Edge detection is the process of identifying points in an image, where image brightness changes sharply.
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2answers
128 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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1answer
45 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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0answers
65 views
Edge detection in Fast Noise Estimation method (link to document inside)
A Fast Method For Image Noise Estimation Using Laplacian Operator and Adaptive Edge Detection
I have some troubles trying to decide edge-map threshold. As i understood this document in link above, ...
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1answer
83 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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0answers
39 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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votes
2answers
118 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 ...
4
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0answers
134 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 ...
5
votes
1answer
520 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
1k views
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 ...
3
votes
1answer
756 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 ...
3
votes
0answers
54 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.
...
5
votes
2answers
824 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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votes
3answers
677 views
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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vote
0answers
193 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
2answers
603 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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vote
1answer
128 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
175 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
167 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 ...
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votes
3answers
1k 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 ...
4
votes
1answer
334 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 ...
11
votes
1answer
391 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 ...
5
votes
1answer
669 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 ...
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votes
1answer
128 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:
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4answers
726 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:
...
8
votes
1answer
252 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 ...
5
votes
2answers
623 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).
...
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votes
3answers
869 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 ...
8
votes
2answers
231 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 ...
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2answers
880 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 ...
3
votes
3answers
402 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 ...
12
votes
1answer
400 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 ...
22
votes
5answers
477 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 ...
