The image-processing tag has no wiki summary.
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15 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:
...
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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 ...
4
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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
...
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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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34 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 ...
2
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1answer
46 views
Unclear on relationship between different dimensionalities of Fourier transform
This is probably a silly question, but it's one that's directly relevant to a project of mine and I figured this was the place to go.
I have some objects that contain a 1d and a 2d array of double ...
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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 = ...
6
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1answer
133 views
A Mathematical way to represent a image kernel?
How to represent the calculation in this image mathematically?
For example: With the discrete convolution
and Fourier Transform.
It tries to do a calculation on the original image (image A/input) ...
2
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1answer
30 views
How to estimate orientation errors of an image with respect to known data (line features)
I think this is very simple but for me, it is confusing to figure out a way.
Here is my problem.
I have been given a 3d line segment list obtained from a field survey. So I know each end point ...
0
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1answer
37 views
obtainig a line 3D from multi view geometry
If I have been given multiple view images having known orientation parameters, then from a selected image line segment (corresponding line segments from each image) how could I compute a line 3D in ...
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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 ?
1
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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 ...
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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 ...
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0answers
25 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 ...
3
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1answer
182 views
SVD and how to get two points on a 3D line from the representation of the line by means of two intersecting planes?
I have a 3D line represented by the intersection of these two planes
$a_1x+b_1y+c_1z+d_1=0$
$a_2x+b_2y+c_2z+d_2=0$
I need to compute two 3D points $P_1=(x_1,y_1,z_1)$ and $P_2=(x_2,y_2,z_2)$ ...
1
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1answer
34 views
Evaluating the similarity of watermarks
I am working on an assignment where we have to use the NEC algorithm for inserting and extracting a watermark from an image file. Using the techniques described in this article. I am at the point ...
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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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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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1answer
169 views
How to use a graph cut
I have to use a graph cut to create a binary image from a grayscale image. I can easily compute both energy functions $E_{data}$ and $E_{smooth}$. But after that, I don't know what is the next step.
...
1
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1answer
82 views
Determining camera orientation (possibly using calibration images).
I need to generate a camera calibration pattern. Cameras are expected to be placed at an average height of 15 to 30 feet above ground pointing downwards at roughly 30 degrees. These cameras are ...
-1
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1answer
59 views
Limiting search space for efficient line matching [closed]
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 ...
1
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1answer
28 views
SVT algorithm and the value of tau.
SVT stands for singular value thresholding. It is an algorithm used in "matrix completion" problems. see http://svt.stanford.edu/ for basics.
What is the meaning of "for large values of [tau]..." ...
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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
63 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 ...
3
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1answer
72 views
Solving ill posed linear equations
Given a set of linear equations $AX=B$, say $A$ is an ill posed matrix (has a few singular values equal or very close to zero), which numerical algorithm (conjugate gradient, least squares or steepest ...
3
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1answer
351 views
Explanation of this image warping (bulge filter) algorithm
I've been researching image warping algorithms lately and haven't found many comprehensive references. That said, there are of course code snippets from GIMP, jhlabs.com, and imagemagick.org but none ...
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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 ...
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0answers
73 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
54 views
Decorrelation KL transform property
Definition: The KL transform of vetor $\boldsymbol{u}$ is defined as
$$\boldsymbol{v}=\Phi^{*T}\boldsymbol{u},$$
where the columns of matrix $\Phi$, $\Phi_k$, are the eigenvectors of the ...
2
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0answers
128 views
Lloyd-Max Quantizer Problem
Consider the function $z = x^2 + y^2$ , for $0 \leq x \leq 10$ and $0 \leq y \leq 10$. Take a regular discretization with steps $\Delta x = \Delta y = 0.1$ and its histogram as the probability ...
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1answer
31 views
Quantization Uniform
Let the output of image sensor take values between 0 to 10. If the samples are quantized uniformly to 256 levels, show that transition and reconstruction levels are
$$t_k=\dfrac{10(k-1)}{256},\, ...
3
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1answer
55 views
Iterative model fitting
I have a sequence of points $\{(x_k,y_k,z_k)\}$ and I need to fit some $2D$ model $P(x,y)$ that approximates $z$ in some sense.
The $z_k$$'s$ are noisy samples of some $2D$ function $z_k = f(x,y) + ...
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0answers
88 views
Calculating the aspect ratio of the rotated rectangle on the image
I need to determine the aspect ratio of the rectangular object (such as mobile phone or credit card) on the image. The problem is that the object might be photographed from an angle or perspective. So ...
1
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1answer
51 views
Gradient of the image
I'm trying to make a gradient flow for an image. For a test I made a small image 3x3 pixels with a black pixel in the middle.
I found how to compute the direction of the gradient for one point given ...
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0answers
27 views
Equalization Histogram
I am ready a book Fundamentals of Digital Image Processing. Here, consider an image pixel value $u$ to be random variable with a probabilty density funcion $p_u(\mu)$. Let be a image histogram ...
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25 views
Cosine Transform Ortoghonal Matrix
Let $C$ be the matrix with
$$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
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= ...
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1answer
40 views
Mean Square Error
I am ready the 101 page of the book [1], and I have a doubt. How I will be able to say:
If $\sigma=\sum_{i=1}^{L}\int_{t_i}^{t_{i+1}}(u-r_i)^2p(u)du=0$; where $u$ is a scalar random variable with ...
0
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0answers
42 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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2answers
105 views
Unitary Matrix for Image Processing
Why usually consider unitary matrices to define image transforms?
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1answer
69 views
What does it mean to convolve a matrix with a kernel?
I have a Matrix, M, of dimensions width x height. The problem is to apply the [-1, 0, 1] filter along the x and y axis (i.e. convolve the image with [-1, 0, 1] kernel along horizontal and vertical ...
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1answer
39 views
image recognition [closed]
Context:
I am writing code that needs to detect an objects borders with high resolution.
My Idea:
perform (Sobel/Canny/Gabor) on the image to get an edge map, and use that to get a new color ...
0
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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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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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1answer
200 views
any idea what fractal algorithm might generate this shape?
I Found this image around, and i'm curious what algorithm generates this kind of shape
In particular, i'm curious how the flow lines are generated, since usually the Mandelbrot iteration just ...
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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 ...
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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
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1answer
146 views
Point spread function (PSF) expressed as a convolution and a sum
The Wikipedia article on the Point Spread Function (link) discusses how an imaging system can be conceptually described using linear system theory. A convolution of the PSF with the image in the ...
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1answer
68 views
recovery plane from 4 point imaging using calibration camera
I have a camera and its K matrix (calibration matrix) also I have image of plane, I know the real points of the 4 corners and thier correspondence pixel. I know how to compute the H matrix if z=0 (H ...
