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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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How to calculate the angular velocity of a rotating cell from a microbe video?

I have a video of Brownian motion of microbes under a microscope. From this video, I need to calculate the angular velocity of a particular prominent cell. From my understanding, what I know is that I ...
Shataneek Banerjee's user avatar
2 votes
3 answers
189 views

Remove Wave Patterns from an Image Using Inpainting

I have been struggling to remove wave like patterns from my image. I tried FFT (Fourier Transform) and it wasn't good. I came across with inpainting and it looked promising but I don't know how to use ...
Ammar's user avatar
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1 vote
1 answer
19 views

How to measure the vibration of an object on a video shot at high speed camera?

I have a video fragment which I split into frames (pictures). I use them in pairs (1 frame with 2, 2 with 3, etc.) to find shifts on x and y axes (i.e. how much I need to shift 1 frame to make it like ...
tryingmybest's user avatar
0 votes
2 answers
41 views

How to determine stripe width of a barcode

A barcode consists of alternating back and white stripes. Thin stripes are one "unit" wide. We'll assume fat stripes are 2 "units" wide. But how big is a "unit"? I can't ...
Peter Balch's user avatar
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0 answers
13 views

Down-scaling image at each step in LoG blob detection

I'm new to CV. I'm currently implementing the LoG blob detection. I've come across this repo on Github: BlobDetector. The main implementation is here: Blob. I'm confused by the down-scaling of image ...
Ak1's user avatar
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0 answers
8 views

What is the best approach when training and HDR model with LDR data?

I am working on this project "EMLight". Data: HDR Panoramic Photos y: Illumination Map of the Panorama X: HDR Croppings from the Panorama I want to make this project work with LDR photos, ...
xtc_'s user avatar
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0 answers
16 views

"Seemingly random numbers" in sobel operator

I understand that Sobel operator approximate "changes in x-y direction" of an image using three consecutive pixels. But why are these numbers 1 2 1? Where do they come from. I tried to ...
MathematicsBeginner's user avatar
1 vote
1 answer
87 views

How do I estimate the position and orientation of two instruments looking at the same target?

Consider the following lab set-up: Two instruments: a laser profiler (L) and a line scanner camera (C) are mounted on a rack so that they are facing a flat target downwards. At time $t=0$, that is ...
Andy's user avatar
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0 answers
14 views

Why is Histogram of Oriented Gradients only 0 to 180 degrees and not 0 to 360 degrees?

Why is Histogram of Oriented Gradients only 0 to 180 degrees and not 0 to 360 degrees? I can see in many videos that it's very common that atan which results values ...
euraad's user avatar
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1 vote
0 answers
103 views

Does ORB-Slam3 perform better than ORB-Slam2?

I was trying to compare ORB-Slam2 performace with ORB-Slam3 performance. Consider following comparison from ORB-Slam3 paper (columns with numbers correspond to different sequences from EuRoC dataset): ...
Mahesha999's user avatar
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0 answers
15 views

How orientation is used in FAST features in ORB?

I was going throught ORB paper. It states that it adds an efficiently computed orientation to FAST features. The description explains how it calculates Moment of patch $$m_{pq}=\sum_{x,y}x^py^pI(x,y)$...
Mahesha999's user avatar
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0 answers
22 views

Why do people use signs in columns/rows of several kernels reversed?

I have observed that different citations/codes use signs in different (reversed) columns/rows for many kernels. Here is an example for Prewitt (but same for Sobel, Scharr, etc); in some cases is ...
Fredrik's user avatar
  • 101
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0 answers
70 views

Detect GUI Buttons in every application window with python

I want to detect every buttons in every application windows. For example, in explorer window, I want to detect every Tags, folders, files and Buttons like "page back", "page forward&...
roy's user avatar
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0 answers
16 views

Face Detection real-time with Local Binary Pattern

I'm writing for code to detect human face by Local Binary Pattern algorithm in webcam, but with my limited knowledge in optimization code, I having to struggle in detect in each frame , I want to say ...
Hau Chung's user avatar
1 vote
0 answers
46 views

Local Binary Pattern rotation

How does LBP work? To learn that, I decided to calculate by hand for the matrix but the problem is about the rotation pixel over the image based on the radius and neighbor of LBP. I do it clockwise ...
chews's user avatar
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1 vote
1 answer
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Using nearest neighbor in RANSAC

I found many resources online talking about nearest neighbor concept in RANSAC. For example, figure 2 of this paper, this article and this repo talk about nearest neighbor in the context of RANSAC. ...
RajS's user avatar
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1 vote
0 answers
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Calculation of disparity in parallel stereo cameras

I'm learning about stereo vision and the slides that my teacher provided aren't very clear on this point. He had a formula for disparity: $$d = \begin{cases} x_L ‒ x_R & \text{if } x_R \ge 0 \\...
Typhaon's user avatar
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1 vote
0 answers
22 views

Understanding and Resolving Singularities in Stereo Rectification using Multiple View Geometry

I am currently working on implementing a stereo rectification algorithm based on the method described in the book "Multiple View Geometry in Computer Vision (MVG)," specifically in Section ...
Lion Lai's user avatar
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5 votes
3 answers
997 views

How do I estimate the pose of a camera looking at a flat horizontal surface?

I have a camera looking down on a flat horizontal surface, Z=0. The position of the camera with respect to the surface: $[XC,YC,ZC]$ is unknown. Also the orientation of the camera with respect to the ...
Andy's user avatar
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1 vote
0 answers
90 views

calculate homography to generate a bird's eye view image

I have a 3D point $(x_w,y_w,z_w)$ with normals $(X_n,Y_n,Z_n)$, with the intrinsic matrix I can project it to image space $(x_i,y_i)$. I want to calculate a homography matrix such that I know how the ...
Dong's user avatar
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1 vote
1 answer
209 views

How to do image segmentation on a binary image with simple shapes

I'm wondering what's an algorithm I can use to segment shapes on a binary image. Below is an example of the wanted result: Thanks
tchiki tchinka's user avatar
4 votes
1 answer
71 views

Video Alpha Matting

I'm looking to composite an opaque object (e.g. 3D art) into video footage of semitransparent fog/clouds before a landscape background so that the object seems immersed in the clouds but occludes the ...
LogicBreaker's user avatar
1 vote
0 answers
66 views

Chebyshev filter analog in computer vision?

Looking at the basic characteristics of a Chebyshev Filter, I was wondering if there were any analogous type filters in Computer Vision? The way that it can minimize the error between the idealized ...
Student CS's user avatar
1 vote
2 answers
145 views

What is coverage count and how can I build it?

For my assignment, I am required to blend multiple square images into a single large image where each square image represents a part of the final image. To accomplish this task, I have successfully ...
Straw User's user avatar
2 votes
1 answer
394 views

How to compute second order derivative of image using the integral image and box filters?

I want to speed up my blob detection function by computing the second order derivatives of the input image using the integral image and some box filters. Initially, I used the following method, which ...
Stefanos Anagnostou's user avatar
2 votes
2 answers
163 views

Camera sensor artifacts next to edges in calibration images; what is causing these?

I am trying to image some ChArUco targets using a monochrome machine vision camera with a CMOS sensor and the attached images show the artifact I am observing: 2-pixel-wide bright vertical streaks ...
sg65's user avatar
  • 41
3 votes
1 answer
147 views

The SIFT Descriptor and Image Resolution

When reading about SIFT I read halving resolution is the same as increasing $\sigma$ of the gaussian in terms of feature detection but reducing resolution has the advantage of reducing processing. ...
FourierFlux's user avatar
0 votes
0 answers
43 views

Discrete cosine transform and histogram equalisation

I found an image hash library for python and this blog In the block Getting Funky With pHash, the author writes: Further reduce the DCT. This is the magic step. Set the 64 hash bits to 0 or 1 ...
Albert Nagapetyan's user avatar
4 votes
1 answer
72 views

How to Estimate a Multi Channels and Multi Kernels Convolution Kernel (Deep Learning Style) Given the Input and Output Images

Is it possible that can estimate convolutional kernel that have multi channels and multi filters ? I saw answer from this to link to estimate kernel for one channel and one filter (Estimating ...
Mint Int's user avatar
5 votes
2 answers
122 views

Analyzing 2 2D Kernels Which Approximates a Gaussian Kernel

I'm new to image processing and am working on mask operations. I was given two kernels A and B, and performed convolutions respectively on an image. Then, I have to get the difference of output image ...
Nightysky's user avatar
1 vote
0 answers
123 views

State-of-the-art non-training based stereo matching algorithm

In the world of 3D vision, constructing a 3D model from multiple view imagery is an important topic. The stereo matching step is one of the most crucial steps. Based on the benchmark of KITTI2012 and ...
Lion Lai's user avatar
  • 213
1 vote
1 answer
69 views

Projection Matrix -- where does it come from?

I've started with these series to teach myself image processing and I am wondering when the camera's projection matrix (i.e. intrinsic and extrinsic matrices) is calculated? Is camera calibration a ...
user2132190's user avatar
8 votes
6 answers
2k views

Why color is coded with two numbers rather than one?

I was thinking why color spaces use two numbers to represent color: Lab, HSV, HSL? Is it possible to use one number and have the same or very similar properties when comparing colors as we have for ...
ivan_onys's user avatar
  • 183
4 votes
1 answer
148 views

The Effect of the Order of Downsampling and Smoothing on the Output

How do I prove or disprove: Smoothing an image with a 3x3 filter using full convolution and then downsampling an image by 2 produces the same result as downsampling an image by 2 and then applying ...
Kumar's user avatar
  • 141
1 vote
1 answer
220 views

Log of Filterbank Energies

In common literature, when generating spectrograms, mel-spectrograms, and cochleagrams, the log of the resulting filterbank energies is taken. Why is this done? I notice that my convolutional neural ...
Lyle's user avatar
  • 11
3 votes
1 answer
89 views

Computer Vision: What is a good approach to find the similarity between 2 screenshots of a screen from a mobile application?

I am trying to find an algorithm to determine the similarity between 2 screenshots of the same screen of a mobile application. I have tried structural similarity index, Peak signal-to-noise ratio and ...
Vinoth RJ's user avatar
0 votes
0 answers
223 views

What image similarity measure is best for measuring the structural similarity of two images?

I am looking for an image similarity measure that can measure the differences between the structural composition of two images. For example these two images have structural differences between them ...
CoderMath's user avatar
0 votes
1 answer
136 views

Segmenting dark spots from a light background?

I need to perform automatic segmentation of dark blue spots on light yellow paper. Here's a very simple example: In this case, a simple threshold based on hue or brightness works well. But here are ...
Hundley's user avatar
  • 101
6 votes
1 answer
702 views

Why is scaling of images / pixels into `[0, 1]` range performed before SIFT (Scale Invariant Feature Transform) algorithm?

The SIFT paper and the paper of Anatomy of the SIFT Method do not mention that the input images should be preprocessed (normalized, re-scaled) before feeding images into the standard SIFT algorithm. ...
Lion Lai's user avatar
  • 213
1 vote
1 answer
71 views

Minimum number of patches needed to find color correction matrix (CCM)

The chart should have at least 9 distinct color patches for 3×3 CCMs (which are generally recommended). Excellent results can usually be achieved with the inexpensive, widely-available 24-patch X-Rite ...
user64826's user avatar
1 vote
0 answers
288 views

How to Measure Image Quality in an Objective Way

I need a method to measure image quality via computer programming (like Python). I'm doing this so as to compare quality of multiple images. I have found stuff like NMSE, PSNR and SSIM, but don't ...
CoderMath's user avatar
5 votes
1 answer
98 views

Relationship / Connection Between Machine Learning / Deep Learning and Computer Vision [closed]

What is the actual relationship between Machine learning and Computer vision? Is Computer vision is subset of Machine learning or is it another independent subset of Machine Learning? I am trying to ...
jkh's user avatar
  • 59
3 votes
1 answer
38 views

Explain the Terms: Semantically Richer and Spatially More Precise in the HRNet Model Paper

High-resolution representations are essential for position-sensitive vision problems, such as human pose estimation, semantic segmentation, and object detection. From HR-Nets we get semantically ...
Harish Battula's user avatar
1 vote
0 answers
125 views

calibrating camera using 3d objects such as rubik's cube?

Hello all hope everyone is doing fine. I have a vision related problem where I want to calibrate my camera using a 3d object such as rubik's cube with known dimensions. I have a cube with 60mm length, ...
umar anjum's user avatar
0 votes
1 answer
181 views

Clarification of some known issues in monocular visual odometry

so I'm reading an academic paper about some state of art algorithm of VO using deep learning, and there are some "known" issues of classical computer vision approaches that the authors bring ...
Ilya.K.'s user avatar
  • 177
1 vote
1 answer
369 views

Problem with "Topological Structural Analysis of Digitized Binary Images by Border Following" by Suzuki Abe

I have a Problem with the Paper "Topological Structural Analysis of Digitized Binary Images by Border Following" by Suzuki and Abe. In the Chapter "Appendix I: The Formal Description of ...
Vanior's user avatar
  • 11
0 votes
1 answer
487 views

Finding rectangle corners by using point cloud

I have a rectangle in the 3D scene, which I know its width and height. It is placed in the 3D scene like the image below. I can manually select all points on the rectangle by mouse click. Given the ...
CVDE's user avatar
  • 103
2 votes
1 answer
150 views

What are the typical annotation styles for optical flow?

I am coming from a background in deep learning techniques for computer vision like image classification, action recognition from skeletal data, and semantic segmentation. I have read several papers on ...
IntegrateThis's user avatar
2 votes
2 answers
92 views

Image warping with heat map that "pulls" on pixels

I am looking for an efficient image warping function $$f: (\text{image}\in \mathbb R ^{M\times N\times3}, \text{heatMap} \in \mathbb R ^{M\times N}) \to \text{warpedImage} \in \mathbb R ^{M\times N\...
Peter's user avatar
  • 143
0 votes
2 answers
52 views

Fixing distortion in photographic reproductions

I am currently building a photographic setup which I intend to use to make reproductions of a large amount of transparencies(positive and negative film strips). As I will be using a fairly small (1&...
MTTI's user avatar
  • 103

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