Questions tagged [edge-detection]

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

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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 image ...
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Find best fitting rectangles after applying edge detection

I am trying to implement a box detection algorithm. In my pipeline, I start with image warping to simulate a frontal view of the shelf containing the boxes (assuming boxes are straight in that ...
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1k 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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113 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 ...
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Chapter 4, section 4.2.1. in Szelisky computer vision, is there a mistake?

I've already asked a similar question in mathematics exchange without getting an answer, I read a bit more and I think the question might be more suitable for the signal processing exchange. ...
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45 views

Texture detection

I am looking for good methods, preferably parameterless, to detect textured areas in an image. I mean random textures, not regular patterns. The final goal is to discriminate between significant edges ...
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266 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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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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37 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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61 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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172 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 mother-...
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202 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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755 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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27 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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428 views

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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15 views

Detecting enclosed regions in an image

I am having a difficult time searching for this, and I am not sure if it has a general solution, but I thought I would ask. Basically, I am looking to detect the inside of a bounded region, but ...
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Measures of edge image continuity and connectivity

Suppose I have a scalar image $I:\mathbb{Z}_{1,m} \times \mathbb{Z}_{1,n}\rightarrow [0,1]\subset \mathbb{R}$, where $\mathbb{Z}_{1,m} = \{1,\ldots, m\}$. (For instance, computed as the (scaled) ...
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1answer
30 views

Recommended approach for extracting specific edges from image?

I have several sets of images with a typical image being: and from each image, I would like to extract the top and bottom curves of the object, shown in red here: What are some possible tools I ...
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74 views

What are the limitations of Watershed Segmentation Algorithm?

I am developing an Android application using Opencv to detect objects from images. I used Canny edge detector to detect the edges and extract contours, and it's working good so far. But I need to ...
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1answer
42 views

Does flat surface detection and orientation require special hardware to compute?

Modern augmented reality platforms such as Google's ARCore and Apple's ARKit seem to only operate on mobile devices, I'm guessing, because their underlying algorithms require specialized hardware that ...
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25 views

Edge detection for bio-film filaments

I have this image of bio-film filaments growing in a matrix and would like to extract just the filaments from the image to calculate the angle at which they are growing. What techniques would be best ...
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13 views

Is there a way to find edges of an image using eigenvalues without thresholding?

How could an edge be detected using eigenvalues and eigenvectors of a second moment matrix? Could it be done without thresholding? If so how? If no, how to find a suitable threshold?
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1answer
126 views

How to find Performance Ratio (PR)?

If we have one image from BSD (The Berkeley Segmentation Dataset and Benchmark) and for this images Ground truth, how to calculate PR? PR is the ratio of true to false edges and can be calculated by ...
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1answer
228 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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473 views

Segmentation and edge linking

I am trying to implement segmentation on an image. after a difference of Gaussians Process and applying weights to my edges I want to go through edge linking by local processing. I have seen this ...
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75 views

Which is faster: image segmentation or line detection?

Some papers use image segmentation techniques and others use edge detection. I need to know which one is faster. update: I need to do semantic segmentation for outdoor sense and the data is optical ...
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1answer
408 views

ICY feature detector and edge detector in opencv

I need to trace the internal feature boundaries of blobs (blood cells) in OpenCV to train a classifier. As a good reference from ICY in java, the following sequence of operations gives good, ...
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614 views

Average gradient of pixels and sum of absolute diference

Studying the research paper Multidirectional Scratch Detection and Restoration in Digitized Old Images, E. Ardizzone et al., 2011: I have several questions regarding this section (5. Restoration), ...
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84 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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187 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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204 views

edge detection of 1-D signals

Would you please introduce me to some methods (or references) to do edge detection on some pulses (rectangular pulses embedded in noise). At first I apply some filters to smooth the signals, then I ...