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# 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 improve quality of the recovered image in compressed sensing technology?

I was trying to use compressed sensing technology in image processing. Basically, I did a code in Python(Spyder IDE) which takes an image, compresses the image and reconstructs it. I tried with the ...
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41 views

### How my digital camera creates itself this picture?

here is a picture produced by my digital camera My camera is an (quite old) Panasonic DMC-FZ200. My question is : what happened, and at which stage of the process the bug was? Months ago, while ...
16 views

### blind deconvolution of astronomy images

Hubble's angular resolution is 0.04 arc seconds. https://en.wikipedia.org/wiki/Angular_resolution The closest star has an angular diameter of 1.02 milliarc seconds. https://space.fandom.com/wiki/...
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1 vote
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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 ...
20 views

### Why Ando operator is worse than Sobel operator when computing gradients in my case?

I am testing different gradient operators for 2D images. I have some differentiable function (let it be $f(x,y) = \sin(2x) + \cos(3y)$). I discretize this function (i.e make a 2D image of it) and then ...
190 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 ...
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28 views

### LED image phase projection

Say you have a goal image G with a phase called phase G. Can you physically construct and project phase G, or is phase not something physical? Like, can you set up an array of LEDs to project the ...
10 views

### Contrast enhancing very faint extended blobs in an image

I have a series of images of the night sky and I'm looking for methods to enhance very faint structures that are barely visible. The movement of those structures is visible when you click through ...
14 views

### How to get surface topology from fringe pattern

I'm trying to recover the surface shape of a body from fringe pattern. There's a interferometer projecting circular fringes on the body. A camera takes a picture of the reflection of these fringes. I ...
27 views

### Derive the filter mask that corresponds to the double filtering process

There are two mask filters, ...
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1 vote
22 views

### Border effects / artifacts for spectral filtering of images

I am working on a spectral filtering problem as follows: I'm given an image with a periodic distortion pattern (see below), and I want to remove the distortion pattern while preserving the main ...
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1 vote
62 views

### What is the type of blurring in such an image?

I can't figure out what type of blur such an image has and how I would be able to generate it in python. I would be grateful for any help. I tried Gaussian blur, bokeh blur, Wolf and Born out of focus ...
40 views

### Pixel Shift when using Fourier Downsampling

I am working on a Super-Resolution network, and want to try to use Fourier downsampling, different from the normally used bicubic downsampling as it relates to MRI imaging. I have tried using this ...
13 views

### What is Roboflow doing for its "exposure augmentation"?

I was able to find a small blurb here that describes what Roboflows exposure augmentation does. I'll reproduce the text here for convenience: Adjust the gamma exposure of an image to be brighter or ...
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1 vote
63 views

### FFT2 to RFFT2 Fourier plane and similarities

I'm trying to understand how Python's fft2 is different from irfft2. Basically, I have some continuous Fourier 2D samples that I need to put in a (n,n) grid (this can be done by a simply count-in-cell ...
1 vote
14 views

### Suggestions for image region separation

I have some SEM images that I need to process,all those images have extra information in the bottom of the images as can be seen in the red bounding box. I need to remove those portion before doing ...
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19 views

### Detecting a large horizontal band in the center of an image

I have a small (228x228) grayscale image that I have created by segmenting the original image and converting it to grayscale after applying colors to the segment. I want to know possible approaches I ...
13 views

### Derive white balance matrix operator in YUV space

Assume that the white balance matrix operator in RGB space is $$W=\begin{bmatrix} \alpha &0 &0 \\ 0 & \beta & 0 \\ 0&0&\gamma \end{bmatrix}$$ where the constants ...
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1 vote
98 views

### Why in 2D Fourier Transform phase seems to be more "useful" than magnitude?

In 1D signals f(t) (e.g. a sound signal - independent variable t-->time) when we want to use informations from the Fourier transform F(ω) in order to reconstruct the signal, using the magnitude |F(...
1 vote
53 views

### How am I supposed to acquire/measure vertical and horizontal effective resolution from my images?

I apologize first for some questions that might be dumb. Unfortunately, I am only a bachelor student (writing my bachelor thesis in physics) and have almost zero image processing experience. And I ...
1 vote
46 views

### Combining Two Grayscale Images Without Overlapping Using OpenCV and Matplotlib in Python

I am working on a project where I have two grayscale images of different sizes, named part1 and part2. Each image has some ...
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1 vote
45 views

### Generating new random phases for DFT of 2d uniform distributed noise image changes image distribution

My goal is to produce a new random noise image from two already existing noise images. For that I take the absolute values of one image and the angles (phases) from another image in Fourier Space and ...
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48 views

### Combining Three Images into One Output Image Python

I have to combine three images that are inside one single image into one output image in Python. This has to be done using Gamma corrections, Histogram equalization, filters convolutions (gradient, ...
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113 views

### Removing dense grid lines & convert into clear image - opencv - python

I want to extract the text from this image. I'm a newbie in opencv. I've tried various opencv codes across various questions, but none is working for me. How can I extract text from this? Or maybe ...
28 views

### Distance Transform & Chamfer Matching -- find actual edges

I have had good success using the Distance Transform and Chamfer Matching to locate a template in an edge image. Is there a recommended technique to then find the actual edges that match the template? ...
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48 views

### Decoding images from sounds in Voyager golden records

I'm interested in a side learning project in decoding the images recorded as sounds in Voyager's golden discs (https://voyager.jpl.nasa.gov/golden-record/). The instructions to be able to decode these ...
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20 views

### real time streaming image encoding options

I'm interested in streaming video real time. There is an issue of deciding how to properly encoder the images and the format they should be. Since the data will be streamed over UDP, it needs to be ...
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### I need help finding the PSF and characterizations of the following

My professor explained this to me in a super convoluted way, so hopefully someone can explain this to me better. I'm trying to find the PSF of the following signals. I also need to check if it's FIR ...
• 149
59 views

### How did law enforcement recover fingerprints from the "blue cheese encrochat picture"

I hope that my question suits well within the topics discussed in this SE website. It was reported some time ago how a man was identified after he shared the photo on the encrypted messaging service ...
26 views

### Issue with cudafft library and fftshift on odd image dimensions

I'm facing with a code I'm implementing for an exam using the GPU. Specifically, the code I'm writing is in C++, and I'm using the CUFFT library to perform the Fast Fourier Transform (FFT). The ...
119 views

### How to find PSNR from two images with different size in python

I have 2 images, one original and other is reconstructed from the original via some processing. I want to find the PSNR for the reconstructed image The original has a size of ...
1 vote
46 views

### Trying to understand significant loss caused by OpenCV's inverse DFT

I'm quite a novice on computing Discrete Fourier Transforms with OpenCV, and I've been attempting to compute the DFT, and computing the inverse of the DFT using the latter as the input. Judging from ...
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135 views

### What is the event that repeats itself in sinusoidal signals

I am studying medical imaging and it has been stated that it is sufficient for Nyquist Theorem to hold for the signal to be Bandlimited. I am trying to understand what is the wave in a signal. What is ...
176 views

### Assumptions of Nyquist sampling theorem [closed]

Hoping I can save the question and it doesn't get migrated to philosophy stackexchange as Hilmar said in any case I don't think it is a different question the question was always meant to be ...
1 vote
41 views

### 2D Fourier downsampling to even number of points gives incorrect modes in the last column

I would like to downsample an image in the frequency domain to an even shape, similar to what is described in this post. I have been able to do this successfully with a 1D signal to both an odd and ...
1 vote
14 views

### Aligning Ir images and RGB images

I was wondering if given a picture from a Raspberry Pi NoIr camera and a Raspberry Pi RGB camera, how can the two images be aligned. From what I understand the NoIR camera when used with the blue ...
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1 vote
51 views

### Statistical technique for distinguishing between artefacts and no artefacts [closed]

I would like to know how to create an algorithm from the table below in order to distinguish between data that has artefacts and data that does not. I'm trying to leverage video attributes like ...
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47 views

### Correct low pass filter after applying discrete cosine transform

I am working on the compression of a bmp image using discrete cosine transform. First, I split the image into 4x4 blocks and then apply a DCT to each block. I know that low frequency coefficents (the ...
1 vote
110 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): ...
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1 vote
37 views

### How can I estimate the number of rows and columns in a chess pattern?

I am working on some code for estimating the position and orientation of a camera. From an image taken by the camera I require that the user select lower left interior corner: green, the lower right ...
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### How to avoid the edge effects that may occur when applying the Hilbert transform (by mirroring)?

How to avoid the edge effects that may occur when applying the Hilbert transform (by mirroring) for image or image series signal? Code is appreciated (in python) please.
1 vote
99 views

### Related to Additive white Gaussian noise (AWGN)

In my research work regarding wireless communication, I came across many research papers wherein AWGN is assumed to be modelled as "complex Gaussian with zero mean and unit variance". I ...
21 views

### HSI formula inconsistency in Gonzalez & Woods

I'm confused about how the book Digital Image Processing by Gonzalez & Woods explains HSI model. It includes a double cone-shaped space for the model (like the figure below) and says every color ...
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183 views

### Discrete Fourier Transform of the Gaussian

Cross-posted from here I encountered the following question in a Digital Image Processing examination: Find the 2D DFT of $\frac{1}{2 \pi \sigma^2} e^{-\frac{(x - x_0)^2 + (y - y_0)^2}{2 \sigma^2}}$ ...
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116 views

### Use DFT (fft()) to Replicate 2D Convolution (conv())

In MATLAB, I tried to convert the fft2-based multiplication using conv2. ...
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### problem with GSAFT (backprojection) algorithm for nearfield millimeter-wave image reconstruction on my simple planar array

I have a planar array containing 16 transmitters and 88 receivers located on the same plane with dimension 30cm-by-30cm. I have an object of size 6cm-by-6cm. Object and antenna array plane are in ...
23 views

### How to know which type of sensing matrix would do the job?

Compressed sensing refers to the recovery of a high-dimensional but sparse vector $x\in\mathbb{R}^n$ from its linear measurement $y = Ax+\eta$, where $A\in\mathbb{R}^{m\times n}$ $(m<<n)$ is a ...
26 views

### Python - CV, contour and measurements

I have small problem with cv in Python and rhombus. I can read frame from the camera and create contours... ...
17 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 ...
1 vote
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 ...
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