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by NicolasRobidoux
2014-06-27T02:02:49-07:00
Forum: Users
Topic: The quality of re-sized image is not good
Replies: 36
Views: 44694

Re: The quality of re-sized image is not good

TO DO list :)
by NicolasRobidoux
2014-06-26T23:55:48-07:00
Forum: Users
Topic: The quality of re-sized image is not good
Replies: 36
Views: 44694

Re: The quality of re-sized image is not good

I have just discovered that "near identity transformations" (like resizes that barely change the dimensions in pixels, or rotations) was a bit of a blind spot, and that the final paragraph of http://www.imagemagick.org/Usage/filter ... borderline falls way short of being dead on.
by NicolasRobidoux
2014-06-24T23:22:08-07:00
Forum: Digital Image Processing
Topic: BC-splines with 2C+B=1 are optimal for EWA resampling
Replies: 41
Views: 126226

Re: BC-splines with 2C+B=1 are optimal for EWA resampling

Fred (and henrywho?): If I remember correctly, you are among some (?) who liked EWA Catmull-Rom. After years of finding this stance somewhat strange, I am finally seeing situations in which such a brutally sharp Keys EWA may be useful. I am actually considering values of Keys alpha = BC-spline C eve...
by NicolasRobidoux
2014-06-23T02:47:17-07:00
Forum: Users
Topic: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling
Replies: 134
Views: 172759

Re: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling

I'm being asked questions about EWA LanczosSharp for video, so here are some quick off the top of my head links for people who are interested in resizing: http://www.imagemagick.org/discourse-server/viewtopic.php?f=1&t=21703&start=90#p111986 You will find lots of useful stuff in these forums, and yo...
by NicolasRobidoux
2014-06-15T06:47:07-07:00
Forum: Users
Topic: Improving sigmoidal image resampling (enlargement)
Replies: 19
Views: 24595

Improving sigmoidal image resampling (enlargement)

I am revisiting sigmoidal resampling ( http://www.imagemagick.org/Usage/resize/#resize_sigmoidal and http://www.imagemagick.org/Usage/filter/nicolas/#upsampling ). Heuristics and some experimentation suggest that: Sigmoidization works much much better when used with an image converted to a color spa...
by NicolasRobidoux
2014-06-09T09:59:42-07:00
Forum: Users
Topic: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling
Replies: 134
Views: 172759

Re: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling

I'll have to revisit the "don't upsample through linear light" diktat. At least with samplers that have little or no haloing, this piece of advice is now quite suspect. With Nohalo-LBB for example (not available in IM), linear light (or, at least, XYZ: I've not checked linear RGB) is the clear winner.
by NicolasRobidoux
2014-06-09T03:05:56-07:00
Forum: Users
Topic: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling
Replies: 134
Views: 172759

Re: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling

Note: Warning about using the clown image for tests: The small version that was re-enlarged by Hyllian in this thread, and re-enlarged at http://www.general-cathexis.com/interpolation/ , contains quite a bit of haloing. Unless you are planning to enlarge such images, be wary of conclusions drawn fro...
by NicolasRobidoux
2014-06-09T02:37:47-07:00
Forum: Users
Topic: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling
Replies: 134
Views: 172759

Re: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling

Interacting with Sergio Barbosa (Hyllian) made me realize something that I should have noticed way earlier: Many people are way more tolerant of posterization than I am, and are willing to trade a fair amount of it for reduced blur and haloing. This explains some preferences that I just "did not get...
by NicolasRobidoux
2014-06-08T11:52:26-07:00
Forum: Digital Image Processing
Topic: BC-splines with 2C+B=1 are optimal for EWA resampling
Replies: 41
Views: 126226

Re: BC-splines with 2C+B=1 are optimal for EWA resampling

Fred: I said I would add it, but have not done it yet. May take me a while.
I got the OK from magick to add RobidouxSoft and LanczosSharpest.
by NicolasRobidoux
2014-06-08T11:19:05-07:00
Forum: Users
Topic: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling
Replies: 134
Views: 172759

Re: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling

Also note that http://www.imagemagick.org/Usage/filter/nicolas/ is slowly going stale: What's suggested there is not "wrong", just not quite my current best.
No time to update now.
by NicolasRobidoux
2014-06-08T11:13:34-07:00
Forum: Users
Topic: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling
Replies: 134
Views: 172759

Re: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling

If any reader has any comment regarding the look of the RobidouxSoft result, I'd like to read it. Also, if Sergio could post the result with EWA Robidoux, I'd be thankful. Nicolas, Sorry if I have missed this, but where have you detailed RobidouxSoft. I do not see it listed at http://www.imagemagic...
by NicolasRobidoux
2014-06-08T10:46:09-07:00
Forum: Users
Topic: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling
Replies: 134
Views: 172759

Re: Sigmoidized Ginseng (pronounced "Jinc-Sinc") resampling

As I mentioned before, I'm also not sure anymore that Keys cubics are best.