The image-processing tag has no wiki summary.
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2answers
35 views
intensity transformation 16-bit image to a 8-bit image
Give an intensity transformation function T for converting a 16-bit image to a 8-bit image, i.e. T takes an integer from {0,1,2,...,65535} and returns an integer from {0,1,2,...,255}.
Can we use $s = ...
0
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2answers
643 views
DFT and DWT difference?
what is the basic difference between the Discrete Fourier Transform and the Wavelet Transform ? and why does JPEG2000 preferred DWT over DCT or DFT ?
4
votes
1answer
36 views
How to solve cross-products including matrices?
I'm a programmer and I'm doing a whitebalance-transformation in RGB colorspace. This should work with this transformation matrix that I've found in literature:
$$
\begin{pmatrix}
R \\
G \\
B
...
1
vote
1answer
20 views
Scale Space - Scales and Octaves
So I'm desperately trying to understand scale space for signals, specifically for 2D images...
I'm having trouble with algorithms that discuss creating a pyramid. Specifically, I don't understand how ...
1
vote
1answer
78 views
Minimizing mean squared error
I want to find a $d$ that minimizes the value of the expression below. I think the first step is to find the derivative w.r.t. $d$ (is that correct? If not, what is the first step?). If so, I'm having ...
1
vote
1answer
51 views
Gradient of the image
I'm trying to make a gradient flow for an image. For a test I made a small image 3x3 pixels with a black pixel in the middle.
I found how to compute the direction of the gradient for one point given ...
0
votes
1answer
30 views
Confusion related to an edge detection filter
I was reading this article related to edge detection and here is a edge detection mask
-1 0 1
-1 0 1
-1 0 1
It's mentioned that this detector detects the edges ...
0
votes
1answer
59 views
Solving this image focal problem?
Suppose you wish to form an image of a 1cm wide object, 50cm away, on a sensor measuring 20mm. How can I calculate the magnification factor required and the focal length of the lens? I'm not sure how ...
4
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0answers
166 views
Reprojecting/converting an orthographic image/grid into a cartesian grid
I'm trying to dewarp a fisheye image into a simple rectilinear image of a subset of the fisheye. As part of this, I'm trying to map the azimuth/altitude values into a point on the image.
The points ...
2
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0answers
55 views
2-D DFT of a matrix PxP and 1-D DFT of a vector of size P^2?
What is the difference between the following two things:
make a 2-D Discrete Fourier Transform of a certain matrix A[p,p],
first reshape this matrix into a 1-D vector a[p^2,1], and compute the 1-D ...
2
votes
0answers
127 views
Lloyd-Max Quantizer Problem
Consider the function $z = x^2 + y^2$ , for $0 \leq x \leq 10$ and $0 \leq y \leq 10$. Take a regular discretization with steps $\Delta x = \Delta y = 0.1$ and its histogram as the probability ...
2
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0answers
46 views
Principal Component Analysis software
I'm looking for a (non-MATLAB) software that can process a image using the PCA algorithm and output it like this:
Regards.
2
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0answers
839 views
About Sum of Squared differences
I found a paragraph in the book about SSD, can't get one thing:
Most commonly, the distance measure is the sum of squared differences.
For two images f(x, y) and g (x, y) it is defined as
...
2
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0answers
124 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 ...
2
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0answers
45 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 ...
1
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0answers
14 views
Produce a 4:2:2 sub sampled Y matrix, Cr matrix, Cb matrix for an image
I have write the matlab code below for to extract Y, Cb, Cr information from the picture:
...
1
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0answers
88 views
Calculating the aspect ratio of the rotated rectangle on the image
I need to determine the aspect ratio of the rectangular object (such as mobile phone or credit card) on the image. The problem is that the object might be photographed from an angle or perspective. So ...
1
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0answers
161 views
image classification problem using Matlab?
I have an image classification problem. I have an image which spesify classes' labels using "imread" funtion of Matlab $(A=imread('r.bmp'))$ the output for example for 3 classes is as
$$A= ...
1
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0answers
141 views
Projection Slice theorem getting rid of artifacts?
I have employed the fourier(projection) slice theorem in matlab. I have a 3D image, P(x,y,z) defines their pixel intensities at a given location int he image volume, it is discrete and uniform. I ...
1
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0answers
97 views
What is the name of this color transformation?
This is a question regarding color transformation in images. I am not sure Math is the right place but I didn't see any site that deals with Image or Signal processing... I have this color ...
1
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0answers
74 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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0answers
30 views
Mymultiple image geometry
I have to work with multiple aerial images. the objective is to reconstruct 3d features.
For a particular object, i want to find the images which are giving good viewing geometry than others. so ...
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0answers
30 views
membership function and fuzzy classification
I want to implement
Convert an image into matrix.
Apply median filtering.
Decide the number and type of Membership functions for the input image by tuning the membership functions.
The ...
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0answers
13 views
What are the most Common Image denoising Algorithms?
I Read a article that states that the Gaussian Smoothing (Old) and Wavelet Method (new) are the 2 most used methods. Are there any other Filtering methods ?
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0answers
41 views
is the “hit or miss” transform really the “hit and miss” transform
I am learning about mathematical morphology, specifically binary morphology. I am learning about the Hit/Miss transform. As I understand it from wikipedia and this book :
the hit/miss transform is ...
0
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0answers
24 views
Wrap Using Delaunay triangulation in 2D
I want to create a Wrap using the mesh created by Delaunay triangulation [Ruperts Algorithms] ? Example By Pinning few Points and by moving others.Can you suggest Algorithms/Papers/Books Related to ...
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0answers
28 views
Weigh between nodes in an image using graph cut based segmentation
I read the piece of theory below in a lot of scientific papers:
...In graph theory a graph $ G=(V,E) $ can be partitioned into two disjoint sets: $ A,B, A \cup B , A \cap B $, by simply removing ...
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0answers
21 views
best way to estimate deviation of 3d line segments with respect to reference segments
I have set of 3D line segments derived in two different method. These line segments represent edges of several 3d cubs and polygons.
(1) first set of line segments are derived by doing field ...
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0answers
45 views
Limiting search space around line segment via rectangular buffer
I have 2D line segments extracted from an image. So i know end point coordinates of them. also, i have some reference 2d line segments. Both line segments are now in vector form. comparing to ...
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0answers
62 views
Can a matrix based “secret sharing scheme” be applied to image based secret sharing?
I was reading this and was wondering if it can be used to do secret sharing with images.
I dont know a lot about image processing, but if the authors have given a scheme for matrices, how can be ...
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0answers
72 views
Maximum absolute deviation
Let be I , J a two gray scale image How I will be able to interpret the Maximum absolute deviation between the histograms of these images?
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0answers
18 views
Correlation Zero mean?
Let be $v$ a vector with $N$ coordinates. If $E[v]=0$ I will be able to say that the elements of $v$ have correlation?
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0answers
53 views
Decorrelation KL transform property
Definition: The KL transform of vetor $\boldsymbol{u}$ is defined as
$$\boldsymbol{v}=\Phi^{*T}\boldsymbol{u},$$
where the columns of matrix $\Phi$, $\Phi_k$, are the eigenvectors of the ...
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0answers
27 views
Equalization Histogram
I am ready a book Fundamentals of Digital Image Processing. Here, consider an image pixel value $u$ to be random variable with a probabilty density funcion $p_u(\mu)$. Let be a image histogram ...
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0answers
25 views
Cosine Transform Ortoghonal Matrix
Let $C$ be the matrix with
$$c(k,n)=\dfrac{1}{\sqrt{N}},\text{ if }k=0,\ 0\leq n \leq N-1,$$
$$c(k,n)=\sqrt{\dfrac{2}{N}}\cos\left(\dfrac{\pi (2n+1)k}{2N}\right),\text{ if }1\leq k \leq N-1,\ 0\leq ...
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0answers
41 views
Energy Compaction and Variances od Transform Coefficients
If $\mu_u$ e $R_u$ denote the mean and covariance of a vetor $u$ and $v$ is a transformed vetor of $u$, using a unitary transform i.e $v=Au$. Then due to the fact that ...
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0answers
165 views
Distance between two objects in a picture
lets say I have a photo that has a picture on a wall and a book upright on the desk. now i know the size of both of these objects. I want to find the distance between two of them on the photo, I was ...
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0answers
66 views
Help me understand “Iterative Amplitude Adjusted Fourier Transform”
I am doing my final year M.Tech (Computer Science) project in Image Processing. I came across a method to remove non-linearity in the images by using surrogate images.
In order to generate surrogate ...
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0answers
135 views
Structure tensor of a function and the distribution of gradients
In computer vision, one often computes what's known as the structure tensor of an image. The structure tensor of a an image (i.e. a function) is a matrix that, I quote from Wikipedia.
"summarizes ...
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0answers
238 views
Circular to linear convolution with matrices
I know how to perform a circular convolution with vectors (http://engineering-matlab.blogspot.it/2010/12/matlab-program-for-implementing_5864.html) and I know that circular convolution can be obtained ...
0
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0answers
223 views
finding sample points of a curve in a MATLAB figure
I am trying to find the points of intersection between two curves in a .fig file of MATLAB. the first curve is constant but I need to change the second curve and find the points for different ones. It ...
0
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0answers
54 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 ...
