This tag is for the mathematics involved in the field of image processing.

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1answer
4k views

What does it mean to divide by the standard deviation?

I'm trying to variance normalise an image, in order to do so, I subtract the mean from the pixel value, to have a 0 mean, and divide by the standard deviation, to have a unit variance, right ? but ...
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1answer
559 views

Explanation of sinusoidal function: $f(x,y) = A\cos(2\pi(ux + vy) + \phi)$

I never got to take a signals and systems course and this has come up in the math of my image processing review. Can this be explained? The equation for a sinusoidal signal is $f(x,y) = ...
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1answer
472 views

Could explain me how eigenvector helps with compute gradient and how make differentiate operation on decrete space like digital image?

Could you explain me how eigenvector helps with compute gradient and how make differentiate operation on descrete space like digital image? I know that this question is so connected with computer ...
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1answer
93 views

Need some help to understanding the formula

This is pinhole camera model (I don't get, is there [R t], or (R, t)) This formula is used to model the projection from a space point M to an image point m. Projection drawing Tilde over vector, ...
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2answers
4k views

What do eigenvalues have to do with pictures?

I am trying to write a program that will perform OCR on a mobile phone, and I recently encountered this article : Can someone explain this to me ?
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0answers
149 views

Singular Value Decomposition

I want to decompose an image $A$ using the Discrete Wavelet Transform and then find the singular values, $S$, such that $A=USV$. I will then do the same to another image such that $B=USV$. I will ...
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0answers
63 views

How can I convert lines intersecting a plane into a focused image?

I am writing a particle transport code. I would like to be able to obtain an image of my geometry when transporting photons given the following information: The photons are incident on a plane. For ...
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1answer
99 views

Taking a derivative of this formula

I reading an article about an Automatic scale selection It is used in image feature extraction. But what I need is the mathematical part of it. I have a problem with understanding the following: ...
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0answers
68 views

Intuition about moment function derivation [OR] derivatives involving a time varying integration domain

$$ m_{{pq}}(t)=\iint\limits_{R(t)}h(x,y) dx dy $$ where $ R(t)$ the domain of integration is time varying (In fact it is the only one which is time varying). And $$ h(x,y) = x^p y^q f(x,y) dx dy ...
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2answers
5k views

Mathematical explanation behind a picture posted (lifted from facebook)

In this image given below, there is an actor's (famous south Indian actor Rajinikanth) image which can be seen only if you shake your head ! I had lifted this from Facebook. I am just curious to ...
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1answer
478 views

Unscramble images without trying all permutations

I try to write an algorithm that unscrambles images that were before scrambled by mixing up small blocks: My idea is that in the bottom image there are more "sharp" corners compared to the image ...
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2answers
108 views

How can I measure the properties of a Point Spread Function?

What quantity or property can I use that describes by how much a point spread function distorts/blurs an image?
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1answer
269 views

Identifying 3D shape from matrices analytically

I have a set of matrices (a 3D matrix, that represents a quantized body), for instance: (the size 5x5 here is just an example, the real size is a lot higher) $ M_1 = \left[ {\begin{array}{cc} 0 ...
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2answers
232 views

What is an efficient way to get blur from source and blurred images?

I'm doing little program to get blur from source image and blurred image. But I haven't learned so much things about math in school yet. The equation used for blurring the image A into B: ...
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1answer
141 views

Reconstructing a ring from a stack of 2D images (radially aligned)

I have a stack of images (about 180 of them) and there are 2 black dots on every single image. Hence, the position(x,y) of the two stars are provided initially. The dimensions of all these images are ...
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1answer
67 views

A function for forming a closing curve on all points on a 2D image

First of all, this is for image processing. The small circles above is on an image and are my list of points. The points are always in order from p1, p2, p3 to pn. And I am to create a curve that ...
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2answers
283 views

Scaling a histogram in the face of outliers

I am trying to figure out how to display a histogram of a digital image in the face of massive outliers (lots of shadows, highlights, or lots of anything inbetween). If I simply choose the bin with ...
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1answer
205 views

Homotopy and watershed

homotopy is a new word to me. Upon trying to understand this property, I immediately think of another well-known segmentation algorithm: watersheds. I see that watershed should exhibit some ...
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1answer
318 views

How to interpolate between these two points in time?

I have an image which is positioned at (x=0, y=177, scaleW=1.0, scaleH=1.0) at say $t_0$, and I need it to be positioned at (x=35, y=110, scaleW=0.65, scaleH=0.65) at $t_1$. How do I find keyframes in ...
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2answers
3k views

Why is 8x8 matrix chosen for Discrete Cosine Transform?

In JPEG and MPEG, why is 8x8 matrix chosen for Discrete Cosine Transform? Why not any other, say 64x64?
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1answer
462 views

Create Fisheye from image

I'm trying to modify a function to create fisheye effect on image (i use a software that permit to modify every single pixel of an image). At the moment i use this function: ...
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1answer
386 views

VQMT image blurring metric

I would like to know how the MSU - Video Quality measurement tool: here calculates the blur metric. What could be the mathematical computation to calculate blur? I want to do something similar in ...
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1answer
221 views

Given a point and a set of triangles, what's would be a fast way to find which triangle the point belongs to?

I'm trying to do a piece-wise affine transform in Python. I have one image with a set of points hand marked and another set of points where I wish to "move" my current points and the texture between. ...
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1answer
191 views

Trouble deriving the Harris Corner Detection

I just started studying a small paper about the Harris Corner Detection. The problem is I don't understand how step 7 is derived from step 6. In step 7 the expression is expanded in a way that we get ...
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3answers
1k views

find the rotation of one image with respect to other in MATLAB

I have two images. One is the reference image and the other is the rotated version of the reference image. I would like to find what is the angle by which the second image is rotated with respect to ...
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2answers
2k views

How do I apply a Gaussian Blur (low-pass filter) to an image made up from a set of points?

I have an image encoded in the form of a list of points, like so: ...