The three Edge_detect implementations

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cesarabravop
Posts: 1
Joined: Wed Jun 16, 2010 4:05 pm

The three Edge_detect implementations

Post by cesarabravop »

Hi there XnView
I had just installed and tested XnView 1.19.5, release 11 Jun 2010, on a Windows 7 box,
and I am impressed by the quality of the results of three different implementations
of the Edge_detect filter algorithm.

I understand that the source code is not disclosed but, can you share the ideas behind the three different implementation of this filter?

Thanks in advance and congratulations for a good job.
César
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xnview
Author of XnView
Posts: 43357
Joined: Mon Oct 13, 2003 7:31 am
Location: France
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Re: The three Edge_detect implementations

Post by xnview »

It's a filter, i use:

/* Edge Detect Light */
0, 1, 0,
1, -4, 1,
0, 1, 0,

/* Edge Detect Medium */
-1, -1, -1,
-1, 8, -1,
-1, -1, -1,

/* Edge Detect Heavy */
1, -2, 1,
-2, 4, -2,
1, -2, 1,
Pierre.
Zack
Posts: 2
Joined: Fri Nov 18, 2016 10:17 am

Re: The three Edge_detect implementations

Post by Zack »

Thanks for posting the convolution kernels for the edge filters. There must be a normalization step in addition to make the negative values produced by this kernel in the correct pixel range. I've tried to see if a simple linear transform using the max and min pixel to 255 and 0 in the grey scale, but this doesn't produce the correct normalization.

Would it be possible to provide more information? Thanks.
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