Questions tagged [computer-vision]

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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180 views

Garment Cropping from mannequin

I have two images – mannequin with and without garment. Please refer sample images below. Ignore the jewels, footwear on the mannequin, imagine the second mannequin has only dress. I want to ...
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3answers
645 views

segmenting region of interest (ROI) from background

I am dealing with images from biological slides and want to segment out the ROI (cells) from the background. I have tried k-means clustering, otsu thresholding, adaptive thresholding, edge detection ...
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370 views

Document image vanishing point detection and evaluation

It is a natural idea to substitute our scanner with mobile phone, and perform OCR with the phone at the same time. If this can come true, two problems must be tackled: one is related to document image ...
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646 views

Correct Fish Eye camera Radial Distortion and blurry effect at the image edges

There are a lot of questions regarding this topic ,but I am trying to get a more clear picture from these questions. I am trying to calibrate a fish eye camera and I am using OpenCV omnidir class ...
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263 views

Points of interest in a spectrogram

We have several audio tracks, all of which are different versions of the same track under one type of distortion: the speed of the track is increased by a constant factor K (hence frequences are ...
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2answers
928 views

Qualitative Evaluation of Interest-Point-Detectors and Descriptors in Computer Vision

I'm writing on a qualitative evaluation study of interest-point-detectors and descriptors. I've read all Mikolajczyk papers as well as most of the surves from Datta et al. etc. Now I'm implementing an ...
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0answers
484 views

Projection Matrix (Computer Vision)

I'm trying to understand a piece of code that is using a camera projection matrix. The camera projection matrix $P = \left[\begin{array}{c}p_1^T \\ p_2^T \\ p_3^T\end{array}\right]$ takes a point $X$ ...
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3answers
466 views

pose estimation

I am doing a final year project which involves finding the position and orientation of a screw which has to be opened by a robot hand having a screw driver as an end effector. I have developed a ...
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1answer
3k views

Detecting edges oriented at certain angle

How would I detect an edge oriented at 22.5° using a spatial filter?
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3answers
247 views

why the ultasound image is noisy by speckle noise?

My first question : I want to know why an image is noisy ?. why the ultrasound, SAR and Laser... images are noisy by a multiplicative noise not an additive noise? Another question : So the ...
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4answers
77 views

Computationally Efficient Ways of Determining If Pixels Are Clumped

I'm working on an application where I get a video frame that's already segmented into good and bad pixels (as in -- the hardware either coughs up a pixel value or a flag that says "bad"). I want to ...
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2answers
150 views

How would you interpret the pattern in this picture? (generated by re-sorting pixels based on their RGB value)

Was playing with some pictures and ran the ruby code below. The code reads an input image using the ImageMagick library, gets an array of pixels, re-sorts the pixels and then writes out an image with ...
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1answer
2k views

Detect circles in image

I have an image that has pixelated circles in it (a cross section of wires). I want to identify the wires, their location and count them. The circles never overlap and the wires are all within a 95% ...
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2answers
9k views

Rectangle detection in “real life” images

I have seen a lot of posts here and on SO and on various websites, using Matlab, OpenCV, name it, on how to detect rectangles in an image. I have done it myself too, using Matlab. My usual steps were: ...
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3k views

Is there any good book regarding 3D reconstruction from 2D images? I prefer to work in MATLAB

I am working on a project regarding 3D reconstruction of 2D images. I have understanding of finding and Mathcing the keypoints and its algorithms; but i am not able to replicate the theory in MATLAB ...
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1answer
91 views

What is localizability in Computer Vision?

Please consider the following excerpt (from Rodrigo R, Zouqi M, Chen Z, Samarabandu J.: Robust and efficient feature tracking for indoor navigation): Robust feature tracking is a requirement for ...
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1answer
3k views

why eigenvalues concerned in Harris corner detection?

In Harris corner detection, as I see, the goal is to find out those points $(x,y)$ which makes $S(x,y)$ a large value for any direction of shifting, $$ S(x,y) = [\Delta x , \Delta y]M\left[ \begin{...
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1answer
323 views

How can I automatically find the boundary of a high intensity region inside an image?

I have an image I(x,y): Red indicates high values and blue low values. Everything in black is drawn onto the image afterwards. The black dot (xp,yp) represents a point clicked by an user and the ...
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1answer
628 views

Approximating pixel location in scale space

I'm implementing a scale-space with o octaves and s scale levels in each octave. Each octave is half the size the previous. I have keypoints found in each octave, I need to approximate the real ...
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2answers
897 views

Triangulation from set of points from left camera

in my program there are stereo cameras. The cameras were stereo calibrated. I have a set of 2D-Points from left image (for example, it could be some Harris Corners from left images). And the task is ...
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1answer
1k views

What's the Difference Between UQI and SSIM Measures for Image Similarity / Quality?

I'm studying image quality assessment (IQA) problem and I'm currently learning about quality measures UQI and SSIM, I know UQI is a predecessor of SSIM, but they look exactly the same for me...
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1answer
779 views

Comparison Between Guided Filter (Edge Preserving Filter) and Gaussian Filter

I am looking for a good example that showing the different between Guided and Gaussian Filters. The example need to show the benefit of Guided filter, (for example: preserving edge...). Could you give ...
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3answers
182 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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2answers
5k views

Edge Detection on a Color Image

I understand the process of using a Sobel kernel for edge detection in greyscale images. The input is a greyscale image, and the output is a greyscale image. I'm having trouble, however, figuring out ...
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2answers
195 views

Constant used to determine the minimum samples in Compressed Sensing

A key result in compressive sensing states that, with high probability on the random draw of an $\ m × N$ Gaussian or Bernoulli matrix $\ A$, all $\ s$-sparse vectors $\ x$ can be reconstructed from $\...
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1answer
542 views

Safe Point Thinning Algorithm - How to?

I am relatively new to image processing and am working on a project that requires the thinning of binary images. In the literature, I've seen references to the Safe Point Thinning Algorithm(SPTA) ...
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1answer
241 views

Automatic Image Enhancement of Images of Scanned Documents (Auto Whitening)

Dropbox have make a blog post about there automatic enhancement method for scanned document image - Fast Document Rectification and Enhancement. I followed the post and they mention a formula to make ...
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1answer
323 views

Algo Name: Detecting Elongated Shape in 2D Image by Convolution with Directed Lines

I am detecting a shape with roughly known orientation (obtained by using Hough line transform) in thresholded binary image by convolving the image with line with that orientation, and counting the ...
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1answer
2k views

How can I track detected objects from frame to frame

I want to track people's faces in a video stream (like a security camera), but I am running into a problem. I was using a Haar classifier to find the faces and sending the detected faces to a system ...
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3answers
185 views

Can I use standard computer vision techniques for images taken in the NIR spectral range?

I'm relatively new in Computer Vision and I need some advice with respect to the general possibilities and shortcomings of images taken in the near infrared (NIR) range. I passed a great deal of time ...
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1answer
97 views

Confusion regarding Sobel operator

I am taking computer vision course, where I learned about Sobel operator for detecting edges. I somewhat understand how it works as described here. But I have a basic confusion. The operator can be ...
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1answer
484 views

How to Use Maximum a Posteriori Probability (MAP) in Classification Task

I have a 2D image defined on a region $\Omega$. Let $I: \Omega \to R$ be a gray image. Assume that the region can be separated into $N$ sub-regions $\Omega_i$ such that $$\forall i,j=1,\ldots ,N:\...
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2answers
4k views

Camera calibration using multiple images

I am trying to get the hang of camera calibration. For this purpose, I have mainly watched this lecture on youtube: Lecture 12: Camera Model by UCF CRCV. I believe that I understood the main ideas: ...
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2answers
118 views

Would the locations of SIFT features generally agree with features detected by Shi-Tomasi method?

I am having a comparison of different feature detection methods. So if we compare the SIFT (Scale-invariant feature transform) and Shi-Tomasi method, will their feature locations agree and why? Are ...
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1answer
59 views

which spatio-temporal properties does dynamic textures exhibits?

know that dynamic textures are spatially repetitive and temporally varying patterns. 1.I read one sentence in one paper i.e. They are sequences of frames exhibiting certain stationarity properties ...
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1answer
960 views

Vector Quantization in Hidden Markov Models

In the field of Gesture Recognition and Speech Recognition (using HMM classifiers), do multiple HMM classifiers (one for each class) share common Codebook (i.e common set of symbols) in Vector ...
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1answer
338 views

How to segment multiple overlapping coins (ellipses)

I am doing a program that counts coins (and tells their value by their size) with OpenCV (C++). Let's say we have an image of some coins. If there is an overlap of two coins at the same time, it is ...
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1answer
569 views

What Are the Differences between Super Resolution, Denoising and Deblurring?

In the fields of computer vision and image processing, what are the differences between Super Resolution, Denoising and Deblurring?
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1answer
746 views

How is WSNR (weighted signal to noise ratio) defined?

I'm studying about comparison between images to determine quality. I've learned about MSE, SNR and PSNR, and now I'm trying to understand WSNR, which I assume is similar to SNR but with weights. I ...
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1answer
75 views

Which is correct representation for function of variable?

I have a function as $$E=\int_\Omega -\log\big( p_i(x)\big) dx$$ where $p_i(x)$ is density distribution which estimated by Parzen window method. $$p_i(x)=\frac{1}{\Omega_i} \int_{\Omega_i}K_\sigma\...
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3answers
1k views

Segmenting and labeling chessboards through computer vision

With almost no experience/knowledge in computer vision, I am currently trying to segment and label the separate squares on a chessboard (i.e. a1 ... h8). My goal is to use the information to ...
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1answer
126 views

Pyramid Match Kernel: How to fit grid around data points?

I am planning to use Pyramid Match Kernel method for object recognition from depth images: I am going to extract a set of feature vectors $x \in \mathbb{R}^d$ for each object instance and then I want ...
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1answer
3k views

Histogram Intersection with two different bin sizes?

I have two images: A and B. Image A is a screenshot of image B, the original image. While there is noise in image A, the original features are still distinguishable. Histogram intersection tells us ...
2
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1answer
672 views

Planar Homographies in MATLAB

I have taken an image in height 2 meters of the ground as the original image and I want to simulate another image in 50 cm's of the ground, such as the simulated image. The focal length of my camera ...
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2answers
435 views

Is there any good book regarding Image Processing Algorithms for Feature Extraction and Matching which gives examples in MATLAB?

I have been looking to implement feature extraction and matching in MATLAB. For this, I've read many algorithms, but i'm not able to understand how to implement these in MATLAB. Is there any Book ...
2
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1answer
864 views

Particle filter, resampling step implementation

I am not very good in statistic neither in probability theory, and I do not completely understand the mathematical background of Monte Carlo simulation or SIR sampling, but I'd like computer vision ...
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2answers
150 views

Segmenting wood chips in an image

I am trying to recognize the wood chips in the image shown below. The ultimate goal is to try and recognize the width and length of each wood chip. Currently, I am using an approach that involves ...
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3answers
1k views

Visualize visual words in bag of words model

I am implementing visual bag of words through these steps: Find interest points using SIFT Calculate SIFT descriptor Build codebook through kmeans clustering of SIFT descriptors. How can I visualize ...
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1answer
161 views

Histogram operation for improving visual object tracking

I'm developping a people tracking with nearest neighbour data association technique and kalman filter for smoothing/predicting. The tracker works quite good but sometimes it mismatch objects if they ...
2
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1answer
5k views

Hand detection in matlab

I am beginner and I want a help to know how to detect hand in Matlab. First, I need code which detects skin and then draw a rectangle around a region so it show to me face and hand. When I try to ...

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