Photo Adding Extra Colours To Affinity File

[SamMN]

Maybe there's a good explanation for this and I'm missing something, but Photo seems to be adding in extra colours to an Affinity file when you open it in Photo. See screenshots of the same file in all 3 programs (originally created in Designer). Black background, with 3 rectangle shapes set to different levels of black. Nice and simple. The whole thing is 100 x 100 pixels, the rectangles were created as smart shapes. I've attached the file in question. Why do the rectangles in Photo have different shaded grey lines on the left and right side of the shape?

Mac OS Sonoma 14.1.2, on an Macbook Pro M2 Max, 32GB RAM

Pixel pattern.afdesign

[walt.farrell]

Probably because

1. your objects are not aligned to the pixel grid (they have non-integer X positions, if you look in the Transform panel and have the right number of decimal places set in your User Interface Preferences/Settings in the application), 
   and
2. Photo uses a pixel-based display rather than a vector-based display. In Designer, you can change the View Mode and probably see the same effect.

[SamMN]

Ah yes, option 1 fixed it! Is there an article or something on why a non-aligned pixel causes that visual behaviour I could read? Just out of interest / curiosity.

[GarryP]

Basically, if the layer is not pixel-aligned (e.g. X/Y = 0.7 pixels) then the software will have ‘partial pixels’ (e.g. 0.3 of a pixel) ‘left over’ which need to go somewhere so that the information isn’t lost so the software (on-the-fly) creates new pixels for the contents of the ‘partial pixels’ to go in.

This isn’t the full technical description of exactly what happens but it’s usually enough to know why it happens without knowing what is happening.

If pixels are important then it’s usually a good idea to set “Force Pixel Alignment” to ON and “Move by Whole Pixels” to OFF on the Toolbar and you shouldn’t (normally) have the problem again.