Legacy ImageMagick Discussions Archive

Suggestion: The min of four values is better computed as min(min(a,b),min(c,d)). (This of course depends on the compiler etc.) The reason is that the two mins can be computed "concurrently". Same with max. And if you really want to save flops, you may be better off combining the computatio...

There is only more to EWA than "computing weights using polar (or cylindrical) coordinates and ignoring the angle" when you are not preserving the aspect ratio, for example when warping or doing texture mapping.
EWA BC-spline is fairly self-explanatory IMHO.

https://github.com/jcupitt/libvips/blob/master/libvips/resample/nohalo.cpp https://github.com/GNOME/gegl/blob/master/gegl/buffer/gegl-sampler-nohalo.c P.S. LBB-Nohalo has not built a huge following (that I know). Maybe it's because it's only found in a library that only recently started picking up ...

Sergio: With a disc of radius 2.5 and enlargement ratios that are not too large (so you can't see the discontinuities introduced by chopping at radius 2.5), I think you should simply use Jinc3 and play with the deblur. Unless this messes up the anti-ring you use, in which case I'd stick to EWA Keys ...

I have the intention to combine a pure pixel art algorithm (xBR) with a pure linear one (a good one with cylindrical coordinates), so that it keeps good textures at nature scenes and a high edge care. I have already tried it before and released a shader called xBR-hybrid, which combine xBR with a v...

The advice about EWA with Keys cubic? I have an implementation of BC cubic family in shader format, so I intend to integrate it with cyindrical coordinates to see what is the output. I think you may get good mileage out of EWA with Keys cubics, and playing with the one parameter that's left (becaus...

EWA (when doing pure enlargement) in a nutshell: Let the 1D kernel function be f(r) This is a univariate function: 1 input, 1 output, both real numbers. The unnormalized weight of the input pixel (i,j) at location (x,y) is v_{i,j} = f(r_{i,j}) where r_{i,j} = sqrt((x-i)^2+(y-j)^2) In other words, th...

Nice to see the idea of "deblurring" kernels instead of using them "straight up" (which of course was in IM way before I got involved, but was not used much I think) exploited to good effect. As some of you know, I've been pushing the idea that there are "special" debl...

P.S. An example of "rigid optimization" concerns the fact that, when used in an EWA (Elliptical Weighted Averaging) resampler, the Keys splines are the BC-splines that most accurately interpolate linear gradients (just like they do when used in a tensor, that is, "orthogonal", w...

Sergio (Hyllian): One last thing: Your choice to limit yourself to diameter 2.5 is reasonable, the other components of your approach also reasonable (at least in what I understand your context is) and the results you showed look good. I won't be offended if you ignore my advice. Good luck!

Nice to see the idea of "deblurring" kernels instead of using them "straight up" (which of course was in IM way before I got involved, but was not used much I think) exploited to good effect. As some of you know, I've been pushing the idea that there are "special" deblu...

And indeed your latest scheme looks very good.

Hyllian: Apologies for telling you, of all people, about the existence of specialized pixel art shaders. (Foot in mouth disease strikes again.)

Our posts crossed. ----- Now that I understand more what you want to do, I really suggest that you try EWA with Keys cubics. This is a one parameter family of schemes which only grab data from a disc of diameter 4, the weights are cheap to compute (there is code that computes some of them efficientl...

If it is truly pixel art (as opposed to line art) see https://plus.google.com/+SevensheavenNL/posts/6nXFi6BHJ1N . If you really want to develop your own method from what you have already, I suggest the following: Instead of blending with your scheme untouched by your AR method, blend with the result...