ROtating image

[Dansandeman]

When in Photo and an image is being rotated it pixelates. Anyone knows why?
see attached image 

[GarryP]

Rotating any image by a number of degrees which is not a multiple of 90 will inevitably cause some distortion as the software needs to ‘guess’ which non-rotated square pixels should contain the colours of the rotated square pixels where the squares 'overlap'. (This is an over-simplification of what actually happens.)

The amount of distortion will normally increase as the image dimensions get smaller and, as such, the software has fewer options for pixel (re-)placement.

What are the dimensions of your original non-rotated image?
My guess is that the face on the left is no more than about 80-100 pixels across and, because of that, if it’s true, there will naturally be some distortion upon rotation.

There may be some techniques to lessen the effect that you are seeing but we need to know what you are working with before we can properly advise further.

[NotMyFault]

It could be a (temporary) rendering issue, depending on HW acceleration and other settings

1. Can you upload a screenshot of the Performance Settings in Photo?
2. Please check "view quality", and set it to "best (slowest)"
3. deactivate HW acceleration
4. What happens if you export the image (in PNG format): does the exported image show the same "blockiness" as the screenshot?
5. Can you upload the actual .afphoto file?
6. if you create screenshots, please include the full Photo Window, and have "navigator Panel" visible (thumbnail and zoom level).

 

[Pšenda]

1 hour ago, GarryP said:

The amount of distortion will normally increase as the image dimensions get smaller and, as such, the software has fewer options for pixel (re-)placement.

I'll just add - this is exactly the case when it pays to work with the "Image layer" (Place command), i.e. with the original in full resolution, which is always calculated in the highest possible quality after reduction/enlargement and rotation as needed. Successive manipulations (reduction/enlargement/rotation) with the "Pixel layer" lead to gradual recalculation of pixels and to a gradual degradation of image quality.

[NotMyFault]

The pixelation show in the OP screenshot is unrelated to using image or pixel layers. I simply took his screenshot (pixel layer, not image layer), cropped to the left side, and rotated it. The quality is far higher, no pixelation. Only the expected minor (1px) blurriness due to bilinear resample. The Pixellation in OP image is about 4-8 pixel which has a different (not yet identified) cause.

[Old Bruce]

We don't know at what zoom level the screenshot was made.

6 hours ago, NotMyFault said:

I simply took his screenshot (pixel layer, not image layer), cropped to the left side, and rotated it. The quality is far higher, no pixelation. Only the expected minor (1px) blurriness due to bilinear resample. The Pixellation in OP image is about 4-8 pixel which has a different (not yet identified) cause.

 

[NotMyFault]

1 hour ago, Old Bruce said:

We don't know at what zoom level the screenshot was made.

 

And we don't need to. 
 

If an image is not pixelated (on the left side), there is no reason that a copy of that image gets pixelated when moved and rotated to the right side. This applies to any zoom level.

Except the OP did something else with the image copy, like scaling down 10x, then rasterizing, and scaling up again - but even this would only cause blurriness, not pixelation.