How does Lowe compute the "repeatability" of his SIFT Algorithm?

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How does Lowe compute the “repeatability” of his SIFT Algorithm?

In his paper of 2004, "Distinctive Image Features from Scale-Invariant Keypoints", he gave many figures of "repeatability" as a function of XXX, for example, figure 3,4 and 6, but he did not elaborate how to compute the "repeatability". He actually gave an simple explanation of "repeatability" in figure 3 of page 8, which is "the percent of keypoints that are repeatably detected at the same location and scale in a transformed image". However, ...

Answer:

If you notice in the first paragraph on page 9, the author goes into a bit more detail on the tolerance...

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user1222309 at Stack Overflow Mark as irrelevant Undo

Other solutions

Why does the Scale Invariant Feature Transform (SIFT) algorithm tend to extract unstable keypoints from non-rigid objects in different illumination conditions?

I was implementing SIFT algorithm as feature extraction method in biometric (face recognition) authentication system. And the result, system has bad performance when authenticating user in different illumination condition (system cannot identified privileged...

Answer:

The standard SIFT algorithm discards low contrast keypoints, such as those that would appear on faces...

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Johnny Ho at Quora Mark as irrelevant Undo

What are steps to compute algorithm complexity?

I have forgotten stuff on how to compute time complexities of algorithms. I am not looking for a Book or 30 page blog to refresh that knowledge. Taking this below algorithm could you please correct in the way i compute the Time Complexity. Thanks Linear...

Answer:

You can read about the basic steps: Determining An Algorithm's Complexity: The Basics

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Octav Druta at Quora Mark as irrelevant Undo

Write a non-recursive algorithm to compute n!?

write a non-recursive algorithm to compute n!

Answer:

nfact = 1 for i = 2 to n nfact = nfact*i next i Or do you consider that "recursive." To me...

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GTKC6IMNF3K7ENQIQXOJKS4TRA at Yahoo! Answers Mark as irrelevant Undo

Computer Vision: How does the SIFT decriptor becomes the drawn vector on the image?

I run sift algorithm in a image; the output is a variable des, which contains n vectors representing keypoints. I know, from the Lowe paper, that each value of the 128 numbers in the descriptor represents a gradient, but how does it turns into the vector...

Answer:

you can find detailed step wise tutorial here @SIFT: Introduction

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Ravi Shukla at Quora Mark as irrelevant Undo

Computer Vision: Why is Gaussian Filter used in SIFT algorithm?

SIFT-Scale Invariant Feature Transform   Gaussian filter is used to generate the Scale space .Why not other filter? Scale-invariant feature transform

Answer:

I think it's because the difference of Gaussian is a great blob detector, as in, it's response when...

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Rakshit Kothari at Quora Mark as irrelevant Undo

What is the algorithm/data structure used by Lucene to compute the term frequency of documents?

It looks like use the Map structure to compute the term frequency, but I wanted to know the more detailed answer.

Answer:

Lucene uses inverted index(http://en.wikipedia.org/wiki/Inv...) to store term vectors.  For more detail...

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Vineet Yadav at Quora Mark as irrelevant Undo

From the set of natural integer numbers Let x = 1234 = {1, 2, 3, 4} Let y = 2410 = {2, 4, 1, 0}  Write an algorithm to compute the rearrangement of x that is closest to y but still greater than y. Both x and y have the same number of digits.?

So in the example above, the answer would be { 2, 4, 1, 3 } = 2413 which is greater than y = 2410 and closer than any other arrangements of x. And whats the time complexity of this algorithm?

Answer:

You can do this in linear time. Iterate over the digits in y and try to match them one by one. If you...

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Nick Wu at Quora Mark as irrelevant Undo

Is Dijkstra's Algorithm a greedy algorithm or a dynamic programming algorithm?

In Dijkstra's Algorithm, we start from a single node and find the shortest path to each of the other nodes in every iteration. If we start from a node A and reach node C via node B, we are in a way using the already solved sub-problem to compute the...

Answer:

Djikstra's algorithm is a very unique algorithm. Initially, it uses a greedy approach to get initial...

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Madhusudhan Krishnamachari at Quora Mark as irrelevant Undo

Computer Vision: What is a SIFT vector? How can I normalize its values? How can I choose one of the best descriptors?

I'm implementing the SIFT algorithm in Python, with OpenCV 2.x My code until now looks like this: import cv2 import numpy as np img = cv2.imread('C:\Python27\lena.jpg') gray= cv2.cvtColor(img,cv2.COLOR_BGR2GRAY) sift = cv2.SIFT() kp = sift.detect(gray...

Answer:

To answer a few of your questions: 1. To process more than one image, simply crawl the directory in...

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Sandeep Subramanian at Quora Mark as irrelevant Undo

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