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Questions tagged [edge-detection]

Edge detection is a tool in computer vision used to find discontinuities (edges) in images or graphs. Use this tag when asking about finding and manipulating edges or edge interaction.

Edge detection is a part of computer vision where the goal is to find edges in images. This often involves computing derivatives of the image with respect to the coordinates, because intuitively if the difference between two neighboring pixels is high, it is likely that there is an edge in the image. A popular edge detection algorithm is the Canny edge detector. Other edge detection algorithm includes Laplace & Sobel.

Discontinuities in image are likely to correspond to

  • discontinuities in depth
  • discontinuities in surface orientation
  • changes in material properties and
  • variations in scene illumination
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How to create border in ciimage in swift

I'm writing a feature for correcting perspective of documents scanned from ios camera. I want to create a border effect around the document whose edge has been determined. CiImage has the initializer property with which i can create a color overlay…
Nutan Niraula
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How to detect smooth curves in matlab

I am trying to detect a bent conveyor in an image. I used the following code using Hough transform to detect its edges %# load image, and process it I = imread('ggp\2.jpg'); g = rgb2gray(I); bw = edge(g,'Canny'); [H,T,R] = hough(bw); P =…
Ahmad
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How to remove some edges after applying edge detection?

I need to find the iris edges, the input images that I use is not a fully rounded iris, sometimes it might be covered by the eyelid. I found a summary of a journal article to find the iris even its covered by the eyelid. However, I stuck in one of…
Dennis
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Blurry edge detection

I have little background knowledge of image processing and recognition. I am trying to detect principal edges/grayscale transitions on a grayscale image such as a portrait. The problem is that on some parts, the edge is blurred (because of focus). I…
Montspy
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MATLAB: detecting non-continuous vertical streaks in greyscale image

In the attached image there are periodic vertical streaks which are random along the x axis and vary along the y axis in their intensity. Any suggestions on how to detect these? Ideally I would like to detect these with an output of a binary image…
user3470496
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Hough Line Transform - artifacts at 45 degree angle

I implemented the Hough Lines Transform in OpenCV (c++) and I get strange artifacts in the Hough Space. The following picture shows the Hough Space. The distance rho is depicted in the rows while the 180 columns represent the angle from 0 to 179…
fishishuntingsharks
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Segment depth image with low contrast

I am trying to segment the hand from this depth image: I tried watershed, region growing, grabcut, but all of them failed mainly because there is not a clear edge. I tried to sharp the image as well, but it didn't give me good results either.
Jäger
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character reconstruction and filling for OCR

I am working with text recognition on tires. In order to use an OCR, I must first get a clear binary map. I have processed images and the text appears with broken and discontinued edges. I have tried standard erosion/dilation with circular discs and…
Wajahat
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Subpixel edge detection for almost vertical edges

I want to detect edges (with sub-pixel accuracy) in images like the one displayed: The resolution would be around 600 X 1000. I came across a comment by Mark Ransom here, which mentions about edge detection algorithms for vertical edges. I haven't…
Saania
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preprocessing steps for business card edge detection using gpuimage hough lines

I'm trying to detect edges of a Business Card using GPUImage's HoughTransform since it seems to be the best way to achieve this task with this framework from what I have found with similar questions/problems. The best results that I'm able to get is…
jdev
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CIImage(IOS): Adding 3x3 convolution after a monochrome filter somehow restores color

I'm converting ciimage to monochrome, clipping with CICrop and running sobel to detect edges, #if section at the bottom is used to display result CIImage *ci = [[CIImage alloc] initWithCGImage:uiImage.CGImage]; CIImage *gray = [CIFilter…
Anton Tropashko
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Canny Edge detector threshold values gives different result

I am trying to find contour of a image, before that I am applying Canny's edge detector. It's giving different result for different images.For one image it's giving perfect contours at threshold value - min-40 max-240 and for other image its…
Rahul galgali
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Extract one object from bunch of objects and detect edges

For my college project I need to identify a species of a plant from plant leaf shape by detecting edges of a leaf. (I use OpenCV 2.4.9 and C++), but the source image has taken in the real environment of the plant and has more than one leaf. See the…
Grant
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Edge detection and segmentation

I am trying to extract an object from a paper currency image. On the original image I applied sobel edge detection. Here is the image: My question is in the following cropped image I want to have only the number 100 displayed with out the other…
user3472037
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Robust card detection/persecutive correction OpenCV

I currently have a method for detecting a card in an image and for the most part it works when the lighting is fairly consistent and the background is very calm. Here is the code I am using to preform this operation: Mat img = inImg.clone(); …
Clip
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