Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

61
votes
4answers
45k 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://...
60
votes
7answers
69k views

Why do we use the HSV colour space so often in vision and image processing?

I see the HSV colour space used all over the place: for tracking, human detection, etc... I'm wondering, why? What is it about this colour space that makes it better than using RGB?
49
votes
10answers
13k views

Is deep learning killing image processing/computer vision?

I'm looking forward to enroll in an MSc in Signal and Image processing, or maybe Computer Vision (I have not decided yet), and this question emerged. My concern is, since deep learning doesn't need ...
45
votes
6answers
18k views

Best way of segmenting veins in leaves?

I have done a lot of research and found out methods like adaptive thresholding , watershed etc that can be used of detecting veins in leaves . However thresholding isn't good as it introduces a lot of ...
44
votes
3answers
19k views

What algorithm does Google use for its “Search By Image” site?

What is your best guess how Google Image Search works? I can upload a photo and can search for similar images. What algorithm does it use to identify similar images?
43
votes
5answers
8k 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 ...
40
votes
1answer
12k views

How to flatten the image of a label on a food jar?

I'd like to take pictures of labels on a jar of food, and be able to transform them so the label is flat, with the right and left side resized to be even with the center of the image. Ideally, I'd ...
32
votes
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 ...
32
votes
7answers
17k views

Finding squares in Image

I need to find the squares in an image using OpenCV (no problem in matlab or any other, generally what i expect are some ideas). Consider the test image below : I need to find those coloured squares ...
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 ...
27
votes
5answers
15k views

Good language for computer vision?

I am trying to implement a content based image retrieval system but before I do so I would like to get an overview of some programming languages suitable for this task (having good libs and such). ...
25
votes
4answers
2k 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 ...
25
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 ...
25
votes
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 ...
24
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 ...
20
votes
2answers
39k views

Step by Step Camera Pose Estimation for Visual Tracking and Planar Markers

I have been working on the topic of camera pose estimation for augmented reality and visual tracking applications for a while and I think that although there is a lot of detailed information on the ...
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 ...
17
votes
3answers
7k views

How to detect gradients in images?

I want to be able to find points in images that are the centre of a radial gradient like the one shown in the left picture below. Any ideas on how I could use a Hough transform or some other computer ...
16
votes
4answers
7k views

Intuitive explanation of tracking with Kalman filters

I would much appreciate an intuitive explanation for (visual) tracking with Kalman filters. what I know: Prediction step: Dynamic system state $\mathbf x_t$: target location at time $t$ Measurement $...
16
votes
2answers
18k views

Why do we use keypoint descriptors?

I just studied about SURF and I'm going for its implementation, but I still didn't understand why we use descriptors. I understand what keypoints are and their purpose, but when we extract the ...
16
votes
2answers
10k views

How does resizing an image affect the intrinsic camera matrix?

I have a camera matrix (I know both intrinsic and extrinsic parameters) known for image of size HxW. (I use this matrix for some calculations I need). I want to use a smaller image, say: $\frac{H}{2}\...
16
votes
2answers
32k views

Are there any good open-source (well, free) handwriting OCR programs?

The title asks it all. I have before me a data entry task that I'm not too enthusiastic about: 50-100 pages of handwritten sign out/sign in logs. The format of the logs may help. Pages are ...
15
votes
4answers
6k views

People detection from above

I am trying to find some method to detect people using only one camera 3 meters above the ground. This is a frame returned by camera: UPDATE: Video test -> http://dl.dropbox.com/u/5576334/...
15
votes
5answers
15k views

Scale and Rotation invariant feature descriptors

Can you list some scale and rotational invariant feature descriptors for use in feature detection. The application is for the detection of cars and humans in video captured by a UAV, using a multi-...
15
votes
1answer
274 views

Fitting new images from a SVD/PCA calculation

I'm trying to replicate the ideas from the Eigenface page on wikipedia. From a hundred sample images represented by a data matrix $\bf X$ (where each image flattened to a vector of length $n$, thus $\...
15
votes
2answers
583 views

3D reconstruction of an image based on depth of intensity levels?

Is there anyway of segmenting objects based on how far they are from the viewer? Can color values assess this sort of a thing for us? How will intensity levels help in determining how far the object ...
15
votes
2answers
554 views

What image-processing techniques are ideal for this particular shift/scale invariant template matching?

A problem I had originally discussed here has evolved, and might have gotten a little simpler as I studied it in some more and attained new information. Bottom line, I would like to be able to detect ...
15
votes
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 ...
14
votes
4answers
2k views

basic hsb skin detection, neon illumination

i hope this is the right place to ask. otherways sorry for my mistake and pleace advice me a better site. i'm trying to implement a super simple skin detector using some range of hsb image. i'm using ...
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
2k views

A (Clear) Line Between Computer Vision and Image Processing

I have been working in and learning about both Computer vision and Image processing for a few years now, and I believe that I am not a complete beginner any more. Still, after all these years, it is ...
13
votes
2answers
414 views

Detecting meandering rivers in images

I have $n$ surfaces: $z_i(x,y)$ with a measured attribute (variable) on each surface: $a_i(x,y)$. Most of the surfaces will have a random distribution of the attribute across the surface, but some ...
13
votes
1answer
5k views

Binary robust independent elementary features (“BRIEF”) understanding

How are the descriptors in the BRIEF algorithm matched to each other? How is the template image found in the another image? How do we compare the descriptors? I have read that article but didn't ...
13
votes
2answers
891 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? ...
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 ...
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 ...
13
votes
6answers
5k 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 ...
13
votes
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 ...
12
votes
4answers
3k views

Slicing and Recognition of book title and author from bookshelf image

I am trying, for my own learning purposes, to develop an implementation of an algorithm that would list books, given an image of a bookshelf like the following: The first step is to slice the image ...
12
votes
2answers
15k views

How do I retrieve texture using GLCM and classify using SVM Classifier?

I'm on a project of liver tumor segmentation and classification. I used Region Growing and FCM for liver and tumor segmentation respectively. Then, I used Gray Level Co-occurence matrix for texture ...
12
votes
3answers
17k views

How to compute camera pose from Homography matrix?

Say I use only one calibrated camera. From this camera, I get images A and B. I know the homography between A and B, computed through OpenCV's findHomography(). I know the pose (rotation matrix R and ...
12
votes
1answer
664 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 ...
11
votes
2answers
4k views

Pedestrian counting algorithm

Currently I am developing a pedestrian counter project (using OpenCV+QT on Linux). My idea about the approach is: Capture Frames Do Background Subtraction clear noises (erode, dilate) find blobs (...
11
votes
2answers
490 views

What methodology to use for discrimination of different (musical?) tones

I am trying to research and figure out how best to attack this problem. It straddles music processing, image processing, and signal processing, and so there are a myriad number of ways to look at it. ...
11
votes
1answer
880 views

Image Denoising with Better Edge Preservation

I have the input image : and the output of vein detection for the leaf using a Gabor filter, but the output is really noisy: I tried using Total variation denoising however the results are not good: ...
11
votes
2answers
5k views

Calculating a homography based on detected lines

I know you can calculate homographies from image to camera plane using correspondence points between a "perfect model" and the image points. I'm doing it for a football pitch/field, and have used ...
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 ...
11
votes
1answer
310 views

Recover curves from noisy collection of points

Background: I'm trying to make a system that tracks a number of bubbles in a video I'm implementing the bubble detection in the single image case using the Circular Hough Transform. Due to occlusion, ...
10
votes
1answer
277 views

Image Processing method for spiky selection

I have an input as a 3D binary image and the preferred output below: Input: Preferred Output: What image processing methods should I look for if I am to have only the spiky object(s) remain, just ...
10
votes
4answers
2k views

Image Recognition

Looking for an open-source system that allows commercial use to do image recognition on a massive and organically growing collection of 2-D images where the only known variations will be: Scaling ...