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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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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Compare image segmentation approaches

I've got a question related to a comparison of image segmentation algorithms. I'd like to compare two algorithm results to each other in step one. In another step I'd like to compare the two ...
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Sequentially get the outer contour of an Edge Image

Hi CV/Pattern Recognition Community, because my last thread was concerning the segmentation as BLOB and started to getting too big, with no clear results. I would like to reconcider the last step of ...
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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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Different representations of images and their purpose

I'm doing a small overview of different image representations used in image processing and computer vision. For every representation, I would like to have (at least) the following information: the ...
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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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Convex Optimization in Signal and Image Processing

In signal processing, convex optimization plays a useful role in problems such as sparse signal recovery and filter design. What other places does convex optimization appear? For example, in ...
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563 views

How do we distinguish between Image Recognition,Detection and Segmentation?

I am reading image processing book.while reading i am getting terms like image detection,image recognition and image segmentation. it seems that all above terms are one and the same.i am totally ...
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Commonly used test image sets

In the image analysis literature there are a variety of ways people show the usefulness of their method. For example, performance on an ideal signal corrupted by noise, an artificial signal ...
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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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Why Should the Sum of Masks / Kernel / Filter in Image Processing be One?

I am studying pyramids (expanding and reducing) and I am a newbie. Why should the sum of the convolution mask be one when we are using gaussian distribution? According to When should the sum of all ...
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Recover myself from Dilate and Erode for noise reduction

i have obtained some skin detection map (i post below two example of detection map). but, i'm using a normal webcam and the map is noisy. Not a lot, just a bit. I think i can remove noise only with ...
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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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Why do we need 4 points for homography but 7/8 points for fundamental matrix calculation?

Sorry if this is a trivial question but I could not find a suitable answer elsewhere. I recently learned about homography and fundamental matrices in a CV class. I understand how these matrices are ...
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Online boosting (training on the fly) for face detection

I want to implement an on-the-fly training process for face detection. I'm not sure but it seems it's called online boosting. Вefore, I have used OpenCV face detection with my own cascades, but I'm ...
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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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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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What is energy in image processing?

There are several web articles on the topic, but, after having read them, I still don't know what "energy" is, in the context of computer vision (CV) and image processing (IP). It is related to ...
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626 views

Can you detect circles only using the hough line transform?

I'm not talking about the Hough Circle Transform (where you replace the representing eqns, hence the parameters with a 3D set) but a Hough Line Transform. My solution to this: A hough line transform ...
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1answer
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Translation invariance in max-pooling and cascading with convolutional layer

I am reading through this page about convolutional neural networks and I am confused about the part about max-pooling (downsampling a signal/image with the maximum value in a block). Apparently, one ...
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Pose from Homography matrix - Zhang method

This post also contributes to the post at Step by Step Camera Pose Estimation for Visual Tracking and Planar Markers by Jav_Rock (since I cannot add any comment there and I don't know why) It can be ...
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Finding similar pictures in a database

I have large database of pictures, about a few million. I need an algorithm to find pictures which are similar to those in the database, up to a scale factor or a crop and shift (I have only these ...
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Opencv color segmentation of traffic signs: HSV ranges

I am working on a project to detect and recognize signs in images from the LISA Traffic Sign Dataset. Since the images are very noisy (in regard to background) I am trying to segment the signs based ...
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Estimating Plane Pose Without Knowledge of Intrinsic Camera Parameters

Assume a camera has no skew, and has square pixels, that is, its camera-calibration matrix, $K$, looks like: $$ K = \left[\begin{matrix} \alpha&0&u_x\\0&\alpha&u_y\\0&0&1 \end{...
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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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Red eye detection [closed]

Project: Red eye detection Description: I want to remove red-eye from images. I am not able to use face detector because, the faces in the images are not always frontal and also the images are of ...
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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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Palm Pilot Graffiti

I have been completely unable to find details on the underlying model that is used for the Palm Pilot Graffiti handwriting recognition. Given the computing power available for handheld PDA technology, ...
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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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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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How Much Zero Padding Do We Need to Perform Filtering in the Fourier Domain?

Consider an $M\times N$ image $f$ and an $G \times K$ filter $h$. Given that convolution in the spatial domain corresponds to multiplication in the Fourier domain, then we can perform a convolution of ...
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Can deep neural networks achieve real-time video analysis?

Recently, convolutional neural network based, deep architectures (DNN) such as AlexNet and VGGnet have been very successful in image classification challenges (e.g. ImageNet) and action recognition/...
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camera calibration: why chessboards?

Chessboards are very frequently used for camera calibration, this website also talks a bit about why: wiki. One of the reasons is, that chessboards define many natural interest points. Now my (very ...
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Licence plate detection with different backgrounds

I just studied the Algorithm of ANPR (Automatic Number Plate Recognition) from the chp 5 of book Packtpub.Mastering.OpenCV.with.Practical.Computer.Vision.Projects in which they detect the vehicle ...
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Detect lanes from a filtered image

I am working on lane detection system and I would like some suggestions from you as to how to detect lanes from a filtered image which I got after performing certain operations. Firstly, I should ...
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Determine when a constant signal changes to another constant value

As a novice to digital signal processing I have a scenario that probably seems trivial but I dont know the answer to. I want to detect when a signal changes but ignore noise. 255 255 255 255 255 ...
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351 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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1answer
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Corner detection using Chris Harris & Mike Stephens [duplicate]

I am not able to understand the formula, What is $W$ (window) and intensity in the formula mean, I found this formula in opencv doc http://docs.opencv.org/trunk/doc/py_tutorials/py_feature2d/...
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Detection periodic elements in image

I am working on a university project in which I need to find a periodic net element in an image. The net is a set of diagonal lines in a specific angle ( which I don't know in advance ) on a noisy ...
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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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how can i perform a registration to 2D images using ''rigid " transformation in matlab?

i need to perform registration to 2D image using"rigid transformation" in matlab .i need this for measuring the similarity between my images .any one know how this can be done using matlab? an ...
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1answer
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When is a network called end-to-end training?

In machine learning, we often see the expression "end-to-end" learning (or training). However, I do not know that it means. When is a network called end-to-end training? How to recognize a network is ...
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1answer
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How are Object Recognition and Content-based Image Retrieval interlinked?

I need help on understanding the linkage between Object Recognition and Content-based Image Retrieval. Does OR use CBIR to find similar objects with the help of algorithms like SIFT etc or does CBIR ...
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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 ...
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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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1answer
761 views

Feature Detection on a Circular Metal Surface for Character Recognition

Hello I'm trying to recognize characters on the circular metal surface. Without any preprocessing I could match cropped features with original image. I've actually cropped 2 characters together to ...
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1answer
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How to detect whether the object has triangular shape?

The task is to detect arrow from medical images. After segmenting, arrow-like objects can be connected with other connected components (noise). In this context, detecting a part of the object that ...
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1answer
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Base line detection of text lines

I came across various works in the literature of document analysis addressing the problem of detecting base lines in multi-oriented texts. But no amount of search could give me satisfactory answer to ...
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Losslessness of Laplacian Pyramid

I was just reading up on the Gaussian pyramid and the Laplacian pyramid, used in compression applications of image. The source is here - Carnegie Mellon 16-385 Computer Vision - Spring 2019, Lecture 3 ...
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Image Shadow Removal Using OpenCV and Python

How do I remove a shadow after MOG2 background subtraction using OpenCV Python? I used all morphological operations, gaussian and median blur, thresholding. it removes noises but deep shadow is ...

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