Image Resize

When scaling down images, apply small doses of USM afterwards to prevent blurriness.


Down-sampling examples

See interactive application at bottom of page comparing these different algorithms

  • IrfanView 3.91
  • IrfanView 3.91 + sharpen (20)
  • Qimage Pre 309
  • QI 310 Low-AA
  • QI 310 Med-AA
  • QI 310 High-AA
  • Photoshop "sharper"
  • Photoshop "bicubic"
  • Photoshop "bicubic"+USM
  • ImageMagick Lanczos
  • ImageMagick Lanczos+USM

Image Resizing for Web and Email

The ideal solution is to use a sinc or lanczos algorithm to avoid moiré artifacts in the downsized image, then follow-up with a very small radius (0.2-0.3) unsharp mask to correct for any interpolation-induced softening. On the other hand, the sinc algorithm is not widely supported and software which uses it is often not as user-friendly.

ImageMagick USM

Sharpening Using Image Magick

Most users will use the unsharp mask filter in the convert command. The option to invoke an unsharp mask looks like this

-unsharp <radius>{x<sigma>}{+<amount>}{+<threshold>}

That is, a radius is expected (or a leading “x” if omitted), followed by optional parameters sigma, amount and threshold. [Note that there is also a -sharpen option to convert. This is not an alias for -unsharp, and (I'm pretty sure) employs a different sharpening routine internally.]

A typical call to convert might look something like the following:

$ convert ... -unsharp 1.5x1.2+1.0+0.10 <input file> <output file>

SML Wiki: Algorithm

FoldUnfold Table of Contents SML Blogs: Algorithm Popular Latest Flickr Interesting Backlinks Social SML Blogs: Algorithm Popular

Eric Fabricant
Search Eric Fabricant Clusty: Eric Fabricant Google: Eric Fabricant Live Search: Eric Fabricant SML Search: Eric Fabricant Yahoo Search: Eric Fabricant FoldUnfold Table of Contents ...

Flickr Analytics
Update: Because of newly discovered US Patent Filing of the Interestingness algorithm, attention has been shifted towards the analysis of this algorithm. Objective Analyze the Flickr Interestingness...

Flickr Interestingness Algorithm
Interestingness is a media (images, videos, etc) ranking algorithm to provide as an additional metric for search results. The algorithm is based upon an algorithm created by the Flickr team, and is...

Image Resize
When scaling down images, apply small doses of USM afterwards to prevent blurriness. FoldUnfold Table of Contents Algorithms Down-sampling examples Image Resizing for Web and Email ImageMagick...

Popularity Algorithm
Variables at play Number of votes Record Age Trustworthiness of user who submitted vote Trustworthiness of user who voted Velocity of vote gain over time1 One-mindedness penalized2 Also See ...

Search Algorithm
Algorithm Search engines can utilize GMAT score honing technique to tweak relevant results. Keyword density (SEO tip from Simon Metz) United States Patent Applications Flickr Interestingness...

Steering Behaviors
Libraries AS3 Looking for one. Flickr Groups: Generative Visuals: iso (Java to AS3 porting tools) OR (AS3 Steering Behavior Lib) C++ MetaAgent OpenSteer Java / Authors:...

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