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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6
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0answers
2k views

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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1answer
382 views

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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2answers
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Blob detection in C

I am trying to do my own blob detection. My program will receive a real time video, and try to detect a white paper sheet, even if something is written on the paper. I need to detect the paper and ...
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3answers
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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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2answers
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Step by Step Camera Pose Estimation for Visual Tracking and Planar Markers

I have been working on the topic of camera pose estimation for augmented reality and visual tracking applications for a while and I think that although there is a lot of detailed information on the ...
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2answers
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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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2answers
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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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9answers
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Why do we use the HSV colour space so often in vision and image processing?

I see the HSV colour space used all over the place: for tracking, human detection, etc... I'm wondering, why? What is it about this colour space that makes it better than using RGB?
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2answers
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A (Clear) Line Between Computer Vision and Image Processing

I have been working in and learning about both Computer vision and Image processing for a few years now, and I believe that I am not a complete beginner any more. Still, after all these years, it is ...
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3answers
497 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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2answers
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iPhone iOS UIImage how to detect a “laser pointer” dot on a camera feed?

I got a tracked robot toy and I'm controlling it with an iPhone. The robot outputs a live camera feed of a known frame size and I'm displaying it on UIImage. I've added a laser pointer to the robot ...
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1answer
386 views

Designing a feature vector for discriminating between different sonic waveforms

Consider the 4 following waveform signals: ...
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1answer
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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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3answers
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OpenCV/C++ connect nearby contours based on distance between them

I have to connect nearby contours in an image based on the distance between them which specifies if the contours are to be connected. Now there's a question already on the same problem here https://...
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0answers
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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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2answers
457 views

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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2answers
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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
357 views

Are all of the edge descriptors necessary to differentiate edges?

My question is about edge descriptors produced from an edge detection method applied on an object image. As we know, an edge has four descriptors edge normal, edge direction, edge position, and edge ...
10
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1answer
3k views

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 ...
41
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1answer
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How to flatten the image of a label on a food jar?

I'd like to take pictures of labels on a jar of food, and be able to transform them so the label is flat, with the right and left side resized to be even with the center of the image. Ideally, I'd ...
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2answers
2k views

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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2answers
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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, \...
16
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1answer
307 views

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 $\...
4
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1answer
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Image comparison using MATLAB

I want to compare a bunch of depth images coming from Kinect and eliminate the similar ones. Those images present posture of a single user sitting on the chair (depicted in). My idea is to create a ...
11
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1answer
342 views

Recover curves from noisy collection of points

Background: I'm trying to make a system that tracks a number of bubbles in a video I'm implementing the bubble detection in the single image case using the Circular Hough Transform. Due to occlusion, ...
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2answers
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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' ...
12
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1answer
981 views

Image Denoising with Better Edge Preservation

I have the input image : and the output of vein detection for the leaf using a Gabor filter, but the output is really noisy: I tried using Total variation denoising however the results are not good: ...
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4answers
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Intuitive explanation of tracking with Kalman filters

I would much appreciate an intuitive explanation for (visual) tracking with Kalman filters. what I know: Prediction step: Dynamic system state $\mathbf x_t$: target location at time $t$ Measurement $...
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2answers
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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 ...
16
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2answers
620 views

3D reconstruction of an image based on depth of intensity levels?

Is there anyway of segmenting objects based on how far they are from the viewer? Can color values assess this sort of a thing for us? How will intensity levels help in determining how far the object ...
4
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1answer
132 views

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 ...
8
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1answer
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How to remove reflections from images?

I've been playing around with making images better and removing all the unwanted disturbances from it. I found out a major concern would be removing the unwanted reflections that might come. I've ...
0
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1answer
5k views

calculating similarity scores between similar and different classes?

I have images for 99 person for each person i have 5 images . i have this function [similarity] = ssim(img1, img2, K, window, L);where K,window ,L are previously determined with their values. now , ...
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2answers
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Object Recognition using bag of features using matlab [closed]

I want to write a MATLAB program for simple object recognition using bag of features. In short, I want to first extract the features from an image, create a visual library using those features, then ...
10
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3answers
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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 ...
3
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1answer
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Wavelength filter with OpenCV

I am new to OpenCV and DSP. I want to code a filter which act like a real optical filter. When you filter the image, the output looks like shotted with a $550nm$ optical filter lens. Like a Bandpass ...
0
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1answer
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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 ...
10
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1answer
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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 ...
12
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2answers
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How do I retrieve texture using GLCM and classify using SVM Classifier?

I'm on a project of liver tumor segmentation and classification. I used Region Growing and FCM for liver and tumor segmentation respectively. Then, I used Gray Level Co-occurence matrix for texture ...
9
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1answer
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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 ...
10
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2answers
4k views

Generate the Convolution Matrix of 2D Kernel for Convolution Shape of `same`

I want to find a convolution matrix for a certain 2D kernel $ H $. For example, for image Img of size $ m \times n $ , I want (in MATALB): ...
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6answers
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Best way of segmenting veins in leaves?

I have done a lot of research and found out methods like adaptive thresholding , watershed etc that can be used of detecting veins in leaves . However thresholding isn't good as it introduces a lot of ...
17
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2answers
636 views

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 ...
16
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2answers
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Are there any good open-source (well, free) handwriting OCR programs?

The title asks it all. I have before me a data entry task that I'm not too enthusiastic about: 50-100 pages of handwritten sign out/sign in logs. The format of the logs may help. Pages are ...
11
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1answer
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Adaptive Thresholding for liver segmentation using Matlab

I need to segment liver from an abdominal CT image using Adaptive Thresholding. But I get the entire foreground separated from the background alone. I need only the liver part of the foreground ...
14
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4answers
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basic hsb skin detection, neon illumination

i hope this is the right place to ask. otherways sorry for my mistake and pleace advice me a better site. i'm trying to implement a super simple skin detector using some range of hsb image. i'm using ...
11
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1answer
312 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 ...
4
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1answer
990 views

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? ...
5
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1answer
403 views

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 ...
4
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2answers
157 views

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 ...