Questions tagged [image-processing]
This tag is for the mathematics involved in the field of image processing. Many such questions are also appropriate for Signal Processing Stack Exchange.
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Hough transformation: get line function from Hough parameters (rho, theta)
I have two an input image (256px x 256px) with a line and Hough space image (256px x 256px) with a mark where the corresponding ...
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Finite Difference For a Fourth Order PDE With Neumann Boundary Conditions.
I'm trying to implement a method I found for image decomposition that boils down to solving a PDE of fourth order. The equation in question is
$$
u_t = -\frac{1}{2\lambda}\Delta\left(\text{div}\left(\...
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Compressed image using SVD draws a clear line between part that's blank and part with a drawing. Why? [closed]
I'm trying to compress grayscale images using SVD. This is the original image:
Yes, there's a lot of blank space.
I then choose the x% largest singular values, perform the transformed matrices ...
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Determining the Center of Rotation in a Video: A Mathematical Approach
I have a video where the camera rotates, causing the images to rotate around a specific point. I need to determine the coordinates of this rotation center.
Here's my plan: I use a function to measure ...
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Solution of $V'(t)=AV(t)+V(t)A^T+\sigma^2I_m$, where $A$ is the discretized Neumann-Laplacian
I'm considering a PDE involving the Laplacian on $[0,1)^2$. I'm discretizing the problem using the finite difference approach. The resolution discretized Laplcian opertor $A$ with Neumann boundary ...
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Algorithm to calculate visual similarity of two point trajectories
I have a program where I let a user draw an image and record the strokes by saving the coordinates. I save the coordinates on every "onMove" event so it is highly detailed, with one point ...
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Doubling the numbers within an image matrix
I have an image Matrix tag that looks like this
...
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How this variational derivative is calculated?
In this paper https://arxiv.org/pdf/1907.09605.pdf \
let $\Omega \subset \mathbb{R}^n$ with $n \geq 1$ be a bounded Lipschitz domain with boundary $\partial \Omega$, $f: \Omega \rightarrow \mathbb{R}$ ...
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Is it possible to extract the translation of an affine transformation matrix independent of rotation center and angle?
I have $2$ images rotated by $60^\circ$ to each other with different center of rotation. The here presented matrices are affine transformation matrices derived from OpenCV: https://docs.opencv.org/4.x/...
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Deriving the DCT-II from the DFT
Recently, I was looking into the theory behind the discrete Fourier transform (DFT) when I frequently encountered the discrete cosine transform (DCT-II). Due to the similarities between the DFT and ...
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Book Recommendation on Edge or Boundary Detection
I have recently being interested in the estimation of discontinuities or jumps from noisy signals or densities and spend some time reading "Image Processing and Jump Regression Analysis" by ...
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How can we calculate the Euler-lagrange equations?
In this paper https://arxiv.org/pdf/1907.09605.pdf \
let $\Omega \subset \mathbb{R}^n$ with $n \geq 1$ be a bounded Lipschitz domain with boundary $\partial \Omega$, $f: \Omega \rightarrow \mathbb{R}$ ...
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Numerical solution of Perona-Malik equation: How to handle the boundary properly?
In the paper Perona-Malik equation and its numerical properties, the following PDE is considered:
The $u_0$ I'm (and so is the author) interested in is given by an image and hence decomposes into ...
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Spatial discretization of the PDE $\partial_tu=\nabla\cdot\kappa(t,\nabla u)\nabla u$ for image processing
The question is basically in the title. I want to evolve an image $u_0$ (i.e. a $n_1\times n_2$ resolution set of discrete values in $[0,1)$, which is a discrete function on $\{0,\ldots,n_1-1\}\times\{...
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Numerical Method for (Total Variation) TV Norm Minimization of Linear Combination of Matrices
I have a matrix $\mathbf{A} \in \mathbb{R}^{2000 \times 2000}$ represented in memory by an array of $2000 \times 2000$ float32 elements and I also have $10$ arrays $...
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