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Questions tagged [vlfeat]

VLFeat is an open source library that implements popular computer vision algorithms

VLFeat includes implementations of HOG, SIFT, MSER, k-means, hierarchical k-means, agglomerative information bottleneck, SLIC superpixels, and quick shift. It is written in C for efficiency and compatibility, with interfaces in MATLAB for ease of use, and detailed documentation throughout.

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Smoothening the image before feature extraction

I am using the vl_phow function (http://www.vlfeat.org/matlab/vl_phow.html) and wondering why the smoothing is applied before the feature extraction. To be more specific in the documentation of vl_phow it is mentioned that: The image is smoothed by…
burak akdemir
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VLFeat opencv 3.0 Fisher Vector empty

Im try to understand how fisher vector work with SIFT in Opencv3.0 and VLFeat library. but i got empty vector and the end. Im not sure where i have did wrong or my logic was wrong? Possible if someone know about this? Appreciated for your advise.…
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How to determine PHOW features for an image in C++ with vlfeat and opencv?

I have implemented a PHOW features detector in matlab, as follows: [frames, descrs] = vl_phow(im); which is a wraper to the code: ... for i = 1:4 ims = vl_imsmooth(im, scales(i) / 3) ; [frames{s}, descrs{s}] =…
jperezmartin
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installing the python wrappers for vlfeat

I have been trying to install the python wrappers for VlFeat for the last 5 hours and it always ends with: cannot find -lboost_python-mt-py27 As suggested in other threads, I changed the setup file to ask it to use the python 2.7 boost libraries.…
Luca
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using dsift of the vlfeat library with cv::Mat

I am currently trying to use the dsift-algorithm of the vlfeat-lib. But no matter with which values I create the filter (sample step, bin size), it returns the same number of keypoints for every frame during an execution (consecutive frames are…
TobiasWeis
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How does vl_ubcmatch work technically?

I am reading through vl_ubcmatch's function source code, provided here, and I am trying to understand, how does it compute the score, and how does it work technically internally. However, this C code has these macros, weird ## variables like, and…
Karl
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Extracting VLAD from SIFT Descriptors in VLFeat with Matlab

I have a folder of images. I want to compute VLAD features from each image. I loop over each image, load it, and obtain the SIFT descriptors as follows: repo = '/media/data/images/'; filelist = dir([repo '*.jpg']); sift_descr = {} for i =…
Chris Parry
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VLFeat SIFT descriptor

I'm reading this code about how to extract SIFT features using VLFeat. In particular the descriptor relative to the keypoint key with direction angles is saved in f.desc: vl_sift_calc_keypoint_descriptor(filt, &f.desc[0], key,…
justHelloWorld
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Conversion of Image to Single and Square

I am performing a descriptor function on an image. In the documentation, the function requires me to input image I - I is a gray-scale square image with odd side length of class SINGLE. I already knew how to convert an image matrix to single using…
ARKhan
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Vlfeat for Ipython

I've been trying to set up vlfeat library for Jupyter which comes with anaconda. I've installed from this https://anaconda.org/menpo/vlfeat but cant import the library in the notebook. Can someone Guide on how to set it up?
user244791
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OpenCV-Python Dense SIFT Settings

This is a follow-up question to the previously posted question about using OpenCVs dense sift implementation in python (OpenCV-Python dense SIFT). Using the suggested code for a dense sift dense=cv2.FeatureDetector_create("Dense") …
Legie
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Alternative to spatial histograms in Bag of Words approach using vlfeat

The phow_caltech101 demo app in vlfeat creates a complete Bag of Words process for image classification on the Caltech101 dataset, roughly put: Feature Extraction Visual Vocabulary building Spatial Histograms computation SVM training SVM testing…
Rolo Villa
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Purpose of void const * argument in function

I'm trying to use a library function from VLFeat that calls for data to be a const void *. I don't really understand how to create the data and then pass it in. This is the function call: void vl_kmeans_init_centers_with_rand_data (VlKMeans * self,…
marcman
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Identification of only a part of an image

I want to identify only this marked part in my image. (marked in red) It should be a scale and translation invariant matching algorithm. Which is the best method I can use? Will the SIFT method be useful here? As I have observed, it outputs many…
Saania
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VLFeat's Image Mosaicing in Matlab

The following is a piece of code that forms a Mosaic of two images after computing the Homography Matrix H using RANSAC pror to which SIFT was used to compute the descriptors: % -------------------------------------------------------------------- % …
Sean Bragança
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