Howtosignalprocessing
- How do you calculate SIFT descriptor?
- Is SIFT a detector or descriptor?
- How does SIFT descriptor work?
- Why are SIFT features better descriptors than the normalized patches ?]?
How do you calculate SIFT descriptor?
SIFT descriptors are computed by either calling vl_sift_calc_keypoint_descriptor or vl_sift_calc_raw_descriptor. They accept as input a keypoint frame, which specifies the descriptor center, its size, and its orientation on the image plane.
Is SIFT a detector or descriptor?
The Scale-Invariant Feature Transform (SIFT) bundles a feature detector and a feature descriptor. The detector extracts from an image a number of frames (attributed regions) in a way which is consistent with (some) variations of the illumination, viewpoint and other viewing conditions.
How does SIFT descriptor work?
For each key point, the dominant orientation is determined to achieve rotation invariance. SIFT descriptors are calculated as a histogram of image gradients around key points to characterize the local appearance of each selected key point. Readers can find more detailed material about the SIFT feature in Ref.
Why are SIFT features better descriptors than the normalized patches ?]?
Switching to SIFT Descriptors
This is due to the SIFT-like descriptor being more abstract than a normalized patch in regards to the actual pixel values of the image. Therefore, it is more difficult to match up keypoints than when using normalized patches, since there is less data about the actual image.
