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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Red Color selection in Python and Skimage

I'm trying to load an image from the disk and then to extract just the red channel of it and display it in grayscale with grey colormap but I don't know what I'm doing wrong.. The image should be ...
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Logarithmic vs Nth root transformation of Image

This is an image for the explanation of Logarithmic Transformation of an Image. I want to ask considering a input pixel value rk, Value of nth root of rk should be greater than corresponding value of ...
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Mean shift algorithm formula

I am watching a lecture on mean shift clustering. In the video, the mean shift vector is first defined and then it's relation to the gradient of a kernel density estimate is shown. The mean shift ...
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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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Spatial frequency and video frequency of an image

in my lecture notes about image sensors (CCD, precisely) I have read the following statement: The transfer function $F(\omega)$ of the image sensor is related to its spatial resolution function $F(\...
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Dataset suggestion: video dataset with accurate depth and pose info

Please suggest some datasets (can be synthetic, like rendered in blender or so) which have video frames (30fps preferred) with accurate ground truth depth maps and pose (rotation and translation for ...
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Where to place origin when warping an image using 3D rotation and translation?

Suppose, I've two images taken by a camera at two different locations. The two locations are related by a Rotation and Translation. So, points $X1$ in first frame will be at $M \cdot X1$ where $$ M = \...
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What is Maximally Stable Extremal Regions (MSER)?

In the paper , MSER is being defined. Please help me understand what is MSER and how to implement it. The paper says, The regions are defined solely by an extremal property of the intensity ...
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140 views

Is rotation of a Fourier transform the same thing as Fourier transform of a rotation?

I'm working on an image processing problem and wondering if DFT(rotation(image)) == rotation(DFT(image)) (1). My final goal is to apply rotations in the Fourier domain then do an inverse Fourier ...
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What is the best technique for underwater imaging?

I am currently researching what the best method to take underwater images/video is. The papers I have read go into several different methods: Lidar, Synthetic Aperture Sonar (SAS), optical camera plus ...
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Image Restoration and Standard Forms of Second Order Cone Programming (SOCP)

I'm studying the application of SOCP methods in Image restoration And I want to understand the difference between the two formulas of SOCP and how they are related. Standard form (1) : min $f^{t}x $ ...
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Is it useful to apply edge detection filter as a preprocessing step before applying CNN?

Background: my future boss would like me to apply a number of low level filters to industrial images before applying machine learning methods on them. From my knowledge this doesn't make any sense as ...
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42 views

How to prepare different input size in CNN

I'm doing a research about personality identification based on their signature using CNN method, however the learning feature for the personality traits have a different input size. I understand that ...
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Detecting Intersections

As a part of a math essay, I am writing a program that detects intersections of a line that is drawn with a shape that is inputted. For example, in the shape below, The polygon is the input image of ...
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1answer
38 views

linear-expansion filter for image (2D array)

I am working in python analyzing 2D arrays and I am looking for a filter or some other routine that would provide a linear expansion of an region boundaries in a 2D array with binary regions (i.e. a ...
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29 views

Finding defects in wall paint (finding difference in textures)

I have been experimenting with computer vision techniques to find defects in paintings, more specifically defective brush strokes. I have tried a handful of techniques such as different filters, One ...
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video resources for learning image processing?(for EE background)

Please kindly recommend some youtube links for learning image processing. I have EE background and i want to study/learn image processing in this way Also i have confusion that Computer science ...
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How to create different Time frequency images from a data

I'm new to Python. I have a time series in a CSV file that has about 5000 rows and 3 columns. I have split the data into training and testing in ratio 70:30 respectively. However, I have a problem ...
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95 views

Licence plate enhancement

Is it possible to enhance the image below and make it more readable? I have tried apply binarization but there is some kind of shadow. So I have tried to convert image to gray scale and then ...
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How to find location of minimum dimension of contour using opencv?

suppose this is our input image and now we have to detect the point of minimum dimension, which I show as the red dot in an output image
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I can't implement plateau limit histogram equalization algorithm using MATLAB

i tried to implement this research paper using MATLAB. Unfortunately, my result is not same with the original result. Here is my try step by step: ...
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61 views

Randomly Generate Synthetic Noise in an Image Text Document

I'm working on denoising dirty image document. I want to create a dataset wherein synthetic noise will be added to simulate real-world, messy artifacts. Simulated dirt may include coffee stains, faded ...
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22 views

Looking for a way to fill holes in objects, and break bridges between them

I am trying to extract building footprints from satellite images. Using a series of morphological operations i.e erosion and opening by reconstruction, I'm able to obtain the footprints, albeit with a ...
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34 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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51 views

My X ray images have black background, which turn gray after low-pass filter. How to recover blackness?

I am applying a low-pass filter to X ray images, which changes the pixel distribution such that the background goes from black to gray. In the attached figure, this amounts to the mode increasing from ...
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22 views

Local noise intensity in an image

Noise can be assessed in uniform regions of an image, by subtracting a lowpass-filtered version of it. Then from the histogram of intensities, a global measure can be obtained (such as the average ...
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Is it necessary to have a reference plane when doing structured-light scanning for depth calculation?

I'd like to create a point cloud of an object using the structured-light approach with either fringe-projection or dot markers but the object I plan on "scanning" won't be in front of a flat ...
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1answer
44 views

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

I was 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. The first step in their ...
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What algorithm generates these “bucket coloring” artifacts?

Context: This is picture (taken with a smartphone*) of a copy of school test. The original answers were in black pencil and the professor made check marks in red. However, the parts of the answer ...
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142 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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215 views

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

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

Fast and Slow motion video detection using Optical Flow

I'm trying to calculate a "video motion" value in a given video sequence, meaning how fast or slow motion the video is. For instance, if a video is about a car racing, the value is high. Whereas if ...
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28 views

Removing striped noise from an image

I was just wondering if anyone could explain to me the approach one would take to removing striped noise from the fourier domain of an image. I was reading an article about MRI image from 1 just ...
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Size filtering on binary images

I have noisy images from which I extract the contours using OpencCV's findCountours, which performs binarization internally. This results in innumerable small ...
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51 views

Robust custom watermark algorithms?

I'm doing research on image and audio watermarking, and so far I've read some literature in order to get basic introduction and good initial understanding of this topic. Right now I'm reading book "...
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51 views

Recreating an image from random samples?

Assume that I have samples from an image, but the samples aren't on a grid, but instead there are multiple lowres versions of the original where the sampling locations are slightly jittered, so the ...
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41 views

How to create 3D signed distance function?

I am trying to segment a 3D shape using levelset. I want to track shape movement in consecutive frames. Now I want to create a signed distance function matrix for ...
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59 views

Implementing Edge Preserving Diffusion (Anisotropic Diffusion)

I am trying to implement edge preserving diffusion. Recall the general diffusion equation to be: $$\DeclareMathOperator{\Div}{div}\delta_t u = \Div(g \nabla u)$$ Where $g$ is the speed of the ...
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How to harvest the highest amount of information from an image?

I wrote a script that detects objects, crops the part of the image where an object is located and tries to increase the quality of cropped image. The object detection runs tensorflow. To increase ...
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39 views

Concept of scales in Gabor filter

I've been reading about Gabor filters, and there is a concept of scale. While I understand that Gabor features help in analyzing both the frequency and orientations of an image, what is the idea of ...
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Understanding performance of Lucas Kanade Iterative Image Registration Technique

I am reading the paper: Lucas, B. D., & Kanade, T. (1981). An iterative image registration technique with an application to stereo vision. I am having some trouble understanding section 4.3 ...
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105 views

Extracting signal from data using Otsu thresholding in MATLAB?

I am very new to signal processing. I am trying to extract a signal from my data using otsu threholding but it's not fully accurate. In this case I know that there is going to be a single signal in ...
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71 views

Crop all written letters from single image

Above image has handwritten hindi / deavanagari letters all on a single image. Task is to Prepare a dataset from the given assignment.jpg image using image processing tools Idon't have clarity ...
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How does phase relate to motions in an image?

There is lots of research based on exaggerating motions by decomposing an image into complex sub-bands using pyramid representations such as the complex steerable pyramid and manipulating phase ...
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What are the differences between Gaussian down-sampling and bicubic down-sampling in Matlab? Which is more accurate for simulating low resolution?

I see in some of the technical papers, good practice for downsampling is to first pass the image through a Gaussian Filter and then take sampling to avoid problems like aliasing and so on. However, ...
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Bundle adjustment optimization parameters

While reading the Wikipedia article on Bundle adjustment, I came across the following objective function used to represent the bundle adjustment problem. I have two questions regarding this objective ...
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Determining Parameters of S Function for Image Global Contrast Enhancement

I know that S-function (membership function from fuzzy set theory) is a commonly used function for image enhancement. I am reading a paper titled - A Novel Fuzzy Image Enhancement Using S-Shaped ...
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44 views

On Human (Face) Detection

There are many face detection and recognition algorithms and APIs out there; however, most of them can produce same results for paintings and avatars as for human face. So, is there any specific ...
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124 views

Burst Deblurring algorithm - Understanding the results

I've attempt to implement the algorithm from the paper "Burst Deblurring: Removing Camera Shake Through Fourier Burst Accumulation". The main idea is to take several frames of the same scene, each ...
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Excluding points too close to a set of coordinates

I was wondering if anyone can help me. My ultimate aim is to take an image like the one shown and draw line between the white and black blobs that show a direction and output the coordinates in the ...

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