Computer vision includes methods of processing, analyzing, images and high-dimensional data to form high level understanding and recognition of the scene or images.

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What exactly affine covariant features are?

I was reading about different blob detection algorithms. And I found an statement that determinant of Hessian is a affine covariant. What does it mean?
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9 views

AR-like marker detection

Let's say I have a grayscale image in which I wish to detect (and later identify) a marker. It is also my task to construct an appropriate marker. As image is grayscale that means the marker should ...
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1answer
18 views

How do I implement LIBSVM for multiclass classification using java?

I am currently working on an image classification project ,where i need to use bag of features model with libsvm(HIK kernel) for classification.I have extracted sift feature and created a visual ...
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11 views

Plotting Basis of 3D Steerable Filter

I am plotting isosurface plots of Basis of 3D Steerable filters which should look like Spherical Harmonics of first Zero, first and second order plots. Correct me ...
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87 views

Detect text regions within scanned documents

I'm working on text detection task from scanned documents to detect text regions only and separate them from images, graph, etc. Here is my idea : First i'm using OpenCV wrapper for C# (Emgu) on ...
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21 views

Characterized image dataset for detection and segmentation

I'm looking for an image dataset for image segmentation and recognition. Additionally, I would like it to be categorized according to several image parameters, such as: object size in image, rotation, ...
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1answer
43 views

I have some questions about background subtraction with Gaussian Mixture Model (GMM)

I'm learning about Gaussian Mixture Model (GMM) for background subtraction.. And have some questions about it.. In Chris Stauffer paper "Adaptive background mixture models for real-time tracking" ...
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34 views

How to straighten the edges?

Are there standard efficient ways/algorithms to make edges in an image more straight or axis-parallel (horizontal or vertical) ? I have images that look like this: This is part of a segmentation ...
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2answers
51 views

Vehicle detection in matlab [closed]

I am new to matlab and computer vision. I used the code given in the link to detect cars. But the problem is the shadow is also being detected and tracked. Can anyone tell me how to modify the code so ...
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61 views

Efficient Hessian-Laplace blob detector implementation

As it is mentioned in a paper for SURF, it is possible to approximate hessian determinant using integral images. If I want to implement Hessian-Laplace detector, is it feasible to also approximate ...
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21 views

contour matching

Im am trying to extract contours from an image and match them with a list of contours I already have. The contours in the image are surrounded by a large black/dark rectangle. Here are the steps I ...
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2answers
76 views

Contrast stretching Equation problem

How to determine $a$ and $b$ in this equation. I know how to determine $c$ and $d$ by looking at the intensity histogram. But what about $a$ and $b$? $$P_{out}=(P_m -c)\left( \dfrac{b-a}{d-c} ...
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1answer
28 views

What does one call this method of grid fitting?

The input space has artefacts that are already in a grid-like layout: I'd like to be able to fit/draw a grid over the artefacts so as to separate them, preferably with lines on average mid-way ...
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1answer
96 views

Circle detection opencv

I Would like an explanation of the parameters for opencv's HoughCircles function. I'm new to image processing in general and I have recently started using opencv. ...
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17 views

How to programatically perform image segmentation in real-time

I am currently trying to segment ultrasound images of blood vessels (video frames), such as the one directly below. Using a simple binary filter on the saturation channel (code below), I can get a ...
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2answers
65 views

Best Car Recognition Algorithm

Could anyone suggest the best algorithm for a real-time Car recognition (say in a parking space)? I am planning to implement the same on FPGA as well. Kindly suggest. Thank you.
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10 views

Need to order a set of colors to build a feature vector

I am working on Computer Vision task of object classification with python and OpenCV. Currently I am extracting some characteristic colors of an image using K-means clustering on all the pixel to ...
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37 views

Non-maxima suppression of gradient image

I'm new to image processing, However I was trying to learn how to detect edges using Sobel filter I had obtained the image gradient in both X and Y directions successfully using Emgu built in ...
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1answer
30 views

How to apply the provided wave transforms on an image

I want to implement one of the following mappings in MATLAB and verify its performance on an image, but I couldn't. Please help me with the implementation
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2answers
206 views

Segmentation of overlapping noisy parallelograms in a binary image

Edited. Previously this question was named "Segmentation of overlapping pulses in a binary spectrogram" and it was stated in slightly different way. I'm apologise to those users, who were affected by ...
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2answers
41 views

Pinhole calibration

This is a conceptual question I am having difficulty to understand due to my limited knowledge of computer vision: If a pinhole calibration or any calibration is a mapping from world coordinates to ...
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48 views

How can I make the background color white for this Grab-cut algorithm written in Python?

I am new to Image Processing and am using Grab cut algorithm to extract the foreground objects from images as a part of my project. Below is the code written in python to do the same. The problem is ...
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31 views

Distinguish between 2D and 3D objects according to depth

I'm trying to distinguish by code between a real 3D object and its picture - a 2D object, based on depth information. However the picture (= the 2D image) might be captured from noisy background, so I ...
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1answer
27 views

Video: Detecting a digital timer and when it ticks

Input: A video with a digital timer, possibly several hours long, such as this video. The timer might use any font or color, and might be located anywhere on the video, but it probably won't fill the ...
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296 views

What is the rate of expansion of an image as it aproaches the human eye?

My intuition about the scaling (x,y) of the 2d representation of the 3d object generated by our native visual processing system tells me it accelerates as it ...
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46 views

How to implement HOG with trilinear interpolation by Matlab?

I am studying HOG. I have find the code code1 and code2 about HOG. However, both of them don't implement trilinear interpolation. I have also read some websites, including web1 and web2. I still don't ...
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3answers
58 views

Training own classifiers using trainCascadeObjectDetector for face detection

I want to train a cascade classifier to face detect. I read this page. But I wont use trainingImageLabeler app, because I already have face and nonface database sized 24x24. How I use ...
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1answer
60 views

How to remove text region in a document image? or extract image from a document image

Given a document image (i.e. newspaper), how to extract photos in it or remove text region? I think traditional OCR methods may not be suitable here, as I don't need to recognize the text, and OCR is ...
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25 views

How do I deal with occlusion, warping, or perspective distortion for object detection

I am using SIFT features for detecting logos in clothes. SIFT is quite powerful, as it is scale invariant, but how do I deal with the problem of occlusion and warping? More specifically, the logos in ...
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18 views

What are the main roles of leverage scores and low rank approximation in computer vision applications?

I'm just starting to learn about the field of computer vision. I would like to hear from experienced SE users regarding the following questions 1) I know that computer vision is driven by numerical ...
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3answers
25 views

Histogram Equalization - mapping a certain portion of pixels to pure black and white

How can I make sure to map, for example, 7% of the pixels to pure black (0) and pure white (255) in a grayscale image?
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24 views

Histogram equalization - to increase “punch” and to limit local gain?

The exercise 3.6 (Histogram Equalization) in Szeliski's Computer Vision - Algorithms and Applications asks: Convert the color image to luminance (Section 3.1.2). Compute the histogram, the ...
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20 views

What are the works done till now in Video Event Detection?

I am doing a final year project on Video Event Detection. I know that there is a lot of work already done in Human Action Recognition. But instead of only human action, I want to work on event,scene ...
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1answer
31 views

Classification from a feature vector

I'm quite new to this; I'm try to classify textures as defective or non-defective. I've used a Gabor filter bank with Matlab which outputs a column vector of the Gabor features of an image. I have a ...
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1answer
28 views

Is there a way to perform 2-D image rotation by matrix multiplication?

In my understanding, unlike shifting and scaling, image rotation actually rotates the coordinates whereby interpolating the pixels at discrete positions. It is like a projection that discrete values ...
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8 views

How to choose scales(or deviations) for sampling in SIFT detection?

In SIFT's key points detection stage I have to make Gaussian filtered images at discrete scales(deviations). Is there any suggestive choice for these scales? Does it depend on specific inputs?
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37 views

extracting audio and video from video file

I tried the following code in MATLAB R2013b ...
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1answer
143 views

Object Detection Algorithms

I'm a complete beginner to object recognition. I need to identify and count how many of a certain type of Lego, in a picture full of different pieces of Lego, using MATLAB. The pieces of Lego I need ...
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3answers
89 views

Generate projection image by OpenGL or Matlab

I want to generate the "projection" image described as bellow. The left picture is the original picture and the right image is what I want. But, I have no idea about how to generate the right image. I ...
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1answer
123 views

Is it possible to hack camera calibration without having access to the camera?

Many times we have a stream of video to process without access to camera. Having access to camera matrix would be beneficial for various processing techniques. Is it possible to hack camera ...
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16 views

Public dataset for monocular visual odometry

I am planning to develop a monocular visual odometry system. Is there any indoor dataset available to the public, along with the ground truth, on which I can test my approach? Note: I am already ...
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1answer
224 views

OpenCV Motion Analysis: Optical Flow vs Motion History

OpenCV Motion Analysis Documentation lists multiple techniques for motion tracking: Sparse Optical Flow | calcOpticalFlowPyrLK, Dense Optical Flow | calcOpticalFlowFarneback, and Motion History ...
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43 views

I'm confuse how to use pdf to predict next state in particle filter

How can I make predict state/equation for next state if I have state space $[C_x,C_y,H,W]$ where $C_x,C_y$ is position of centroid object and $H,W$ is height and width of object contour?
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16 views

SURF SIFT detection

Do you have any idea if the surf extracted or detected interest points belongs to the same objects? I explain: SURF descriptor account the orientation of ip based on edges intensities around it. In ...
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1answer
29 views

Does accurate translation estimation using a camera matrix mean the orientation estimation will also be accurate?

Pose Estimation of single camera and planar pattern: If I have an appropriate camera matrix with intrinsic parameters that allows me to calculate translation of the camera relative to a chessboard, ...
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3answers
39 views

Can you average out focal length from different camera calibration sessions?

If I perform a number of camera calibration routines at a fixed resolution, with various sizes of calibration patterns (like checkerboards), at various distances and get various values for focal ...
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1answer
74 views

Why do eigenvectors specify the direction of fastest and slowest changes in the image

I'm reading Szeliski's Computer Vision:Algorithms and Applications. On page 212-213, corner detector is discussed. I can understand upto equation 4.8. From then on, I don't understand how come ...
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30 views

What is the difference between Harris Corner Detection and SUSAN Corner Detection?

What is the difference between Harris Corner Detection and SUSAN Corner Detection
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1answer
35 views

How does chessboard configuration effect camera calibration?

When calibrating a camera with a chessboard, are more squares better or worse? When would you use more or less? And how does the size of the blocks effect the calibration results?
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How to get extrinsic parameter in android?

Ultimately, I want to implement the following. http://www.cv-foundation.org/openaccess/content_cvpr_workshops_2013/W03/papers/Saponaro_Towards_Auto-calibration_of_2013_CVPR_paper.pdf I get rotation ...