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

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Poster detection in OpenCV?

I'm really new in image processing, so please sorry I'm a newbie. I tried to use the squares.cpp for detecting posters (since they usually are rectangles) without using expensive feature detectors ...
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10 views

Is there an optimal range for Pratt's Figure of merit?

I am working on a new edge detection method. However, when I tried to evaluate it based of FOM values, I got really small values, though my algorithm's performance is good comparatively. What I ...
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18 views

what is the differences between thin structures and edges in image

I want to know what are the differences between the thin structures (filaments, point, segments) and edges of image. How to detect the fine structure. why the Bi-Laplace operator can detect the ...
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25 views

edge detection evaluation medical test images MATLAB

I programmed an algorithm for edge detection, i want to compare it with other algorithms but with a criteria (Pratt's figure of merit, GMC1) not only a a visual comparaison. the thing is PFOM needs ...
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14 views

Analytical expression for salient Blob detection in scale space

I am working on exact mathematical expression which can be obtained in image processing tasks.(I do not know much about image processing but my work is more mathmatical) In Gaussian scale space, we ...
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3answers
94 views

2nd order edge detectors more susceptible to noise?

I am reading about edge detection and I read that 2nd order detectors are more susceptible to noise. Is there a mathematical proof to this ?
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2answers
42 views

detect to rising, stable and falling point in non-smooth rectangular wave

I am working on basic signal processing problems in MATLAB. I have found a signal from the internet (i don't remember the site exactly). The data is organized in column wise. 1st and 2nd column is ...
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1answer
60 views

How to find a noisy line in a picture

Hi I would like to find a line in a noisy image as showed bellow. I tried gabor filter and cany edge detection, but it didn't produce anything usefull. I am looking for lines of specific orientation ...
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67 views

What is different between gradient and imgradient functions in MATLAB

I would like to compute the gradient of an image I. I have the following two options : [Gx, Gy] = gradient(I); g = sqrt(Gx.^2+Gy.^2); or ...
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35 views

How to detect a signal pattern distorted with noise?

Signal transmitter will send the series of single notches with predefined spaces between them (all spaces can be different). This packet is a single bit of information. I assume that on the receiving ...
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25 views

necessity of patch size in edge detection algorithms

I have recently started learning about the image edge detection methods. I studied few of these methods including Sobel and Canny. I observed that edge detection is performed using patch/kernel size ...
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24 views

Beginner question: extracting features for image classification?

I'm a Python programmer, but a beginner to image processing :) Apologies if this isn't a suitable question for the forum, happy to rewrite or move. I want to create a supervised classifier to ...
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55 views

Algorithm to extract polygones with holes

I have this picture and would like to extract the bones. First I thought of contour-Tracking, but as you can see in some bones there are holes (Like for example at the left finger, in the bone in the ...
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96 views

How to do edge detection using Curvelet transform?

I wanted to use Curvelet thresholding for edge detection, that is first take discrete curvelet transform then choose coefficient which are for curve and then reconstruct back to get an edge map. ...
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24 views

Methods for edge detection with non-equidistant samples

This posting describes two methods of edge detection for wave analysis in a water pipe. I am not sure about advantaged and disadvantages. Therefore I want to evaluate the best method for this ...
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65 views

how to count plain objects in image using canny edge

im working on a project matlab that uses canny edge to extract edges of objects. in my project o have to find number of objects or better say plain objects like shapes or words in image. as canny edge ...
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143 views

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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22 views

Detecting discontinuities in derivatives in images

Considering an grey-scale image as a function z=f(x,y). (Specifically, I'm interested in f=h∗h∗...∗h, where h is the indicator function of a regular hexagon.) I am interested in finding places where f ...
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2answers
64 views

Convolution theorem for “weighted” convolution?

Consider what I call a "weighted" convolution of a two-dimensional signal (image) with itself: $f({\bf r}) = \int d {\bf r}' \, g({\bf r}') s({\bf r},{\bf r}') g({\bf r}-{\bf r}')$ where $s$ is a ...
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82 views

How do I compute the gradient vector of pixels in an image?

I'm trying to find the curvature of the features in an image and I was advised to calculate the gradient vector of pixels. So if the matrix below are the values from a grayscale image, how would I go ...
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206 views

Detecting water level in an image

I have designed a surface with a shape like a rounded rectangle and I want to detect its exact boundaries in a photo I take from it. A sample photo is like this: I have tried thresholding the image ...
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75 views

Help Understanding the Robert Cross Operator

I have been reading this Wikipedia article: https://en.wikipedia.org/wiki/Roberts_cross And it says this: Now I have also been reading this for the Robert Cross operator (from Feature Extraction ...
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54 views

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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52 views

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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62 views

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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471 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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387 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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33 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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2answers
169 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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1k 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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57 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
342 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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296 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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1k 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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19 views

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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97 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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44 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
175 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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85 views

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
64 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?
3
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1answer
624 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 ...
2
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1answer
984 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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2answers
142 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
703 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
65 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 ...
5
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2answers
3k 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 ...
3
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1answer
511 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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1answer
253 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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85 views

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 ...