Automatic deskew is jaggy

[Fixx]

OK, here is an example what is the quality of deskew rotation compared to Photoshop:

Photoshop:


And XnConvert:


Maybe rotation algorithm should be updated? (notice: images above are scaled (but not resampled) by board software. Defects are more visible when you open images full size to its own tab.)

[cday]

Might be best to attach original images for comparison: source image, Photoshop output and XnConvert output. Current forum attachment limit 2MiB, image formats other than JPEG and PNG may need to be attached as a ZIP or similar archive format.

As XnView MP is a tabbed image viewer, it will then be easy to compare the original and output images, zoomed-in if necessary...

[Fixx]

Well, as problem is so obvious there is no need for fancy displays...
Here is simple rectangle skewed 2 degrees:


Here is Photoshop rotated -2 degrees to make it straight:


And here is XnConvert automatic deskew:


Difference is quite visible.
Original files are here: https://www.dropbox.com/s/2fqk7aeq8mhn2 ... s.zip?dl=0

[cday]

I think, after a very quick look at the Rotate and Automatic deskew actions, the answer is that the XnConvert Automatic deskew action currently does not have the 'Smooth' option available in the Rotate option...

And for completeness, in XnView MP the rotate tool has a 'Use anti-aliasing' option, which may or may not use the same algorithm as XnConvert's Rotate 'Smooth' option, but the Rotate -- Automatic Deskew tool also does not have an anti-aliasing option.


I have attached my own test image, a rectangle aligned with the horizontal axis, which can be used to see the effects of rotation and anti-aliasing when starting with a perfect rectangle. As in your test image, the canvas pixel dimensions are quite small, which results in the image quality degrading more rapidly than would be the case with larger pixel dimensions.

Image 1.png