All Questions
Tagged with image-processing image-processing
3,214 questions
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Variation of phase due to changes in features in the spatial domain
Let say there is a white ball at the center of a black background in a image. And i move that ball to (x,y) position. So what changes will that cause in phase and by how much. And since phase has a ...
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Finding the gradient direction from a derivative image
I am working on a task with reconstructing an image from its derivative image on only one direction.
Currently I managed to do this on a derivative image which was taken on X direction, by integrating ...
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Reducing ringing artifacts during numerical differentiation of depth image
I need to obtain a normal map from dense depth image. Naive differentiation results in serious ringing artifacts near the sharp edges. I have tried using a Sobel filter instead, but it does not really ...
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23
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Gaussian blur with variable standard deviation
I'm trying to find fast ways to evaluate the following integral defined over points $\mathbf{x} \in \mathbb{R}^2$:
$$\Phi(\mathbf{x}) = \frac{1}{2\pi\sigma^2(\mathbf{x})}\int d^2y\, \exp\left(-\frac{|\...
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What are good algorithms to smooth scanned text?
I have a document scanned on an old scanner. I'd like to smooth the letters to make them easier and more pleasant to read. I am not trying to do OCR, simply to make the document more legible.
Some ...
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Measuring signal of color in Euclidean distance
How signal can be measure by using Euclidean distance? Given by the formula like this ones:
$\text{signal}(m, n) = \sqrt{(R(m, n)^2 + G(m, n)^2 + B(m, n)^2}$
where $m,n$ is the pixel coordinate. Can ...
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Measuring signal of image in Euclidean distance
How signal can be measure by using Euclidean distance? Given by the formula like this ones:
$\text{signal}(m, n) = \sqrt{(R(m, n)^2 + G(m, n)^2 + B(m, n)^2}$
where $m,n$ is the pixel coordinate. Can ...
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1
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What are different methods to track a moving object with stationary monocular camera
I am new to computer vision and trying to learn object tracking using vision. I read different books on vision where object tracking is discussed. Most of the books mention following two methods: 2d-...
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Detect Largest connected component in a scatter plot (on bivariate data)
I have bivariate data representing the position of an identified reference point along a y axis which ranges from -100 to 100 mm. When I plot this data in a scatter plot I can see outliers and groups ...
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2
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Aggregating Image Stream (Video) to Audio in Real-Time
For the simplicity, aggregation technique is just averaging (pooling) entire grayscaled image pixel into one amplitude.
So, in other word the camera is acting as light sensor, where more white pixel ...
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24
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RGB to HSV representation
When altering RGB image representation to HSV in Matlab (rgb2hsv) should the human eye notice the difference? because the result image differs vastly.
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Pixel size and Fourier domain
I'm developing an off-axis digital holographic camera. Initially, I employed a CCD camera with 6.7-micrometer pixels and successfully observed the first-order interference pattern in the Fourier ...
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1
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33
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Effect of ICC Profile Metadata of JPG images
I am using GThumb to assign tags to my images. Recently, I noticed that GThumb does not only alter the tags I manually change, but also deletes some tags that were set by the camera/phone, ...
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How does the image resolution converts to frequency limits of Fourier space?
Sorry if this question has been asked before.
I have an image that has a dimensions 5x5 um$^{2}$ and resolution 256x256 pixels, and I do a Fourier transform of it. Based on the resolution, I can't ...
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Estimate 3D location of a tracked point with Known Camera parameters and Distance
EDIT: Camera has fixed orientation and position with respect to the world coordinates, it is not moving. Therefore, the found [R₁ ∣ t₁] extrinsics are assumed to be constant throughout the moving of ...
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Determine scale of paper grain/tooth from scan
Drawing papers come in a defined weight (gram per square meter), but the texture of the surface isn't quantified. I'd like to create some quantitative measurement for the texture of paper that I can ...
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Estimate position of object based on global image layout and image from another camera
I have a global map with all the positions of the cameras and their specs. I want to estimate an object's position on the global map based on image collected from the camera. What are some methods I ...
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Image Pyramid for template matching - how will it work with target of arbitrary scale
Consider the classical computer vision problem of template matching. To detect targets of arbitrary size, one approach would be to build an Image Pyramid of the input template: lowpass filter the ...
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Analytical Proof of LoG Filter Separability
I've been studying the Laplacian of Gaussian (LoG) filter, and I understand its importance in edge and blob detection. However, I’ve come across some references that mention the LoG filter being ...
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Is there a relation between Low-pass filter cutt-off frequency and 2d DCT coefficients?
I'am trying to make a low pass butterworth filter for an image. I try to find a relation between dct coefficients and cutoff frequency.
I know that the low frequencies are top left side in dct, high ...
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Is there a relation between Low-pass filter cutt-off frequency and 2d DCT coefficients? [duplicate]
I'am trying to make a low pass butterworth filter for an image. I try to find a relation between dct coefficients and cutoff frequency.
I know that the low frequencies are top left side in dct, high ...
yysmonyy
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39
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DFT on images: quantitative measurements on magnitude spectrum
I was wondering whether I can use Discrete Fourier Transformation to quantify aspects of complexity and variability in images. My goal is to compare patterns found in images, such as color patterns of ...
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Build the Affinity Matrix of Edge Preserving Multiscale Image Decomposition based on Local Extrema
In the paper Edge Preserving Multiscale Image Decomposition based on Local Extrema (Available at DSpace@MIT - Edge Preserving Multiscale Image Decomposition based on Local Extrema or the writer page ...
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Extracting frequencies from a 2D image, what is the sampling frequency?
I have a set of images that are effectively different types of banded animal patterns. I would like to be able to compare them in the frequency domain. My intention is to extract the frequencies that ...
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Question regarding global thresholding algorithm for images
I am trying to mathematically prove that for an initial choice of threshold To, if we compute the successive thresholds as average of foreground and background means, the thresholds will follow a non-...
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Smoothing out data
I have a an array of 2d coordinates where each coordinate is some float.
For the rest of my project, I need a binarised image of 1s and zeros.
Essentially I need the 1s to be where the coordinates are ...
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Slope Detection in Frequency-wavenumber Spectrum
I am doing analysis on acoustic data to estimate speed of sound propagation in a flowing fluid through a pipe. The slopes of the bright straight lines in the frequency-wavenumber spectrum of the ...
user67390
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Correct geometrical distortions from camera
I have video recordings of a behavioral experiment on mice. The camera is rigidly attached to the ceiling. Below the camera is a round table with round holes. Unfortunately, the camera is not strictly ...
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wavy pattern in FFT of image
I'm trying to diagnose poor image quality from a cheap camera. In addition to normal noise and blocky jpg compression, there's a pebble-like quality to them. Trying to understand this, I took the fft ...
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Comparing large 3d datasets for Grid map data
I am working on Grid maps.Grid maps are a representation of the environment in terms of 2d or 3d cells which store a value in them that can be plotted to make a map of the area.
I am having a lot of ...
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1
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An OCR steps to detect and extract the line pairs english text from image
I am trying to extract the text from an image using OCR. The challenge I am facing is how to map the key and value. For example, the key - Last Name should have the value XYZ. After getting the key ...
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16
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Determining Object Visibility with Metrics
I am wondering if anyone has suggestions for metrics to use to quantify the edge strength and contrast of a target from its background in single channel images. I am trying to find the effectiveness ...
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Beginner's troubles with binary thresholding for particle tracing in ImageJ
I'm a researcher working on making crystalline microspheres (100-400µm diameter), and have recently begun taking SEM images of my samples. It would be really useful to be able to have a quantitative ...
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1
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134
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Spotlight SAR image formation
I've created a Synthetic Aperture Radar (SAR) simulator and am testing it to ensure its correct operation. One of the last steps is to process the data into a final image, but I'm having trouble with ...
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UQI and VIF as image generation metrics
The aricle briefly describes various metrics for image generative models. It categorizes them into pixel-, feature-, task- and novelty-based metrics.
Following such categorization I understand that A ...
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How do a article compare images of different resolution using MSE and SSIM?
I have come across an article in the field of medical image processing using super-resolution (SR) where the author is comparing a low-resolution (LR) image with its super-resolution (SR), high-...
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How are values assigned to pixels in hyperspectral imaging for airborne cases?
From what I know, hyperspectral images can have up to hundreds of bands. During acquisition, each pixel seems to store only one value. Later, algorithms are used to calculate the missing values across ...
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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 ...
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Recreating the `dwt` function from Matlab
I am trying to implement DWT (Discrete Wavelet Transform) on a given signal, without using the dwt function in Matlab. My approach was to get the synthesis filter coefficients using,
...
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How does MATLAB's edgetaper function work?
MATLAB has a function edgetaper that does something I haven't seen before:
J = edgetaper(I,PSF) blurs the edges of the input ...
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How to improve quality of the recovered image in compressed sensing technology?
I was trying to use compressed sensing technology in image processing. Basically, I did a code in Python(Spyder IDE) which takes an image, compress the image and reconstructs it.
I tried with the ...
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How my digital camera creates itself this picture?
here is a picture produced by my digital camera
My camera is an (quite old) Panasonic DMC-FZ200.
My question is : what happened, and at which stage of the process the bug was?
Months ago, while ...
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blind deconvolution of astronomy images
Hubble's angular resolution is 0.04 arc seconds. https://en.wikipedia.org/wiki/Angular_resolution
The closest star has an angular diameter of 1.02 milliarc seconds. https://space.fandom.com/wiki/...
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How to calculate the angular velocity of a rotating cell from a microbe video?
I have a video of Brownian motion of microbes under a microscope. From this video, I need to calculate the angular velocity of a particular prominent cell. From my understanding, what I know is that I ...
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Why Ando operator is worse than Sobel operator when computing gradients in my case?
I am testing different gradient operators for 2D images. I have some differentiable function (let it be $f(x,y) = \sin(2x) + \cos(3y)$). I discretize this function (i.e make a 2D image of it) and then ...
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Remove Wave Patterns from an Image Using Inpainting
I have been struggling to remove wave like patterns from my image. I tried FFT (Fourier Transform) and it wasn't good. I came across with inpainting and it looked promising but I don't know how to use ...
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LED image phase projection
Say you have a goal image G with a phase called phase G. Can you physically construct and project phase G, or is phase not something physical? Like, can you set up an array of LEDs to project the ...
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Contrast enhancing very faint extended blobs in an image
I have a series of images of the night sky and I'm looking for methods to enhance very faint structures that are barely visible. The movement of those structures is visible when you click through ...
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How to get surface topology from fringe pattern
I'm trying to recover the surface shape of a body from fringe pattern. There's a interferometer projecting circular fringes on the body. A camera takes a picture of the reflection of these fringes. I ...
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Derive the filter mask that corresponds to the double filtering process
There are two mask filters,
...
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