Re: SIFT image descriptor patch

[Søren Hauberg]

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
> 
> 



-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
-------------------------------------------------------------