All Questions
112 questions
3
votes
1
answer
588
views
Estimate Image power spectrum of the noise
I want to implement Wiener filter. I have original image and image blurred with linear motion. The one thing I am lack of(to implement it) is Noise power spectrum.
I know that it is hard task. I've ...
CommunityBot
- 1
2
votes
1
answer
120
views
Thresholding Algorithm for Separating Skin from Clothes
I have an several images that look like the following:
I would like to separate the skin from the trousers here without specifically training a segmentation model. Can anyone suggest any such ...
CommunityBot
- 1
1
vote
1
answer
42
views
Intensity uncertainties in 2D image
I am trying to detect patterns in a raw image file where each pixel has an intensity. I can imagine fitting a 2D surface to the image (or to a portion of it) using a chi2, but for that, I need the ...
- 1,417
4
votes
3
answers
439
views
Any Relationship Between the Entropy of an Image and Its Spectrum?
Is there a relationship between the Shannon entropy of image and the output of the 2D Fourier transform (DFT) of the image?
- 101
2
votes
1
answer
91
views
Estimate 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 ...
CommunityBot
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-3
votes
1
answer
185
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 ...
- 107
-2
votes
2
answers
137
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 ...
- 13.3k
1
vote
2
answers
203
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 ...
- 1,764
0
votes
3
answers
378
views
How do I know if an Image contains Noise?
I am working on a set of Images captured by an Industrial camera. However, I am not sure if I need to apply any Denoising (e.g. Gaussian or Laplacian etc) on it ?
Is there any metric that I can used ...
- 761
1
vote
0
answers
398
views
Calculating the Mean Square Error (MSE) in Wavelet Denoising
I´m currently reading the paper (to be more precise: it´s a chapter from the book "Shearlets, Multiscale Analysis of Multivariate Data" by Kutyniok and Labate) "Image Processing Using Shearlets" by G....
- 20.5k
11
votes
4
answers
67k
views
Peak Signal to Noise Ratio (PSNR) in Python for an Image
How do I calculate the maximum signal to noise ratio (PSNR) in Python? Is there any library that can calculate PSNR for Image?
- 3,590
4
votes
1
answer
2k
views
Fourier transform of Image to identify sinusoidal sources of interference
I'm a statistics grad student, and I just started getting into Digital-Image-Processing (an analogy for processing super-large contingency tables). In the book "Digital Image Processing" by Gonzalez ...
- 28.4k
7
votes
4
answers
6k
views
Which domain used for denoising additive and multiplicative noises
I want to know what is the difference between additive noise, multiplicative noise.. In what domain these noises are handled to remove?
I am interested particularly in image dataset
Does different ...
- 101
-1
votes
1
answer
126
views
Can FFT2 be used as a randomness test for image encryption?
Based on this link
Is it possible to consider a model to introduce FFT2 as a parameter to determine how random the image is? (randomness test like Entropy)
consider Lena's image and its FFT2:
If we ...
- 111
1
vote
2
answers
570
views
What's the FFT2 of white noise image?
I try to compute the FFT2 of the white noise image.
I use this image
with Entropy 7.995 and
pixel scatter plot:
based on this python code:
...
- 111
0
votes
1
answer
122
views
Measurement of blocking artifacts in images
I want to define a threshold for maximal blocking artifacts in an image.
What is a good key value to measure blocking artifacts?
I have no reference image
non natural image
Example:
I looked into ...
1
vote
1
answer
2k
views
How to interpret PSNR value?
Say, I have original image, noised and denoised. By PSNR value I want to find out how good does my denoising algorithm works.
For which pair of the images should I calculate it? I've tried it for ...
- 32.3k
0
votes
1
answer
71
views
Which type of noise can we see from the given image signal and its abs of 2D FFT?
1. Background:
I get an 128*128 2D one-channel noisy image as follows:
I get the shifted absolute values of 2D FFT result by the following Python code:
...
CommunityBot
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2
votes
1
answer
585
views
Noise Reduction - noisy lines
I'm trying to reduce the noise in this photo. What type of filters/techniques should I use to cancel out the noise?
I've tried using box filter and Gaussian filter to blur out some of the noise, but i ...
- 26k
2
votes
1
answer
1k
views
Finding circle in binary image (R, not matlab)
How would I extract 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 am using R ...
CommunityBot
- 1
0
votes
0
answers
49
views
removing stripy artifact from fMRI
I have fMRI images, some of which have a stripy artifact that looks like a Gabor filter. Removing this kind of noise is not, to my knowledge, a standard part of any fMRI processing pipeline. I am ...
- 101
7
votes
1
answer
816
views
Which Noise Reduction Algorithms Are Used in Commercial RAW Image Processors?
I'm trying to guess what noise reduction algorithms are used in commercial processors for raw images from digital cameras. I find this fairly easy to do for the sharpening algorithms (most use unsharp ...
- 324
3
votes
2
answers
943
views
Adaptive Gaussian Filter for Image Denoising
I am looking for methods to enhance noisy images, where:
some pixels in the image are very noise,
some other pixels do not contain so much noise.
My first thought is to build an adaptive Gaussian ...
- 3,590
3
votes
2
answers
647
views
Reducing Pepper Noise from an Image
For an image with pepper noise, presuming it is desirable to reduce the pepper noise, which operations, in which sequence, would you apply? Find an image, add pepper noise, and demonstrate your ...
- 20.5k
4
votes
1
answer
1k
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 $...
- 20.5k
4
votes
3
answers
437
views
How to denoise a video stream from poor CCTV lighting
I have grainy CCTV footage that will need some amount of clean up. I request for ideas on the best way to clean out the noise. I am attaching a frame extracted from the video here for hints on the ...
- 3,590
5
votes
2
answers
399
views
The Effect of Spatial or Temporal Averaging on Noise Properties
I generate two noise images using MATLAB's function imnoise().
If I average the two noise images, the resultant image looks like the original noise
image but only ...
- 20.5k
5
votes
1
answer
1k
views
Poisson Noise Removal from an Image
What type of filters can be used to remove Poisson noise in an image? I tried applying Gaussian filter to few points in the spectrum.
- 20.5k
2
votes
1
answer
197
views
Extracting ridges in automatically in image
I am trying to extract ridges from an image, calculated using the eigenvalues of the Hessian matrix (see answer in Best way of segmenting veins in leaves?). In this image I have zeroed out the ...
CommunityBot
- 1
1
vote
1
answer
433
views
Help generating non-Gaussian noise
I'm trying to add non-Gaussian noise to an image. The purpose is to synthesize realistic camera noise. I am doing the following:
Obtain a noisy image sample by subtracting a low ISO photo from a high ...
- 2,275
4
votes
1
answer
363
views
How to Remove Temporal and Fixed Pattern Noise and Apply Tone Mapping?
I have a video, whose frames I have extracted and require to work with. 16 bits and grayscale images.
My task is to improve the quality of the images, by removing the noise + adding tone mapping and ...
- 20.5k
4
votes
1
answer
15k
views
What does zero-mean noise mean?
I don't know where to start from. and this question might be very silly,
I have found such as comment from someone at Poisson noise and curve fitting - denoise first?,
"I think if your noise is ...
- 3,590
4
votes
2
answers
2k
views
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 ...
- 2,393
7
votes
3
answers
8k
views
What is the difference between MSE and PSNR of images?
I have some doubts.
What is the difference between quality parameters MSE and PSNR?
Which is used when?
Is there any advantage of PSNR over MSE or vice versa?
Also I have heard people saying that ...
- 32.3k
4
votes
2
answers
526
views
Is Image Noise Removal Image Enhancement or Image Restoration Operation? [closed]
I am working in digital image processing field, recently I am studying about Image Noise, I just want to know that whether this noise removal is part of image enhancement or image restoration.
I ...
- 3,590
0
votes
0
answers
84
views
standard deviation of two constant noised signals related through interpolation
Let us say say we have a noised constant signal and want to evaluate the standard deviation (std) of the noise. We calculate the std of the said noised signal and call it $\sigma_1$. Now we process ...
- 9
0
votes
2
answers
418
views
How to detect defects at a contour?
I am detecting a contour of a smooth metal. I do binarization first then use openCV contour function. But sometimes the metal has defects such as dots or dusts at edge. This leads a unsmooth edge. Is ...
- 761
4
votes
1
answer
3k
views
Image Noise Detection Using MATLAB
I want to implement the following algorithm. Let $I$ denote noisy image and for each pixel of $I$ is represented by $I(x,y)$. A Sliding window of size $3\times3$ centered at $I(x, y)$ is ...
- 20.5k
0
votes
0
answers
228
views
How can I add any kind of noise to image for a given SNR?
What is the best way to add any kind of noise (not only Gaussian noise) to 2D signal (image) for a given SNR?
- 32.5k
1
vote
1
answer
798
views
How to calculate variance of noise on a noisy image (Noise+Signal)
I have a long exposure image captured at 70ms. (I1) (As attached)
I also have another image captured at 0.7ms with Gain24. (I2) (As attached)
This image has both noise and signal together.
I would ...
- 11
0
votes
1
answer
157
views
Measure how Straight/Smooth the Borders are Rendered in an Image
I have two images:
I want to measure how straight/smooth the text borders are rendered.
First image is rendered perfectly straight, so it deserves a quality measure ...
- 32.5k
0
votes
1
answer
70
views
Regarding the nature of white noise in images
I have just started learning the very basics of noise.
I have come to understand what white noise is in sound samples, but I do not understand the meaning of white noise in images.
In sound samples, ...
- 32.5k
0
votes
1
answer
254
views
How to add additive noise to an image?
I have the following image I and I want to add additive noise using the array N below. Can you please give me a calculation example of how to achieve this?
Do I have to move from image space to ...
CommunityBot
- 1
0
votes
2
answers
2k
views
confusion regarding correlation in noise?
I am reading online article about image processing at following link
https://www.electronicsforu.com/electronics-projects/software-projects-ideas/image-processing-using-matlab-basic-operations-part-2-...
- 2,621
1
vote
2
answers
2k
views
Estimating the Variance of Noise Using Median Function Applies on the Gradient of the Image
By investigating the implemented code of an accepted paper, I encounter with following relation to estimate the variance of noise in an image:
$$ \sigma = \frac{median (|\nabla^hx-median(\nabla^hx)|)}...
- 20.5k
1
vote
1
answer
803
views
What Do We Expect Likelihood Function to Be Used For?
In my understanding, I let make a example.
For example, you can see in the following picture.
Consequently, We want to find ^sigma. and We have already known the observation data(which is random ...
- 20.5k
0
votes
0
answers
45
views
Dirty Image Quality Assesment Measure
I was looking for a way to measure how dirty is the document in image processing. Example images below:
a. Dirty Backgrounds
b. Dirty Backgrounds with Text
Can someone give me an initial idea to ...
- 127
3
votes
1
answer
6k
views
How to Estimate the Noise of an Image / Estimation of the Noise in an Image?
I want to know how to estimate the noise of an image?
Also is this represent the camera's noise?
Does anyone know how to estimate the noise of an image or camera?
Update:
Especially, I want to know ...
CommunityBot
- 1
1
vote
0
answers
210
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 ...
- 127
4
votes
1
answer
615
views
How to Get Rid of Ripples from a Gradient Image of a Smoothed Image?
I have a gray scale UINT8 image. When I smooth it with a Gaussian filter and then compute the gradient image with a Sobel filter in OpenCV, ripples would appear.
...
- 20.5k