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Re: Small Resize Quality

From: gak (
04496@xyz.molar.is)
Date: Sun 06 Jan 2002 - 13:10:31 UTC

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    Hello Arnar,

    Thanks for your response. To address this issue I tried to use some of the filters to remove the blur. Specifically I tried unsharpmask and conv sharpen. The conv sharpen worked GREAT (i.e. $scaled->filter(type=>'conv', coef=>[-0.2, 1, -0.2]);

    Thanks for the help!

    P.S. This is an AWESOME perl module. A big thanks to those that made it possible! THANKS!

    The following message was sent by Arnar Mar Hrafnkelsson <04462@xyz.molar.is> on Fri, 4 Jan 2002 11:52:33 -0500 (EST).

    >
    > 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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