SURF feature extraction on a dense grid with MATLAB

Question

I would like to use SURF (speed-up robust) features to implement a classification system based on a bag-of-visual-words approach. I have read some papers about the use of a dense grid to extract these features, but I can't find how to use it with MATLAB.

Does anybody know how to do SURF feature extraction on a dense grid with MATLAB?

Answer 1

[nRows, nCols] = size(grayImg);
STEP = 10;
colInd = (1 : STEP : nCols)';
rowInd = (1 : STEP : nRows)';
[A, B] = meshgrid(colInd, rowInd);
densePoints = [A(:) B(:)];

[featuresDense, validPointsDense] = extractFeatures(grayImg, densePoints, 'Method', 'SURF');
figure, imshow(img)
title('Dense SURF')
hold on
plot(validPointsDense)