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Questions tagged [sift]

Scale-invariant feature transform (SIFT) is an algorithm in computer vision to detect and describe local features in images. This tag is for programming questions related to SIFT implementation or programs that use SIFT algorithm for computer vision applications.

Scale-invariant feature transform (SIFT) is an algorithm in computer vision to detect and describe local features in images, introduced by prof. David Lowe in 2004.

The local features extracted from an image with SIFT can then be used to identify an object from that image. This visualization illustrates homologous SIFT keypoints in two separate pictures of the same magazine cover:

enter image description here

Applications of SIFT include object recognition, robotic mapping and navigation, image stitching, 3D modeling, gesture recognition, video tracking, and match moving.

Algorithm Steps

  • Scale-space extrema detection

  • Keypoint localization

  • Interpolation of nearby data for accurate position

  • Discarding low-contrast keypoints

  • Eliminating edge responses

  • Orientation assignment

  • Keypoint descriptor

More information can be obtained here

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How to create a SIFT's descriptors database [with Python]?

How do I create a database of SIFT descriptors (of images)? I'm using OpenCV in Pyhton 2.7, and my intention is to implement a supervisioned training set on Support Vector Machine. Here is my code so far, for 1 image import cv2 import numpy as…
user2967127
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How to convert a matrix of SIFT features into a archive readable by Support Vector Machine?

I'm just starting a project using OpenCv to extract SIFT features from multiple images. Then I will make a database for training machine with SVM. Untill now, I studied this code which is very basic. But i would like to know, how should i proceed to…
user2967127
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Impossible to create SIFT detector and extractor

I'm trying to detect SIFT keypoints, using this code: #include "opencv2/features2d/features2d.hpp" #include "opencv2/nonfree/nonfree.hpp" #include "opencv2/nonfree/features2d.hpp" [...] Ptr detector = FeatureDetector::create(…
arthur.sw
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use of sift keypoint radius in calculating feature vector

I have followed many tutorials on SIFT and have a good understanding of how key points are detected.But while extracting SIFT feature vectors where does the keypoint scale play the role. As I understood, we just take a 16 X 16 window around a…
code4fun
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Set histogram of size surf descriptors

I'm trying to compute a motion histogram of the region around surf descriptor, and i don't know if there is a method to compute the size of the histogram (how many bins) and the size of the patch (the region of the neighborhood around the interest…
Video retrieval
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How to crete a SIFT's descriptors database

How do I create a database of SIFT descriptors (of images)? My intention is to implement a supervisioned training set on Support Vector Machine.
user2967127
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Sift implementation in Opencv 2.4.6 ubuntu

I am trying to compute correspondence between 2 images and am actually interested in the number of correspondence points, rather than the correspondence themselves, so that I can sue it to get the best match image. This is my following code : …
Lakshmi Narayanan
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Python - Sift Class SIFT.compute

I am trying to retrieve descriptors for key points that I have already found. I am using the following lines of code: sift = cv2.SIFT() self.features,des = sift.compute(self.gray,self.features) However, I am receiving the error: 'cv2.SIFT' object…
user2268507
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How to find (and rank) similar images in a bigger set of images?

The problem I need to solve is the "matching" of a smaller set of images to a bigger one. More than that I want to rank their similarity. The first think that came to my head was to use sift features and found out the vl_sift function did the job…
nVolteX
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Null Pointer Exception in SIFT Feature Detector on OpenCV for Android

*sorry if my english is bad -.-" Greetings, I'm a student and only have a little experience with both OpenCV or Java. I try to make a program that can stitch two images into one panorama images using SIFT and RANSAC. I also downloaded OpenCV Library…
Aisyah Darojati
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how to visualize the bag-of-word codebook(image classification)?

I want to use bag-of-word feature on image classification, and how to visualize the codebook? I use keypoint-sift then kmeans to do clustering. e.g., http://fias.uni-frankfurt.de/~triesch/courses/260object/papers/Fei-Fei_CVPR2005.pdf (figure 4)
songzw
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OpenCV SIFT out of memory error

I am using a SIFT as a feature detector in a program, creating it with the default options: cv::SiftFeatureDetector detector; When I use the detection function (detector.detect( image, keypoints );) it throws me the an out of memory error: OpenCV…
jsalvador
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call matlab dll from c++: fail to initialize the library

I try to use Demo code for detecting and matching SIFT features of David Lowe (lowe@cs.ubc.ca) in my code. So I compile the (.m)file in Matlab to generate DLL. Here is the command code in Matlab: mcc -B csharedlib:SiftMatch match.m sift.m…
lucky
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How to pass data to Mat using pointer of image data

In my code, I don't want to read data from rout of images,such as cv::Mat img_1 = imread("F:\1.tif"); Instead I wanna read data from pointer: float* srcImage;//pointer to image data cv::Mat img_1(height, width, CV_32FC1,…
lucky
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computing PCA matrix for set of sift descriptors

I want to compute a general PCA matrix for a dataset, and I will use it to reduce dimensions of sift descriptors. I have already found some algorithms to compute it, but I couldn't find a way to compute it by using MATLAB. Can someone help me?
oulcan
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