Edge detection is the process of identifying points in an image, where image brightness changes sharply.

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Singularity Detection from 2D Wavelet Modulus Plot

I was wondering if I could get some tips/resources on how to pick out the singularity from my 2D Continuous Wavelet Transform Coefficient Plot (scalogram) using the Gaussian Derivative as the ...
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Edge Detection on small images

I just newly join to this community. Recently I work on edge detection that is applied on the attached picture. The objects that I want to detect are the white square images (there are 4 of them). So ...
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Sobel Filter Operatios

I have an image which has a vertical line which is 2 pixels wide and 4 pixels long and the remaining image is black. Now I want to find the edges in the vertical direction and for that I use the ...
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Completing an image edge using MATLAB

I'm trying to complete the right edge of the rectangle in the following image: The approach I've tried involves running a Sobel filter for edge detection on the image rotated by 45 degrees, ...
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Need Help how to remove unwanted edge detection

Hye everyone. Really need help. How to remove the branch that i circle in the image. What parameters i should use. Really appreciate your help.
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1answer
51 views

In opecv function Hough circles how does parameter 1 and 2 affect circle detection and how can i adjust them to increase accuracy??

http://docs.opencv.org/doc/tutorials/imgproc/imgtrans/hough_circle/hough_circle.html I'm using houghcircle function to detect circle.Problem is if i set minimum radius to null it detects wrong center ...
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What's the best technique to determine if the contents of two images are the same?

I need to run comparisons on the output of hundreds of frames of simple 3D-rendered characters. Perceptually, many of the frames are exact duplicates. Based on this, I assumed something like a ...
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75 views

Corner detection of image in Matlab

I'm trying to detect the corner of a binary image(boundary image)Function using Freeman Chain Code algorithm.Code for corner detection is taken from Matlab Central(function name is "chaincode") I ...
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58 views

Edge detection of image in matlab

I'm trying to extract edge from an image. I used the following algorithm.Input image(e11) which is a 512 * 512 grayscale image is also given. Find the morphological gradient of input ...
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42 views

How to straighten the edges?

Are there standard efficient ways/algorithms to make edges in an image more straight or axis-parallel (horizontal or vertical) ? I have images that look like this: This is part of a segmentation ...
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44 views

Non-maxima suppression of gradient image

I'm new to image processing, However I was trying to learn how to detect edges using Sobel filter I had obtained the image gradient in both X and Y directions successfully using Emgu built in ...
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1answer
82 views

Ridge finding in noisy 2D image

I'm using MATLAB, and have experience with it but not with this kind of problem. I'm trying to identify white lines in noisy 2D images such as the one below. I can separate the brighter ones just by ...
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21 views

SURF SIFT detection

Do you have any idea if the surf extracted or detected interest points belongs to the same objects? I explain: SURF descriptor account the orientation of ip based on edges intensities around it. In ...
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1answer
24 views

Tracking a Predefined Curve in a Series of Images

I have a series of images. I want to be able to draw a curve on the image and track the curve in the series. For example, in the figure below, the left image illustrates the original image at time ...
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53 views

Creating graph from edges, shape detection

I am writing a shape detection program (for example, I make a triangle with fingers and algorithm finds it). My idea was to detect edges, "straighten" them, create graph from all the segments and ...
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2answers
69 views

Laplacian Operator with and without diagonal direction

This is a general question on the laplacian operator, which has two different versions. The first version is : \begin{matrix} 0 & 1 & 0 \\ 1 & -4 & 1 \\ 0 & 1 & 0 ...
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2answers
417 views

Rectangle detection in “real life” images

I have seen a lot of posts here and on SO and on various websites, using Matlab, OpenCV, name it, on how to detect rectangles in an image. I have done it myself too, using Matlab. My usual steps were: ...
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44 views

Image Processing - Identifing/locating Random Solid Blocks of Colour

I am not overly familiar with image processing. I know a little about it from University, but I have not really done any for a while and I have found myself with a problem that requires it. What I ...
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1answer
176 views

What's the state-of-the-art algorithms in image edge detection?

There are several state-of-the-art algorithms in image denoising including Non-Local Means, BM3D and so on. I am wondering whether there is some well-known state-of-the-art algorithms in image edge ...
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Extraction of a decision boundary (LDA) after a systematic querying of the feature space and convolution with Sobel filter (examples in numpy)

I am doing some experiments with LDA (Linear Discriminant Analysis), in python. Now I am at the point in which I would like to display the separation planes in the 3-dimensional feature space. I ...
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158 views

Visual regression test - Extract elements of GUI-Screenshot - MSER OpenCV

For a visual regression test I need to compare screenshots of webpages (different release-versions). I started with pixel by pixel compare. Actually I split the screenshot in different parts (maybe ...
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1answer
332 views

An alternative algorithm for blob detection

Here's a sample image of my experiment which is to be processed for finding the information of all the blobs (centre, dimension etc.). Basically the image contains some noise, few bold lines, and of ...
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Need to batch detect, measure, calc DPI for a consistently placed ruler in large set of technical images

I have a large set of photographs of pieces of rocks. In each photo there is a 4 inch ruler bar placed next to the rock, consistently on the left near the edge, see example: Over 10 years the ...
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58 views

Edge-preserving smoothing

I'm searching for a method that can smooth a 3D volume whilst preserving the edges in my volume. I researched anisotropic diffusion filtering and bilateral filtering but I'm having trouble to evaluate ...
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40 views

Optimal way for curve detection

I am totally new to image recognition and image analysis and have a project concerning detecting a smooth curve on a uniform background (white/black/any color) and then be able to follow this curve ...
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2answers
78 views

Edge detection on a color image

I understand the process of using a Sobel kernel for edge detection in greyscale images. The input is a greyscale image, and the output is a greyscale image. I'm having trouble, however, figuring out ...
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Detecting blades of a wind turbine

I have many close-range images of a single wind turbine blade (taken from different positions, same angle): I need to separate the blade image from background like this: The problem arises in ...
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1answer
52 views

Why are 2nd order edge detectors such as Laplacian more susceptible to noise?

I've been told that they are influenced by noise considerably more than that of a first order edge detector such as a Gaussian. But why?
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423 views

Algorithm for finding length and end points of a curly human hair

I'm trying to do some analysis of a curly human hair on an iPhone app. I've been using the openCV library. Particularly I want to be able to estimate the length of the hair, and locate its end points ...
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1answer
670 views

How to trace the edges on matlab

I am doing my Bachelor's project on Road extraction. I have detected the line segments(edges) in the image using hough transform. I need to detect the curved lines in the road and link them(edge ...
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109 views

detecting “deformed” lines

I have a project in which I have to recognize 2 lines in different "position", the lines are orthogonal but can be projected on different surfaces. I'm using opencv. I'm not asking for code, ...
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3answers
199 views

Which sigma to use for edge detection

I know that in many edge detection algorithm the first step is choosing a scale to work on. We actually operate on the chosen scale by applying a gaussian blur on the original image. I wanted to ...
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2answers
62 views

Is it feasible to try and classify an enclosed space as being a. Very crowded b. Less crowded & c. Sparsely crowded using image processing?

The idea is to get three classifications for crowd: High, low and medium based on an image captured inside a train compartment. Something like this: This gets classified in the 'High' category ...
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2k views

How do convolutions become matrix multiplications?

I know this question may not be very relevant to programming, but if I don't understand the theory behind image processing I'll never be able to implement something in practice. If I got it right ...
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390 views

Keypoint orientation with the oFAST from Rublee's ORB

I've just read the papers from Rublee et al. (ORB: an efficient alternative to SIFT or SURF) and Rosten et al. (Machine learning for high-speed corner detection) (=fast-detector). Rublee tries to ...
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235 views

best robust feature detectors for detecting similarities among archeological signs

I would like to implement edge detectors for creating a feature vector for archeological signs. Which are best features, algorithms to retrieve? That could be loaded in a Support vector machine for ...
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Finding optimal detectors by numerical optimization (Canny)

In "A Computational Approach to Edge Detection", John Canny explains that the optimal "detector" for finding step edges profiles in an image via convolution is a non-closed-form function closely ...
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2answers
397 views

Why is Prewitt filter High Pass

Prewitt filters are popular filters in image processing for edge detection http://en.wikipedia.org/wiki/Prewitt_operator Can anyone give a proof on why Perwitt and other edge detecting filters are ...
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729 views

Difference of Gaussians

I use the following formula for DoG: $$\frac{1}{\sigma} (\frac{x^2}{2\sigma^2}-1.0) e^{\frac{-x^2}{2\sigma^2}}$$ What is the relationship between this formula and the difference of two Gaussian ...
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1answer
4k views

Differences between OpenCV Canny and MatLab Canny?

does anyone know why the MatLab Canny (MLC) is so different compared to the OpenCV Canny (OCC)? ML-C delivers precise and more connected edges than the OCC, but how is that possible? The reason why I ...
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6answers
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Image segmentation issue of different materials

Hi CV/Pattern Recognition Community, I've got a serious problem regarding the segmentation of an image. The scenario is an atmosphere within a furnace which makes my head go insane. And I need to ...
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1answer
5k views

EmguCV: Detect a ball in the frame

I am having a VERY hard time capturing when the ball comes into frame in this video http://www.youtube.com/watch?v=x1V6_OHrXIo I have no idea what to set the parameters too, and trying random values ...
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1answer
98 views

learnable segmentation or learnable edge detection

Is there some learnable segmentation or learnable edge detection algorithm exist? For example I mark N fotos by hands and than program "learns" how to do it best way and can do it on similar images. ...
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5k views

Straight lines with an edge detection algorithm

I've been thinking of an algorithm for object recognition but it would relies heavily on straight non-noisy lines and as far as I know this is hard to obtain with edge detection algorithms. What's the ...
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Can edge detection be done in the frequency domain?

Can we take advantage of the fact that high frequency components in the FFT of an image generally correspond to edges, to implement an edge detection algorithm in the fourier domain? I did try ...
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Edge detection gives pixel ids, why?

This questions is in conjugation with this one here! Canny edge detector gives ids of pixels in an image. Not the locations of the edges. To be specific, after all it should be an edge between two ...
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2answers
3k views

Connecting edges detected by an edge detector

I have a binary image obtained from a canny edge detector. The edges are not nicely detected in the center and I need to join them. The connection of edges is orientation and neighborhood dependent. I ...
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1answer
165 views

Are all of the edge descriptors necessary to differentiate edges?

My question is about edge descriptors produced from an edge detection method applied on an object image. As we know, an edge has four descriptors edge normal, edge direction, edge position, and edge ...
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2answers
200 views

Identify the correct spot to place a label

In the image shown below, I have a 2D data set where I have identified four clusters labeled [0,1,2,3]. I'm looking for an algorithm to place the labels in a ...
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Could you describe the effects for varying different parameters of a canny edge detector?

Last couple of questions touched upon Canny edge detector What are the limitations of a Canny edge detector? and Best way of segmenting veins in leaves? The basic outline of the algorithm is as ...