resize performance

  • mymy

    mymy - 2008-07-29


    on , developpers of graphicsmagick say that resize could be faster.

    Do you know a software to make resize faster ?

    • Bob Friesenhahn

      Bob Friesenhahn - 2008-07-29

      GraphicsMagick contains several different resize algorthms.  The 'sample' algorithm is by far the fastest but results in lowest quality.  The 'scale' algorithm is slower but usually provides decent results.  The 'zoom' algorithm is actually a family of algorithms (selected by -filter) and is the slowest one.  At the C code level, there is a ThumbNailImage function which uses a combination of sample and zoom to great good thumbnails very quickly.  First the image is sampled down to a somewhat larger size, and then zoom is used for the final resize to minimize aliasing.

      The comment that resize could be faster is due to the zoom algorithm's current apparent "random access" which thrashes the cache for large images.

  • pmsaue0

    pmsaue0 - 2009-11-17

    How could I use the ThumbNailImage function (or something similar) from the command line?

    I've previously used **-thumbnail** with ImageMagick, but alas that command does not exist for GM.

    Is there a tutorial or guide for using functions that only exist at the C code level?


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