Photo on Windows and iPad, general rendering issue

[NotMyFault]

Hi,

 

i reported issues with thin lines visible (depending on zoom level) before, which where not acknowledged at that time.

Again i have severe and reproducible issues. With a very simple

Test setup

• RGB/8 document with RGB profile
• Size 256x300px
• Document contains 3 rectangle shapes 256x100px of 100% color, red, green, blue atop each other
• You can export this document as PNG with expected result.
• I "merged visible" to rule out any "normal" rendering issues
• Set zoom to 100% by shortcut Ctrl-1
• Tested on several monitors, Dell 4K with RGB profile, LG 5K with P3 profile.

Issue

• The rendering in Photo shows 1px blurry lines around the 3 parts
• If you take a screenshot with windows snipping tool, and paste this back into the file, you can clearly see the damage (which is otherwise not easy to spot directly on a 5K display)
• All layers are blurry at the edges (assuming 0.5px mis-alignment), despite perfect alignment in transform panel

To be clear: i can see the issue already with my eyes when looking at the screen. The screenshot is only "helping evidence" for the forum, not the primary proof.

• The issue only occurs for 100% zoom. If zooming to 400%, issue is not visible.
• The screenshot was made in "rectangle" mode and contains background pixels around the image. This can be removed. I cannot create a screenshot of exactly the screen region i want, as my mouse does not allow such fine work.
• You can use the "Screen Magnifier" tool to clearly spot the issue.
• If required, i will use any tool you name to screen record, snapshot or otherwise document the issue. For my PC, it is always there. Every single day.
• The issue occurs especially when using procedural texture filters in combination with rectangle shapes used for masking, inside the image between layers.

Edit:

• Similar issue on iPad. You get a transparent line of estimated 1/100px size on right and bottom side when opening test file there, and zooming in really deep. The transition between colored rectangles is blurred by 1px, too
• I asked in an older post why PT filter show x/y positions with a 0.5 offset on windows and got no answer. This might be related.
  https://forum.affinity.serif.com/index.php?/topic/148988-potential-roundig-bug-with-procedural-texture-filter/&tab=comments#comment-831914

rebnder bug primary colors.afphoto

Edited September 27, 2021 by NotMyFault

[Chris B]

Hi NotMyFault,

Can you see this if you switch to Nearest Neighbour in Preferences > Performance > View Quality - I think this is just how it's being rendered with the Bilinear setting.

[NotMyFault]

Can’t check on Windows right now, PC down and needs maintenance.

Even if solved, it is not a full solution, and the consequences are quite shocking for me.

Windows

• Is the interpretation correct that bilinear rendering mode will blur every high contrast edge for every image looked at 100% zoom?
  If yes, it would make this default rendering mode absolutely useless to check local contrast and sharpness.
• How does bilinear rendering (for display) differ from bilinear resample (used for export)?
• Is there any option to get an accurate rendering in Photo (looked at 100% zoom level) that exactly matches what will be exported?
• I don’t want to use “export preview” as its way too much effort (clicks / steps).
• If using “nearest neighbor “ is the only option to avoid this visible rendering issue, then there is no option available to correctly preview the image (except actually exporting it & opening in another app). The image might contain areas which differ intentionally (not caused by the issue discussed here) depending on rendering method, e.g. stretched pixel layers.

IPad

On iPad, there is no option, only “Retina Rendering Only” which doesn’t solve the issue.

 

PS

to say it in a different way: 

• the main issue is that the rendering method is a global setting.
• It would help if rendering method could be selected per layer (similar to anti-aliasing, which only impact edge pixels).
•  

Edited September 28, 2021 by NotMyFault

[NotMyFault]

Now tested again on Windows:

• Nearest shows weaker blurriness (1px into 1 direction rectangular to edge)
• Bilinear shows stronger blurriness (1px into both directions -> 2px effectively)

[NotMyFault]

To close this old thread: the issue is caused by RGB subpixel alignment. 
the individual red / green / blue subpixels forming an RGB pixel are distributed horizontally on the displays i use. When creating shapes with contrasting primary colors this leads to noticeable color artifacts caused by micro- misalignment depending on color.

So nothing Affinity apps can influence.