export of files with fractional dimensions wrong in extra added edge pixels

[NotMyFault]

When using a file with fractional dimensions, Photo rounds up to the next integer when exporting.

When calculating the colors of that extra edge pixels, affinity makes questionable decisions on how to calculate the color values.

There are two variants of the file:

• 1dot5 square.afphoto covers only the document canvas with square rectangles of 1x1, 0.5x1, 0.5x0.5 size.
• 1dot5 square from 2.afphoto covers the "fractional" pixels with 1x1 rectangles.
• You can see that the smaller rectangles lead to less saturated colors, this is expected as the colors get resampled with the "invisible" part according to their areal coverage.
• The strange think is that it makes no difference when you export PNG with 2x2 size from both files. They look all identical, but: 
• it seems that the export colors get a second round of resampling, leading to almost desaturated colors. This double-resampling is not correct in my view, as the rendered (single pass resample) is already the correct version, and another resample for export leads to wrong colors.

This issue has absolutely no priority. It only exists as Photo creates these (in most cases absolutely unwanted) extra pixels instead of cutting them off. Affinity could solve 2 issues at once by simply cutting off extra pixels resulting from fractional document sizes - as it already does when displaying the document dimensions in UI (expect export).

see 

 

Canvas in Photo showing already desaturated edge colors

PNG Export showing double-desaturated edge colors

 

1dot5 square.afphoto 1dot5 square from 2.afphoto

[NathanC]

Hi @NotMyFault,

Thanks for the post, I've raised this internally with the QA team and this has been considered more as an improvement than a bug. As such I've moved this over to the Feature Requests board.