opening a jpg in AP2 results in image artifacts that aren't present when using any other image editor

[numberonesoniafan]

1. Are you using the latest release version?
I am using 2.0.4, the latest version of Affinity Photo 2.
2. Can you reproduce it?
This is 100% reproducible with the attached bird.jpg.
3. Does it happen for a new document? If not can you upload a document that shows the problem?
This happens immediately upon opening the attached bird.jpg in Affinity Photo 2.

* What is your operating system and version (Windows 11, OSX Ventura, iOS 16 etc)?
macOS Ventura 13.2.1 on MacBook Pro 16-inch, 2021 (M1 Max). I am just using the laptop monitor for this. I have also tried changing the operating system color profile presets (System Settings->Displays->Preset) but that has no effect on this.
* Is hardware acceleration (in Preferences > Performance) ON or OFF ? (and have you tried the other setting?)
I have tried with it both on and off and it doesn't affect the result.
* What happened for you (and what you expected to happen)
To show the problem I am providing two images:

• bird.jpg - the original image
• bird-jpg-to-png-in-GIMP.png - the jpg converted to a png in GIMP (so even though png is lossless and jpg is lossy, in this case we expect our png to be identical to the jpg, since the jpg is the source image.)

Expected: Upon opening bird.jpg and bird-jpg-to-png-in-GIMP.png in Affinity Photo 2, there is no visible difference between them, since the png is simply the jpg re-exported.
Actual: Upon opening bird.jpg in AP2 there are visible artifacts in it (especially obvious when zooming in on the green tail feathers, but really quite noticeable all over the illustration). The artifacts noticeably form 16x16 pixel square regions. When opening bird-jpg-to-png-in-GIMP.png in AP2, it does not contain these artifacts. We can also place one image on top of the other, difference blend the top one, and the artifacts are also immediately apparent there. 

I've attached a screenshot circling the locations for some of the more obvious artifacts.

I've opened the same images in Preview, GIMP, and Google Chrome, and in all of those programs bird.jpg looks identical to bird-jpg-to-png-in-GIMP.png (neither image has the blocky artifacts), even when zooming in very closely. This is more confirmation that Affinity Photo 2 is introducing the artifacts.

Additionally I can do the following test:
1. Open bird.jpg in Affinity Photo 2 and export bird.jpg as a png called bird-jpg-to-png-in-AP2.png
2. Open bird-jpg-to-png-in-AP2.png in Preview or GIMP (or AP2), and zoom in to the green tail feathers. Now the artifacts are present. This shows that Affinity Photo 2 has actually changed the pixel values (and it is not merely an image display issue).

Did this same thing used to work and if so have you changed anything recently?
I do not know of an earlier version of Affinity Photo 2 that works as expected.

[stokerg]

Hi @numberonesoniafan,

Could you zip up the original image and either attach it here or upload it to our Dropbox here and I'll see if I can replicate the issue and get it logged with the Developers.

[numberonesoniafan]

@stokerg Thanks for the reply! I've attached these same files as a zip here.

bird.zip

[immewnity]

Can confirm that this is occurring in AF1 on Windows too (1.10.6.1665).

Here's a diff of the two, it's quite noticeable:

[numberonesoniafan]

Confirmed this is still an issue in Affinity Photo 2.2.0.