Feature points in image, Keypoint extraction

Finds, matches, plots feature points in images.

Description

All this files I've done when I took course in image proc, I haven't changed a thing, hope it'll be useful to students and interested in subject. All codes have comments, it's very easy to understand, as well there is my report file, find there all theoretical background and descriptions.

Feature points (read corners) in images are points that invariant under view changes, zoom, lightening conditions etc.
Implemented a SIFT like descriptor, as well ASIFT (search in Google).
Shortly about ASIFT - simulates view changes of images, for each such view finds FPs and create descriptor for it for future matching. It's slow (in internet authors submitted a C++ version which is quick), so my version of ASIFT is not so applicable, but good for studying, understanding, I think.

There are a lot of options, parameters, you can influence every step of calculations, to make it quicker etc.
 
Used pdist2.m code from Piotr's Toolbox
http://vision.ucsd.edu/~pdollar/toolbox/doc/
as well k nearest neighbors from Matlab exchange server, author of which I can't find now.

• MATLAB release: MATLAB 7.6 (R2008a)

[bin yao]

I have a question. In Findlclmxm.m, there is d2Fdxdy = [ 1 0 -1; 0 0 0; -1 0 -1 ]/4;

I think it should be [1 0 -1; 0 0 0; -1 0 1] ?

[Artiom Kovnatsky]

Hi,
yes, u right, need to be what u've written.
I'll change it.
Thank you.
:)

[fastidious]

hi!!!
I found your code very interesting, but it gave the following error...
??? Error using ==> minus
Matrix dimensions must agree.

Error in ==> Findlclmxm at 83
rowSPA = row - RowDeltaY( ind2 );

Error in ==> harrislpls at 80
     [ row, clmn, rowSPA, clmnSPA, MxMtr ] = Findlclmxm(HrF, NBHOOD,
     BorderDistance, ThreshType, HarrisThresh );

Error in ==> demoSIFT at 59
[ HrLPoints1 ] = harrislpls( img1gr, TypeOfNBHOOD, NBHOOD,
TypeOfCornerDetector, BorderDistance, ThreshType, HarrisThresh, k, Dilate,
radius, sigma_nmbr, dispPlaces, SwitchWaitbars );