Questions tagged [image]
This tag covers signal processing where input is an image, such as a photograph or video frame and the output could be an improved or altered image, parameters related to the image or information about features within the image.
518
questions
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The Effect of the Order of Downsampling and Smoothing on the Output
How do I prove or disprove:
Smoothing an image with a 3x3 filter using full convolution and then downsampling an image by 2 produces the same result as downsampling an image by 2 and then applying ...
- 131
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0
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9
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Detect Cyclinderical Shape of İmage Signal
I want to detect lid of barrel is open or not in image. For this , I'm thinking of using deep learning and ı am colleting data. Besides, instead of inserting the picture directly into the deep ...
1
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1
answer
27
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Before the fft2, why need fftshift for the kernel?
When I study some paper, I have some questions about usase of convolution theorem.
...
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0
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36
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What image similarity measure is best for measuring the structural similarity of two images?
I am looking for an image similarity measure that can measure the differences between the structural composition of two images. For example these two images have structural differences between them
...
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1
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0
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Proof symmetry after 2D-convolution with $1/\lvert \mathbf x\rvert$ implies 2D-symmetry [closed]
Let be two 2D functions $f(x,y)\geq 0 \ \forall (x,y)\in \mathbb R^2$ and $g(x,y)=\frac{1}{\sqrt{x^2+y^2}}$.
I have, furthermore,
$$\int_{\mathbb R^2} f(t_1,t_2)g(x-t_1,y-t_2)dt_1dt_2=\int_{\mathbb R^...
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2
votes
1
answer
39
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Edge / Pixel Type (Homogenous, Edge, Texture) Classification as Part of an Image Denoising Procedure
For most noise reduction algorithm, the same process is applied to every pixel no matter
the pixel belongs to one of three types of pixels such as homogeneous regions, edges or textures.
Different ...
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0
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27
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Minimum number of patches needed to find color correction matrix (CCM)
The chart should have at least 9 distinct color patches for 3×3 CCMs (which are generally recommended). Excellent results can usually be achieved with the inexpensive, widely-available 24-patch X-Rite ...
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4
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72
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What Measure to Compare the Color Depth (Distribution of Colors) of Images
I am looking to compare the color depth of multiple images, in order to see which one has the best color depth. I was wondering what is the best way to compute color depth computationally?
I've seen ...
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1
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0
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85
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How to Measure Image Quality in an Objective Way
I need a method to measure image quality via computer programming (like Python). I'm doing this so as to compare quality of multiple images. I have found stuff like NMSE, PSNR and SSIM, but don't ...
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105
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Why Is PDE Based Image Processing Not as Active as It Used to Be?
I can see from the literature that PDE-based image processing (especially inpainting) was a "hot topic" at one point. Why does it not seem to be an active area of research anymore, yet it ...
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17
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I can assign a texture to the video, but how can I make this texture realistic?
I want to assign texture to the eyebrows, but first I need to delete the original eyebrow. Otherwise, the texture I added does not look realistic. How can I do this?By detecting the eyebrows, I can ...
1
vote
1
answer
92
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How to upscale an image using a Gaussian filter in R?
I want to resample a raster from 15m to 460m using a Gaussian filter.
The goal
I am having a coarse image which I want to downscale. I also have a fine resolution band to assist the downscaling. The ...
- 111
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0
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50
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Stitching images with common "static" element using OpenCV
I need to stitch images from the camera attached to the robotic arm. OpenCV has a nice feature (Stitcher), though it's not working correctly, as there is one static element (in the same position on ...
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2
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64
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How can we compute power spectral density ($P_n$) in Weiner filter?
I have an image which I corrupted with white gaussian noise in order to have SNR (Signal to noise - ratio) 10 dB . I want to apply Weiner filter to image which has noise . If I want to compute Pf I ...
0
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1
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123
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Why does upsampling and interpolation by convolution introduce a shift compared to imresize?
For purposes of understanding the process - not for any practical purpose for which I could use imresize - I wanted to show that 2x upsampling followed by convolution with an appropriate kernel (...
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5
votes
1
answer
107
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Denoising a Grayscale Image Using Random Matrix Theory (RMT)
I am applying RMT on grayscale images. Basically for any matrix, it consists of two parts: one is pure noise and other is information. Now, to distinguish noise from information, RMT comes handy. We ...
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votes
1
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106
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Filter Artifacts from Periodic Filtering
I have a merged image containing 20 segments. When I concatenate them directly, I have obviously observable patches in the whole image. I want to get rid of them while distorting the original image as ...
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0
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25
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How to determine transmittance over wavelength range of an LC shutter?
Given an LC shutter where the illumination level can be controlled by a voltage (similar to: https://www.digikey.com/catalog/en/partgroup/liquid-crystal-light-valve-lcd-controllable-black-out-panel/...
5
votes
1
answer
101
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Algorithm that enlarges the image to a resolution of $2N \times 2N$ using DFT operations
I'm trying to solve the following question:
Given an image at a resolution of $N \times N$. Describe an algorithm that enlarges the image to a resolution of $2N \times 2N$ using DFT operations.
As I ...
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0
answers
27
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Uniform partitioned convolution on a 2D image across height and width
I have 2D convolution with a large input image (512x1920). I am trying to partition the image across height and width to perform this convolution as N pieces.
This would involve having an intersection ...
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1
vote
1
answer
122
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Simulate chromatic filter on RGB image
My question is quite similar to this one but I believe it is slightly different, which is why I am posting a new question.
Given an image in RGB format, I want to know if it is possible to simulate (...
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0
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18
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How to systematically ignore image features (from a spatial light modulator)
(I am unsure if this is the best Stack Exchange site for this question. If not, please point me to the right one.)
I am generating light patterns with a device called a spatial light modulator (SLM). ...
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2
votes
1
answer
69
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Ideas on detecting holofoil trading cards?
I'm relatively new to image processing but am working on a trading card sorting machine, and would like to detect holographic cards. I'm currently identifying cards using ORB matching (moved from p-...
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2
votes
3
answers
299
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Understanding FFT output in Matlab
I'm very new to Fourier transform and I want to plot the Fourier transform of an image in Matlab. I've seen many examples and in all of them, the fft() of the image is a black picture with some white ...
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0
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17
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Eliminating shadow-like noise from wafer map images
I'm trying to eliminate a shadow-like noise from the wafer images and only leave the most prominent defects as shown in Image1 below.
I thought I could treat it like salt-and-pepper noise. Hence, I ...
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3
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0
answers
62
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Overall approach for building a footfall/age/gender counter using CCTV footage
I would like some advice to validate my approach for building a computer vision system.
Design brief:
Using existing CCTV cameras in a retail store, detect the footfall in the shop (count individual ...
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0
answers
13
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Are the sparsity of transform coefficients comparable when their frequency ranges are different?
I have obtained a graph-based Fourier transform from an optimization problem, and for evaluating the sparsity of transform coefficients, I was going to compare it with other transform coefficients ...
-1
votes
1
answer
23
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Synthetic channel creation using linux software
I have a RGB image in FITS format (though I can easily convert it to another format if that makes things easier). I wish to use the R, G, B channel data from each pixel in the original image, weighted ...
0
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0
answers
38
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Removing the Dot-Patterns Like Noise
I am dealing with an image restoration problem with noisy measurement. I use the classical total variation norm to remove the noise, specifically, the TV-$L_2$ problem. I used the famous Lena image ...
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2
votes
1
answer
93
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Generate a PSF based on MTF Mapper's SFR measurement
Not sure if I should post this here or on Stack Overflow
I have a .csv file from MTF Mapper with 2 columns from SFR measurement - frequency and contrast:
...
user60345
2
votes
2
answers
396
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How to quantify the asymmetry of an image?
Now I have two images:
We can see that Figure 1 shows obviously asymmetry while Figure 2 is totally symmetric. Now I would like to quantify the asymmetry of Figure 1. Is there any reliable and ...
- 79
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0
answers
38
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Why is this minimum cost function returning an insane cost of registration value?
I have a sample program that uses the minimum cost function to align image B to image A.
The method takes two arrays of points and does the summation of all the points in the images for both Matrix A ...
0
votes
1
answer
56
views
IP Block and Integrated Circuit using Image Compression and Parameters
I have to research and compare IP cores for FPGA and ICs that use image compression algorithms.
1.) I couldn't find any IP Cores apart from a few IP Cores(JPEG IP Core KJN Series). At the same time, I ...
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2
answers
56
views
Trouble understanding how image digitization works
Quoting Image Processing, Analysis, and Machine Vision, 4th ed.
An image to be processed by computer must be represented using an
appropriate discrete data structure, for example, a matrix. An image
...
- 267
2
votes
1
answer
71
views
Expression of the convolved image
I have an image of a 2D-sinusoidal pattern $f(x, y)$ with wavelength $\lambda$ which I would like to convolve with a 2D circular pill-box function $h(x,y)$ of radius $r$.
The image is given by
$$
f(x,...
2
votes
1
answer
65
views
What exactly is "connectivity" between pixels in an image?
So, my professor says that two pixels are connected if:
they are neighbours; and
their intensities satisfy a specified criterion of similarity.
And depending on the type of neighbours they are, they ...
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1
vote
0
answers
89
views
Convert pictures from the same camera with different FOV to pictures with same FOV
I have a camera device that produce two pictures at the time:
depth picture with FOV: 87° × 58°
RGB picture with FOV: 90 × 65°
I expect that they "share" the same objective so their origin ...
- 647
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votes
1
answer
58
views
Image conversion - raw ultrasound data to convex image
As a project, I'm trying to decipher raw data coming from a medical ultrasound device.
The data contains a 128x1008 matrix. Each one of the 128 columns represents a sensor element. Each row in each ...
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5
votes
1
answer
68
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 ...
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votes
2
answers
2k
views
Is there a way to find the contours of instances in a binary mask image by color?
I need to find the contours for each of the instances of microscopic cells in a binary image mask of dimensions 256 x 256 shown below.
My approach involves thresholding the image to get a binary mask ...
8
votes
2
answers
189
views
Locate Non Homogenous Areas in an Image
I need to choose some points on an image. These points should be chosen more where there is lots of color changes, transitions and variations. Which techniques can I use for determining where most ...
- 204
2
votes
1
answer
80
views
Basic Wiener application
I'm trying to filter this $g(x,y)$ WGN added
image
My Wiener filter is:
$$H(u,v) = \frac{P_{f}}{P_{f}+P_{n}}$$
Where the image power spectral density $P_{x}$ is estimated as $\frac{|X(u,v|^{2}}{N^{2}}$...
- 21
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votes
0
answers
82
views
How to enhance thermogram image in grayscale?
I'm trying to do some image processing to improve the image below but I'm having some trouble. I already tried to do histogram equalization followed by laplace sharpening, I tried to implement a ...
5
votes
1
answer
115
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What is Label Refinement in the Context of Image Segmentation
I have been reading the paper entitled Measures of Similarity by Unnikrishnan and Herbet, in which they discuss some metrics to evaluate image segmentation. They use the word refinement of labels/...
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0
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163
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Removing feature matched outliers within same image using RANSAC
I'm a student working on a copy move forgery detection algorithm.
I have a forged image. By far I have,
Found keypoints and descriptors from the image
Matched the descriptors using 3 Nearest ...
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1
vote
0
answers
80
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Image downscaling methods
I am researching downscaling methods for image downscaling. I've both read and found area-averaging to work well in Python using CV2, but the settings in MATLAB allow for it's bicubic interpolation ...
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0
votes
1
answer
203
views
What exactly is a connected componnent in an image?
The following is a paragraph from "Digital image processing, 4th edition, Gonzalez and Woods".
Let S represent a subset of pixels in an image. Two pixels p and q are said to be
connected in ...
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0
answers
561
views
Image convolution using FFT
I just can't get my head around Fourier transform and convolution in 2D. I am trying to implement image convolution using fast Fourier transform (in julia). So the first thing I need to do is to pad ...
- 11
1
vote
1
answer
154
views
T1 Mapping in Python?
I'm trying to write a simple program to perform T1 mapping of a few MRI Images.
My understanding is that all I need is to plot the pixel intensity values by inversion time then fit a curve. The output ...
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3
answers
118
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Beginner Educational Resources
New member here. Recently got hired into a mid level EE position. Have a BSEE but performed more radar performance analysis at a higher system level previously. In my new group we're doing a lot of ...
