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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230 views

Log energy and Shannon entropy?

For best tree decomposition using wavelet packets, i have tried both Shannon and log energy entropy functions. I noticed that log energy leads to images with higher PSNR values. Could you please help ...
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40 views

Why use Active Contours segmentation (snake) over Level Sets segmentation and vice versa in image processing?

I am reading about segmentation and I cannot seem to figure out why use active contours over level sets and vice versa. Basically the way I understood it, level sets is relatively the same ...
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50 views

Impact of Interpolation Types in Image Filtering (Laplacian Pyramids)

I am trying to construct Laplacian pyramids with different interpolation schemes such as bilinear, nearest neighbor, cubic and spline to observe the effect of interpolation types. I wrote a code in ...
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44 views

sharpness in DCT domain image

How can we calculate the sharpness of Discrete Cosine Transform domain of an image?Is it worthy in image quality assessment?
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What is the relationship between luminosity of Lab color space and intensity of HSI color space?

I am wondering whether one can simply convert the intensity of a color in HSI space to the luminosity value in Lab space. I am referring to te CIELab color space as discussed here: https://en....
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41 views

zernik moments and Local binary pattern

Both of zernik moments and Local binary pattern (LBP) are feature detectors and can achieve rotation invarient. How can they achieve rotation invarient over an image? What are the advantages of ...
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why double desity DWT use two HPF?

The double-density DWT is an improvement upon the critically sampled DWT with important additional properties: It employs one scaling function and two distinct wavelets, which are designed to be ...
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363 views

SSIM index: Clearly explained

I am trying to understand the SSIM index to compare two images for similarity, but I am having difficulties understanding how it is done. Therefore, I would like to ask, if someone can explain it ...
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51 views

Low pass image filter

I have feature in my camera that indicates "Low Frequency Flat Field correction" and I want to evaluate its impact on the image. How can I do this? Currently I can only take pictures of a uniform ...
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77 views

Obtaining Subpixel Resolution for Video Processing in Python

I am working on a video processing application to calculate distance between two points using opencv Specs : Linear Pixels - 1600. FOV - 100 mm Resolution per pixel using above data : 62 micron ...
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49 views

Cartoonize and colorize

I'm trying to make a specific image filter, processing a picture to cartoonize and change the colors. Here you can see the original and the expected result: http://codingfocus.com/ieffect.jpg I'm ...
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435 views

Removing bright lights from image using Matlab

I want to remove a bright spot in an image. This is the image I used: and this is the Matlab code I wrote: ...
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191 views

How to remove artefacts from this image?

There is some vertical banding near the tree trunks in the following image. Is there a way remove this type of artefact, preferably using Mathematica?
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1answer
93 views

Normalization of signal against reference

I am trying to figure out if there is any standard way of normalizing a sequence such as a time series against a reference sequence. I am not an expert on signal processing but I was hoping someone ...
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35 views

Removing uncommon objects from bunch of images

The problem I am facing is the following: I want to take a picture of the entrance to a building. I fix the camera on a tripod stand and place the stand on the footpath in front of the building. The ...
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269 views

What is a segmentation mask in the paper “Fast Edge Detection Using Structured Forests”

I've read the paper about edge detection, in this paper they treat edge detection as a learning problem which takes an image patch as input and output a label, a binary edge map or a segmentation mask,...
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38 views

Finding Patch Offsets in an Image

I have an image in which I am trying to find the statistics of the offsets for 8 x 8 patches that are taken by sliding them pixel wise. To be more clear, what I do is I take a patch and try finding ...
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59 views

Images similarity measure using j-divergence

I need to reproduce the result of Xu, Xiaocong, et al, 2016 paper . Mutual information code already was done and work fine. can anyone help me to write Jeffrey’s divergence code? because the I use ...
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43 views

Offset Wall Color From Reflected Image

I have a movie projector which is projecting an image on a brown wall. The projector allows me to adjust 6 values. Red brightness, Green brightness, Blue brightness. Red contrast, Green contrast, Blue ...
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328 views

OpenCV denoising a 3x3 pixel pattern noise

This picture shows two photos captured by a camera from a black photographic paper. The cross is marked by laser. The left one shows a 9 pixel pattern of noise. This gets in the way of auto-focus ...
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75 views

Edge linking by adaptive mathematical morphology

I'm trying to implement the Adaptive Morphological Edge-Linking Algorithm (Frank Y. Shih, Image Processing and Pattern Recognition: Fundamentals and Techniques, section 5.5.2 OR Article link). The ...
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25 views

Recognize irregular repetition of unknown feature (stamps at random locations)

I have an image which is generated by convolution between (1) a simple small patch and (2) larger image composed of localized point-like features (e.g. slat-and-pepper noise, sum of shifted $\delta$-...
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63 views

Image feature extraction for discrimination

I am using linear/quadratic discrimination to guess who is the artist of a painting. All the images are RGB format and I use matlab. I have used both original image and images that are resize to be ...
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79 views

Neural Networks for rotated character (or shape) recognition

I have built a program that recognizes shapes and characters, using Neural Networks. Now, one of the main requirements of the task is that the program can recognize them regardless of rotation or ...
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87 views

Dot or point pattern recognition for Braille Paper

we are very new to image processing field. We are gonna do a study about braille to text conversion, by the way braille is a method of writing for blind. !(https://fryemuseum.org/images/...
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423 views

Filter image in Fourier space imaginary components after ifft (R)

I want to high-pass filter an image in Fourier space. It works but the retransformed image has an imaginary part, what shouldn't be the case http://math.stackexchange.com/questions/867337/how-to-...
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249 views

VLFEat: How to extract the SIFT descriptor without SIFT feature detection?

I am using the MATLAB interface to the VLFeat toolbox in order to calculate a SIFT descriptor for image patches extracted around key points. Due to the greater framework of what I'm doing, I cannot ...
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98 views

Shot boundary detection using SVM's

I'm trying to do shot boundary detection using SVM's. I'm differentiating between 3 shots, cut, fade and dissolve + (normal frames). I had used two features, shannon's entropy and variance, it gave ...
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69 views

Position vector of Lukas-Kanade optical flow algorithm

The classical optical flow equation by Lukas-Kanade can be simplified as follow: $$ \frac{\delta I}{\delta x}\triangle x+\frac{\delta I}{\delta y}\triangle y + \frac{\delta I}{\delta t}\triangle t=0 $$...
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is there upper limit on averaging window size for images?

An amateur question. I take an image and average pixels over a window 3 by 3, thus obtaining a smoother image. Then I increase the averaging window size - obtain an image with even less details, but ...
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2k views

Image preprocessing for facial detection->embedding->clustering pipeline

I am trying to implement an end to end pipeline for facial clustering so that it can group people with the same faces. This will be quote a long post as I know that this is a very broad topic, so I ...
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46 views

Get slopes of integer shift of an image in radians

I tried to reproduce the result from this paper, However I'm stuck at the Section III of the paper which involve integer shift. Two images which their phase correlation $\theta(k_1,k_2)$ was ...
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499 views

Intensity Transformation using Fuzzy sets

I'm doing a project on intensity transformation using fuzzy sets. In the book Digital Image Processing by Rafael C. Gonzalez. The author says this Consider the general problem of contrast ...
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363 views

Difference between Gabor filters, Gabor wavelets and Log-Gaber wavelets

I am a beginner in the field of image processing, and I am trying to understand Gabor transform but the more I read, the more I get confused. So I wish to find someone who can help me answering this ...
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1answer
219 views

2D DWT computation order

In 2D the discrete wavelet transform (DWT) of an image using lifting based 5/3 filter, if I perform a row-wise operation first then perform column-wise operation then I will get 4 sub-band LL, LH and ...
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59 views

Locate first minima in signal

I have many datasets which all looks roughly like this: All the datasets have this in common. First there is an artifact around 0 with an unknown (but likely very high) intensity. Then there is some ...
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1answer
246 views

How can I properly detect a ball moving in a film capture?

I have problem in detecting a ball moving in a flume (image below). since converting the frames into grayscale format didn't work I converted it into rgb and make it more saturated. problems are: 1- ...
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1answer
775 views

How to get the scale bar of an FFT for a 2d image

I've been analyzing some images from a transmission electron microscope, including their FFTs, and I'm not sure how to apply a scale bar to the FFT images. I have calibrations for the real space image,...
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60 views

Watermark insertion process in image

I'm new in the field of image processing and I'am trying to implement a watermarking algorithm (for medical images in DICOM format) based on this paper. As written in the paper, this algorithm is ...
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87 views

Image Processing: 360x180 panorama from discrete images

I'm coming from math as I was told that this would be a more fitting place for this question. For the last few weeks, I have been trying to create a full 360°x180° spherical panorama from distinct ...
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382 views

Gaussian Mixture Model-UBM based for image recognition

Scenario: Open set recognition: Unknown individuals may appear on scene (CCTV). Gallery = 10 individuals with a mug-shot image per individual. Approach: Gaussian Mixture Model-UBM based Use video ...
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1k views

Line Detection with OpenCV

I'm trying to use the native functions of OpenCV HoughLines and HoughLinesP to detect the lines from an image. The Canny edge output of that image is the folllowing: The problem is that the OpenCV ...
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103 views

Extrinsic Camera Parameters without introducing control points?

I am new to the field of Camera Calibration. We have successfully calibrated our camera through classic method (using checkerboard etc). I recently realized there is a field of research for Automatic ...
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132 views

Wiener filter with no WSS process

I'm trying to learn something more about Wiener Filters and I can't find anywhere what happens when I feed a Wiener Filter with a non WSS process. Could anyone give me an explanation or any book (...
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2answers
2k views

Binarization of image for varying background and foreground colors for OCR

I am trying to develop an automated OCR system for images obtained from the internet. The images mostly consist of computer generated text imposed on a background, so the OCR should produce near ...
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229 views

Image Segmentation based on coordinates from reference points

I have a set of colors in a card, as below (I can modify the card as required) I have 4 reference points at four corners. I have a bunch of colors at known coordinates (in mm) from these reference ...
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124 views

Fast greyscale image segmentation on 16x16 image

I have a 8-bit greyscale 16x16 image where I want to extract coherent shapes with a more or less consistent pixel arrangement if possible (like: a rectangle, staircase, line). Currently, I'm doing ...
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2k views

Measuring sharpness/contrast for autofocus

For the implementation of an auto-focus for the raspberry cam I need some measure of image sharpness. I used the following sample picture: The first approach was to compute the shannon entropy of the ...
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81 views

Anti tremor motion detection

I'm programming in c# using opencv (emguCV). I use motion detection approach to detect some changes in a paper wall. For example it's may be colored by a laser pointer. My problem is that when I use ...
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94 views

Target detection for UAV landing

I would like to detect and track the following target to land an UAV. Target size is $1\rm m \times 1\rm m$. I have tried SIFT + FLANN but there is too few keypoints to have a good match. Have you ...

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