From help-request at octave dot org Wed Feb 15 02:23:14 2006
Subject: Re: SIFT image descriptor patch
From: =?ISO-8859-1?Q?S=F8ren?= Hauberg <soren at hauberg dot org>
To: etienne at cs dot uky dot edu, etienne@isr.ist.utl.pt, etienne.grossmann@laposte.net
Cc: Octave Help <help at octave dot org>
Date: Tue, 14 Feb 2006 13:07:08 +0100

tir, 14 02 2006 kl. 05:56 -0500, skrev Etienne Grossmann:
>   Are the rsults ugly?
Before my hack I don't get any result shown, but after my hack 
I get some result that look just fine.
The lines could use some anti-aliasing, but I can live with that.

Did that answer the question?

/Søren

> On Mon, Feb 13, 2006 at 09:36:33PM +0100, Søren Hauberg wrote:
> # Etienne,
> # Thanks for doing this, it's nice to have SIFT in Octave.
> # I get the following error on some images:
> # 
> # error: linspace: npoints is 1, but x1 != x2
> # error: evaluating argument list element number 1
> # error: evaluating argument list element number 2
> # error: evaluating assignment expression near line 28, column 6
> # error: evaluating for command near line 22, column 1
> # error: called from `imglines' in file `/home/sh/Dokumenter/Robot
> # projekt/Octave siftDemo/imglines.m'
> # error: evaluating assignment expression near line 42, column 9
> # error: evaluating if command near line 14, column 1
> # error: called from `showkeys' in file `/home/sh/Dokumenter/Robot
> # projekt/Octave siftDemo/showkeys.m'
> # 
> # I fixed this by a very dirty hack. That is, 
> # if (len <= 1) len = 2; endif
> # in imglines.m
> # 
> # Thanks,
> # Søren
> # 
> # tir, 27 12 2005 kl. 11:32 -0500, skrev Etienne Grossmann:
> # >   Hi All,
> # > 
> # > this patch could be of interest to octave users who do image
> # > processing.  You can apply it to the matlab code in siftDemoV4 [1] to
> # > allow octave to extract SIFT image features [2] with David Lowe's
> # > package.
> # > 
> # >   The SIFT image detector identifies interest points, somewhat like a
> # > corner detector does, and gives them a local descriptor. The
> # > descriptor can then be used for matching purposes (another way to
> # > perform matching could be correlation of a small window around the
> # > feature). Wrt to corners + local window correlation, SIFT features are
> # > more robust to changes in illumination and viewpoint [3] and they are
> # > increasingly used in computer vision.
> # > 
> # >   The siftDemo has functions to find sift features and to perform
> # > matching. I've tested the patch under octave+linux, matlab+linux (it
> # > works) and octave+win (it fails, probs w/ imagemagick + double).
> # > 
> # >   Hth,
> # > 
> # >   Etienne
> # > 
> # > 
> # > 
> # > [1] http://www.cs.ubc.ca/spider/lowe/keypoints/siftDemoV4.zip
> # > 
> # >   Synopsis: 
> # > 
> # >     unzip siftDemoV4.zip;
> # >     cd siftDemoV4; 
> # >     patch -p1 < mySift.patch
> # >   
> # >     In octave, make sure sift.m is in your path, then
> # > 
> # >     >> [image, descriptors, locs] = sift("/home/etienne/prog/various/siftDemoV4/book.pgm");
> # >    >> showkeys(image, locs)
> # > 
> # >    See also 'help match'
> # > 
> # > [2] http://www.cs.ubc.ca/~lowe/keypoints/
> # > 
> # >   David G. Lowe, Öbject recognition from local scale-invariant
> # >   features," International Conference on Computer Vision, Corfu,
> # >   Greece (September 1999), pp. 1150-1157.
> # > 
> # > [3] A performance evaluation of local descriptors Krystian
> # >     Mikolajczyk, Cordelia Schmid International Conference on Computer
> # >     Vision & Pattern Recognition - June 2003
> # > 
> # >     http://lear.inrialpes.fr/pubs/2003/MS03/mikolajczyk_cvpr2003.pdf
> # > 
> # > 
> 



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