Read about image processing | 33 Discussions | Page 1

  1. Boltzman Oscillation

    How can I create an equation in matlab for image processing?

    Here is the documentation for the 2DFFT: https://www.mathworks.com/help/matlab/ref/fft2.html how would I go about creating this formula on matlab to apply it on an image? My guess is that I need to create the equation and then multiply it to the image I need such as: $$U = VI$$ where V is my...
  2. S

    Find the sampling matrix and sampling structure for R, G and B components

    Hello, everyone. :) All I could gather is that, if I'm correct, lattices are spans of the column vectors of the matrix within the "LAT()" notation and the X and Y occurrences are unit placeholders (such as the pixel unit (since this is in the context of image processing)). And, as an attempt...
  3. A

    MATLAB Bilinear spline interpolation MATLAB using MESHGRID and SURF

    Hello. So, I must provide a solution for an image processing course I am taking (implemented in MATLAB). The task is as follows: 1. I must provide a MATLAB script that takes in a DISCRETE N x N matrix (Greyscale picture) and does Bilinear spline interpolation on it. This is the spline...
  4. O

    Java I need help about how to get a pixel value in Java

    Greetings! Hey guys, I need help on how can I get pixel value of an image with pixels more than 100px (10x10). Here the code that I execute in order to get the pixel value try{ File f = new File ("input image location"); BufferedImage img = ImageIO.read(f)...
  5. M

    I How does the inverse square law apply to a focused detector?

    I am interested in evaluating light intensity variation in a digital image. A colleague wants to apply an inverse square law correction to account for distance variation. I am trying to justify that in this case, the inverse square law does not apply. Treating each pixel as a detector, it has...
  6. T

    MATLAB High pass filtering FFT2 matlab

    I am having a slight issue with my code and honestly cannot understand what I am doing wrong. I am currently trying to using a high pass filter in the frequency domain to form the following image. So my approach so far after numerous of attempts which I wont list as I believe I am on the...
  7. F

    I Maximum Likelihood to find the original data or estimation directly

    I make confusions in the using of Maximum Likelihood to find (approximately) the original signal knowing the data observed and the using of Maximum Likelihood to find estimations of parameters of the PSF 1) Find (up to some point) the original signal : I start from this general definition (in...
  8. T

    I Informational content in 2D discrete Fourier transform

    When you do a discrete Fourier transform (DFT) of a one-dimensional signal, I understand that the second half of the result is the complex conjugate of the first half. If you threw out the second half of the result, you're not actually losing any data and you would be able to recreate the entire...
  9. R

    I 2D Fourier transform orientation angle

    The orientation of frequency components in the 2-D Fourier spectrum of an image reflect the orientation of the features they represent in the original image. In techniques such as nonlinear microscopy, they use this idea to determine the preferred (i.e. average) orientation of certain features...
  10. Raazi

    Medical Content based medical image retrieval using barcodes

    Hi, I am doing research in content based image medical image retrieval using radon barcodes. I have replicated an approach found in this paper 277011226_Barcode_Annotations_for_Medical_Image_Retrieval_A_Preliminary_Investigation. I have tried to make some improvements to this process regarding...
  11. Avatrin

    Python Working with PNG images in Python

    Hi I have to run a few algorithms using Python on PNG-images. However, I also know that PNG is compressed... How do I do this? I need to learn the following: 1: Extracting the RGB information about the pixels. 2: Isolating parts of the image (for example, importing an image and only working on...
  12. J

    MATLAB Highlight an object in an image?

    Hi Everybody I'm a new user and hope I have posted in the correct section. I'm a beginner in matlab and image processing. Using matlab, I have to highlight in an object in an image. I have an input image where there is a plate with a food. I need to produce an output image where only food is...
  13. R

    Frequency domain filtering in Matlab

    I am trying to implement several filters in Matlab for Fourier domain filtering. They are the cosine, Shepp-Logan, and Hann/Hamming window filters. These filters are defined as multiplying the ramp filter by the cosine function, sinc function, and Hann/Hamming windows respectively. This is how...
  14. E

    I How to do the Dark Frame Subtraction? (camera imaging)

    I have an image with uneven contrast. Now to correct the image, I need a dark frame to remove the noise inherent to the sensor or to the camera itself. How can use the dark frame into the image? I have been searching the net but most of them use photoshop or similar softwares. How can I apply it...
  15. B

    How to convert all pages of a pdf into A5?

    I have a PDF file in which different pages are of different size because I made it up from images of different sizes. For printing purpose I want all the pages to be of A5 size, How can I do that ? Sorry if this is silly but I have no experience in working with PDF, this is the first time I...
  16. M

    How to interpret a complex Matrix as a Probability Matrix?

    Hello everyone, I'have implemented a Maximum-Likelihood-Expectation-Maximization Algorithm in order to reconstruct a bild. let say, we have such a system Ax=b, where A is a complex matrix, b is a complex vector. A and b are known and we will iterately try to find the best x (which should be...
  17. E

    I Horizontal Noise Stripes in an Image

    What are the possible causes of the horizontal noise stripes in this image: http://dsp.stackexchange.com/questions/20061/removing-periodic-noise-from-image-using-fourier-transform I'm currently studying on these kinds of noise, and how to eliminate them. Can these be caused by diffraction...
  18. G

    What is the basis for bessel function as we have for wavelet

    Hi, I have recently studied about basis for wavelet function which is helpful to design any function. Likewise, what is the basis for bessel function and how can it be implemented for an image ( because image is also a function). Specifically, I am interested to know how bessel function can be...
  19. L

    I Why is the Fourier transform of a sinusoid assumed as this?

    Hello everyone. I'm trying to better understand structured illumination microscopy and in the literature, I keep coming across bits of text like this. Source: http://www.optics.rochester.edu/workgroups/fienup/PUBLICATIONS/SAS_JOSAA09_PhShiftEstSupRes.pdf From Fourier analysis, if I take the...
  20. stalin

    Why shadows become dark when light intensity increases?

    I observed following phenomena today: in my room with some lightings, there is a stuff toy placed in front of a wall. The ambient lighting doesn't cause any shadow on the wall currently. Now, I switched ON a torch and pointed it to a stuff toy which was kept in front of a wall and a shadow...
  21. E

    MATLAB Image Processing and MatLab (Deconvolution Process)

    I have these two images: And I have this impulse response function, or the point-spread function (PSF): The first image is the actual size of the PSF, and the second image has zero pads included. I tried deconvolving the images this way (with MatLab): deconvolved_image =...
  22. E

    Shape Detection and Recognition

    How can I detect shapes in an image using an algorithm? I have heard of using edge detection and from there the shapes can be identified, but how? Also, edge detection only is effective if the shape has a high difference of contrast from its surrounding area, what would be an effective technique...
  23. B

    MATLAB Want gray scale image of a matrix in matlab

    I am creating a gray-scale image of a 2000*2000 matrix using mat2gray and imshow command.But highest number of matrix entries that imshow can implement is 500*500 approximately.After that it shows------ "Warning: Image is too big to fit on screen; displaying at 8% > In...
  24. E

    Fresnel Relations and the Sensitivity of a Camera

    Reflectance, according to the Fresnel Relations, is given by ##R \equiv \frac{I_r}{I_i}##, and Transmittance is ##T = \frac{I_t \cos \theta_t}{I_i \cos \theta_i}##. Do these values depend on the wavelength of light? For example, if I have a beam of white light rather than a monochromatic...
  25. R

    MATLAB Single vehicle tracking using Fourier transform-MATLAB

    I am working on a project which is based on importance of phase only reconstruction of a signal obtained from fft. Now ,I have detected vehicles from the Video of Traffic on road taken using stationary camera ( Please download the 1.47 MB video for testing MATLAB Code by ( step1) click on the...
  26. R

    Algorithm to compute Basis images of an image

    I know from the Fourier Analysis that any signal can be represented as summation of elementary signals i.e. basis functions .Likewise,any image can be represented as summation of Basis images. Is there any available code, or even an algorithm, that would allow me to compute Basis images of an...
  27. R

    How to find phase values at neighboring pixel in an image?

    I have computed magnitude and phase spectrum of very famous image of cameraman using fft function in MATLAB.Here,we get magnitude and phase spectrum of the whole image. But I want to find phase values of the neighboring pixels . So if given gray scale image is of dimensions 256*256 and if I...
  28. R

    Puzzle to puzzle you:image

    Suppose 3 1D Signals x(t), y1(t) and y2(t) are given as x(t)=sin(40*pi*t); y1(t)=.5*sin(40*pi*t) and y2(t)=x(t)+y1(t). Left side =Right side Here,values of x(t)and y1(t)i.e.(Right side) are given and we get y2(t)(Left side).The plots of x(t),y1(t) and y2(t) are plotted below...
  29. R

    Fourier Decomposition

    Hello everyone have a look at this video of Fourier Decomposition of an image.also we know that Fourier series is given in the image as...
  30. R

    Fourier maths behind an image

    I am beginer in image processing. Any signal whether it is 1D,2D or any multidimensional signal can be represented using combination of number of sine and cosine waves.Similerly any image can be termed as a sinusoidal function. Fourier series and transform plays vital role in image processing...
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