Legacy ImageMagick Discussions Archive

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 p...

Isn't "Y" of XYZ linear but "L" of LAB nonlinear?

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.

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 te...

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.e...

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.

The overall image will become darker too, not just halos. Try downsizing a photo of cactus.

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

http://www.my-spot.com/RHC/RHC_Cameras.htm

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...

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...

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...

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

Anyway, I will see if I can compile a more recent version of IM6+HDRI+FFTW with mingw@amd64.

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...

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).

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/hh51...