long edge of 1200px. But once you've seen it you can find the white dot in every export at the same place.

Also the top layer contains the final picture, all other layers could be removed and the issue is still there. I just left them in case they help you with the investigation.

Thanks for taking care!

Christian.

PS: I just noticed I wrote "PDF" in my first post. Actually I want to export to JPG of course, not PDF.

 

Edited February 1, 2020 by Christian S.
removed attachment

[Gabe]

Thanks. I believe this is because, in that area, you have some negative values. When you apply a negative value for Luminosity shift in that HSL adjustment, they become "Nans". I suggest you don't use Luminosity Shift in 32 bit  What is the reason for working in 32bit, if you export as a jpeg? 

As a workaround, you can change the document format to RGB/8 and you should be fine. 

[Christian S.]

Thank you for the explanation. The origin of this picture was an HDR. I will try that solution and report back here. 

[Christian S.]

I can confirm: Just by converting to 16bit the issue was solved. Thank you!