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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periodic noise detection in image's frequency domain

Since I'm learning frequency domain and I'm really curios about this topic, I'm trying to solve a problem (that I have already solved it using morphology [detecting lines by their thickness]) in ...
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Is there a good metric to compare character images by similarity?

Good evening, I'm thinking about a good way to compare images of characters with a metric. Infos: Image colors - black/white; one may think of it as a matrix with a value from 0 to 255 for each pixel ...
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Blocking out Periodic Background Motion for Background Subtraction

I have a motion detection project that relies on background subtraction. I have noticed some frequent movements on a specific point which been found as an air conditioner blades. Away from manual ...
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What are the kernels that are used in the Smooted Psuedo Wigner-Ville distribution?

Defined in Matlab's docs for WVD, SPWVD is given by: $\int_{-\infty}^\infty g(t) * H(f) x(t + \frac{\tau}{2}) x^*(t - \frac{\tau}{2}) e^{-j2\pi\tau\,f} \, d\tau$ H(f) and g(t) are the smoothing ...
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Which Image pre-processing method is the best for Histopathology images? (H and E stained image)

I am working on classification of breast cancer histology images (Dataset:ICIAR BACH challenge 2018). But I don't really know which method is the best way to enhance the features of H&E stained ...
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Replicate MATLAB's `conv2()` in Frequency Domain

When conv2d is on valid mode, the image needs no padding, because the result is the same size as the image. When conv2d is on ...
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Removing feature matched outliers within same image using RANSAC

I'm a student working on a copy move forgery detection algorithm. I have a forged image. By far I have, Found keypoints and descriptors from the image Matched the descriptors using 3 Nearest ...
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How can i center the optical mark image?

I want to recognize optical mark using image processing algorithms. There is a wide variety of optical paper and i want to recognize all off them. For example; If i create a template I can superimpose ...
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Simple Image Edge Preserving Filter

I am after a simple, yet effective, Image Edge Preserving Filter. I need something which is faster than the Bilateral Filter with similar quality (The Guided Filter isn't good enough). Are there such ...
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how to analyze thousands of histograms?

I have about four thousand histograms from a tumor image dataset. I have no idea how to proceed after this. what should I do with the histograms to be able to glean information? should I, perhaps, ...
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How to Calculate Local Spatial Variance of an Image?

For those who work often on image processing, I'm facing an algorithm of Non-Uniformity Correction (NUC) that requires the calculation of a parameter called "Local Spatial Variance". I can't ...
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Illumination Normalization Paper: Help understand equation

I hope this is the right place to post this question. Im reading a paper titled "Illumination Normalization Based on Weber’s Law With Application to Face Recognition" Im only interested in ...
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How can internal energy be calculated in the active contour model when the spline/contour is Piecewise linear?

I have been trying to understand the active contour model and I have started writing a Python script to implement the model myself. Based on the following slide from these lecture notes I found that ...
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Image downscaling methods

I am researching downscaling methods for image downscaling. I've both read and found area-averaging to work well in Python using CV2, but the settings in MATLAB allow for it's bicubic interpolation ...
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How to detect rectangular images inserted into another image?

It's just for a simple binary classification, so it's not needed to find the location of the inserted image or the content. I'm only interested in checking whether something like that is present or ...
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Using Scipy.correlate2d output matrix to determine best image match

I'm struggling to wrap my head around how I can use the output of a correlation matrix to determine if my image is present. If I am trying to match characters, how can I compare the outputs of these ...
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Spatial domain vs. Frequency domain filtering of an image. Which one is better?

The question might seem naive but I'm new to this and a little confused. So, I recently came to know that gaussian smoothing can be applied to an image both in spatial domain and in frequency domain. ...
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Adaptive removal of structured noise

I am trying to use a scanner with vertical banding. The scan head's black and white point calibration numbers have a modulation pattern on top of them. I am not sure if the calibration's banding is ...
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Generating new 2D data using power spectrum density function from spatial frequency domain via ifft?

This is my first post so apologies for any formatting related issues. I also tried posting in stackoverflow but I'm more optimistic that I might get a response here. So I have a dataset which was ...
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1answer
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Image Processing : How can I remove double lines detected along the edges?

I'm trying to take real time input for hand gestures with web cam, then processing the images to feed them to a neural network. I wrote this processing function to make the hand features look ...
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What exactly is a connected componnent in an image?

The following is a paragraph from "Digital image processing, 4th edition, Gonzalez and Woods". Let S represent a subset of pixels in an image. Two pixels p and q are said to be connected in ...
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Erode image until all objects are a single pixel?

Suppose I would like something more dramatic than skeleton, and would like to erode everything connected to a single point -- but stop there. As in, I want to keep the single point. Is this possible ...
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T1 Mapping in Python?

I'm trying to write a simple program to perform T1 mapping of a few MRI Images. My understanding is that all I need is to plot the pixel intensity values by inversion time then fit a curve. The output ...
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Complex Distance Transform containing distance and angle info?

Is it possible to obtain a distance transform with the distance (float) and angle (in radians) from the nearest pixel? I would be using python and the library I am ...
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1answer
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image processing find liquid level (only with images processing, no AI)

I want some ideas to get the level of a water/liquor in a cup. i tried many ideas (contours, edges,...) but nothings is working. So any ideas that i can explore.
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Does this Lucas-Kanade registration MATLAB script appear to be correct?

I'm currently writing a MATLAB script to replicate the Lucas-Kanade registration algorithm discussed here: https://cecas.clemson.edu/~stb/klt/lucas_bruce_d_1981_1.pdf Specifically, I'm attempting to ...
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How up sampling of a signal is done in real world?

I know that up sampling by L means padding L-1 zeros between each samples. My question is how it is done practically? Do we use MATLAB or any other software, or there are hardware circuits to do so.
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1st and 2nd Gaussian derivatives for edge detection

I have a project about edge detection, I made research on internet about filters and read many articles but there is an article talked about using Sobel and Gaussian derivatives then it mentioned &...
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How to calculate the magnitude while calculating Blur in an image using using OpenCv based on Fast Fourier Transformation

I am working on image blur detection and found 3 methods for it. One is Laplacian Method but it works good with Gaussian, average, median and other distribution ...
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How to add a fake thermal effect to images

I am working on a project to convert a normal RGB image to thermal images. I applied color maps using Matplotlib library and got an array which then I converted back to the RGBA image using Image....
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How to convert CIE xy value to gray scale value

Is there a way CIE chromaticity coordinates to gray scale value (0 to 255)? Any existing implementation in ImageJ, R or Python? Or formula? Here is the table taken from here. Purpose Description To ...
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1answer
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Align low-res images of a moving feet

I have a pressure platform that provides 64x128 pixel grayscale images (1px aprox 5mm) of a subject walking on top of it. If I capture the whole step, I can obtain the average distribution of pressure ...
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What is the function of init in Active Contour Model

In practice of image processing using scikit-image, I didn't understand the role of constructing init numpy array in Active Contour Model example. Is it the red section drawn in the example astronaut ...
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How is non-integer upres downres (1080p game on a 1440p screen etc) calculated

Please redirect me if this is not the right place to ask. I was unable to find a straightforward answer to this question. What I am wondering is, if I am playing a 1080p game on a 1440p display, what ...
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Analysis Received Signal at receiver side

I'm trying to understand something which is really confusing me and I made my best to understand it but still confused. If I have transmitted and receiver. Assume I want to transmit S(t) data and ...
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1answer
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Square Block Detection

I possess a binary sparse symmetric matrix with square blocks centered on its main diagonal (white=0, black=1). These can be of any size and can overlap. I aim to detect centers of these squares using ...
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Bilinear Interpolation Algorithm for up-sampling 2D images

In keras it is possible to use UpSampling2D layer to up-sample an image. You can use Bilinear Interpolation. Given an image ${h\times w}$ it is possible to increase its size in ${h*k\times w*l}$, ...
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Correlated signal components from uncorrelated and incoherent source after reflection

To this point, it has been assumed that the point sources composing the source are uncorrelated, generating fully incoherent signals. Thus, capturing the reflected signals and after sufficient time ...
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Filter for DC component in FFT2 of image

I am trying to get the main frequency of the Fourier Transform of the image below, which is the intereference pattern detected by a CMOS sensor. When I apply fft2, I got the DC peak at 0 frequency, ...
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Python how to detect white image [closed]

I am searching for python code or library to detect blank/white images like [png ,jpg ,bmp].
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good open source api to register hand writing (with math-formulas)

I'm just wondering what the current state of open-source APIs is for handwriting recognition. Especially in converting math-formulas to LaTex code. I've heard of 'myScript' but they are not open-...
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Several Questions Regarding Color Space Representation

As part of my seminar, I have to make a full representation on the many color spaces. I took a deep dive in the internet and on YouTube and managed to gather a lot of information. BUT I have a few ...
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Homography valid for patch within the image but not the entire image?

The homography I have is non-degenerate (det!=0), and generated from a valid planar pose. When I use it to warp the four corners of image, it returns something like the following: ...
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Calculate surface of objects (rocks) in an image with lots of noise

Is there a way to caculate the size/surface of every individual rock visible in this image? I have tried: Contours - this doesnt seem to work the contours touch, gets real messy. Watershed algorithm -...
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How to obtain height above ground, angle the pixel’s local surface normal makes with the inferred gravity direction from depth map of image?

For extraction of the HHA features from the image depth map we need to calculate the height above ground, angle the pixel’s local surface normal makes with the inferred gravity direction. How to ...
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What is the name of the filter or technique to reduce depth aliasing around object edges when working with camera depth?

I'm working with a point cloud, created by sampling a 2D camera texture and a depth map. The color is combined with the depth and is projected onto a 3D scene to create a "point cloud". The ...
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Laplacian filter in matlab

I want to compute the output image by first dividing the image into 8*8 blocks and applying laplace filter separately and combine them but I am not getting the correct output Here is the code: ...
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Active vs. Attentive vs. Machine Vision

I would like to know a short definition of the three fields Active Vision Attentive Vision Machine Vision For me it is quite hard to find a specific definition in literature. Sometimes authors group ...
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Why Does the Median Filter Minimize the Absolute Value Error $L_1$ Cost Function?

I can easily prove that the mean filter minimizes the square error $L_2$ cost function using simple calculus. However, how do you prove that the median filter is optimal with respect the absolute ...
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Removing halo effect in image composition: Google Meet's solution

Wanted to understand how google meet is removing halo effect when composing their image. They describe their method briefly in their blog as: "The blur shader simulates a bokeh effect by ...

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