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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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57 views

Thresholding for Movement Classification

I have an application which creates a Gaussian model of the background based on consecutive frame difference and auto-generates a threshold for separating no-changes to movements. The application ...
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1k views

Limitation of Wiener filter in image denoising

In image processing, up to which value of mean and variance can a Wiener filter be used to denoise the image? Wiener filtering can be used when variance of the noisy image is low, but I don't know ...
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199 views

Analysing 3D image FFT

I'm looking for a way to visually inspect the amplitude of frequency components in a 3D image that I have taken the fftn of in matlab. Does anyone have any idea how to go about this?
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83 views

Errata Corridge in Gabor Filter Documentation and Frequency Response

I have a really simple question regarding this tutorial I found on Gabor filters. Check the very beginning section, equations (1), (2), (3) and (4). Is there any chance that equation (4) is missing ...
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66 views

Geometric models to discard image features

I am working on the implementation of a location recognition pipeline as detailed in the section 5.4 of the paper Leveraging 3D City Models for Rotation Invariant Place-of-Interest Recognition: ...
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174 views

How to compute sinc period in frequency domain and width of pulse

I have an image convoluted by a rectangular PSF of a blur kernel. The fourier transform of the PSF has pattern of a sinc function: $\frac{\tau sin(\pi \tau f)}{\pi f}$. The image size is 256x256. ...
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1answer
1k views

Finding circle in binary image (R, not matlab)

How would I go about extracting the circular area of a binary image which looks like: The two rods emerging from the side of the circle are noise. I know of the hough transform in Matlab. However, I ...
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244 views

Evaluation of Keypoint Detector and Feature Descriptor Combos for Vehicle Detection

I am currently doing a research project into the effectiveness of different keypoint detector and feature descriptor combinations for the task of vehicle detection. At the moment I am using a SVM for ...
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309 views

Separating similiar object in an image

I have posted a question on Stackoverflow and was suggested to post here. Please refer this question for the images: Similar Question: I have used SURF Keypoints and a FLANN Based matcher and ...
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144 views

Local signal-to-noise ratio for an image

I want to do one of these common experiments to see the effect of increased noise on the performance of a feature detector. To do this add zero mean gaussian noise with fixed sigma to the image and ...
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6k views

Find branches in skeleton image using matlab

I have a skeleton image. I am able to detect branchpoints, endpoints and able to label image using BWMorph, BWLabel. Now I want to differntiate between skeleton center line and branches. In short I ...
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199 views

How to categorize the images based on Illumination / shadow?

Input: Cropped face or Non Cropped face images. Detailed explanation: My project is face authentication. I am using OpenCV face detector to crop face from images. I am using OpenCV implementation of ...
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524 views

Use fourier transform to calculate image pixelation coef in python

I want to calculate a coef of image pixelation to remove bad pictures from a bunch of files. Some pictures results from bad compression and we can see a lot of pixelation on them like img a here: ...
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1answer
280 views

ROC curve with classification problems

I am working with face anti-spoofing. For classification, the Euclidean distance measure is used. The test image vector is compared with all real image vectors , and the minimum distance is chosen (...
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1answer
22 views

KL (Karhunen-Loève) transform of images

I know how to implement the Karhunen-Loève (KLT) for one 2D image. Which we first find the covariance matrix of the image vectors of length N along the column and the row dimension and etc. When we ...
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12 views

Signal similarity analysis after cross correlation

I have a time series signal and using this as reference, from the main data set extracted possible matching sections using cross correlation technique.(xcorr matlab).Based on with the threshold xcorr ...
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1answer
29 views

Designing a 2d low pas filter in fourier domain for an image

Firstly this is not a homework question. I am working on a project and my professor gave me this task so I can also learn about filters and fourier domain. I have a picture that is 2800 x 4500 pixels....
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11 views

Power spectral density of surface roughness

I am currently working on understanding how visually and intuitively the power spectral density is the fourier transform of the autocorrelation of a signal. I was wondering if anyone had a good ...
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7 views

how to do OTSU thresholding?

i want to use OSTU method for my research purpose. I have already downloaded OTB but not able to put it in QGIS for Analysis. could please tell me how can i solve my problem?
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19 views

What does total variation norm mean in an image?

What is the notion of total variation and how is total variation norm calculated in an image? More exactly, I want to calculate and understand the meaning of $ \left \|X \right \|_{TV} $ if $X$ is an ...
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29 views

SIFT between 1 image and dataset (2 images)

I use SIFT, and I want to find the angle of inclination of an image compared to two reference images, in short: I have 3 images : Image x: input image Two images 1 and 2, reference images that are ...
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24 views

How to implement plateau limit histogram equalization algorithm

I'm trying to implement this paper using MATLAB: Power-log based plateau limit histogram equalization algorithm for infrared image enhancement My results are not bad. But when i created a matrice to ...
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20 views

Calculating a transform with a circle and lines

I am trying to determine the transformation (rotation + translation + scale) between two images in order to shift them. The images are taken with two different modalities that produce very different ...
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22 views

How to apply logarithm-power histogram modification?

I'm trying to implement logarithm-power histogram modification using this formula: and here is my try: ...
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10 views

Want to create a function that calculates the ISO and Shutter speed based on the brightness of previous image

I want to calculate the shutter speed and ISO of Picamera using the brightness information of the previous image I captured. I have already calculated the brightness of the previous image but I am ...
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17 views

MIMO FMCW radar - back-projection

any suggestion how to start implementing the back-projection algorithm in a FMCW MIMO radar? Currently I'm using 2D FFT to get radar image, I would try time-domain algorithms to improve the overall ...
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1answer
43 views

Zone Plate Reconstruction

I am trying to reconstruct the Zone Plate image and am struggling to remove the last remaining aliasing. ShaderToy: https://www.shadertoy.com/view/wdGGWK In the shader above you can see that I am ...
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10 views

Detect circle using Hough transform

I am new to image processing and try to learn how to detect circles using the hough transform in Matlab. I have a shortcode that seems to contain no errors but when I run it I get the image but with ...
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12 views

How to do colour map in MRI?

For this question, I assume if we do a colour map, it is based on the magnitude of the magnetic strength? After that how do we know where each coordinates belong to? Like for example at p= 0 degrees,...
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1answer
87 views

Detect valve position without colors

I can't find a solution for my problem and I need your help. I have to create an application to detect if a valve is open or close like this : https://www.youtube.com/watch?v=VY92fqmSdfA Some ...
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26 views

Determine Gaussian distribution parameters from the signal-to-noise ratio

Is there a straightforward formula for determining the mean and standard deviation of the gaussian distribution followed by noise applied on an image, knowing the signal-to-noise ratio between the ...
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1answer
25 views

Palmprint Identification - Why do we align the images before we use the Fourier Transform?

I have been reading the paper PALMPRINT IDENTIFICATION BY FOURIER TRANSFORM by WENXIN LI, DAVID ZHANG and ZHUOQUN XU about identifying persons based on an image of their palm, one version of the paper ...
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19 views

Matching Coordinates between two images

I am using images and corresponding lidar values for depth estimation CNN. I have RGB images. Corresponding to each RGB images, there is another image representing a subsets of pixels and distances to ...
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8 views

SSD object detection - Class score and bbox coordinates computing

How does SSD ( single shot multibox )object detection model computes the the confidence score and the bounding box coordinates, referring to SSD paper, it said that this process is done with the aid ...
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14 views

Face image quality assessment

I'm trying to filter out bad face images (with artifacts) generated by StyleGAN. Is there a good image quality measurement mechanism in python for doing this? I've tried using BRISQUE but it is not ...
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59 views

How to sharpen hair strands in an image?

I have an image like this: I am trying to build a semantic segmentation and matting model which currently gives an output like this: One can see that some regions between the hair strands are fuzzy....
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15 views

Different images between MATLAB and ImageMagick

I'm using ImageMagick 7.0.8-64 Q16 for Windows and MATLAB R2019. I'm doing the same operation (resizing with bicubic interpolation method) in both programs. ImageMagick code: ...
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14 views

Detecting enclosed regions in an image

I am having a difficult time searching for this, and I am not sure if it has a general solution, but I thought I would ask. Basically, I am looking to detect the inside of a bounded region, but ...
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19 views

Is it possible to read raw voltage values from an iphone CMOS sensor?

I am not an iOS developer, and I'm not sure this is the right place to ask this question, but I was curious whether using the developer sdk (or other means) it is possible to read voltage from the ...
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13 views

Efficient image matching technique for small match library set

Background A scene captured from video frames from an Android mobile device camera are to be analyzed in real-time. The scene will contain up to 12 distinct photos. The library images to be matched ...
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18 views

Image Processing Perspective Transform

This youtube video shows the current world record for smb1 speedrun, but it is recorded from a phone on a CRT TV. https://www.youtube.com/watch?v=IuVLtaB8uQk Is it possible through perspective ...
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19 views

Can “Frame Difference Method' be apllied for ”Motion Detection Based Anti-Theft Project"?

I am new with image processing. I will start to a project named "Motion Detection Based Anti-Theft Project" as i said. I have to use MATLAB and STM32F4 microcontroller in this project. I don't want to ...
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17 views

PSNR calculation with float arrays

The PSNR definition provided by wikipedia is often quoted in discussions regarding PSNR and other similarity metrics. Essentially the PSNR calculation has two components: the mean squared error and ...
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1answer
51 views

Finding Homography Matrix Using Lines

I have some Points and Lines from original image and the corresponding points and lines from top view image. -> I tried to find homography using points Used OpenCV function findHomography(...
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15 views

center of oblique viewed disk with known radius

I also posted this on the math stackExchange, but it also fits to this forum, so I hope it's fine to post it here as well. I'm working on an issue related to image processing that I simply cannot ...
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What is the different of Maximum Aposteriori Probability (MAP) method and image registration with reconstruction in multi image super resolution?

I am working on multi image super resolution (MISR) for thermal imaging. I have read several papers and slide about it but there are some confussions. First, I know that the basic of MISR is combining ...
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10 views

Measures of edge image continuity and connectivity

Suppose I have a scalar image $I:\mathbb{Z}_{1,m} \times \mathbb{Z}_{1,n}\rightarrow [0,1]\subset \mathbb{R}$, where $\mathbb{Z}_{1,m} = \{1,\ldots, m\}$. (For instance, computed as the (scaled) ...
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25 views

Deriving transformation from input and output images

I will preface this by saying that my undergrad signal processing course is very far back... Context: I am comparing images of global illumination (GI) passes. I want to be able to change the ...
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48 views

Implementing rotation in frequency domain and map it back to spatial domain

Please consider the following small example: ...
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10 views

What are the Red-Black Wavelets transformation for color (RGB) images?

I am looking for Red-Black Wavelet transform implementation on internet but I am unable to find it. Or How wavelets can be used for Images. Please help if you know how wavelets can be used for images.