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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1answer
117 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
172 views

How do I detect the sharp edges in the following image?

I am looking to count the sharp pointy triangular things in the image. However I was unable to do so. One approach I did try was take a convex hull of the contour and then find convex defects but it ...
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1answer
59 views

Recommended approach for extracting specific edges from image?

I have several sets of images with a typical image being: and from each image, I would like to extract the top and bottom curves of the object, shown in red here: What are some possible tools I ...
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23 views

Normalizing directed graphs from image space to compute joint differences

My question is how to transform a 'skeleton' (directed graph) from image space so that I can compare it joint-wise against another 'template' or reference skeleton that may be differently sized/...
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40 views

Understanding rho and theta in hough

I understood the concept behind Hough transform. One thing i am still unsure is the rho and theta range of hough transform. The range is given below. If theta is in the range [0,pi), then rho values ...
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4answers
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How is digital signal processing related to Computer Vision?

Keeping in reference this image, I want to build a concrete understanding of interconnection between Digital Signal Processing and Computer Vision. What would be the applications of this co-relation?
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Help or suggestions with Line detection in microscopy images

I'm doing a personal project in which I want to select some very specific lines in a microscopy image. The first picture is the raw image, the second picture is the image for the lines (in yellow) I ...
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0answers
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What is the difference between full octave and half octave pyramid?

I couldn't find a good source to explain the diffrence between the Full octave and Half Octave pyramid in Computer-Vision. I saw the Gaussian-Pyramid, and the Laplacian Pyramid, but I didn't see ...
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8 views

Implementing Felzenszwalb's segmentation for 3D images

Is there an implementation available for unsupervised 3D segmentation using the Felzenszwalb's Graph Cut algorithm? If implemented what do you think are the bottlenecks of such an algorithm? In ...
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291 views

stones' detection in jewel image

The project I am doing is to detect stones in an image of a jewel, so as to get the idea of the deduction to be made in the gross weight of the jewel. I have done image-segmentation in the HSV color ...
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Problem definition in KLT tracking

I am studying about the KLT tracker algorithm. In the KLT tracker, we can try to estimate the optical flow for corner points (because these are good features to track) between frames and the computed ...
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1answer
20 views

Comparision between SSIM and MAD Image Quality Assessment Algorithms

I have been working with Most Apparent Distortion(MAD) tool to evaluate the quality of images. I have read a paper that compares SSIM, PSNR, FSIM, etc. with MAD. I am uncertain about some calculations ...
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1answer
23 views

Why not use synthetic datasets for training machine vision (deep learning) algorithms?

I am studying some examples of how to perform 3D instance segmentation in indoor scenes, and I have noticed many of the available datasets are from real environments. I was wondering with the ...
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1answer
24 views

Kalman Filtering with measurement latency

The timing involved in this problem is a little hard to explain, so I'll start with my specifics: I'm developing a program that visualizes output (a bounding box) from a computer vision model on top ...
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1answer
2k views

How can I detect pipeline cracks using OpenCV and Python?

I have developed a robot that captures images of the pipeline interior as it moves. The requirement was to be able to detect cracks inside. So far i tried several OpenCV codes that find the crack ...
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21 views

multi-frame image restoration

Suppose we have a sequence of still images each of which has been contaminated by some particles(ex, dust/sand/smoke) making the images very poor in certain areas. What approach would be best to teach ...
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1answer
83 views

What function to apply a Metamorphopsia (grid warp) translation?

How would I go about finding or creating a function to warp images dependent on grid lines surrounding an origin (I don't wish for a grid on my actual images): It should work in practically the same ...
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3answers
2k views

How to Zero Pad in Order to Perform Filtering in the Fourier (Frequency) 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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1answer
58 views

Camera Calibration of a Depth Camera

For a regular RGB camera, reading the wikipedia page for camera resectioning/calibration here, they divide the paramters into two categories: Intrinsic: - focal length, scale factors in x and y, and ...
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1answer
52 views

Understanding legacy code: Algorithm to remove radial lens distortion

The method below to remove lens distortion from a camera was written more than ten years ago and I am trying to understand how the approximation works. ...
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1answer
42 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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Which one is better method and why? Manually Handcrafted sound features vs spectrogram + convolution

I am working on classifying different sounds ( not speech or words exactly something like ambulance alarm, police alarm, cough sounds etc) I read few paper which suggested to extract dsp features such ...
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1answer
720 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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3answers
1k views

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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3answers
282 views

Effect of Resizing (Up Scaling) an Image on the Ability to Detect / Recognize Objects

I work in a research lab and am currently setting up a system to image objects approximately 30 microns in diameter with a 250x USB microscope, then use image subtraction to isolate the objects as ...
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2answers
309 views

How Is the Gaussian Kernel Related to the Euclidean Distance of the Neighborhoods in the Non Local Means Denoising Algorithm?

I am reading the paper A non-local algorithm for image denoising that describes the original non-local means algorithm. They define (p. 3 of the pdf) the distance between two square fixed ...
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3answers
60 views

Pixel Binning: Effect on SNR for Hardware vs. Software Binning

Is there a difference in SNR (or any other measure of image quality) between using 2x2 pixel binning in the camera and shrinking the full resolution image in software (cv::INTER_AREA) to the same size ...
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1answer
81 views

Licence plate enhancement

Is it possible to enhance the image below and make it more readable? I have tried apply binarization but there is some kind of shadow. So I have tried to convert image to gray scale and then ...
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1answer
23 views

How does transformation matrix and camera matrix change when indexing pixels from -1 to 1 instead of 0 to N-1

I'm trying to warp frames for view synthesis. Specifically, given a frame1 and poses of frame1 and frame2, I'm trying to warp frame1 to frame2's pose/view. For this, I'm indexing pixel locations as $[...
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1answer
40 views

How virtual ads work in stadiums?

I was looking at a technology which enables virtual advertisement on the perimeter ads in soccer. It's relatively an old technology for a few years back, but I'm surprised to see the quality of it. ...
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1answer
12 views

Is Mask R-CNN a good fit for what I want to do?

I'm looking at isolating the foreground from a set of photos, and I think I want to use instance segmentation so that I can try to gauge how well-focused the main subject of each photo is. I have ...
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1answer
267 views

Low Pass Filter to Maintain Edge Information

I am looking for a kernel acting as a low pass filter that satisfies these conditions: $$K(-\mathbf{u})=K(\mathbf{u}) \tag{1}$$ $$K(\mathbf{u}) \ge K(\mathbf{v}), \;\; \text{if} \;\; |\mathbf{u}|<|...
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0answers
43 views

Understanding the math used to generate a point cloud from a depth image

In reviewing various algorithms for converting a depth image to a point cloud where the camera has extrinsic parameters $c_x, c_y$ the center point of a camera $f_x = f*m_x$, where $f$ is the focal ...
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46 views

Interpreting the accuracy of solutions to the correspondence problem

I have two pictures of the same object, taken by a car travelling down the road like shown on the right side of the image below. I want to find pixels of the object in each frame that correspond to ...
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40 views

Obtaining a horizontal disparity image from a depth image

In the paper Learning Rich Features from RGB-D Images for Object Detection and Segmentation available here, the authors encode depth images using three features computed from the depth image, called ...
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1answer
115 views

Why reprojection error is minimized instead of triangulation error for bundle adjustment?

For bundle adjustment optmization why is reprojection error minimized instead of traingulation error or ray-to-3d point error? Disadvantage with reprojection error is: for perspective camera, its ...
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1answer
69 views

Faster R-CNN and 4-step Alternating Training

I am reading the paper Faster R-CNN available here. In section 3.2, page 6 bottom left, the authors describe what they refer to as a 4-step Alternating Training between the Region Proposal Network, ...
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Is there an algorithm in Matlab that could track moving objects that present change of color?

I'm studying the photomechanical behavior of photochromic thin films. They react to specific light wavelengths exhibiting bending movement. I use a yellow light, which turns the film from blue to ...
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1answer
44 views

How to calculate the plane at infinity? either in Matlab or Python

I tried to implement this function to compute the plane at infinity $n_\Pi$ from the equation: where $w^{-1}$ is the image of the absolute conic IAC, $M_j$ is the Projection Matrix of image $j$, but ...
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2answers
769 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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1answer
18 views

Are location in BRIEF feature descriptor reused?

In the BRIEF feature descriptor ("BRIEF: Binary Robust IndependentElementary Features", Calonder et al., 2011) they investigate five different methods of choosing point pairs to compute the ...
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1answer
3k views

What is a good distance measure for matching SIFT descriptors depending on the distribution of their noise?

I have read some papers about distance measures like Euclidean, Manhattan or Chi-Square for matching gradient based image descriptors like those computed from the SIFT Algorithm (128-D vectors). Most ...
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2answers
43 views

2D to 3D view conversion

I came across this demo by Fox sports: https://youtu.be/N9SxFf5WCb0 Where they show a player's view in a 360 space. Very smooth and nice. I was wondering how do they achieve it without any cameras ...
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1answer
123 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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3answers
801 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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2answers
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Why are 8 points needed to compute a fundamental matrix?

Homograpies have 8 degrees of freedom. Fundamental matrices have 7. Essential matrices have 5. To the best I could find, all those matrices are obtained by using the 8 point algorithm. I don't see ...
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1answer
1k 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
66 views

Detect non rectangular bounding box for objects

I have a short video where a TV is shown. I need to detect the TV there (let's assume it's all pure black or it's covered with a green screen), and overlay a video on top of it on the same area. But ...
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1answer
132 views

What is the difference between an image plane and a virtual image?

I have the following diagram that describes a camera model (I believe it is the pinhole camera model). Wikipedia has an article about the image plane and virtual image, but these articles do not ...
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2answers
1k views

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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