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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Predicting Positional Displacement with a Bivariate Gaussian Distribution

In my computer-vision problem, a blob can move either forward or backwards (with a slight chance of moving sideways) along its directional axis. I am seeking a bivariate model because I need to ...
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Algorithms for detection of fingertips or nails

Can you give me some advices on what could be the best algorithm(s) to use for detection of fingertips/nails in image. First thing that crossed my mind was Viola - Jones. After rethinking I concluded ...
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Jacobian Matrix of a Quaternion $q$ respect to Angular Velocity $\omega$

In the context of visual tracking and video processing I need to estimate variations of the orientation related to the angular velocity. I am trying to calculate the Jacobian matrix of a quaternion $\...
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How do I numerically calculate a function from its noisy gradient?

I have the model $\ s(x,y)=x^2+y^2, 0 \leq x \leq 1, 0 \leq y \leq 1 $. Instead of observing the model directly I am observing the derivatives of the model + some noise (e): $\ p(x,y)=s_x+e, q(x,y)=...
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Resources for an introduction to computer vision

Does anyone have any suggestions on good resources or sites for learning about computer vision?
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hough voting, turning transformation into a vote

I need help understanding how/what does it mean to "turn" a transformation parameters into a vote. I know how to recover the transformation parameters (in my case: 6 DOF), but how this turns into a ...
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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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Confused about HSI and HSL color spaces

I am reading a book for image processing algorithms (Andreas Koschan, Mongi Abidi: Digital Color Image Processing) and for the contrast algorithm it says that I can either go ...
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How to estimate octave and size for visual features positioned at Harris corners

I am currently working with and comparing the performance of several feature detectors provided by OpenCV as basis for visual feature matching. I am using SIFT descriptors. I have accomplished ...
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what is the starting point of a contour as given by cvConvexityDefect() function in OpenCV

i have to distinguish between palm and elbow in my contour(I'm using cvconvexitydefect for that purpose). Here's the image: I'm taking contour of left image. the 2 topmost points in right image are ...
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Camera calibration/pin hole camera model and working out 3d position

I have a calibrated camera and have the intrinsic parameters. I also have the extrinsic parameters relative to a point (the world origin) on a planar surface in the real world. This point I have set ...
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FIXED POINT conversion Problem (DSP)

Actually after reading the data from ADC is an $Q15$ format (ie. ADC supports 0-3.3v, ADC is an unipolar type). then the $Q15$ data is converted to $q31$ format ($Q31$ value = $q15_{data}$ <<16)....
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What is the link between the homography computed over 2 images and the homography computed over the same images upside down?

With OpenCV, I compute the homography between, say, these two images: and Don't worry about the strange white form on the right side, it is due to the smartphone holder I use. The homography, given ...
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OpenCV detecting elbow

I have to detect my elbow. I'm able to produce an image in which I'm facing the camera, standing before it and my arms are in my body plane(body plane is plane containing my head,chest,and legs)(i.e. ...
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Detecting meandering rivers in images

I have $n$ surfaces: $z_i(x,y)$ with a measured attribute (variable) on each surface: $a_i(x,y)$. Most of the surfaces will have a random distribution of the attribute across the surface, but some ...
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Connecting edges detected by an edge detector

I have a binary image obtained from a canny edge detector. The edges are not nicely detected in the center and I need to join them. The connection of edges is orientation and neighborhood dependent. I ...
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1answer
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Vehicle counting from a video

Disclaimer: I posted this question on StackOverFlow but learned that it is better suited here. I am a bit new to image processing so I'd like to ask you about finding the optimal solution for my ...
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How to fit an ellipse to 2D data

I'd like to find the "best" fit of an ellipse to contiguous, possibly concave shapes such as: What have I tried? I thought that one could assign the direction of the major and minor axes $\vec a, \...
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1answer
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Fitting new images from a SVD/PCA calculation

I'm trying to replicate the ideas from the Eigenface page on wikipedia. From a hundred sample images represented by a data matrix $\bf X$ (where each image flattened to a vector of length $n$, thus $\...
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Are there any computer vision algorithms specifically targeting depth images?

I've been looking into marker detection algorithms to use with a kinect based application, and the majority of the work I've been able to find is obviously focused on feature detection in 'normal' ...
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Viewpoint dependant deformation of objects in photos

I have a question concerning the deformation of objects in photos. Which deformations can an object depicted on a photo undergo through viewpoint and condition changes? Some deformations I have in ...
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2answers
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Struggling to find a good definiton for Gabor-Descriptor

I am attempting to implement the Gabor Descriptor based on the following paper Image Copy Detection Using a Robust Gabor Texture Descriptor. It is the best paper that I have found on the subject. It ...
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1answer
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How to get to shoulders localization on image photo? [closed]

I have a project on my university. I have to localize from video where are shoulders of person in movie. Do have any advise how to get to this? I thought about corner detection or some kind of ...
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what is the possible solution for the Intra-class variations poblems?

my poblem is that i have a database for human dorsal hand veins ,but with intra-class variations , so this problem have a large effect on my results when i need to do matching between my samples for ...
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What image-processing techniques are ideal for this particular shift/scale invariant template matching?

A problem I had originally discussed here has evolved, and might have gotten a little simpler as I studied it in some more and attained new information. Bottom line, I would like to be able to detect ...
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Good features / algorithms for recognizing car-models in images

I have a question concerning object recognition, especially recognizing car-models! I am at the beginning of a work about identifying the same car-model in different images. At the moment I think one ...
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1answer
309 views

Image Processing method for spiky selection

I have an input as a 3D binary image and the preferred output below: Input: Preferred Output: What image processing methods should I look for if I am to have only the spiky object(s) remain, just ...
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Topological skeleton matching techniques

What are the most common and best topological skeleton matching techniques? Suppose I have skeletonized object and corresponding 2D model of this object. What are the next steps to match pattern? ...
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1answer
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image feature extraction

We are given a set of grayscale image patches obtained from images after edge detection. Each patch is 10x10 pixels with intensity varying between 0 and 255 for each pixel. This set may contain a very ...
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1answer
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one to many images matching in matlab?

i have database for 50 person ,it is 250 images (5 images/person) , i need to perform one to many matching between images for recognition persons. so , i divided the image as 2 parts (one for ...
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What methodology to use for discrimination of different (musical?) tones

I am trying to research and figure out how best to attack this problem. It straddles music processing, image processing, and signal processing, and so there are a myriad number of ways to look at it. ...
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is it possible to matching b / w images without feature extraction steps? if possible which algorithm may be more suitable?

these are example of my image i have a 245 images similar to it ,i obtained these b/w images after preprocessing stage , i want to use them for recognition persons(not verification) in matlab. can i ...
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Get histogram of edge lengths/orientations in an image using OpenCV

In the process of trying to estimate whether a ROI contains [Japanese] text, I need to get a rough count of edges, hopefully binned by length and/or orientation... I think this would give me strong-...
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1answer
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List of all available ARM+DSP processors for surveillance

I have come across TI's C6000/Integra. I want to know is there any other similar or better ARM+DSPs available. Specially for surveillance/vehicle number plate recognition etc. Having camera input at ...
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2answers
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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
967 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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2answers
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Function for response over image scales

I want to write code in matlab to find a characteristic scale of an image patch. I have an image patch X, I need to maximize function F(X,sigma) so that sigma is ...
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2answers
464 views

How do you measure the accuracy of a stereo system?

I have a philosophical question of sorts for users familiar with a multi-view stereo setup. Imagine that I need to measure the dimensions of a large building and I take several photos of the building ...
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1answer
431 views

Which are the steps to extract contours/shapes from depth videos?

I am trying to create a histogram of the depth videos (converted to grayscale first) in order to apply a threshold to keep only highest values, and then do some dilation in order to extract contours. ...
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1answer
229 views

How to amplify regions with specific color in an image?

I want to amplify regions with a specified color in an image. For this purpose I have defined a simple function $B(x,y)=s_r(x,y) \cdot w_r + s_g(x,y) \cdot w_g + s_b(x,y) \cdot w_b$ which produces a ...
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Profile Matching in a Point Cloud

A point cloud is generated using uniform random function for (x,y,z). As shown on the following figure, a flat intersecting plane (profile) is being investigated ...
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Surface detection

How would one segment large area's of gray (ranging from white to black) from an image ? (If you know this in opencv, you may answer by saying what you would do in opencv). For example given this ...
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How can I compare two pictures from the camera and tell if there are enough differences to detect movement?

I want to use my phone as a CCTV system to control a room in my house, and display an alert when something is moving. For now, what I have succeeded in doing is to grab a picture every minute and ...
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1answer
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Interpretation of the eigenvalues of the inverse Hessian in a KLT tracker

I'm a masters student, preparing a seminar in computer vision. Among the topics is the Kanade-Lucas-Tomasi (KLT) tracker, as described in J. Shi, C. Tomasi, "Good features to track". Proceedings ...
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1answer
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How do I reconstruct a covered-over part of a regular pattern

I have a set of images which consist of a fairly regular pattern - essentially a set of roughly concentric distorted ellipses - with a small area (<1% of the total image area) obscured by a ...
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1answer
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find a line go through the center mass and that line must be inside object area

I have an object (orange color object) and I know its centroid/center mass C. I want program to automatically find another point ( can be point 1, point 2, point 3 or point 4 and so on) such that the ...
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1answer
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Given some parameters, how do you determine how much of an image sensor an object will consume? [closed]

If I have the details of a scene and a camera, how can I tell how much of my camera's image sensor will be taken by a certain object in space? For example, if I have a painting that is 1m by 1m, it ...
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1answer
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Skel to infinity morphological operations on 3D volume

I have a 3D volume image that consists of 2D tomographic images. In MatLab, for 2D images, we can use bwmorph and call for 'skel' operation to infinity to get a pixel thick overall outline of the ...
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Are there preferred patterns for creating texture on objects to aid computer vision?

In the comment to this answer using a laser diode and diffraction grating to provide texture on a surface was suggested to aid in height calculations in a computer vision system. I believe the ...

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