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by NicolasRobidoux
2014-07-29T23:59:40-07:00
Forum: Users
Topic: [SOLVED]Windows script driving IM: basic arithmetic on param
Replies: 5
Views: 4229

[SOLVED]Windows script driving IM: basic arithmetic on param

Bart van der Wolf, with some assistance from Fred Weinhaus, Alan Gibson and myself, has been polishing a Windows script that combines several ImageMagick commands to produce excellent quality when resizing. (Right now, it only works "perfectly" with sRGB input and output, but this may be extended to...
by NicolasRobidoux
2014-07-23T02:43:53-07:00
Forum: Digital Image Processing
Topic: minimize resize halo by luminance-weighted gamma blending
Replies: 6
Views: 17387

Re: halo minimization by luminance-weighted gamma blending

This viewtopic.php?f=1&t=25945#p113621 and some of the preceding posts in the same thread are relevant to this subject.
by NicolasRobidoux
2014-07-22T18:07:26-07:00
Forum: Users
Topic: convert from Adobe RGB to some kind of linear RGB (and back)
Replies: 19
Views: 13420

Re: convert from Adobe RGB to some kind of linear RGB (and b

Fred: This is what's going on: Indeed, one could do a resize in sRGB then convert to linear RGB, convert to linear RGB then resize, compute the luminance from the latter, blend the two results, and convert the blend back to sRGB. What I showed was actually exactly the same replacing sRGB by Adobe RG...
by NicolasRobidoux
2014-07-22T16:33:50-07:00
Forum: Users
Topic: convert from Adobe RGB to some kind of linear RGB (and back)
Replies: 19
Views: 13420

Re: convert from Adobe RGB to some kind of linear RGB (and b

If I understand correctly how profiles etc are handled with IM, and assuming input_small.tif is Adobe RGB 8 bit (if already 16 bit, I imagine the first parentheses can be skipped) this would be the one in which linear is blended with a gamma version which here is neither 2 nor 3. This is different t...
by NicolasRobidoux
2014-07-22T15:22:51-07:00
Forum: Users
Topic: convert from Adobe RGB to some kind of linear RGB (and back)
Replies: 19
Views: 13420

Re: convert from Adobe RGB to some kind of linear RGB (and b

Fred: When I have a minute, I'll post a simplified version that exploits the fact that we may as well use gamma 2.19921875 intead of gamma 2 or 3.
(It's already tomorrow where I live.)
by NicolasRobidoux
2014-07-22T11:57:27-07:00
Forum: Users
Topic: convert from Adobe RGB to some kind of linear RGB (and back)
Replies: 19
Views: 13420

Re: convert from Adobe RGB to some kind of linear RGB (and b

Alan: I'm totally fine with "different RGB colorspaces". Actually, I'd be fine with other primaries than RGB. So this works for >>me<<. But indeed, without the "Longer answer", people may think that they are getting the same linear RGB as doing -set colorspace sRGB -colorspace RGB. And of course thi...
by NicolasRobidoux
2014-07-22T10:02:47-07:00
Forum: Users
Topic: convert from Adobe RGB to some kind of linear RGB (and back)
Replies: 19
Views: 13420

Re: convert from Adobe RGB to some kind of linear RGB (and b

So, to go from Adobe RGB to linear RGB with Adobe RGB primaries

Code: Select all

... -gamma .4547069271758437 ...
(with possibly a -set colorspace RGB or two to avoid confusion) and to go back to Adobe RGB

Code: Select all

... -gamma 2.19921875 ...
by NicolasRobidoux
2014-07-22T04:22:31-07:00
Forum: Users
Topic: convert from Adobe RGB to some kind of linear RGB (and back)
Replies: 19
Views: 13420

Re: convert from Adobe RGB to some kind of linear RGB (and b

Alan (snibgo):
Cool: Adobe RGB is a "straight" gamma space \o/
by NicolasRobidoux
2014-07-20T02:07:16-07:00
Forum: Users
Topic: convert from Adobe RGB to some kind of linear RGB (and back)
Replies: 19
Views: 13420

convert from Adobe RGB to some kind of linear RGB (and back)

How can this be done? Looked at http://www.imagemagick.org/Usage/formats/#color_profile and am not 100% sure I got the full picture. If the profile is embedded in InputImage, is convert InputImage -profile (stuff I want to do in linear RGB) OutputImage enough? I don't particulary care which linear R...
by NicolasRobidoux
2014-07-18T01:29:02-07:00
Forum: Digital Image Processing
Topic: minimize resize halo by luminance-weighted gamma blending
Replies: 6
Views: 17387

minimize resize halo by luminance-weighted gamma blending

As discussed initially in http://www.imagemagick.org/discourse-server/viewtopic.php?f=1&t=25736 and http://www.imagemagick.org/discourse-server/viewtopic.php?f=22&t=21804#p89728 and further developed in http://www.luminous-landscape.com/forum/index.php?topic=77949.msg745796#msg745796 and http://www....
by NicolasRobidoux
2014-07-15T00:36:24-07:00
Forum: Users
Topic: Improving sigmoidal image resampling (enlargement)
Replies: 19
Views: 19148

Re: Improving sigmoidal image resampling (enlargement)

Preliminary findings I am pretty sure that sigmoidization is dead as a general purpose resampling method. The simple version of what works better is to use mapping through a gamma space (with a matching pair of -gamma commands, like -gamma 3 -distort Resize 800% -gamma .33333333333333 ) to reduce t...
by NicolasRobidoux
2014-07-09T23:37:55-07:00
Forum: Announce
Topic: Windows/Linux/OSX ImageMagick GUI
Replies: 9
Views: 50661

Re: Windows/Linux/OSX ImageMagick GUI

Will it try to load and save as 32-bit float tiff? Whatever it loads (unless a depth command is issued?) will generally be stored, internally, in a floating point format. If this is not acceptable, stick to the standard Q16 version. There may be ways of controlling this behavior, but I don't have t...