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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How does image masking work?

I am new to image processing and I am interested how image masking can be used to extract a portion of a image. Have a look at this OpenCV tutorial. In the section Application of Mask, they say that ...
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How to properly detect segments in a LCD segment display

I have been given the task to develop a code which checks if the display of a device is showing information correctly (i.e. any segments are activating when they are not supposed to). To meet this ...
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Web Online tools for feature detection methods in image processing

I'm doing a research about image processing, I would like to access common feature detection methods online, ex: Blob detection: Laplacian of Gaussian (LoG), Difference of Gaussians (DoG), ...
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Edge linking using local processing - why is this criterion imposed

I'm reading Digital Image Processing by R. Woods and R. Gonzalez. In it, a section on edge linking using local processing in an image details a simplified algorithm, that imposes a criterion on the ...
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Classify areas of an image based on color

I have some tree canopy images that I would like to process, but not sure how to get started as image processing is a little outside my area of expertise. Any help would be appreciated. I have tree ...
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152 views

What is the image power law?

What exactly is the image power law mentioned at page 15 in here: Is it related to Gamma correction or the statistical power law Or anything to do with PSF of a camera?
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272 views

Haralick features, am I approaching this correctly?

I'm trying to personalise a custom CBIR by adding more features not only based on colour, but based on textures' features. What I don't know is if I'm approaching this well with Haralick's features. ...
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3k views

Is it possible to have negative PSNR?

I have been working on image processing. I have an image and then add it a Gaussian noise with standard deviation=0.005. then using averaging filter to denoise it (I know it is not a good idea). then ...
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435 views

Efficient Hessian-Laplace blob detector implementation

As it is mentioned in a paper for SURF, it is possible to approximate hessian determinant using integral images. If I want to implement Hessian-Laplace detector, is it feasible to also approximate ...
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Horizontal banding (flickering) due to electronic rolling shutters

It is a well-known artifact that in CMOS cameras with electronic rolling shutter, horizontal banding (flickering), i.e. brightness intensity variations, are observed when the image is recorded under ...
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Normalized cut segmentation output correct or not?

I have implemented "normalized cut" segmentation. The change here is that, instead of giving an image as input, I have given an matrix of image. As my output looks odd to me. I need to know whether my ...
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MPEG-7 descriptors' implementation in OpenCV

I'm looking for implementation of MPEG-7 descriptors which are compatible with OpenCV's recent versions and containing "region-based shape descriptor ART(Angular Radial Transformation)". I ...
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103 views

How to quickly calculate all the line segments when their coordinate in the Hough transform is given

Hough transform is a very powerful tool to find dominant straight lines in a black-and-white image. A very common practice of analyzing Hough transform result is to find some local maximum points in ...
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219 views

Realtime image-stitching using a CMOS camera array

I am very new to DSP so please excuse any brevity... I have to design a 4x4 CMOS camera array and stitch the images together for further processing... I have tried doing that with opencv but the ...
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2answers
314 views

Anisotropic Diffusion Filter - Intuition Behind Parameters

I need to know what is iteration and divergence in anisotropic diffusion filter technique. Isotropic diffusion $$\frac{\partial I(x, y, z)}{\partial t}={\rm div}\left[c\cdot \nabla I\left(x, y, ...
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164 views

Region growing Vs Clustering

In image processing, how do region growing and clustering differ from each other? There are many papers like clustering based on region growing. I couldn't able to draw a fine line between these two ...
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Artifacts in image after super resolution using delaunay triangulation in MATLAB

i have to do super resolution of two low resolution images to obtain a high resolution image. 1st image is taken as base image and the second image is registered with respect to it . i used SURF ...
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252 views

Landmark Extraction via Kinect

I am working on a SLAM algorithm as part of my research and I am having issues reliably extracting landmarks from sensor (Kinect) data. (I've never dealt with machine vision before.) I am looking ...
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1answer
246 views

Image watermarking in wavelet domain (data hiding in images)

I am working and researching on Image watermarking/steganography and I'm stuck at a point and want to know which technique is better in image processing for data hiding. Bit Plane Complexity ...
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Phase of an image in the frequency domain

The following picture is amplitude and phase of an image filtered using Gabor filter in the frequency domain. I'm trying to reproduce the results, I'm getting valid results for the amplitude I think, ...
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40 views

Finding areas covered by features

I have an image as attached The blue to yellow to red points are the points of interest the algorithm found, while the pink points are the radius per point. This maps pretty fine, but the issue I am ...
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175 views

Affine detector + SIFT descriptor

I am approaching to the Oxford Buildings dataset which contains already computed SIFT descriptors from affine detected keypoint locations. Usually SIFT detector provides to its detected keypoints ...
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1answer
1k views

Finding circle in binary image (R, not matlab)

How would I go about extracting the circular area of a binary image which looks like: The two rods emerging from the side of the circle are noise. I know of the hough transform in Matlab. However, I ...
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Could someone please explain to me about Directional Filter Bank?

I'm learning about Directional Filter Banks for my Thesis about Image Enhancement. I read it from some papers (Bamberger(1992) and Park(2004)) but I still cannot understand it clearly in detail. Could ...
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Compare luminosity beetween groups of images

We have a set of images which are immunofluorescence stainings of mice brain slices. These image show the expression level of a marked protein. We have two groups of mice, which underwent behavioral ...
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752 views

Why do object-boundaries look better on a badly rectified image?(openCV stereo correspondence)

I got 2 pictures which is almost parallel, and not positioned very far from each other. I'm using OpenCV to try to create a disparity map (Stereo correspondence). Because I'm trying to use it in a ...
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104 views

Phong Reflection Model Parameters

Question: Can anyone refer me the Phong reflection model parameters for a face image taken for web-cam? Details: I am doing 3D reconstruction of 2D images using 3D Morphable Model as in this paper ...
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There are other shape properties scale-rotation invariant except HuMoment?

There are other shape properties scale-rotation invariant except HuMoment? There are example that show me how can i implement them? I find this example in c++ https://stackoverflow.com/questions/...
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Fourier transform of images and phase filters

What are the known possibilities to date for filtering the phases of an image and what are they used for? Phases are used in some edge detection algorithms. They are also used for cross correlation of ...
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How to recognize a zebra crossing from top view using OpenCV?

How to recognize a zebra crossing from top view using OpenCV? It is not a straight zebra crossing - it has some twists and turns. I have some ideas: parallel line detection, but the available ...
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445 views

STASM or AAM which is more efficient

I am working in face detection and recognition project. I am using STASM for face detction and locating face landmarks. On googling I found AAM (Active Appearance Model) and found that it is also used ...
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OpenCV detecting elbow

I have to detect my elbow. I'm able to produce an image in which I'm facing the camera, standing before it and my arms are in my body plane(body plane is plane containing my head,chest,and legs)(i.e. ...
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1answer
574 views

KLT tracker implementation

I'm working on a object tracker based on KLT algorithm using matlab. Can anybody guide me how I can find the features and calculate the distance in the sequence of the frames? Thanks.
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Finding defects in wall paint (finding difference in textures)

I have been experimenting with computer vision techniques to find defects in paintings, more specifically defective brush strokes. I have tried a handful of techniques such as different filters, One ...
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video resources for learning image processing?(for EE background)

Please kindly recommend some youtube links for learning image processing. I have EE background and i want to study/learn image processing in this way Also i have confusion that Computer science ...
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How to create different Time frequency images from a data

I'm new to Python. I have a time series in a CSV file that has about 5000 rows and 3 columns. I have split the data into training and testing in ratio 70:30 respectively. However, I have a problem ...
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9 views

How to find location of minimum dimension of contour using opencv?

suppose this is our input image and now we have to detect the point of minimum dimension, which I show as the red dot in an output image
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I can't implement plateau limit histogram equalization algorithm using MATLAB

i tried to implement this research paper using MATLAB. Unfortunately, my result is not same with the original result. Here is my try step by step: ...
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20 views

Randomly Generate Synthetic Noise in an Image Text Document

I'm working on denoising dirty image document. I want to create a dataset wherein synthetic noise will be added to simulate real-world, messy artifacts. Simulated dirt may include coffee stains, faded ...
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Looking for a way to fill holes in objects, and break bridges between them

I am trying to extract building footprints from satellite images. Using a series of morphological operations i.e erosion and opening by reconstruction, I'm able to obtain the footprints, albeit with a ...
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24 views

What does total variation norm mean in an image?

What is the notion of total variation and how is total variation norm calculated in an image? More exactly, I want to calculate and understand the meaning of $ \left \|X \right \|_{TV} $ if $X$ is an ...
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My X ray images have black background, which turn gray after low-pass filter. How to recover blackness?

I am applying a low-pass filter to X ray images, which changes the pixel distribution such that the background goes from black to gray. In the attached figure, this amounts to the mode increasing from ...
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Local noise intensity in an image

Noise can be assessed in uniform regions of an image, by subtracting a lowpass-filtered version of it. Then from the histogram of intensities, a global measure can be obtained (such as the average ...
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27 views

Is it necessary to have a reference plane when doing structured-light scanning for depth calculation?

I'd like to create a point cloud of an object using the structured-light approach with either fringe-projection or dot markers but the object I plan on "scanning" won't be in front of a flat ...
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What algorithm generates these “bucket coloring” artifacts?

Context: This is picture (taken with a smartphone*) of a copy of school test. The original answers were in black pencil and the professor made check marks in red. However, the parts of the answer ...
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1answer
52 views

Localized Gamma Correction

Question: Is there an algorithm that does (what I would call) "localized" gamma correction? That is, applying different gamma corrections on different parts of an image, using a masking filter or ...
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Fast and Slow motion video detection using Optical Flow

I'm trying to calculate a "video motion" value in a given video sequence, meaning how fast or slow motion the video is. For instance, if a video is about a car racing, the value is high. Whereas if ...
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Removing striped noise from an image

I was just wondering if anyone could explain to me the approach one would take to removing striped noise from the fourier domain of an image. I was reading an article about MRI image from 1 just ...
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Size filtering on binary images

I have noisy images from which I extract the contours using OpencCV's findCountours, which performs binarization internally. This results in innumerable small ...
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Robust custom watermark algorithms?

I'm doing research on image and audio watermarking, and so far I've read some literature in order to get basic introduction and good initial understanding of this topic. Right now I'm reading book "...