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Re: Small Resize Quality

From: Arnar Mar Hrafnkelsson (
04286@xyz.molar.is)
Date: Fri 04 Jan 2002 - 16:52:33 UTC

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    Typically when it comes to downsampling there is a little tradeoff between
    sharpness and noise in the scaled version. It's also possible that the
    scaling ratio is more important than the actual final size, then there is
    a possible issue in the scaling code. It's also just possible that they
    look blurry if there is just too much high frequency in the image for that
    size.

    There was an issue in versions older than 0.39 where resizing could nasty
    artifacts. The downsampling method used is effectively a lowpass filter
    followed by decimation. The filter is a lancoz kernel, There are some
    parameters (that are not exported right now) which can be altered. One
    idea is to have a callback that specifies the lowpass filter to be used.

    -- Arnar

    On Fri, 4 Jan 2002, gak wrote:

    > Happy New Year!
    >
    > I see a 'qtype' (quality type?) variable described under the Image Resizing section of the Imager documentation. Are there other settings other than preview?
    >
    > I've found that images resized by Imager to a relatively small size (100 to 125 pixels wide) come through slightly blurry. Larger resized photos (400+ pixels wide) look GREAT! I'm wondering if a qtype=high setting exists to improve the quality for small images.
    >
    > Anyone have experience with improving the quality of smaller images? Maybe there is another method.
    >
    > Thanks!
    >
    >



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