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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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11 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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4answers
60 views

Understanding correlation in image processing using examples

I have been trying to understand the intuition behind the correlation. I understand from this guide that correlation is a way to detect a known waveform in a noisy background. I have seen from this SO ...
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2answers
44 views

Understanding the Bilateral Filter - Neighbors and Sigma

I have been reading about the Bilateral Filter in - Fast Bilateral Filtering for the Display of High Dynamic- Range Images and have felt crippled and confused while understanding its working and the ...
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12 views

What does dynamic range values in SSIM image quality technique refers and how to calculate?

http://en.wikipedia.org/wiki/Structural_similarity Below is java implementation of SSIM. ...
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2answers
67 views

why do directional derivatives work better with a gaussian filter?

I've been working on image segmentation and computing the directional derivatives of a grey-scaled image, with the objective of detecting contours and edges. I have realised that if I apply a gaussian ...
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2answers
37 views

What are the measurable factors of image sharpness?

I need a way to present data on an essay written about image sharpening algorithm. So I've thought that if I measure a factor of sharpness from image or relative sharpness (between test img and ...
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1answer
25 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
30 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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12 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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0answers
10 views

Create a mask like DAVIS dataset

I am testing the dataset DAVIS from here with one of the papers it has. The codes works fine with DAVIS dataset but it does not work for my data. In particular, the code does not accept the mask I ...
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0answers
13 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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7 views

how to do OTSU thresholding? [closed]

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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1answer
22 views

Sharpening Using Laplacian Kernel - How to Handle the Output (Specifically Negative Values)?

In order to sharpen an image using Laplacian kernel, it should be convolved with the original image. It is evident that the result might have negative values. I am not sure what to do with these ...
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20 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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Proof of derivative of convolution $(h * f)' = h' * f$ [duplicate]

I have a convolution $h * f$ and I should proof $$\frac{\partial}{\partial x}(h * f) = (\frac{\partial}{\partial x}h) * f$$ but I can't know how to proof it.
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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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44 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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1answer
29 views

How to identify text size using image processing?

For a side project at home, I have several pdf documents in "standard" form (White background, black font for text). For several pages, I have footnotes which are different in size from the main body. ...
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25 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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0answers
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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4answers
120 views

What Information Is Lost by Histogram Equalization?

I cannot think of a way to restore an original image after histogram equalization. But this latter seems to "enhance" (= increase contrast of) the image's details. What information is then lost by ...
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4answers
105 views

Layman Description of the Kalman Filter

I want to know about Kalman Filter but i tried searching different links including Electrical Engineering StackExchange but the information available there was hardly digestible. All I am able to ...
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28 views

How to isolate features (lines and shapes) from a noisy radar image?

I need help in radar image processig: I would like to detect lines (or more generally to clean up (remove the noise) radar images like the one attached below. Any suggestion? Thanks a lot in ...
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1answer
17 views

Can some one give me an example of cross correlation's high value where template matches with image?

I find it difficult to understand how result of cross correlation of a patch of image and image is high at matching point? what if patch contains small values and other non matching point contains ...
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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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0answers
19 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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0answers
10 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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2answers
53 views

Losslessness of Laplacian Pyramid

I was just reading up on the Gaussian pyramid and the Laplacian pyramid, used in compression applications of image. The source is here - Carnegie Mellon 16-385 Computer Vision - Spring 2019, Lecture 3 ...
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1answer
34 views

How to produce color image using edge detected images?

Hi I am trying to produce an image which is a combination of multiple images such as in focus stacking. Now I have 6 photos and I want to produce a final image such that the final image uses blocks of ...
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0answers
24 views

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 ...
2
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1answer
47 views

Estimate Variance of Additive White Gaussian Noise (AWGN) Given Multiple Realizations with Different Mean

Given $ N $ images of the same scene, where each image is corrupted by additive white Gaussian noise of the same variance $ {\sigma}^{2} $. How can $ {\sigma}^{2} $ be estimated? So we have an Image $...
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1answer
41 views

How to synchronize audio and video streaming for not fixed FPS streaming?

It's a 3-stage process. In the first stage, a video (with audio) is recorded at a fixed 25 FPS rate. In the second stage, it's demuxed in two different channels and the video is processed. In the ...
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0answers
27 views

How to simulate Zoom, Pan, Tilt transformations? [closed]

Say we are looking at a football field from a broadcast view. To give us another tool, we also have a transform of that view to a topdown view. So our two views are like so: How would one simulate ...
0
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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 ...
2
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1answer
46 views

Discrete wavelet transform disadvantages

I read in a paper that the discrete wavelet transform (DWT) has two disadvantages The first one is the shift variance property due to the downsampling process. Could you please help me understanding ...
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0answers
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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0answers
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 ...
0
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0answers
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 ...
1
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2answers
72 views

Understanding the Probability Distribution of Intensity Values

From "Digital Image Processing 4th ed. - Gonzalez, Woods" Let $p_r(r)$ and $p_s(s)$ denote the PDFs of intensity values $r$ and $s$ in two different images. A fundamental result from probability ...
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1answer
32 views

Dynamic Range and Image Contrast

Please explain the terms: dynamic range, and image contrast, and the difference between these two. Also, how can these two be understood by seeing an image by naked eye for the sake of understanding. ...
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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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2answers
45 views

Estimating Convolution Kernel from Input and Output Images

Given an original image and a convolved version of it, I need to calculate the convolution kernel. For example, given: and I would like to calculate the convolution kernel that generated the second ...
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0answers
20 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 ...
2
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0answers
36 views

Combining two images with different resolutions?

I am attempting to combine two radar images, each of which is a 3-dimensional cube with a range dimension, an azimuth angle dimension, and an elevation angle dimension. One image has high azimuth ...
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0answers
9 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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1answer
38 views

Filtering in the Frequency Domain - DIP [closed]

I am trying to do some filtering with a gray scale image in the frequency domain. I am just getting into matlab after some time away from any signal processing or coding and can't quite seem to get my ...
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0answers
15 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 ...