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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37 views

Is there a difference in SNR between using 2x2 pixel binning in the camera and shrinking the full resolution image in software?

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
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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
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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
262 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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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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1answer
53 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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0answers
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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
109 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
39 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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1answer
36 views

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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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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41 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
760 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
694 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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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
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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
42 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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1answer
17 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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3answers
790 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
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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
33 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
98 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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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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1answer
34 views

Find camera pose by knowing triangle coordinates

I have this concrete problem where I know the 3 coordinates of a triangle $ABC$ in a $xyz$ frame reference and I need to estimate the position $P$ and direction $\vec{n_{p}}$ of a stationary camera ...
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29 views

2d motion field

I have a theoretical question regarding motion field within a scenario and have searched the internet to get the answer though have been unsuccessful in doing so. If I have a camera in my hand and I ...
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1answer
222 views

Image Segmentation - Comparing GrabCut Method vs. Level Set Method

Checking the literature about image segmentation, if I am not wrong, there are two main approaches: Variational approach e.g. level-set optimization in Chan-Vese Combinatorial approach e.g. using ...
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1answer
3k 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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Poor convergence/generalization with few-shot learning object detection with “efficientdet”

Tensorflow's 2x object detection library utilizes a toy example for few-shot transfer learning using a few rubber ducky images (which is not a class in the original trained dataset....nor are ducks in ...
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2answers
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Background Removal and Object Tracking - Track Fish Jumping Out of the Water

0 down vote favorite I am totally new to Image processing. I just started my Master thesis in the area of Computer vision and Machine learning. My background is Informatics. Now, my first task is to ...
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1answer
529 views

How to Use Maximum a Posteriori Probability (MAP) in Classification Task

I have a 2D image defined on a region $\Omega$. Let $I: \Omega \to R$ be a gray image. Assume that the region can be separated into $N$ sub-regions $\Omega_i$ such that $$\forall i,j=1,\ldots ,N:\...
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1answer
888 views

How to warp a pixel patch to another camera

I have two cameras with rotation and translation starting from the world origin and a patch in the first camera's reference coordinate system. I want to warp this patch into the second camera's ...
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1answer
188 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
21 views

Different type of padding in image?

I want to implement a gradient operator on an image in Matlab. Should I have to pad the image before its implementation? How do I decide which padding to use e.g. whether to use zero-padding or ...
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1answer
254 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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0answers
12 views

Image processing with .HPG files

I have files with extension .hpg and I want to perform image processing on those file as they are hp plotter file. I tried googling but no luck there. hence hope someone can help me tackle this with ...
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0answers
30 views

Remove noise from VGA image

I have 2 color images generated from same X-ray machines, but one of the image is obtained using VGA cable. Therefore the RGB intensities differ in the 2 images. I am using Object detection to detect ...
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1answer
34 views

Equal probability quantizer in Python

I am trying to apply Haralick textures to a SAR image (float32). As far as I know, the image first needs to be quantized to a reasonable bit depth prior to calculate the co-ocurrence matrix. In the ...
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1answer
115 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
25 views

Terminology: Camera Tracking, Camera Relocalization

I am reading the paper RGBD Datasets: Past, Present and Future available here, and two terms that I am not familiar with are presented. On page three, middle left side of the page, the author refers ...
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1answer
144 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
101 views

Fundamental matrix rank

Is there any way one can prove that $\text{rank}\big(F+F^{T}\big)=3$? where F is a fundamental matrix. If you have any idea, do let me know. I am trying to solve this problem. I am just trying to ...
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1answer
52 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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1answer
50 views

Detecting corners using structure tensor matrix

How does eigenvalues of structure tensor matrix help in detecting corners? For eg, in Harris corner detection, we consider the matrix $$M = \sum_{w} w \cdot \begin{bmatrix} I_x^2 & I_x I_y \\ I_x ...
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1answer
4k views

Remove Shadows from Contour of an Object (Grapes)

I want to extract only the grapes from the images. Unfortunately, sometimes I don't get the grapes exactly. I have a code that doesn't work well in all cases. Sometimes, it does not differentiate ...
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0answers
14 views

Understanding R-FCN

I am reading the paper R-FCN: Object Detection via Region-based Fully Convolutional Networks available here, a fully convolutional network for object detection. The backbone architecture describes : ...
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1answer
30 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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1answer
28 views

Significance of outer product in structure tensor / second moment matrix

How does one interpret the outer product $\mathbf{M} = \nabla I \otimes \nabla I = \begin{bmatrix}\left(\frac{\partial I}{\partial x}(x)\right)^2 & \frac{\partial I}{\partial x}(x) \cdot \frac{\...

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