Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

1
vote
0answers
87 views

Extrinsic Camera Parameters without introducing control points?

I am new to the field of Camera Calibration. We have successfully calibrated our camera through classic method (using checkerboard etc). I recently realized there is a field of research for Automatic ...
1
vote
2answers
715 views

Comparison between watershed and grabcut

I know that watershed and grabcut algorithms are both common tools for image segmentation. They both seem to rely on predefined markers to form something like a source-sink system and then uses the ...
1
vote
3answers
151 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 ...
2
votes
1answer
5k views

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 ...
0
votes
1answer
134 views

How to get Harris corners that are present in watershed segmented Bitwise image(road part)?

This is Harris corner image of test image: This is Bitwise watershed segmented image: I want to get that Harris corners which will be in segmented part of image(road part).
3
votes
1answer
210 views

How can I learn image processing in a practical way?

I am a beginner in image processing and I have to learn to program in MATLAB as soon as possible. I started with Rafael Gonzalez book, but understanding this theoretical knowledge and mathematical ...
0
votes
2answers
962 views

The difference of downsampling an image and smoothing an image?

I am, at the moment, trying to read up on some simple computer vision elements, in which i have become a bit comfused on the terms downsampling and smoothing, and whether there is a difference between ...
1
vote
0answers
52 views

How to use Mikolajczyk evaluation for detectors/descriptors?

I want to compare different detectors/descriptors (both binaries and not) for my application and I want to use the Mikolajczyk evaluation framework, which is became a standard in the community about ...
1
vote
1answer
395 views

Point cloud comparison

Let me preface this question with the fact that two hours ago I had no idea what a cloud point was. I do however have a solid mathematical background although geometry has never been my focus. I do ...
1
vote
2answers
3k views

How to calculate to structure tensor?

Structure Tensor is a matrix in form: $S=\begin{pmatrix} W \ast I_x^2 & W \ast (I_xI_y)\\ W \ast (I_xI_y) & W \ast I_y^2 \end{pmatrix}$ where $W$ is a smoothing kernel (e.g a Gaussian kernel)...
4
votes
1answer
386 views

Detecting sloppy hand-drawn arrows in images

How can I easily and efficiently detect hand-drawn arrows and their directions from an image? They're probably drawn lightly, with something like a pencil, on a piece of paper. If I had ...
0
votes
1answer
65 views

Detecting objects in real world video feed?

I have an image which consists on an object in a plain black background. This is the reference image of the object. Now, My task is to take a webcam and obtain the video feed and I have to detect if ...
0
votes
1answer
22 views

looking for simplified version of motion capture for simplified situation where objects are solid and have no joint (no internal degree of freedom)

The whole question is about a simplified algorithm for tracking a single solid object which has no joint, with assumption that i have full control on adding some markers in real world to it. For ...
1
vote
1answer
145 views

How should calibration points be distributed?

I do camera calibration for a single camera with a chessboard pattern in opencv for the first time. The focus is fixed. I'm not sure how to do it, there seems to be many questions: How many images ...
0
votes
0answers
108 views

Point cloud color blending after registration

I have succesfully registered two point clouds of the same scene obtained from different camera positions. Color values are different due to changes in light condition between both positions. I would ...
1
vote
1answer
91 views

Kalman for 3D position and 1D orientation

Is the following state correct for a Constant Acceleration (CA) model KF applied for tracking an object which moves in (x, y, z) and have the freedom of rotation $\phi$ around the $z$ axis? \begin{...
3
votes
1answer
72 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\...
1
vote
2answers
189 views

Segmentation of small artifacts - Image Processing

I am working on a task of segmenting small artifacts from a set of images like below: I am looking for a generic approach, but unsure of what to search? I tried looking at density flow analysis, but ...
8
votes
1answer
704 views

Removing noise from dental radiography

I'm working on a project of applying Active Shape Model to locate tooth in dental radiograph. For those familiar with the technique, I'm currently trying to sample along normal vectors for each ...
3
votes
1answer
311 views

How to calculate particles sizes for spheric particles with overlapping and superposition? (Example image included)

I'm trying to automatically calculate particles sizes histogram for images like this one: Common threshold and segmentation doesn't seem to work. What filters and algorithms do you suggest to be used?...
0
votes
3answers
658 views

How to filter objects on basis of orientation of regionprops

I am trying to detect straight vertical lines in an image. I used vertical edge detection and then I tried to check which objects has the ...
5
votes
2answers
7k views

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/...
0
votes
1answer
82 views

Finding crosses and their orientation on a given image

I want to recognize table structure from some arbitrary photo image and store it in some formal notation (Let it be HTML table notation). For example I have this blurry image as input: After ...
0
votes
2answers
441 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)...
1
vote
2answers
233 views

Estimate camera generalized velocity from consecutive frames

Let's suppose I have a camera which can move freely in 3D space and has 6 degrees of freedom. Is it possible to estimate the linear and angular velocity of the camera from 2 or more consecutive frames?...
0
votes
1answer
5k views

What is different between gradient and imgradient functions in MATLAB

I would like to compute the gradient of an image I. I have the following two options : [Gx, Gy] = gradient(I); g = sqrt(Gx.^2+Gy.^2); or ...
-1
votes
0answers
39 views

Retrive texture / data from photos of sphere object

I've built a photo box for taking photos of spherical objects (balls etc). I take photos cubical from six different angles. Now I want to extract the bitmap texture from the object with most ...
1
vote
0answers
34 views

How can a medical doctor use the information given by someone working in medical image computing(shape analysis)? Details follow

Posted also here, where it's been put on hold. I did modify it afterwards though. https://biology.stackexchange.com/questions/43997/how-can-a-medical-doctor-use-the-information-given-by-someone-...
1
vote
2answers
849 views

How to approach detection of anomalies in a video feed?

As part of a project I have a video from a quadrotor that captures the road and the environment around it and I want to identify and detect potholes and speedbumps on the road using image processing. ...
1
vote
2answers
661 views

Generate a nonuniform illumination (bias field) 2D image

I am creating a nonuniform illumination in MATLAB R2015. The nonuniform illumination (known as bias field) is defined as Nonuniform Illumination (intensity inhomogeneity) which manifests itself as ...
0
votes
1answer
2k views

How do I understand Fourier descriptors more visually and intuitively?

I read the book Image Processing, Vision and Machine Vision and find the concept Fourier descriptors hard to understand, although literally its derivation is somewhat reasonable. Can anyone give me a ...
1
vote
1answer
523 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 ...
1
vote
2answers
389 views

Seeking segmentation methods for this light microscope image

Although I am not new to math or programming, I am a total newbie to image segmentation. I have the following light microscope image and I would like to segment it into cytoplasm (the magenta ...
0
votes
0answers
105 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 ...
2
votes
1answer
81 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 ...
0
votes
2answers
196 views

Beginner Question: Extracting Features for Image Classification

I'm a Python programmer, but a beginner to image processing :) Apologies if this isn't a suitable question for the forum, happy to rewrite or move. I want to create a supervised classifier to ...
1
vote
0answers
241 views

How to match a thumbnail to an area in the original image?

Suppose that you have a thumbnail and the original image from which it was generated. You need to match the thumbnail to an area in the original image that represents the original selection from which ...
0
votes
1answer
74 views

How can I use a trained model to generate related images?

Suppose I have a data set of a large number of related images and I extract HOG features and train it using SVM Classifier or KNN Classifier. How can I use this model to generate a new image which is ...
2
votes
1answer
2k views

NORM_HAMMING2 vs NORM_HAMMING

I'm trying to use ORB features with a cv::BFMatcher. ORB is based on binary descriptors so HAMMING must be the choice, but I'm not sure I understand the difference ...
0
votes
1answer
379 views

Extracting DCT coefficients from H.264/AVC bitstream

Is it possible to extract DCT coefficients from H.264/AVC bitstream without doing a full-decoding of the video? There are a lot of papers on compressed domain video processing which are based on the ...
1
vote
1answer
185 views

How the noise in time series can be reduced?

I have asked the question in the following link: Are time series data always contain noise? I wonder if we could use variational methods to denoise the time series data just as in computer vision? ...
1
vote
1answer
177 views

Low Pass Filter - pixel correlation

I am trying to understand low pass filters for image processing, I came across an article that stated that low pass filters effect noise more than the real data due to that the image Noise always ...
0
votes
1answer
228 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 ...
1
vote
1answer
91 views

How can I approximate a signal

I have a signal as the below figure. I am looking for some schemes to approximate the signal. I have found some ways for that task: Using basis function (polynomial) to approximate the signal ...
0
votes
1answer
111 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 ...
1
vote
1answer
107 views

Essential Matrix from line correspondences

I'm looking for some library with a function to compute an essential matrix from line correspondences in multiple images. All the computer vision libraries I know use point correspondences to compute ...
1
vote
0answers
17 views

How is per-class rate defined?

I've recently read the following For our pixel labeling, consistent with [20], we report the number of pixels correctly classified (per-pixel rate) and the average of per-class rates. The per-...
0
votes
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 + ...
0
votes
1answer
733 views

Converting from RGB to Lab to reduce colors

In many papers I see the following: First we have to convert image from RGB to Lab color space to reduce colors then ...
-1
votes
1answer
380 views

How does the PASCAL VOC challenge evaluate the task of object detection?

I fail to understand the evaluation parameters like true positive, false positive and false negative in detection and classification tasks. can anyone help me to figure out what does each of these ...