Questions tagged [image-processing]

In general, image processing is any form of signal processing for which the input is an image, such as a photograph or video frame.

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Building a spatio-temporal filter

I want to implement a spatio-temporal filter for my images which are a set of silhouettes of a cycle of walking. So I gather all the images in an array and convolve the 3D array with my spatio-...
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How do you apply DCT steganography on an RGB image?

I am working on a DCT-based steganography program in Python and I found a working model in Github. The program, however, can only encode on one of the RGB channels. Resulting in a discolored image. ...
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The application of sparse Fourier transform

I try to understand the concept of sparse Fourier transformation, I can summarize it according to what I understood as following: Assume we have a sparse signal $x$ of size $N$x$1$ with only $k$-non-...
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3D reconstruction of moving object

I am pretty new to the field of 3D reconstruction and overwhelmed by the large amounts of different methods. I am trying to find the correct method for my use case: Setting: I have a stationary ...
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On the channel estimation based on vector

I have a matrix $X$ of size .i.e $(8,8)$ with $M$ columns and $N$ rows. Suppose I took it's $iFFT$ column wise resulting matrix $x$ of size $(8,8)$ too, $x = F^HX_{(:,m)}, $ ...... (1), where ...
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Calculation of derivative projection of differential Radon matrix

I am trying to write a matlab code for finding the differential Radon Matrix. . Above are formula for Radon Transform and differential Radon Matrix . What I get is the formula for Radon Matrix <...
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Looking for a good implementation / API for the radon transformation in C/C++

I am currently working on a project about Metal artifact reduction (MAR) for CT images. I am looking for a good implementation of the radon transformation and a backtransformation, ideally filtered ...
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Maximally Stable Extremal Regions (MSER) Implementation in Document Image Character Patch Identification

My task is to identify character patches within the document image. Consider the image below: Based from the paper titled "CG-DIQA: No-reference Document Image Quality Assessment Based on ...
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“removing” parts of an image with matlab

for an assignment, I'm supposed to work with matlab, with the image below. The task is to convert this image to a grayscale version (which wasn't a problem) and then to alter the image with imadjust ...
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Why is my Fourier descriptor not rotation invariant?

I am trying to implement a simple contour based Fourier descriptor to classify some MNIST images. Nothing fancy. As expected, if I discard the first coefficient, I achieve translation invariance. ...
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DFT vs DCT Discrete transform

The discrete Fourier transform transforms a sequence of $N$ complex numbers $x_n := x_0, x_1, . . . . x_{N-1}$ into another sequence of complex numbers $X_k := X_0, X_1, . . . . X_{N-1}$ , which is ...
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How does PIL.QUAD work internally?

I am working on a computer vision problem involving some basic transformations and could use your help. Input image: Transformed image I understand that we take this quadrilateral and tilt it and ...
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How to Generate Sensing Matrix with Variable Probabilities on Fourier Domain?

Recently, I found a good resource of Compressed Sensing applying on MRI, Michael (Miki) Lustig - Compressed Sensing MRI Resources. The variables "pdf_unif" and "pdf_vardens" store the probabilities of ...
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Whats the Correct Approach to Estimate the PSF of a Moving Detector

In lab, I did a bunch of scans using a radiation source and a detector. My source emits a gaussian beam (whose dimensions I know), and my detector is a uniform 7mmx7mm square. These are stationary and ...
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Signal reconstruction using discret wavelet

I am doing a discrete wavelet transform on a Lena.bmp image using the code ...
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How do i calculate the accuracy of an algoruthm?

I'm doing research on an machine learning image processing algorithm (segmentation algorihtm)i.e. computer vision performs when an image takes as an input and objects in an image are segmented and ...
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342 views

Spatial wavelength

I was reading a paper on motion magnification, Eulerian Video Magnification for Revealing Subtle Changes in the World by MIT CSAIL researchers, where the equation (14) of the paper uses spatial ...
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54 views

How to perform dot annotation for crowd counting in a image file using Matlab?

I have some crowd images having more than 300 people in each image. I want to label each person(i.e. head) with dot annotation such that coordinate of each dot(x,y) is saved in a .mat file. I hope ...
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Image processing for camera health monitoring

I have a set of cameras. I would like to monitor the output of the cameras to make sure they are operating well. So far my ideas: standard deviation and the mean of the picture - to find out if the ...
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Unexpected Results in Rank Transform Based Disparity Estimation

I am applying a normal rank transform of size 7 x 7 to the right/left shifted images in order to obtain their disparity map using a typical block matching algorithm in MATLAB. My code to obtain to the ...
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22 views

remove outlier spectra

I have a set of spectra (hyperspectral imaging) per class (~10000) and want to remove those spectra which behave different then the mean of the spectra. I want to remove the entire spectra (not ...
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Flat Field Correction - When images are taken at different exposures

The light source I am using is known to have a Gaussian intensity distribution along the height. I took the raw images at "x" seconds of exposure. However, while taking the bright field image, the ...
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64 views

What is the “bilinear interpolation kernel” in personlab paper?

please excuse my ignorance in computer graphics, but what is this bilinear interpolation kernel in the personlab paper page 6 equation (1)? Here it is: $$ h_k(x) = \frac{1}{\pi R^2}\sum_{i=1:N}p_k(...
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62 views

What is the difference between an image plane and a virtual image?

I have the following diagram that describes a camera model (I believe it is the pinhole camera model). Wikipedia has an article about the image plane and virtual image, but these articles do not ...
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23 views

How to estimate the frequency of a feature in an image?

I have a background in the 1-D signal analysis but I am totally new to image analysis. I would appreciate any help. Given the following original image and the downsampled image, as you could see, ...
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94 views

RMS contrast of image interpretation

I have two grayscale images, say A and B, and I want to determine, which one is more contrast. For that I'm calculating an RMS contrast as it is described in Wikipedia. The results are about ...
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Dirty Image Quality Assesment Measure

I was looking for a way to measure how dirty is the document in image processing. Example images below: a. Dirty Backgrounds b. Dirty Backgrounds with Text Can someone give me an initial idea to ...
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Wavelets: Manipulate its phase and reconstruct

Usually when I read about wavelets in image processing, the authors tend to make use of its coefficients and rebuild based on certain criteria, for example de-noising an image where you usually filter ...
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1answer
34 views

Producing images with subpixel shift in region of interest

Let's say for a zebra image, and at certain pixel location, I would like to makes it "vibrate/warp" to and fro in horizontal direction at a certain frequencies in a sequence of images of time ...
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Create 2-d Dirichlet kernel for use in image processing

I am working on frequency domain CNNs for image classification task, in which I initialize complex kernels of size (k*k). For performing point-wise multiplication between the kernel and the Fourier ...
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Adaptive threshold value transformation based on brightness

This is the homework of my son: My wife gets such images taken with a mobile phone form other mothers, whenever my son misses a lesson. She can not print those images, because they are almost black, ...
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1answer
36 views

Identifying the boundary points of a shape based on the centroid

I have a set of binary 2D images with objects in white and their boundaries in black (attached example). I also have a list of centroids (x,y coordinate pairs) identifying all objects. For each ...
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41 views

Frequency contour detection in spectrogram

I have an image of a spectrogram and I wish to detect the tracks/contours of prominent frequencies present in the spectrogram. In the end, I want to be able to get various prominent curves from the ...
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Fast Document Enhancement

I followed Dropbox's blog - Fast Document Rectification and Enhancement To enhancement image, I need solve this formula J(x,y) = gain(x,y) * I(x,y) + offset(x,y) Where J is image after ...
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Detecting and Recognizing a pattern in the 2D-FFT

More theory before I ask a practical question based on the task I have. I've discovered that performing a 2D-FFT (python or matlab implementations) on some test imagery I have results in a unique ...
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Image Transformation Functions to Identify if the Text in the Document Originally There or Just Synthetically Overlaid

I have a copy of scanned ancient dirty document and synthetically generated ancient dirty documents. I want to use Discrete Cosine Transform to characterize noise types existing in the document and ...
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Parameters for inverse image distortion

I'm trying to simulate camera (barrel/radial) distortion, and to reverse it. I.e. a process that would do: Image --> Distorted Image --> ~ Image In ...
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Grading Images According to the Noise It Contains

I have collected a lot of dirty blank pages and each image is varied in the noise it contains. How will I grade images according to the noise it contains in terms of amount, and other aspects? What ...
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Overlaying A Distorted Text According to its Background

I have several dirty background images, sample image is below: I want to overlay a text on it but I want the text to be as distorted as the background. Example, if the background is a bit wavy, I ...
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Image classification in c

i have to do a project for university which is basically to program a tool to classify small greyscale images like those below into person or non-person, in C. The project is scheduled for around ...
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Measure that Compares an Actual Old Document from a Synthetic Old Document

I have collected dirty background images, below is the sample: I have also a collection of an actual image of a dirty document with text on it, just like below: My problem with my actual image of a ...
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24 views

Reconstract the image from the modulus of its Fourier transform

In Reference, it is shown than one can recover the image by using only the modulus of its Fourier transform. It provides two iterative algorithm which is really similar to Gerchberg–Saxton method. ...
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Image extraction post processing to increase similarity

I’m trying to train an OCR model, but I need to get my extracted images to look more like the training images. However I’m not sure of how to go about it and what techniques I can use. For instance ...
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How can I get better results from Phase Correlation

I am using Phase Correlation to register 3D data. There's a clear distinction in the y direction so the resulting shifts seem to be correct. But since there is a lot of similarity in the x direction ...
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60 views

Licence plate enhancement

Is it possible to enhance the image below and make it more readable? I have tried apply binarization but there is some kind of shadow. So I have tried to convert image to gray scale and then ...
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How to calculate linear index of fuzziness of an image?

i am trying to calculate linear index of fuzziness of an image using this formula: i have to see a positive value according to the paper. But i see a negative value, so i think i am doing something ...
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Could anyone explain the sliding factor and min neighbours aspect of the Viola-Jones detection?

I'm looking at code that has a scale factor of 1.1, presumably meaning it's being increased by 10%, what are the advantages of this? Secondly, I don't understand what minNeighbors actually mean and I ...
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How to improve interpolation for chroma upsampling (4:2:0 to 4:4:4)?

I am trying to perform the best possible interpolation in order to perform proper chroma upsampling from 4:2:0 YCbCr to 4:4:4 YCbCr. I have implemented the improved interpolation proposed at this ...
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Infrared image dataset for enhancement?

I'm working on near infrared image enhancement. I'm searching for low-contrast images. Example image is below.
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Creating a combination of extrusion to a point, and motion blur

I am attempting to generate a effect that allows me to use original color of image, but also mimic a pinched extruded 3d surface from orthographic view. To do this, I used the G'MIC-QT scripting ...

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