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Date: Fri, 7 Jul 2000 17:24:12 +1000
From: Martien Verbruggen <mgjv@comdyn.com.au>
To: Geoff Armstrong <geofstro@monaco.mc>
Cc: ImageMagick Mailing List <magick@wizards.dupont.com>
Subject: Re: converts new sharpen factors
Message-ID: <20000707172412.C23320@martien.heliotrope.home>
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In-Reply-To: <00070515380200.26142@berlioz>; from geofstro@monaco.mc on Wed, Jul 05, 2000 at 03:35:26PM +0200
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-- Geoff Armstrong wrote on Wed 5 Jul 15:35 PM --
> Hi,
>
> I know the sharpen factors for convert have changed since 5.2.0; but I
> can't find the new factors documented anywhere.
The factors are no longer really factors, but orders for a convolution
kernel, if I've understood it all correctly. Since convolution has
become available in ImageMagick, many of the old filters have been
rewritten to use a kernel (blur, sharpen, charcoal, emboss, edge).
The convert manual page mentions that good values are odd numbers
between 3 and 31.
Martien
PS. If you don't know what convolution is: apply a matrix to each pixel,
and it's surrounding neighbors covered by the matrix. The values of each
covered pixel get multiplied by the matrix cell's value, and all added
together. The new value for the target pixel is this sum. The 'order'
that I talked about above is the height and width of the matrix involved
(in ImageMagick they're always square).
--
Martien Verbruggen |
Interactive Media Division | "In a world without fences,
Commercial Dynamics Pty. Ltd. | who needs Gates?"
NSW, Australia |
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