Questions tagged [sift]

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Creating a Gaussian Pyramid

I'm trying to recreate a gassuain pyramid using the following scales: There seems to be two concepts used here: 1) When an image is halved, applying a gaussian kernel of σ will apply as 2σ. 2) When ...
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179 views

Affine detector + SIFT descriptor

I am approaching to the Oxford Buildings dataset which contains already computed SIFT descriptors from affine detected keypoint locations. Usually SIFT detector provides to its detected keypoints ...
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74 views

Are there algorithms that can match SIFT's key points of 2 images using their mutual arrangement?

I'm solving image matching task using SIFT as a feature extractor To match obtained descriptors I used FLANN based Matcher (provided by OpenCV) and result looks good: But applying same algorithm to ...
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24 views

feature extraction techniques for iris recognition

I want to ask how I can divide feature extraction techniques to feature detectors and feature descriptors. I have big problem how to understand it. For example I can use Gabor filters (feature ...
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261 views

VLFEat: How to extract the SIFT descriptor without SIFT feature detection?

I am using the MATLAB interface to the VLFeat toolbox in order to calculate a SIFT descriptor for image patches extracted around key points. Due to the greater framework of what I'm doing, I cannot ...
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45 views

Analytical expression for salient Blob detection in scale space

I am working on exact mathematical expression which can be obtained in image processing tasks.(I do not know much about image processing but my work is more mathmatical) In Gaussian scale space, we ...
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70 views

Geometric models to discard image features

I am working on the implementation of a location recognition pipeline as detailed in the section 5.4 of the paper Leveraging 3D City Models for Rotation Invariant Place-of-Interest Recognition: ...
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9 views

Where is the Hessian matrix computed in SURF?

I understood that, in SIFT, the Hessian matrix is used to remove edges from previously detected keypoints. Hence, if I understood well, in SIFT the Hessian matrix is computed only in the locations ...
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20 views

Octaves and the SIFT algorithm

My current understanding is that the full algorithm is applied for each octave and then we have four images (the original image and its downsampled version) each with their key points and ...
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15 views

How to find objects via SIFT when there are multiple occurrences?

I am trying to find objects (defined via a template image) in smartphone screenshots. Since smartphones have different resolutions, I need scale invariance, so I can't use a template matcher. The use ...
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8 views

Can we combine the application of SIFT with Kalman filter for 3D reconstruction of structural buildings?

This is just a novice question from somebody who just got into this topic. Can the application of Scale-Invariant Feature Transform be combined with extended Kalman Filter?
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Understanding the Extrema in Sift Keys

I am trying to understand the summary of Sift Keys presented here. From what I understand, we are concerned with finding extrema in scale-space of a difference of gaussians pyramid. So we have an ...
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48 views

SIFT between 1 image and dataset (2 images)

I use SIFT, and I want to find the angle of inclination of an image compared to two reference images, in short: I have 3 images : Image x: input image Two images 1 and 2, reference images that are ...
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216 views

How to obtain the relative position (coordinates) of SIFT feature from image center coordinates?

I have extracted SIFT features (keypoints and descriptors) of training set and saved in an inverted index form. My question is how can I calculate the coordinates of each visual features in an image ...
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43 views

Counting percentage of fouling on a surface

I am completely new to image processing and python. I hope I can find some help here. I am trying out a project on detecting fouling% on a ship hull using raspberry pi. I am trying to learn how this ...
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593 views

Distance-metric for SIFT descriptors matching

Will using Cosine-Similarity or Histogram Intersection as distance-metric, for matching SIFT descriptors, help to get better results? Anybody tried on that ever?