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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Frameworks comparison for Object Detection (Pytorch)
I'm trying to compare or choose a framework for object detection, meanwhile, I found two:
MMDetection + MMYOlo
Detectorn2
If someone have experience with above, please share pros and cons.
Or if there ...
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Comparing large 3d datasets for Grid map data
I am working on Grid maps.Grid maps are a representation of the environment in terms of 2d or 3d cells which store a value in them that can be plotted to make a map of the area.
I am having a lot of ...
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Determining Object Visibility with Metrics
I am wondering if anyone has suggestions for metrics to use to quantify the edge strength and contrast of a target from its background in single channel images. I am trying to find the effectiveness ...
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UQI and VIF as image generation metrics
The aricle briefly describes various metrics for image generative models. It categorizes them into pixel-, feature-, task- and novelty-based metrics.
Following such categorization I understand that A ...
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Seeing perfectly camouflaged objects
Consider a perfectly camouflaged object which perfectly mimicks the texture of its surrounding. One can see the object and its shape only when it moves - otherwise it is completely invisible.
When ...
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Seeing edges where there are no edges
The human eye is able to detect a square inside the square in the following two images, even though there are no obvious edges and no obvious local changes in the density of dots.
GPT4o believes to ...
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How are values assigned to pixels in hyperspectral imaging for airborne cases?
From what I know, hyperspectral images can have up to hundreds of bands. During acquisition, each pixel seems to store only one value. Later, algorithms are used to calculate the missing values across ...
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How to do spectral averaging to get satisfactory results?
I’ve been trying to implement spectral averaging as an experiment to familiarize myself better with FFTs and their uses for the past couple of days.
Until I've hit a wall when I tried to replicate the ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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, ...
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"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 ...
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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 ...
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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 ...
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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):
...
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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 $$m_{pq}=\sum_{x,y}x^py^pI(x,y)$...
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Why do people use signs in columns/rows of several kernels reversed?
I have observed that different citations/codes use signs in different (reversed) columns/rows for many kernels. Here is an example for Prewitt (but same for Sobel, Scharr, etc); in some cases is ...
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Detect GUI Buttons in every application window with python
I want to detect every buttons in every application windows.
For example, in explorer window, I want to detect every Tags, folders, files and Buttons like "page back", "page forward&...
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Face Detection real-time with Local Binary Pattern
I'm writing for code to detect human face by Local Binary Pattern algorithm in webcam, but with my limited knowledge in optimization code, I having to struggle in detect in each frame , I want to say ...
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Local Binary Pattern rotation
How does LBP work? To learn that, I decided to calculate by hand for the matrix but the problem is about the rotation pixel over the image based on the radius and neighbor of LBP. I do it clockwise ...
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Using nearest neighbor in RANSAC
I found many resources online talking about nearest neighbor concept in RANSAC. For example, figure 2 of this paper, this article and this repo talk about nearest neighbor in the context of RANSAC. ...
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Calculation of disparity in parallel stereo cameras
I'm learning about stereo vision and the slides that my teacher provided aren't very clear on this point. He had a formula for disparity:
$$d = \begin{cases}
x_L ‒ x_R & \text{if } x_R \ge 0 \\...
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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 ...
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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 ...
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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 ...
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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
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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.
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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
...
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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 ...
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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. ...
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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 ...
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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 ...
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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 ...
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