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Resampling algorithms
This probably belongs in the retouching forum, but I think it might apply here, too. I use CS2 for heavy duty retouching, ACDSee Pro for workflow. When resizing, ACDSee gives me several different filters, including Bicubic, Lanczos, Mitchell, box, triangle, bell and Clear IQZ. I always pick bicubic, but can't tell if the others are better or may be better for certain situations. Can anyone steer me to some explanations? Help files are always so unhelpful... Doc Apr 03 10 07:48 pm Link DocG1 wrote: For photos, Bicubic is the basic standard. But recently, Adobe has added Bicubic Sharper and Bicubic Smoother. Apr 03 10 08:09 pm Link I think these filters are basically the weights that neighboring pixels have in calculations. In a box filter, all the neighbors withing a certain distance have equal weight. In a triangle filter the nearer neighbors count more than the farther ones and the profile of the influence dropoff curve is a line on all sides, hence the 'triangle' (or cone, since it's a 2D zone of falloff) In a Gaussian filter the influence falloff is a bell curve. Bi-cubic is a cubic curve in a 2D zone of falloff. Beyond that I don't know, other than the others are other curves, and I would experiment and see which one works best for a particular application. Apr 03 10 08:26 pm Link Apr 03 10 09:03 pm Link It gets a lot easier to pick the one that works best for you if you over use it as a test. Start with an image you have sharp lines and curves on. Textures too. Upsize, Upsize, downsize downsize upsize, downsize, a few more times, then standard size. Do this for every algorithm. It is easier to choose after this. Apr 04 10 12:18 am Link See here for a comparison of the major methods and an analysis of their strong and weak points. I personally hope Adobe give us Lanczos at some point in the future, but it's something we've all lived without so long, how many will really notice?  .Apr 04 10 05:55 am Link Tom Sidock Photography wrote: I use Bicubic Sharper most of the time when downsizing. Apr 04 10 06:14 am Link A late edition, this is Don Mitchell (of "Mitchell Filter"). That filter, by the way, was designed for enlarging images. But I generally use Lanczos for both enlarging and shrinking, it's a more expensive filter that takes in a wider window of pixels as input. Lanczos is a "windowing" function applied to an infinitely wide ideal filter called "sinc". I've found Kaiser windowing is superior, but I don't know anyone who does it. The Lanczos filter was made famous in a paper by Steve Gabriel (Microsoft Research, and formerly one of the designers of the Ampex ADO. There are always tradeoffs in filters, nothing works perfectly. You will always get some degree of blurring, ringing, or aliasing (jaggies). It's more a matter of taste sometimes. For example bicubic (that's probably the Catmull-Rom filter) is sharper than the Mitchell filter, but it will produce more edge ringing or haloing. Oct 23 14 03:41 pm Link In ACDsee the best is Lanczos. Here the best of the best http://www.luminous-landscape.com/forum … #msg762951 Here an alternative version http://www.luminous-landscape.com/forum … #msg766264 Must be logged to be able to download. Oct 24 14 07:11 am Link Luciform wrote:
Oct 24 14 07:44 am Link It has always been my understanding for maybe 20 years of using Photoshop, that bicubic was preferred for photographic images. Some of the others were more targeted at graphic design layout, typefaces, etc. Oct 24 14 06:23 pm Link |
