I have read some literature about SIFT and watched some videos also. I understood most of the concepts behind SIFT but one thing which confuses me is about SIFT descriptors.
In SIFT:
- we find a keypoint
- we take
16 x 16
pixels around the keypoint. - Divide the
16 x 16
blocks into 16 number of4 x 4
blocks - Calculate a
8 bin
histogram for each4 x 4
block - Therefore, we get
4 x 4 x 8 = 128
dimension SIFT descriptor for this keypoint.
My confusion:
- Lets say, my image have 50 keypoints.
- The SIFT descriptor i receive for this image (i.e. Mat descriptor) has
128 columns
and1 row
.....why??? - I got
128 columns
and1 row
for a single keypoint then if i am getting 50 keypoints then shouldn't it be a50 rows
and128 colmuns
matrix?