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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Multivariate Histogram Matching for Image Color Matching

Suppose X is random variable that is spatial position in finite range, which its Cumulative Distribution Function (CDF) could be calculated easily, then if I have two random variable X and Y spatial ...
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How Simulink can be used to obtain 64 basis functions of an $8 \times 8$ Matrix [closed]

I had tried to get DCT Matrix for 'cameraman.tif' image in MATLAB using instructions such as imread, imdouble, ...
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How to solve this math problem regarding Histogram matching?

Please help solve the problem in the picture. I am confused due to the piecewise nature of the density functions. If it was a simple curved PDF, I would simply integrate over full range and use the ...
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How can i solve .edf.seizure file error? [closed]

I need to read chb01_03.edf.seizures file from CHB MIT database in MATLAB for seizure detection. i execute this command in matlab ...
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1answer
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What is the difference between object detection and target detection? Are they the same thing?

I was reading some articles regarding object detection and target detection and have a hard time understanding the difference between object detection and target detection. i want to know whether they ...
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1answer
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Importance of Phase in FFT of an image

While processing digital images in the Fourier domain, mostly we exploit the amplitude and not the phase. This could be because the amplitude is much more structured and the amplitude spectrum reveals ...
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What does a sketch of difference of gaussians convolved on an image look like for different value of sigma?

What happens when I convolve an image $I(x,y)$ defined by the table below, with a $DoG = G(\sigma^{2}) - G(\sigma^2*{k^2})$ where $k^2=2$? What would be a sketch of $\sigma^{2}$ (on the x-axis) and ...
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Stochastic Methods for Image Deconvolution Problem

If we convolve an image with a point spread function and from the resulting image to find the input image, can we use any stochastic approaches? I feel like we will not be able to. A single image ...
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How to set matrix multiplication to control the resulted matrix organization

I have two matrices $F$ and $W$ where their multiplication produces a matrix $C$ which contains zeros except few non-zeros values $F*W = C$. What I need is to organize the second matrix $W$ to get ...
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1answer
56 views

Lossless rectangular-polar transformation

Right now, I am in a search of a lossless rectangular-polar transformation. To clarify, this is what rectangular-polar coordinate map looks like: So, these are the two axis of a rectangular-polar ...
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How to distinguish the same object entering the camera field of view

We want to set photo cameras in the field and capture images of insects that visit flowers. We want to place these cameras above the flowers and then they should get triggered whenever an insect lands ...
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1answer
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Compute the Second Order Derivative of Digital Image with Finite Differences

I was looking for how to compute second order derivative of an image and came across the question kernels to Compute Second Order Derivative of Digital Image. In the top voted answer, it gives an ...
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Is there a repository for source separation test images e.g. the star-galaxy images?

I'm having trouble finding standard images used for testing source-separation algorithms in image processing. For instance, a common example I see is the "star-galaxy" images. Most papers I'...
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Concrete use of convolution algebraic properties [closed]

There are 3 main properties of convolution in every image processing lecture notes I read : Commutativity: $f\star h = h\star f$ Associativity: $f\star (h_1\star h_2) = (f\star h_1)\star h_2$ ...
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Compressed Sensing in DOA processing

I'm trying to apply the compressed sensing theory (CoSaMP algorithm) to the DOA estimation in FMCW ULA (made of 48 elements). In the dechirped signals processing I use a first FFT to solve the range ...
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Is the Laplacian Filter an High Pass Filter (HPF)?

Is this kernel name as mean difference kernel or Laplacian filter? Is mean difference just a method?
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Feature extraction for IRIS recognition

What are types for feature extraction in iris recognition? How can I divide it on types which detect phase, edge, etc.?
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LPF and HPF filters in ENVI

Since we know about convolution filter in image processing, it is basically a matrix applied to an image and a mathematical operation comprised of integers and it works by determining the value of a ...
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Quick technique for comparing images better than MSE

I have been using Structural Similarity Index (through tensorflow) for comparing images, however it takes too long. I was wondering if there is an alternative technique that doesn't take so much time. ...
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How detect if an object is missing from an image and set a Raspberry Pi GPIO output

I'm pretty new in OpenCv and Python. I want to detect an image. If a particular object is missing from the image set a GPIO output using on a Raspberry Pi. What would be the right way? I don't want ...
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22 views

feature extraction techniques for iris recognition

I want to ask how I can divide feature extraction techniques to feature detectors and feature descriptors. I have big problem how to understand it. For example I can use Gabor filters (feature ...
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1answer
27 views

Where do you recommend getting “standard” images for testing algorithms?

I've noticed that there are a LOT of websites which claim to have a standardized repository of images (for image processing algorithms). However, I don't know which ones are actually trusted by the ...
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How can I compute the magnitude of edges of an image?

if I have an image with 11x11 pixels and In the center of the image is a square of 5x5 pixels. The gray level of the background is 0 and the gray level of the square is 50. How can I compute the ...
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2answers
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Are there standards/references for determining spatial scale in photographic images?

EDIT, 12/12/20: Images below are of the radial sinusoid pattern. Left side is the "unrotated" version. Right side is what the a photograph of the pattern would look like if the disc was ...
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After upscaling a signal what noise metric to use for noise qualification

If I have a 2d signal (like image) and interpolate (linear) it to get an upsampled signal, how can I qualify the noise, with which metric? STD changes between the signal and its'upsampled counterpart ...
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2answers
37 views

Testing if a random signal was modified or if it contains noise

Given a random signal, is there a method of finding if it was modified or if it contains noise if you don't know the original signal? E.g.: given a random image, can I find out if it was modified if I ...
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1answer
39 views

Edge detection in spatial or in frequency domain?

I want to ask why everywhere is used to do edge detection in spatial domain and not in frequency domain with FFT of image and apply HP filter. Thank you.
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1answer
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What Are Intuitive Explanations for Shrinkage in the Context of Image Denoising?

I have occasionally come upon the term "shrinkage", mostly in the context of denoising methods. My rough understanding is that it refers to the part where the real distribution might not be ...
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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 ...
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How can I compute the result of the magnitude of edges of an image?

I have a random image with 11x11 pixels. In the center of the image is a square of 5x5 pixels. The gray level of the background is 0 and the gray level of the square is 50. How can I compute the ...
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1answer
49 views

Meaning of lines on x- and y-axis of a centered FFT-spectrum of an image

I am currently learning about the Fourier transform of digital images, but I am wondering about one aspect. In most visualisations of fourier transforms of images, a horizontal and a vertical line in ...
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1answer
43 views

Easiest Pattern to Recognize with Machine Vision

I need to detect the exact position of some kitchen tools using machine vision. I've the possibility to label the tools with a pattern, to make the detection (more specifically the image segmentation) ...
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2answers
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Find the minimum number of arithmetic operations required for 2D Filters [closed]

Find the minimum number of arithmetic operations required for 2D Filters
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How do I find the coefficients to know if this color combination is realizable? What am I doing wrong in my solution?

I tried to solve the following problem: Part A was solved without any problem, however with part B there is a problem: Second the digital signal processing, to be more specific, image processing, I ...
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1answer
40 views

Semantic Distance Measure Between Images

I would like to compare 2 generic images, with same sizes and normalized values. Which metric would be better than the baseline Eucledian distance?
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1answer
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Extracting color information from lit regions to adjust shadow regions, HSV space

If I wanted to match the color of a shadow region to the color it is supposed to be in the lit region, would this, purely color information, be preserved in the hue of the HSV space of the image?
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1answer
66 views

Is it possible to identify the “blank data” in a JPEG without knowing the image history?

I am pretty much a begginer in matters of Image signal and to be honest, not that much versed into mathematics. I hope my question will not sound too naive. (sorry in advance) (Also if it has been ...
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Can you do temporal frequency filtering for a spatially moving signal in image sequence?

Context : A static camera captures video footage of a still indoor environment at given framerate (1080p@30fps or 720p@60fps) A low power line laser projects a line shaped beam in the camera field of ...
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Thresholding algorithm for separating skin from clothes in python

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 ...
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1answer
32 views

Cropping binary images based on pixel counts in python

I have a numpy binary masked image that looks like the following: I want to automatically crop this image like the following: Can I achieve this using some sort of image processing rather than ...
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1answer
34 views

Taylor series expansion in mean shift tracking

I am trying to understand the first order Taylor series expansion when deriving the math behind mean shift tracking. Given the Battacharya coefficient between the target descriptor and candidate ...
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40 views

N, N-Discrete fourier transform

What is $N$,N-point Discrete fourier transform? Is it different from 2D Fourier transform? and how to compute $N$, N-point Discrete Fourier Transform of a given laplacian filter kernel? say for a ...
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Calculate perimeter and area of Head CT from DICOM

I’m trying to calculate the perimeter and area of the outer lining of the skull from head computed tomography scans. I have these scans as a DICOM, and single slices can be exported as image files. ...
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2answers
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Applying Circular Cross Correlation in MATLAB

I have searched Google for circular cross correlation using Matlab, and I have found it only for one dimensional signals. Could you please help me implementing circular cross correlation between two ...
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1answer
33 views

Impulse response of the system image processing

In case of the signal, when we plot an impulse response we have our x-axis - samples (or time), y-axis - amplitude, but in case I work with image processing? x-axis is pixels? and y is still amplitude?...
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Find points that are mapped to the original grid with image rotation by a non multiple of 90 degrees

I would like to find the point that are "not interpolated" when I rotate an image with e.g. Matlab's imrotate() by an angle which require interpolation e.g. 6 degrees, i.e. not a multiple of ...
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1answer
45 views

What are the 'phases' in this 2D scaler filter

I am pretty new to DSP and have been looking at how image scaling is done in hardware. I and came across a 2D scaler core for an FPGA here. I have read up a bit about polyphase filters, but am ...
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1answer
58 views

Image Restoration by Solving Constrained Least squares in Frequency Domain (Frequency Domain Filtering)

I am trying to implement the constrained least squares filtering as described in Rafael C. Gonzalez, Richard E. Woods - Digital Image Processing 3rd Edition Section 5.9. The equation (...
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1answer
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Help or suggestions with Line detection in microscopy images

I'm doing a personal project in which I want to select some very specific lines in a microscopy image. The first picture is the raw image, the second picture is the image for the lines (in yellow) I ...
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Implementing Felzenszwalb's segmentation for 3D images

Is there an implementation available for unsupervised 3D segmentation using the Felzenszwalb's Graph Cut algorithm? If implemented what do you think are the bottlenecks of such an algorithm? In ...

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