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Questions tagged [computer-vision]

Computer vision includes methods of processing, analyzing, images and high-dimensional data to form high level understanding and recognition of the scene or images.

5
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2answers
334 views

Function for response over image scales

I want to write code in matlab to find a characteristic scale of an image patch. I have an image patch X, I need to maximize function F(X,sigma) so that sigma is ...
61
votes
4answers
43k views

What are some free alternatives to SIFT/ SURF that can be used in commercial applications?

As far as I understand, both SURF and SIFT are patent protected. Are there any alternative methods that can be used in a commercial application freely? For more info on the patent check out: http://...
13
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2answers
884 views

How can I change the formula to detect the barcode in every angle? - MATLAB

How can I change the formula to detect the barcode in every angle? ...
5
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2answers
448 views

How do you measure the accuracy of a stereo system?

I have a philosophical question of sorts for users familiar with a multi-view stereo setup. Imagine that I need to measure the dimensions of a large building and I take several photos of the building ...
5
votes
1answer
202 views

How to amplify regions with specific color in an image?

I want to amplify regions with a specified color in an image. For this purpose I have defined a simple function $B(x,y)=s_r(x,y) \cdot w_r + s_g(x,y) \cdot w_g + s_b(x,y) \cdot w_b$ which produces a ...
23
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3answers
1k views

How to find tennis courts in aerial imagery

I'm interested in finding all tennis courts (and other similar well defined features like basketball courts) in my county, and I have aerial imagery of good (but varying) resolution, but I'm not sure ...
-1
votes
1answer
398 views

Which are the steps to extract contours/shapes from depth videos?

I am trying to create a histogram of the depth videos (converted to grayscale first) in order to apply a threshold to keep only highest values, and then do some dilation in order to extract contours. ...
9
votes
2answers
2k views

Surface detection

How would one segment large area's of gray (ranging from white to black) from an image ? (If you know this in opencv, you may answer by saying what you would do in opencv). For example given this ...
8
votes
1answer
589 views

Accurately measuring relative distance between a set of fiducials (Augmented reality application)

Let's say I have a set of 5 markers. I am trying to find the relative distances between each marker using an augmented reality framework such as ARToolkit. In my camera feed thee first 20 frames show ...
7
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1answer
181 views

Minimization of Essential matrix

A problem in computer vision and 3d reconstruction is getting the camera's intrinsics parameters. A common solution is to use an object in which one knows the measurements of the shape before hand, ...
14
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3answers
6k views

Contours matching - finding contours displacement

I found contours on two images with same object and I want to find displacement and rotation of this object. I've tried with rotated bounding boxes of this contours and then its angles and center ...
13
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2answers
2k views

Profile Matching in a Point Cloud

A point cloud is generated using uniform random function for (x,y,z). As shown on the following figure, a flat intersecting plane (profile) is being investigated ...
24
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4answers
1k views

Find the stomata in a plant microscopy image

Here is a question for image processing experts. I am working on a difficult computer vision problem. The task is to count the stomata (marked below) in DIC microscopy images. These images are ...
7
votes
1answer
97 views

How do I reconstruct a covered-over part of a regular pattern

I have a set of images which consist of a fairly regular pattern - essentially a set of roughly concentric distorted ellipses - with a small area (<1% of the total image area) obscured by a ...
17
votes
5answers
3k views

How can I compare two pictures from the camera and tell if there are enough differences to detect movement?

I want to use my phone as a CCTV system to control a room in my house, and display an alert when something is moving. For now, what I have succeeded in doing is to grab a picture every minute and ...
9
votes
1answer
865 views

The Scale Space Theory Understanding

In the scale-space theory the scale-space representation of the signal $f(x), x = (x_1, ..., x_d)$, (in case of image $d = 2$) is given as: $L(x, y; t) = g(x, y; t) * f(x, y)$ where $g(x, y; t)$ is a ...
43
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5answers
7k views

Point Pattern Recognition

Having two different size of sets of points (2D for simplicity) dispersed within two different size squares the question are that: 1- how to find any occurrence of the the small one through the ...
12
votes
1answer
654 views

Interpretation of the eigenvalues of the inverse Hessian in a KLT tracker

I'm a masters student, preparing a seminar in computer vision. Among the topics is the Kanade-Lucas-Tomasi (KLT) tracker, as described in J. Shi, C. Tomasi, "Good features to track". Proceedings ...
31
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2answers
14k views

What's the difference between the Hough and Radon transforms?

I'm familiar with the Radon transform from learning about CT scans, but not the Hough transform. Wikipedia says The (r,θ) plane is sometimes referred to as Hough space for the set of straight ...
6
votes
1answer
487 views

find a line go through the center mass and that line must be inside object area

I have an object (orange color object) and I know its centroid/center mass C. I want program to automatically find another point ( can be point 1, point 2, point 3 or point 4 and so on) such that the ...
29
votes
5answers
2k views

Detecting Trail in Forest Images

Is anyone aware of any research/papers/software for identifying a trail (as a line or point-to-point curve) in an image of a forest scene (from the perspective of the camera standing somewhere along ...
13
votes
4answers
9k views

How to detect corners in a binary images with OpenGL?

I have binary 160x120 images such as: I would like to detect corners of those white blobs. They are previously closed by mathematical morphology so there shouldn't have any inner corners. In this ...
13
votes
2answers
5k views

Why is the difference of gaussians scale space scale invariant?

I'll use the Scale-invariant feature transform algorithm as an example here. SIFT creates a scale space based on scaled gaussian filtering of an image, and then computes the difference of gaussians ...
2
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1answer
73 views

Given some parameters, how do you determine how much of an image sensor an object will consume? [closed]

If I have the details of a scene and a camera, how can I tell how much of my camera's image sensor will be taken by a certain object in space? For example, if I have a painting that is 1m by 1m, it ...
6
votes
1answer
1k views

Skel to infinity morphological operations on 3D volume

I have a 3D volume image that consists of 2D tomographic images. In MatLab, for 2D images, we can use bwmorph and call for 'skel' operation to infinity to get a pixel thick overall outline of the ...
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votes
5answers
3k views

FIXED POINT conversion Problem (DSP)

Actually after reading the data from ADC is an $Q15$ format (ie. ADC supports 0-3.3v, ADC is an unipolar type). then the $Q15$ data is converted to $q31$ format ($Q31$ value = $q15_{data}$ <<16)....
8
votes
1answer
127 views

In computer stereo vision, what does it mean to “look in”?

In trying to understand this answer to my earlier question, can someone explain why it is important that the cameras are not in the same plane when the focal distance is large compared to the ...
23
votes
3answers
2k views

How can I reconstruct a 3D structure from a set of images?

I have a set of contours (set of line segments) grouped in the following way: $S_i = \{I^0, I^\frac{\pi}{4}, I^\frac{2\pi}{4}, \ldots, I^\frac{7\pi}{4} \}$ where $S_i$ denote sequence of photos of ...
11
votes
1answer
113 views

Are there preferred patterns for creating texture on objects to aid computer vision?

In the comment to this answer using a laser diode and diffraction grating to provide texture on a surface was suggested to aid in height calculations in a computer vision system. I believe the ...
24
votes
8answers
2k views

Are Computer Stereo Vision techniques appropriate for sub-millimetre measurements?

I have a project where I would like to image an object and be able to derive the heights of features in this image to sub-millimetre precision (exactly how precise is still yet to be determined, but ...