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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26 views

Can Normalized Cut be used to find connected components in binary images?

I'm unsure whether Normalized Cut can or can't be used to find connected components in binary images. I would argue that it could, but could not validate this argument.
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126 views

Removing lines of certain length from an image in MATLAB

I want to remove the portion of the line (highlighted by the yellow circles) where pixels form a straight vertical line segment. If I use the strel ...
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1answer
101 views

given an image and its fourier transform, find another image fft using fourier properties

I managed to solve few of those questions , but I'm not manage to answer 3 of them correctly, the question is: given an image and its fourier transform, find another image fourier transform ,using ...
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1answer
330 views

Laplacian of Gaussian Approximation and Gaussian Blur as the Solution of Heat Equation

While I was reading SIFT paper(Lowe, 2004), I came across the method that he apply "heat diffusion equation" to Gaussian function to derive that $$ \frac{∂G}{∂σ} = σ∇^2G $$ I searched Wikipedia and ...
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What are some current algorithm(s) for finding if two images are copies of each other?

Could anyone enlighten me on what are the current best ways to detect if two images are the same (i.e. a copy or edited copy of each other)? What feature detection method do they use (SIFT, DWT, pixel ...
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Scan an Auditorium, Count People, and Display Open Seats

I'm looking for any recommended approaches to be able to digitally process a room full people, like an auditorium or a movie theater and output the following information: Goals: How many people are ...
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1answer
71 views

What is difference between along the edge and across the edge

I am trying to implement a paper called structured tensor based image interpolation. In the paper I came across a concept called tangent direction and normal direction. What they mean is tangent ...
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2answers
2k views

Camera calibration and extrinsic parameters for perspective transformation

I'm working in a photogrammetry camera and laser application where I need to measure a displacement in a specific plane, this is a quick diagram of the setup: In order to get proper measurements I'm ...
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1answer
1k views

MatLab - Can not detect all lines in a “simple” image using houghlines

I try to detect all lines in an image with some common geometric figures. The obvious choice, hough of MATLAB wouldn't print out the desired results. I used the ...
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93 views

How to overcome effect of intensity variation in image processing?

I want to process an image for which I need the method to be robust to lighting conditions. For that the only thing I can think of is normalising intensity. I did this by dividing the image with ...
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1answer
252 views

Frame overlapping

I 'm reading the following article from NVIDIA which involves some audio processing a the beginning : link just here (part 3.2) I don't understand the following part : In practice, we use 520ms ...
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2answers
342 views

How should someone start to learn machine learning and computer vision for mobile applications? [closed]

I am very interested in learning Machine Learning and Computer Vision for mobile apps, for iOS and Android. But I have no clue or even a slight idea on how to even begin. I know this is heavy on math ...
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93 views

Estimating exterior camera parameters by matching lines using least square estimations (Lowe, 1991)

I'm new to computer vision and graphics. I want to estimate exterior camera parameters using non-linear least square estimation as suggested by "Lowe, David G. "Fitting parameterized three-dimensional ...
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32 views

Kalman Filter - Gaussian representation

I'm trying to understand well the kalman filter, as a result i'm having this question : Why do we represent noise with a Gaussian ? what does this really mean intuitively ?
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510 views

How can l extract characters withe same bounding box size?

l have a set of images which represent a sequence of characters. l'm wonderning whether OpenCV can segments and crop each character from the image with same bounding box size. My numbers are not ...
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1answer
654 views

Hand tracking, state of the art

I am looking for a framework for extracting hand region from the video feed from the webcam(analogous to Viola Jones HAAR detection of face). This region of interest will serve as input for a CNN for ...
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1answer
707 views

Two-View 3D reconstruction using the sparse Levenberg–Marquardt algorithm

I have trouble implementing the Levenberg-Marguardt algorithm as described in the book Multi View Geometry in Computer Vision. To be more specific I have trouble calculating the partial derivatives ...
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2answers
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Segmentation of warped text lines

I am trying to segment warped text lines found in photos taken from a page of a book (from the camera of a smartphone). This is meant as a preprocessing step before running OCR on them. I have found ...
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473 views

Segmentation and edge linking

I am trying to implement segmentation on an image. after a difference of Gaussians Process and applying weights to my edges I want to go through edge linking by local processing. I have seen this ...
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1answer
111 views

Image reconstruction using Irradiation

I am a bit confused as to how to go about this. I have a surface [x,y,z] given by: ...
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1answer
789 views

Image processing: Image recognition and classification on fish

I need to identify the type of fish caught from fish images. How can I locate anchor points/landmark points to extract features from the image? Namely, I want to locate eye position, dorsal and ...
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1answer
65 views

Face detection in videos [closed]

I have to detect faces in videos using machine learning methods like SVM, I have to build it from scratch not using any inbuilt face detectors.My time limit is like 15hours from now.Can I get any ...
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2answers
530 views

Image distortion and alignment on 3D mesh / pointcloud

Currently I have a fairly accurate (50 µm) and large dataset from a 3D scanner and a set of high resolution pictures. Sadly the 3D scanner (a Nikon/Metris arm-based CMM that was hanging around the lab)...
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115 views

Object localization down to the pixel

I am somewhat confused on the terminology used in Computer Vision. Suppose I wanted to detect (localize) an object (say, a human) in an image. However, a box around the human is not sufficient, what I ...
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1answer
240 views

Can I segment characters from this image with CSV?

I am trying to segment my characters on this image with using column sum vector. This method actually works on the paper I've read about license plate recognition. it looks useful for my images ...
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1answer
117 views

camera calibration change orientation of axis

I want to solve for the extrinsics by using direct linear transformation on corresponding 3D LIDAR points and 2D camera points. I already have the intrinsics. Problem is, points behind the camera ...
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1answer
24 views

Getting composition of a mixture of colours

I wanted to validate a thought on blending of colours digitally. Imagine I have two colours, $C_1$ $(R_1,G_1,B_1)$ and $C_2$ $(R_2,G_2,B_2)$. Now, I create colour $C3$ as follows: $C_3 = \alpha C_1 + ...
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1answer
2k views

What is the difference between a range image and a depth map?

https://en.wikipedia.org/wiki/Depth_map https://en.wikipedia.org/wiki/Range_imaging To me, it sounds like they are the same thing, except depth map implies only having the z coordinate info. But ...
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2answers
699 views

Calibration (intrinsic) parameters of a virtual camera with some known information

I need the calibration matrix of my simulated camera, I am trying to fully comprehend and follow the steps from Step by Step Camera Pose Estimation for Visual Tracking and Planar Markers as well as ...
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505 views

how to compute horizontal angle of a pixel from a computer vision camera

My program needs to compute the angle of a pixel from a computer vision camera that has 120 degrees field of view, and resolution of 640 pixels wide and 480 pixels high. Program receives an X,Y array ...
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1answer
132 views

Machine Vision - Infinity Focus effect

I am working on a research project that involves machine vision. The camera we are using implements infinite focus - I have been informed that this can affect the accuracy of computer vision ...
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1answer
591 views

3D point cloud to 2.5D graycale image (metric) [Halcon?]

I have a problem ragarding transferring a point cloud to a 2.5D metric grayscale image (gray value gives depth information). I start with a three channel image of 32bit floats with each pixel ...
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726 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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203 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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4answers
126 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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1answer
774 views

Is my algorithm about blob tracking for vehicle following correct?

I'm doing vehicles tracking project. The video is a one-way, no vehicles occlusion. After doing background subtraction, erosion and dilation, I get bounding box objects for each frame, and I can find $...
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1answer
1k 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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61 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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1answer
118 views

Equal contribution criteria during image pyramid construction

In their paper on Image Pyramids, Burt and Adelson state the following about pyramid generation. An additional constraint is called equal contribution. This stipulates that all nodes at a ...
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51 views

Best method for texture classfication

I am working in medical and nature images processing . I want to find a popular method to segment texture image. Could you suggest a popular method to do it? For example: Gabor filter, tensor...
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1answer
936 views

What are the various techniques for detecting Walls in the Building(Architectural) floor plan Images?

I have to process building floor plan images to extract Walls from the structure. It is trivial in case of binary images; but the images in our case are colored, and each have different color of walls....
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1answer
183 views

Incremental Online Update of Tf-IDF Indices for Image Retrieval

In their paper Scalable Recognition with a Vocabulary Tree, Nister and Stewenius mention that after an offline training stage, new images can be inserted on-the-fly into the database. However, at the ...
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59 views

What is contextual Knowledge?

Contextual knowledge (CK) is used in some AI application, Can someone give me a concrete definition of this term. I am working on ontologies( a set of concepts and relationships among them) and ...
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132 views

How to estimate gradient orientation?

I have a general task of discriminating images of shaded cylinders that significantly vary in 3d orientation, and almost insignificantly in size and shape. I have treated it as a regression problem ...
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3answers
726 views

How to select the specific frame with object

I am detecting the object from the live camera through feature detection with svm , and it read every frame from camera while predicting which affect its speed , i just want that it should select the ...
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1k views

HOG descriptor algorithm

I would like to implement a HOG descriptor in C++. I found an implementation of this code here. An extract of the code follows: ...
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0answers
85 views

How can I create polygon estimates of each body part/limb that is present in an image which always contains one person?

Background I am working to identify and isolate each human limb of a known person, in pose, in an image which is relatively noisy. It should also be noted that the image is a snapshot extracted from ...
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731 views

Using GavabDB for 3D face reconstruction from frontal image

Project: 3D face reconstruction Input: 2D frontal face Image Output: 3D face Reconstruction and expression simulation Platform: Matlab or Opencv cpp. I found out after study that 3D Morphable Models ...
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1answer
308 views

Incoherence: Compressed Sensing (CS) vs Matrix Completion (MC)

I am seeking a clarification of the concept of Incoherence within the MC framework. Specifically, 1) the literature mentions the application of a "strong incoherence" given a set of assumptions. ...
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Calculating Hamming distance effectively: a fast approach

Let us say that we have a database of 5000 entries. Each entry is a 32 point discrete signal (min. amplitude: 0 and max. amplitude: 10 (signal value ranging only in integers)) i.e. each discrete point ...