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High-quality arbitrary-angle rotation
Posted: Tue Dec 25, 2007 11:36 pm
by stephan_g
Currently XnView supports two quality modes of rotation by arbitrary (custom) angles:
1. Crappy - nearest-neighbor interpolation.
2. OK - with "smoothing" checkbox enabled, does bilinear interpolation or somesuch.
What about a really high-quality option that uses e.g. the excellent Lanczos algorithm already employed for resizing? The "Smoothing" checkbox may need to mutate into a 3-state quality (vs. speed) slider, but other than that the necessary code should basically already be there.
Posted: Sat Jan 26, 2008 4:50 am
by XnTriq
This is a very good idea, no doubt.
For resizing photographic images I never use any other programs.
Posted: Sat Jan 26, 2008 10:47 am
by Troken
I agree, the quality of the arbitary rotate could be better. If Lanczos could be an option it would be splendid.
Posted: Mon Sep 01, 2008 2:19 pm
by Troken
Any news on this matter? I stongly belive this should be a feature soon. Rotation quality should be much better, since XnView otherwise is such a competent piece of software.
Re: High-quality arbitrary-angle rotation
Posted: Fri Sep 05, 2008 11:34 pm
by DOS386
stephan_g wrote (almost 1 year ago):
Currently XnView supports two quality modes of rotation by arbitrary (custom) angles:
1. Crappy - nearest-neighbor interpolation.
Actually it's a nearest-neighbor pick, no interpolation at all.
2. OK - with "smoothing" checkbox enabled, does bilinear interpolation or somesuch.
What about a really high-quality option that uses e.g. the excellent Lanczos algorithm already employed for resizing?
Troken wrote:
Any news on this matter? I stongly belive this should be a feature soon. Rotation quality should be much better, since XnView otherwise is such a competent piece
I
highly support this.
Also I did test (
download results - 150 KiB ) :
- Bilinear zoom is only marginally worse than Lanczos (at least in this test)
- Rotate "smooth" is very ugly compared to Bilinear zoom, and I have no idea why
- Zoom bilinear vs zoom Lanczos results in a diagonal drift
... seems to be a bug
- The "smooth" thingie does
not work at all in NCONVERT:
- "rotate_flag smooth" is "recognized" but ignored ... ROT0.PNG and ROT1.PNG are identical and both use NN pick
- "rotate_flag smiley" complains about bad
resize flag
- Still visible OS/2-bug, DOS/32A junk not visible because I had patched it off
Thus the IMHO only possible solution:
- Make
all sampling algos available for rotate also (GFL + NC + XN)
- Delete the "rotate_flag smooth" completely
- Rename "rtype" into "samp" and use it for both resize and rotate
- Update the help: quick=NN ???
Code: Select all
-samp : Sampling algorithm for resize and rotate
quick (nearest neighbor pick)
linear (bi-linear)
hermite
gaussian
bell
bspline
mitchell
lanczos (Lanczos 3)
Re: High-quality arbitrary-angle rotation
Posted: Mon Sep 08, 2008 7:20 am
by xnview
Use -rotate 1 -rotate_flag smooth
Re: High-quality arbitrary-angle rotation
Posted: Tue Sep 16, 2008 12:35 am
by DOS386
xnview wrote:Use -rotate 1 -rotate_flag smooth
COOL ... it helps, thanks
so my "does not work at all in NCONVERT" was wrong, OTOH most of the points of my post and this thread are still valid, however
, most notably the syntax inconsistence and availability of Lanczos sampling algo for rotating. Also, I have some further ideas about possible improvements of NCONVERT syntax - should I post them ?
Bump!
Posted: Sat Nov 08, 2008 10:48 pm
by dandv
+1 for high-quality rotation, and please make "smooth" checked by default in the Rotation dialog box. The first time I used Rotation in XnView, I thought "OK, this is probably be as good as in Irfan", and after saving the image, I noticed the jigsaw effect
Re: Bump!
Posted: Mon Nov 10, 2008 8:06 am
by Troken
dandv wrote:... and please make "smooth" checked by default in the Rotation dialog box. ...
Good idea! I support this suggestion.