Questions tagged [edge-detection]

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

Filter by
Sorted by
Tagged with
13
votes
2answers
7k 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 ...
1
vote
1answer
322 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 ...
12
votes
2answers
225 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 ...
10
votes
1answer
1k 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 ...
17
votes
4answers
11k views

What Are the Limitations of a Canny Edge Detector?

Broadly a majority of the literature on edge detection algorithms and applications that uses edge detection, references Canny's edge detector. So much so that it looks like almost "the solution" to ...
7
votes
1answer
5k views

How can I detect elements of GUI using opencv?

Given a screenshot of an application, is there any way of finding GUI elements of that application using only opencv? (something like in the image) I tried to play with blending the image and other ...
13
votes
1answer
3k views

Detection of circles (ellipses) in 2D point cloud

Given a set of points (2D) i.e., point cloud (PC), the question is about a robust, accurate and ...
7
votes
1answer
3k views

Get histogram of edge lengths/orientations in an image using OpenCV

In the process of trying to estimate whether a ROI contains [Japanese] text, I need to get a rough count of edges, hopefully binned by length and/or orientation... I think this would give me strong-...
0
votes
1answer
577 views

What kind of edge detection use paint.net?

What kind of edge detection is used Paint.NET program? It allows me to choose the angle of the edge not like the one used by opencv (Canny). Here an example:
5
votes
4answers
2k views

Do the DCT coefficients correspond to particular pixels?

Getting the DCT coefficient based on what I've read, is usually done through a matrix, usually 8x8 or 16x16 using these formulas: $$B_{pq}=\alpha_p\alpha_q\sum_{m=0}^{M-1}\sum_{n=0}^{N-1}A_{mn}\cos\...
10
votes
1answer
6k views

Roberts Edge Detector how to use?

I am trying to use Roberts edge detection to process an image. Do I just apply both of the masks to the image and perform convolution as normal? Could someone give me the breakdown of how to use this ...
7
votes
2answers
5k views

Detection of lines in a point cloud

What are the best solutions to detect line in a point cloud? Comparison being made with and between Hough Transform, Radon Transform, RANSAC (see wikipedia) and Brute-Force Search (see wikipedia). ...
19
votes
4answers
6k views

How do I detect distinct objects when their edges touch each other?

I need to find all the contours in an image retrieved from the camera. So I first use the canny edge detector to find the edges and then find the contours. Pretty simple. However, my contours get "...
10
votes
2answers
348 views

Explanation on Haarlets

Would someone be able to give me some info or a link etc ... regarding haarlets aka Haar wavelet-like features. I'm reading several papers for my master dissertation and several of these papers ...
8
votes
2answers
4k views

How to implement a gradient based Hough transform

I am trying to use the Hough transform for edge detection, and would like to use gradient images as the basis. What I have done so far, given the image I of size <...
4
votes
3answers
3k views

Bitmap border/stroke alogirthm?

I am looking for an algorithm that adds borders to a bitmap image(very much like the photoshop stroke effect) but one that will also have antialiasing to the borders(or one that copies alpha from the ...
14
votes
1answer
1k views

Estimating onset time of a tone burst in noise?

What techniques might one use to estimate the onset time of a sinusoidal tone burst in a noisy signal? Assume the tone burst has a known fixed frequency (but unknown phase) and a very sharp rise ...
31
votes
5answers
3k views

What Factors Should I Consider in Choosing an Edge Detection Algorithm?

I've learned about a number of edge detection algorithms, including algorithms like Sobel, Laplacian, and Canny methods. It seems to me the most popular edge detector is a Canny edge detector, but is ...