Search found 188 matches

by henrywho
2012-07-26T02:50:35-07:00
Forum: Users
Topic: best downsampling method for DSLR photographs
Replies: 273
Views: 389519

Re: best downsampling method for DSLR photographs

Fred: Your observations jive with "why" Henry tried EWA Catmull-Rom: To give "pixel peepers" all the sharpness they crave. His context was downsampling, but still. Hey, I thought I had made myself clear in some posts that I prefer EWA Lagrange over EWA Catrom for downsizing in place of unsharpening...
by henrywho
2012-07-19T23:22:31-07:00
Forum: Digital Image Processing
Topic: future of image enlargement?
Replies: 61
Views: 127180

Re: future of image enlargement?

Isn't "Y" of XYZ linear but "L" of LAB nonlinear? :shock:
by henrywho
2012-07-18T19:34:15-07:00
Forum: Digital Image Processing
Topic: "Sigmoidal" minimization of resampling filter haloing & blur
Replies: 136
Views: 265566

Re: "Sigmoidal" minimization of resampling filter haloing

NicolasRobidoux wrote:@Henry: I checked downsampling with the Nokia picture and it looks like linear light wins, as usual.
To me, downsampling in linear RGB with sigmoidal minimization looks much like downsampling in sRGB plus cooked highlights. I think it is better suited for upsampling.
by henrywho
2012-07-18T05:26:43-07:00
Forum: Digital Image Processing
Topic: "Sigmoidal" minimization of resampling filter haloing & blur
Replies: 136
Views: 265566

Re: "Sigmoidal" minimization of resampling filter haloing

Henry: I enlarged the small version of the image (..._m) 400% and I see no colour drift. I think you are using a version of IM with the sigmoidal-contrast "bug". I copied the wrong commands and it's now corrected. I was doing downsizing of the original version and see if this sigmoidal technique is...
by henrywho
2012-07-18T02:04:04-07:00
Forum: Digital Image Processing
Topic: "Sigmoidal" minimization of resampling filter haloing & blur
Replies: 136
Views: 265566

Re: "Sigmoidal" minimization of resampling filter haloing

Seems sigmoidal-downsizing increases the brightness of all interpolated areas. Try it on http://www.dcfever.com/phones/viewsamples.php?set=755&picture=7234 , the buildings over the other side of the harbour looks brighter and the tall building on the left looks more "cooked". convert.exe 755_1340939...
by henrywho
2012-07-17T19:47:52-07:00
Forum: Digital Image Processing
Topic: future of image enlargement?
Replies: 61
Views: 127180

Re: future of image enlargement?

NicolasRobidoux wrote:I think that my worries about high contrast leading to colour drift were just that?
P.S. No, they are not: It depends on the sharpness of the input image.
Let me try Avisynth+NNEDI3+EEDI3 tonight.
by henrywho
2012-07-12T00:16:26-07:00
Forum: Digital Image Processing
Topic: "Sigmoidal" minimization of resampling filter haloing & blur
Replies: 136
Views: 265566

Re: "Sigmoidal" minimization of resampling filter haloing

The overall image will become darker too, not just halos. Try downsizing a photo of cactus.
by henrywho
2012-07-11T19:29:11-07:00
Forum: Digital Image Processing
Topic: [SOLVED] Donate a high quality raw image to science?
Replies: 67
Views: 130554

Re: [SOLVED] Donate a high quality raw image to science?

It looks great! Hope it would support my Panasonic GX1 in some future.

http://www.my-spot.com/RHC/RHC_Cameras.htm
by henrywho
2012-07-11T09:25:46-07:00
Forum: Users
Topic: best downsampling method for DSLR photographs
Replies: 273
Views: 389519

Re: best downsampling method for DSLR photographs

Henry's -gamma trick that adds acutance. No, that gamma trick is intended to purposely obtain darker interpolated value, which is much welcomed when downsizing lines or characters on a light background. When the background is dark and the content is light, I do the opposite. Edit: And the negate-ne...
by henrywho
2012-07-10T17:16:59-07:00
Forum: Users
Topic: best downsampling method for DSLR photographs
Replies: 273
Views: 389519

Re: best downsampling method for DSLR photographs

Some preliminary downsize testing with the Astro/HDRI binary: while EWALanczos3Sharpest is nearly as sharp as EWALanczos4Sharpest, it seems to ring much less (or acutance?), especially for sharp CG pictures. When I really need acutance, I will use EWA-Lagrange. EWALanczos4Sharpest is sitting somewhe...
by henrywho
2012-07-09T23:21:59-07:00
Forum: Digital Image Processing
Topic: Image resizing with LCD sub-pixel awareness (aka ClearType)
Replies: 18
Views: 66259

Re: Image resizing with LCD sub-pixel awareness (aka ClearTy

One surprising result is that the HDRI enabled binary at http://blog.astrophotographytargets.com/ is producing sharper and more contrasty images (both -gamma and -colorspace tested) than normal Q16 binary with the above textual image. Tiny difference but noticeable. I believe such test cases are cha...
by henrywho
2012-07-09T19:01:31-07:00
Forum: Users
Topic: best downsampling method for DSLR photographs
Replies: 273
Views: 389519

Re: best downsampling method for DSLR photographs

It's http://www.imagemagick.org/Usage/windows/ that directs me to that astrophotography blog. :D

Anyway, I will see if I can compile a more recent version of IM6+HDRI+FFTW with mingw@amd64.
by henrywho
2012-07-09T16:38:45-07:00
Forum: Users
Topic: best downsampling method for DSLR photographs
Replies: 273
Views: 389519

Re: best downsampling method for DSLR photographs

With a very recent version of ImageMagick 7, the linear light versions of these schemes are .... With a recent enough version of ImageMagick 6, just replace "magick" by "convert". I am using the stock binaries at http://www.imagemagick.org/script/binary-releases.php#windows . So I presume they are ...
by henrywho
2012-07-07T08:50:07-07:00
Forum: Users
Topic: Gamma correction for JPG file
Replies: 7
Views: 14715

Re: Gamma correction for JPG file

Why not "-colorspace RGB". It converts your image to linear RGB for further operations.

sRGB is very similar to gamma 2.2, but not exactly the same. Not sure about AdobeRGB (some DC produces AdobeRGB instead of sRGB).
by henrywho
2012-07-07T02:10:18-07:00
Forum: Digital Image Processing
Topic: Image resizing with LCD sub-pixel awareness (aka ClearType)
Replies: 18
Views: 66259

Re: Image resizing with LCD sub-pixel awareness (aka ClearTy

It seems to work better with B/W textual materials. 1000x500 picture with contents quoted from: http://zh.wikipedia.org/wiki/%E8%9F%B9%E7%8A%B6%E6%98%9F%E4%BA%91 http://i1249.photobucket.com/albums/hh512/henhen456/msg2.png "Plain" resize to 200x100: http://i1249.photobucket.com/albums/hh512/henhen45...