Created attachment 131254 [details]
Attachment contains image, and how the boundary between it and the background looks when rotating or changing position

SUMMARY

When using effects (such as rotation or changing position), on the boundary between image and background, the color is that of a background, with no contribution from the color of image. That can be seen by moving a picture 5 pixels within 3 frames. So on frame 1, image is in its default position, on frame 2, its position should be 1.67 pixels to the right, on frame 3 it should be 3.33 pixels, and on frame 4 it should be 5 pixels to the right. So, on frame 2, the edge of image should participate with 1/3 on the second, and with 2/3 on the third pixel, but it seems as if it participates with 0 on the second and 2/3 on the third pixel (see attachment, transparent background is rendered as black). And similarly for frame 3. The same happens if we use rotation.


STEPS TO REPRODUCE
1. Load image (one is provided in the attachment)
2. Change position with Position and Zoom as explained in summary, or rotate image
3. Set background color
4. Render as Images Sequence (PNG)


OBSERVED RESULT

Described in summary, and can be seen in the attachment.


EXPECTED RESULT


SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION