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.
2,442
questions
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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 ...
2
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2answers
35 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
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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0answers
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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0answers
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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0answers
9 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 ...
0
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0answers
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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1answer
21 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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0answers
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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0answers
13 views
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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0answers
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
26 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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0answers
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 ...
0
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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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0answers
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:
...
2
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4answers
98 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 ...
3
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4answers
101 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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0answers
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 ...
1
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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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0answers
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
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 ...
1
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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 ...
3
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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
44 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
26 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
45 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,...
0
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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
71 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 ...
0
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1answer
31 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
41 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 ...
0
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0answers
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 ...
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 ...
0
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0answers
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 ...
0
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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 ...
0
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0answers
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 ...
0
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0answers
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....
0
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2answers
53 views
What Is the Bilateral Filter Category: LPF, HPF, BPF or BSF?
I`m reading about Bilateral filter with images, I knew that it uses Gaussian filter (which is a LPF) as a domain filter plus a range filter and it is used to preserve edges(high freq component).
Can ...
1
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1answer
61 views
How are line pairs and pixels related in image resolution?
I hope this is the correct place to ask this. If not, please refer me to a better place, thanks. Now to my question,
I am learning about digital image processing, and the book I am reading is ...
0
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1answer
20 views
What does structure matrix do
can anybody explain to me what does structure matrix exactly do in image processing? What happens to the pixels?
By structure matrix I mean:
$$S_w[p] = \begin{pmatrix} \sum_{r}w(r)[I_x(p-r)]^2 & ...
