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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Calculate surface of objects (rocks) in an image with lots of noise

Is there a way to caculate the size/surface of every individual rock visible in this image? I have tried: Contours - this doesnt seem to work the contours touch, gets real messy. Watershed algorithm -...
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How to obtain height above ground, angle the pixel’s local surface normal makes with the inferred gravity direction from depth map of image?

For extraction of the HHA features from the image depth map we need to calculate the height above ground, angle the pixel’s local surface normal makes with the inferred gravity direction. How to ...
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What is the name of the filter or technique to reduce depth aliasing around object edges when working with camera depth?

I'm working with a point cloud, created by sampling a 2D camera texture and a depth map. The color is combined with the depth and is projected onto a 3D scene to create a "point cloud". The ...
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Laplacian filter in matlab

I want to compute the output image by first dividing the image into 8*8 blocks and applying laplace filter separately and combine them but I am not getting the correct output Here is the code: ...
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Active vs. Attentive vs. Machine Vision

I would like to know a short definition of the three fields Active Vision Attentive Vision Machine Vision For me it is quite hard to find a specific definition in literature. Sometimes authors group ...
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Why Does the Median Filter Minimize the Absolute Value Error $L_1$ Cost Function?

I can easily prove that the mean filter minimizes the square error $L_2$ cost function using simple calculus. However, how do you prove that the median filter is optimal with respect the absolute ...
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Removing halo effect in image composition: Google Meet's solution

Wanted to understand how google meet is removing halo effect when composing their image. They describe their method briefly in their blog as: "The blur shader simulates a bokeh effect by ...
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Image noise reduction

I have an image of a cross-section of soil where the main object of interest are the plant roots. I would like to segment or extract the roots from the background noise of the soil itself and other ...
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image processing, edge enhancement

*Hello I used k mean method to detect edges and that’s my results as shown in the pic but I want to get more accurate results so I need to enhance my edge detection more what methods would you suggest ...
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How to find a pixel's image coordinates by its rgb value in MATLAB?

The color value of the pixel that I want to find is $RGB=(144,127,11)$. Is there any function or quick way I can get the pixel's image coordinates in MATLAB?
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How unauthorized access is prevented in biometric identification systems

biometric access control is a rapidly maturing technology that is used to police our ability to gain access to places, allow us access to software and hardware as well as guard against unauthorized ...
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How can I generate an ideal 2D low-pass filter in MATLAB?

I've been tasked with creating a 32 x 32 half-band low-pass image filter in MATLAB. My thinking is to generate the ideal filter mask in the frequency domain and compute the corresponding convolution ...
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Help me with the impulse response please [closed]

Using the separability property where appropriate, write the minimum total number of arithmetic operations (number of additions and multiplications summed together) per sample needed to filter a 2D ...
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Feature Based Methods for Quality Inspection Problem

I am currently working on an image classification problem to classify thermal images (can be interpreted as false-color images) of certain products as with or without defect. From an initial search in ...
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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 ...
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PSNR and SSIM on non-rectangular image regions

My goal is to compare the quality of an image with its low-resolution versions using an object quality metric like PSNR. Since such metrics can only be applied on same-sized images, I first upscale ...
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What is the requirement to reconstruct a spatial domain signal if we sample in the frequency domain?

I've come across an interesting question with regarding to signal reconstruction. The sampling theorem states that a signal in the time or spatial domain must be sampled at twice a rate twice the ...
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Couting exact number of mutiplications in Separable filters with Zero Padding

I'm convolving an Image $I$ of dimension $2\times 3$ with a kernel of size $2 \times 2$ and counting the exact number of multiplications.My image and kernel are given as follows $$ I=\left[\begin{...
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How to get a depth map from a Kinect 360 depth sensor?

I'm trying to understand how Kinect 360 depth sensor works. At the moment, I know that this sensor is composed by an infrared pattern generator and a infrared camera. IR camera gets the pattern ...
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What is the between spatial frequency of an image and pixel size of the sensor?

In my lecture notes about the sampling of an image I've written that: Since pixels have a finite dimension the spatial frequency response is attenuated before the "ideal" Nyquist frequency ...
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Suggestions for creating 3D Bounding Boxes of Books on a Shelf from RGB-D Images

I am new to image processing, so I beg your pardon if this is a trivial question. I am trying to use an RGB-D camera to detect 3D bounding boxes of books on a shelf. Here are some examples of possible ...
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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 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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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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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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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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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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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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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
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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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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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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
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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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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
70 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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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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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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