Questions tagged [image-processing]

In general, image processing is any form of signal processing for which the input is an image, such as a photograph or video frame.

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How to convert bytes to video using python? [closed]

I made a python program that basically sends a tcp signal to a gateway from the drone and receives another signal, but that signal comes in bytes and I don't know how to convert it into an array or ...
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Zero Padding in image reconstruction

I need to zero-pad the image for a better reconstruction but according to my project details, I will be given a Fourier-transformed image so can someone tell me how to pad the image in such a ...
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Recover Frame Compression Lossiness from Many Similar Frames

With many very similar frames of video that have been compressed with an unavoidably lossy encoding and available now as jpeg stills, are there available good mathematical techniques for recovering ...
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Questions on the Generalized Tikhonov Regularization

My first question is about the quadratic functional that is used in generalized Tikhonov regularization: $$\Psi(f)=\frac{1}{2}\|f\|^2_\Gamma=f^T\Gamma f.$$ In the above equation what does $\Gamma$ ...
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Image Matrix Vector Representation for the Degradation Model

I am trying to understand the the degradation model equation but I have doubt that how come y^t.x.h will be equal to x^t.h^t.y . Aren't they transpose of each other.
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Applying which kernel or technique contours are detected in image? [closed]

How contours are calculated from image ?? How calculating contours is different from calculating the edge detection ??
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What does the visual representation of matched filtering of images look like?

So I am using the Source Extractor to find point sources in my images and it offers the possibility to use matched filtering to enhance the detection results. In the documentation they also claim that ...
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1answer
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Apply the Discrete Fourier Transform as a Matrix Multiplication in MATLAB

0 I have a vector x of length N x 1, I need to perform the iDCT operation for it using MATALB. I performed that using the below method: ...
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1answer
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Variational Regularization Method in Image Processing

I would like to understand better variational regularisation methods in image processing. In particular, the formulas in this image: Why formula (3.13)? In the notes that I read I cannot find ...
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Making a 3D point cloud from multiple RGB-D images

I have multiple (4 kinect) cameras that give RGB-D (color and depth) information of the same scene from different points of view. I want to make a 3D point cloud out of these depth maps. I can get a ...
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The Concepts Behind SVD Based Image Processing

I am interested in information about the output of SVD of the matrix. Mathematical part of SVD process is clear to me but I don't understand how to read figures with graphs of SVD of a matrix. As I ...
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Regularization for Inverse Problems using the Singular Value Decomposition (SVD)

I am reading these lecture notes on Optimisation and Inverse Problems in Imaging, and I have difficulties understanding how figures on page 20 (Figure 3.2) or page 21 (Figure 3.3). Precisely, I don't ...
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How does image rotation affect the intrinsic camera parameters?

I am considering the problem of how to (manually) change camera model parameter to make it "valid" on a rotated image. This question tackles resizing, but does not consider lens distortion. ...
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Mathematics behind the creation of 3d face mask at runtime

I'm new in Image processing and Machine learning area. I want to create 3d mask of face at runtime. ...
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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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Perform 2D convolution on a 2D unit step function

I am stuck with the following 2D convolution: Consider the sequence $f$ defined by the following: $f[m,n] = \begin{cases} 1 & \text{0≤ m ≤ n} \\\ 0 & \text{otherwise}\\ \end{...
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Convolution and Cross Correlation Blackbox

Suppose I was handed a blackbox that I know is either a Convolution filter or Cross-Correlation filter, and my job is to find out which it is. My idea is to pretend that it's Cross-Correlation and ...
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Correlation in Image Processing vs Correlation of statistics

I am new to image processing. Please forgive me if you find this question naive or meaningless. I was studying about correlation filtering in images to smoothen the image. I want to know if ...
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How Come the Low Pass Filter in Sobel Operator Isn't Normalized?

I am relatively new to the field of computer vision and I have just learnt about the sobel operator. The sobel operator in the x direction is a convolution of the finite difference kernel $[1,0,-1]$ ...
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What is the purpose of the filtering the image data in the PNG file format

I am reading the W3C description of the PNG file format, in particular section $9$ on filtering. The filter functions: None(x) : the identity filter Sub(x) : subtract the pixel value of $x$ by the ...
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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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Processing and combining binary masks of multiple sources for the same image to use in machine learning

(I'm not entirely sure this is the right site to ask this question on. If not please point me to the right one.) Context I'm working on a convolutional neural network (CNN; called Mask RCNN) that I ...
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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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Having trouble calculating the correct Gaussian Kernel values from the Gaussian function formula

I'm having trouble calculating the same values for a Gaussian filter kernel as those derived in the Canny edge detector Wikipedia page It states: The equation for a Gaussian filter kernel of size (2k+...
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Fourier coefficients of images?

For a continuous function $f$, it is well-known that the decay of $f$'s Fourier coefficients $\hat f_n$ is related to the differentiability of $f$. Some examples: for a smooth periodic function $f$, ...
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Python, Is there a way to find the properties of a subregion within a larger image region?

The goal: I have images with particles that I need to find the area of. Each particle also has four to five sub-regions that I need to know the area of. Think of a bunch of stripped shirts in a ...
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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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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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Object identification based on both shape and intensity — i.e., identify the stars and their diffraction spikes at the pixel level

Here's an example image to make the problem very clear: I've used OpenCV's blob_log() as well as the rank.otsu threshold approaches. The problem with the blob detection is that the blob radii are ...
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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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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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Isolating text on a photograph

I hope this is the right place to ask. In the movies, it is always possible to extract text from an image no matter how faint or blurred! As a layperson I don't know to what extent this is possible. ...
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Discrete Fourier Transform on images using OpenCV

I applied DFT on an edge image (attached both). I expected the output image to not have very low frequencies (~0).[Refer this link for more info] But the output I got consisted of low and high ...
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Denoising 3D matrix

Are there any standard techniques I can use to denoise a 3D matrix? I hope to apply something like simple SVD denoising methods (e.g., reconstructed the images with salient singular values) to a 3D ...
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MATLAB: Prepare an RGB image for digit and letter recognition

I need a Matlab function that prepares an image for digit and letter recognition. What I need now is to convert the original RGB image to a binary image that every pixel in it is white except the ...
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How to calculate fisheye distortion error

OpenCV offers a fisheye library for calibrating wide-angle lenses. I have implemented the calibration and want to verify the reprojection error by using a new set of images. So is there a function to ...
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2D Fourier Transform [closed]

Is it possible to get a 2D Fourier Transform by first taking 1D Fourier transform in first dimension and then performing another 1D Fourier Transform in the other dimension? If yes, can you explain
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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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How to Make a Gaussian Filter?

The 2D Gaussian function is defined as: $$G(x,y) = \frac{1}{2\pi \alpha}e^{-\frac{x^{2}+y^{2}}{2\alpha}}$$ And this is a Gaussian kernel: If I take the top left corner as the origin and set $\alpha=1$...
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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
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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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Side lobe reduction [closed]

How can side-lobes be reduced in an Level-1 SAR image in Spatial Domain?The input here in this problem is an complex SAR image?which parameters(like amplitude) of SAR image should be considered mainly ...
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brightest amplitude of an image pixel

How can amplitude of an image pixel be calculated?Do we need to perform any FFT on the image? and how to find the brightest value among the amplitudes in python or matlab?
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How to use Joint Probabilistic Data Association Filter (JPDAF) for varying number of targets?

I have been working on JPDAF for two days, and I have to implement it using varying number of targets. As far as I studied, it is mainly used for fixed number of targets. I have studied different ...
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FFT of shifted image in Numpy

I want to prove using numpy the theory of Fourier transforms in which translation in space corresponds to a shift in the phase domain (frequency domain remains constant). I have generated these three ...
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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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How do you perform range compression of SAR data on a 2D matrix?

I am building a Matlab program to process RADARSAT-1 data that came with this book. The book describes the steps to creating SAR image as follows I am currently implement the range compression step. ...
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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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How to calculate variance of noise on a noisy image (Noise+Signal)

I have a long exposure image captured at 70ms. (I1) (As attached) I also have another image captured at 0.7ms with Gain24. (I2) (As attached) This image has both noise and signal together. I would ...
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Eroding noisy borders of polygons in an image

I am new to image processing, and this is the task at hand. I have a mask image of shape 500x500x1 that contains polygons. These polygons (=vector data: common term in remote sensing and GIS) are ...

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