# Tagged Questions

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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### What would the derivative of this objective function be?

My question comes from image processing community, In our Machine Learning algorithm, we have a predicted value $D$ and its equivalent ground truth $D^*$ where their difference is: $d_i=D-D^*$. (...
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### represent an image in linear algebra

Can we represent a grayscale image as a matrix of values, and then apply all our linear algebra techniques to that? Like finding the column space and null space, reason about the matrix structure. ...
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### What does it mean to project all rotations of a function onto a different function?

Steerable filters allow me to optimally select an orientation of a filter without iterating over the set to find the optimal response (I'm doing this with a computer). The exact words from the paper ...
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### Applying distortion to Bézier surface

I am trying to simulate the image warp effect, that is used in Adobe Photoshop. The rectangular image is warped according to a cubic Bézier surface (in 2D, all Z components are 0). Having any Bézier ...
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### Calculation for getting dimension of object in image not working

I am trying to calculate the dimensions of an object in an image. This is a sample image I took to get height of blue shirt: image of blue shirt I am following the math from this page with sastanin'...
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### How to find a basis function of 2d zero mean template function

Given a 2d zero mean template $t^{'}\left ( x,y \right )$, and $\sum_{x=0}^{u-1}\sum_{y=0}^{v-1}t^{'}\left ( x,y \right )=1$, $\bar{t^{'}}(x,y)=0$ How to expand the $t^{'}\left ( x,y \right )$ ...
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### I am looking for a mathematical equation to warp an image [closed]

Theoretically, I know that to warp an image, each pixel $(x,y)$ in the source image is transformed to $(x', y')$ using a function f (i.e. $x'=f(x,y)$ & $y'=f(x,y)$ ). But what mathematical ...
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### gradient of total variation norm in total variation denoising

I am learning total variation denoising. The gradient of TV norm need calculated. From the link: http://www.numerical-tours.com/matlab/denoisingsimp_4_denoiseregul/ It says that the gradient is ...
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### Is there any approach to computer vision that doesn't make use of geometry?

I've long been interested in applying my background in functional analysis (especially wavelets) and other related areas to actually create something with "real world" value (not that I don't enjoy ...
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### What different between huffman and EBCOT?

I have a question about entropy coding and Image compression. Huffman coding and EBCOT coding are entropy coding. correct or not? I knew about huffman coding but I don't know EBCOT, How it working?...
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### Compute two 1D lookup tables for computing DCT of a 2D Laplacian

I am following a paper that I have to implement through coding and I am struggling understanding what it means exactly with the sentence "create two 1D lookup tables for computing the DCT of a 2D ...
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### Morphological operations with even sized structuring elements

The well-known morphological operations, such as dilation/erosion, opening/closing, top-hat... , widespread in digital image processing, are defined by means of so-called structuring elements. For ...
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### Phase correlation vs. normalized cross-correlation

In 2-dimensional discrete signal analysis (specifically image processing), a definition I found for the normalized cross-correlation between two images, both of size MxN $g_1(x, y)$ and $g_2(x, y)$ is:...
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### Image processing, optimization via regularization - efficient strategy

i would like to solve the following system: $J(x) = |Ax-b|_2^2+\gamma|\nabla x|_2^2$ subject to: $x \geq 0, \sum_i x_i = 1$ The underlying problem is to derive the PSF from a sharp and blurry ...
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### To get boundary of xy coordinates around object inside an image using active contour method

Trying to extract the XY coordinates around the boundary of an lesion object inside an image of plain background. I am using the active contour method as suggested to find x and y coordinates along ...
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### Largest four line segments of polygon

I have some polygon (see darkblue contour): It consists of very small segments, pixel by pixel, so angles differ although they seem to be the same. Visually we see 4 large line segments. How can I ...