Magic kernel resizing

The “magic kernel” is a method of resampling images that gives clear results free of artifacts.

Description

The “magic kernel” is a method of resampling images that gives amazingly clear results (free of “aliasing” artifacts, free of “ringing”, and free of “width beat” for thin features) yet is lightning fast (the simplest version only requires a few integer additions and bit-shifts).

The full method description is available at http://johncostella.webs.com/magic/

• Required Products: Image Processing Toolbox
• MATLAB release: MATLAB 6.5 (R13)

[bmv]

I mean : B=magickernel(magickernel(A),'DOWN');

[bmv]

After these transformations:
A;
B=magickernel(magickernel(A),'DAWN');
Should A and B be the same? (A=B ?)

[Anton Semechko]

The cambridgeincolour link is pretty awesome. Thanks!

[Jan Motl]

It's a trade-off. Either you can have sharp images with halos (that's the case of bicubic interpolation) or blurred images without halos (like with Magic kernel).

More details about the interpolation trade-off are available at http://www.cambridgeincolour.com/tutorials/digital-photo-enlargement.htm

The artifacts particularly present in bicubic interpolation are described, for example, at Wikipedia: https://en.wikipedia.org/wiki/Bicubic_interpolation#Use_in_computer_graphics

Magic kernel is useful if you need extreme blow-ups or if you further post process the image and the used algorithm is sensitive to artifacts introduced by interpolation.

[Anton Semechko]

So what are the artifacts that are present in the image interpolated with a cubic spline?