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# Questions tagged [canny-edge-detector]

Use for questions about the Canny edge detector

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### Explaination on this "more accurate implementation" of Gradient magnitude thresholding

I'm reading the implementation of "Canny edge detector" in Wiki page: Canny edge detector. In the section "Gradient magnitude thresholding", it says: In more accurate ...
1 vote
1 answer
192 views

### How many directions are there in the Non Maximum Suppression part of the Canny Edge Detector

In the Non-maximum suppression algorithm, each pixel has a total of 4 directions since there are 8 neighboring pixels. But why there is not 8 directions instead, please? I see below there are 8 ...
2 votes
0 answers
67 views

### Numerical optimization method for optimal edge detector

John Canny, in his paper "A Computational Approach to Edge Detection" (PDF), finds the expression of an optimal edge detector by first using an analytical approach (Euler-Lagrange equation). ...
2 votes
2 answers
873 views

### Edge following using Hough transform

I am trying to improve an edge following algorithm developed by some students who did a project at my work. The algorithm is supposed to make a robot follow a line with the use of a camera. Their ...
12 votes
2 answers
11k views

### Why Is the Canny Edge Detection Used Instead of Sobel / Prewitt Edge Detection Before Hough Transformation?

I know that for the Hough Transform to work on an image, it needs to be a binary image. To convert from a grayscale image, an edge detection algorithm should be employed. I notice that people always ...
4 votes
1 answer
541 views

### How to Remove Double Lines Detected Along the Edges by Edge Detector?

I'm trying to take real time input for hand gestures with web cam, then processing the images to feed them to a neural network. I wrote this processing function to make the hand features look ...
0 votes
0 answers
2k views

### Having trouble calculating the correct Gaussian Kernel values from the Gaussian function formula

I'm having trouble calculating the same values for a Gaussian filter kernel as those derived in the Canny edge detector Wikipedia page It states: The equation for a Gaussian filter kernel of size (2k+...
0 votes
0 answers
98 views

### MatLab-Finding error in hough line transform

Can I calculate the number of error in Hough Line Transform using MatLab? I did Hough Line Transform process from Canny Edge Detection, but it is unable to detect all the lines. Thanks.
5 votes
2 answers
2k views

### 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 ...
1 vote
0 answers
108 views

### Perona Malik Noise Estimator using Canny

In Perona and Malik, they state: a histogram of the absolute values of the gradient throughout the image was computed, and K was set equal to the ...
0 votes
1 answer
452 views

### detecting edge direction using Julia-language

Let say we have following image: made with following Julia-code: ...
1 vote
1 answer
5k views

### Lane detection and tracking using B-snake?

I am truly sorry if my question sounds little bit stupid, but I am getting stuck at this part for a long time. I am currently working for my final year project of lane detection for curved road using ...
1 vote
1 answer
825 views

### Getting rid of Canny outliers

I have been using the Canny edge detection function in OpenCV to detect the edge of an elliptic annulus (light object, dark background). In theory there should be two edges. However, it sometimes does ...
3 votes
1 answer
2k views

### Canny non-max suppression intro

I have rich experience signal-processing, but haven't touched image processing since my happy university days... so: Working on a side project, I need to enhance ridges (continuous lines) in a 2D ...
2 votes
1 answer
7k views

### Influence of image size to edge detection in OpenCV

I need to scan an image in OpenCV and obtain the lines. For this I use the canny edge detector and then the propabilistic Hough transform, with which I actually get the lines. The problem now is that ...
0 votes
1 answer
472 views

### Is the Canny algorithm enough for creating a feature descriptor image for input to an SVM?

I retrieve contours from images by using the Canny algorithm. Is this enough preprocessing to have a descriptor image for input into an SVM to find similarities? Do I need other features like ...
1 vote
0 answers
434 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 ...
10 votes
1 answer
2k views

### 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 ...