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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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Call exe file from java code

I am trying to use the colosift detector provided here: colorDescriptor. I am actually try to call the executable colorDescriptror.exe file from java. I am already run it with bat file and I want just to call the exe from my java code. My code is…
Jose Ramon
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keypoints match between using optical flow

I have two pictures PlanA : I detect SIFT key poitns in picture A and using optical flow to find the corresponding points in picture B Plan B: but if i detect SIFT key points in picture B and do the match thing between picture A and picture B What…
Moore liu
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Assertion Error while implementing SIFT algorithm :opencv

I am using opencv 2.4.8 and studio 2013, n i am getting a run time error.my main code is…
Pruthvi P
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Open CV : Assertion failed while implementing SIFT

I am trying to implement SIFT in studio 2013 and opencv 2.4. And I am getting the following error. OpenCV Error: Assertion failed (dims <= 2 && data && (unsigned)i0 < (unsigned)size.p[0] && (unsigned)(i1*DataType<_Tp>::channels) <…
Pruthvi P
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SIFT object detection bounding box

I am trying to track object from video stream using SIFT algorithm. I want to detect the object and track it by drawing a rectangle surrounding it. The problem is, the rectangle gets skewed and not accurately drawn most of the time. I am using the…
Nasir
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About function sp_find_sift_grid(I, grid_x, grid_y, patch_size, sigma_edge)

I found some code to calculate SIFT descriptors from Githut with three functions: sp_find_sift_grid(I, grid_x, grid_y, patch_size, sigma_edge) GenerateSiftDescriptors(opts,descriptor_opts) normalize_sift(siftArr) And I found there are some…
Shan Luo
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Why Vlfeat generates same number of descriptors for different images?

I notice that Vlfeat/Sift generates same number of descriptors for different images, why? And what is the aim of orientation assignment? It seems there is a similar process in the descriptor formation process. I am quite new to the SIFT and…
Shan Luo
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VLFeat error in MATLAB R2010a - hists{ii} = getImageDescriptor(model, im);

I am using the vl_sift tool of to extract features from a set of images for classification. On running phow_caltech101(), the command prompt throws me an error as follows, hists{ii} = getImageDescriptor(model, im); ??? Undefined function or method…
user236956
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how to get matches drawn by "drawMatches" in an array (for example in a DMatch structure)?

I know that drawMatches function does not show all of the matches of its matches1to2 parameter. This is based on its other parameters and flags (e.g. "do not show single lines"). I am wondering is there any way to get access to the output matches…
Bahar S
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Ubuntu error: "filename" cannot execute binary file

I am working on matlab R2013a on Ubuntu. I am referring this code: sift_bin = fullfile('lib/sift/bin/siftfeat'); [pf,nf,ef] = fileparts(filename); desc_file = [fullfile(pf,nf) '.txt']; im1=imread(filename); if (size(im1,1)<=1000 &&…
sam
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Dense sift using VLFeat

I am having trouble understanding the dense sift documentation in vlfeat shown at http://www.vlfeat.org/matlab/vl_dsift.html. They have mentioned a bin size parameter for the width of the grid at a pixel and have mentioned a step parameter for…
anon
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Insufficient memory when using SIFT::detect

I am using sift to detect keypoints of two images of 3264x2466. Here follows my code. However, I got an error saying that opencv error: insufficient memory. Is there anything wrong? Here is the image http://img42.imageshack.us/img42/6963/v839.jpg…
flexwang
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I am trying to match 2 images using SIFT keypoints at which threshold of matching can I say that these images are almost the same thing?

I am using SIFT keypoints atm on matlab to get the keypoints of each image , and then i use a match function that appends 2 images and finds the macthed keypoints between the images , My problem is that the number of keypoints that appears sometimes…
Karim Bibars
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how to generate feature - image incidence matrix?

please help me to understand this idea from a paper which titled is "Scene Summarization for Online Image Collections" by Ian Simon Noah Snavely Steven M. Seitz, University of Washington. Computing the Feature-Image Matrix : We first transform the…
go eng chun
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Describe SIFT with OpenCV without repeatedly creating image pyramid

I'm working with OpenCV 2.4.6 and I need to compute SIFT descriptors at different locations many times on one certain image. The code runs extremely slow. I realize that it's probably because every time I call sift(image, mask, locations,…
Bei
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