Questions tagged [computer-vision]

Questions about algorithms for processing and analyzing images and videos.

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1answer
24 views

Are there any articles or software which can infer original shapes from overlapping shapes?

Given that some shapes overlap in an image, are there any papers or articles or code which can infer the original shapes from the overlapping? I am thinking to apply some machine learning to this ...
2
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0answers
97 views

Learning Image Processing/Computer Vision

What do I need to learn dense correspondence? I am a newbie in Image processing/CV. Please help me by suggesting a kind of syllabus or show me a way to learn about Dense Matching. What are the things ...
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0answers
103 views

How to train a Conditional Random Field/Markov Random Field Model for Object Classification in images given the features?

I want to classify superpixels in a image using a Markov Random Field/ Conditional Random Field model but have found no place that can help me with this (references don't even show how the network is ...
3
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1answer
165 views

Image Comparison tuned to Human Perception

Say I have two systems that take the same drawing commands and starts drawing on their respective platforms (i.e. HTML Canvas). After this is done, I want to save and compare these two images to ...
1
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0answers
1k views

What happen to the Zero Mean Normalized Cross Correlation (ZNCC) if one of the vectors is a Zero Vector?

I am studying the Zero Mean Normalized Cross Correlation (ZNCC) method for pattern matching. I would like to match the pattern of a square region of size $N \times N$ from two different images. Hence ...
2
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1answer
336 views

Alignment of RGBD with a thermal camera

I have a thermal camera that I would like to overlay, automatically, to the output of a RGB-D camera (e.g. Kinect). I have retrieved the intrinsic and extrinsics parameters of both cameras. My ...
5
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1answer
108 views

What is the point of an active shape model in facial recognition?

From what I understood, the Active Shape Model (ASM) is used in facial recognition. I figured out how the ASM works but I don't get why we use it. How this shape is suppose to be interpreted for ...
2
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1answer
74 views

Looking for Methods in Computer Vision for Distinguishing Disappearing and Fading Objects

Suppose I have a video in which there are two objects $A$ and $B$. Object $A$ appears suddenly at time $Ta1$, and then disappears suddenly at time $Ta2$. Object $B$ appears suddenly at time $Tb1$, and ...
2
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0answers
244 views

How to select a good window size in the Running Gaussian Average method for Selective Background Updating?

I have been studying the Selective Background Updating in Running Gaussian Average Method, as discussed in the Wikipedia (the Variant method). The details of the algorithm, as I understand, is as ...
4
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1answer
612 views

Register images containing objects with varying distance to the cameras

I'm learning about using image registration to align two images, e.g., two photographs of the same scene taken from a slightly different location. What factors influence how well we can align the ...
0
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1answer
3k views

Clustering a set of images using keypoint descriptors

I'm trying to cluster around 16000 images into ~200 clusters, using kmeans with metric as euclidean distance or cosine distance. I understand that i need to extract keypoint descriptors to compute ...
2
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1answer
683 views

Algorithm for Filling Regions with Small Gaps

I am looking for an algorithm that fills a region with one color, but the edge of the region is not completely closed (i.e. one or more gaps are being left). The result is like the use of the Paint ...
2
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1answer
438 views

Selective Background Updating in Running Gaussian Average Method for Background Subtraction

I am studying the Running Gaussian Average Method for background subtraction. One alternative, as described in Wikipedia, also known as Selective Background Updating, is to only update the ...
3
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1answer
167 views

Multi object image segmentation methods

I want to survey the state-of-the-art in image segmentation. Is there a paper on how to segment multiple objects in an image? The segmentation papers I read, normally identify one of the many objects ...
1
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1answer
885 views

Intrinsic matrices in stereo camera calibration

Suppose I have two cameras, c1 and c2, observing the same scene. I can now Calibrate each camera independently (e.g., with MATLAB's Camera Calibration App) Calibrate both cameras simultaneously (e.g.,...
1
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1answer
191 views

Is the Projection Matrix estimated using least-squares pose specific?

I am calibrating a camera and estimating the projection matrix using the least-squares technique described here. So far, I thought that the projection matrix that I got with this method was ...
1
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0answers
115 views

Any applications that need fast insert or delete for quadtrees?

I know that quadtree could be used in collision detection. But most articles I found are related with quadtree construction and retrieval. I wonder if there are some circumstances which involve both a ...
0
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1answer
154 views

Featurizing images of different dimensions

I'm building a non linear svm for images to solve a classification problem with domain {0, 1} and I'm currently doing featurization. What I want to do is create 3 features for each pixel representing ...
2
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1answer
973 views

Getting the essential from the fundamental matrix

Is it possible to get E from F? I suppose that can't work, because then I could calculate the the extrinsic (and maybe also intrinsic?) parameters of the cameras without a calibration object of known ...
2
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1answer
123 views

Fundamental and essential matrices, value of intrinsic parameters

I observe a scene with two cameras, c1 and c2, that produce two images i1 and i2, respectively. What I ultimately want to do is to use information of image i1 and image2 simultaneously, e.g., for ...
3
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1answer
216 views

Calibration and overlay of RGBD with a thermal camera

I have a thermal camera that I would like to overlay automatically to the output of a RGBD camera (e.g., Kinect). I can retrieve the intrinsic parameters of the thermal camera by using a special ...
1
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1answer
81 views

Bringing images into alignment

I observe a scene with two cameras, c1 and c2, that produce two images i1 and i2, respectively. What I now want is to bring i1 and i2 into alignment, that is I want to know where pixel (x,y) in i1 is ...
1
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1answer
198 views

What is the reason of using Gaussian model for Background Modeling?

I am a new learner to Background Subtraction (Background Modeling) and I am reading a few previous works on how it is performed. Starting with Wikipedia (by searching "Background Subtraction"), I ...
5
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2answers
8k views

find the actual size of an object from pixel coordinates

I am quite new to vision and OpenCV, so forgive me if this is a stupid question but I have got really confused. My aim is to detect an object in an image and estimate its actual size. Assume for now ...
4
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1answer
62 views

Feature detector that doesn't use corners

I'm trying to use computer vision to identify objects an image. I am currently using the SURF algorithm, but Harris and SURF both find virtually no points on our objects (a paper ball and a deodorant ...
1
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1answer
404 views

How to test image segmentation algorithms? [closed]

What would be an ideal environment/manner to judge the effectiveness of multiple segmentation algorithms? The goal is to determine which algorithms provide the best results for pre-clinical imaging. ...
6
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1answer
2k views

How to compare SURF points in two images

I know how to find SURF feature points and have code to find them, but I have no idea how to find the same point in 2 different images, I have laplacian, scale, orientation, descriptor, response and ...
1
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1answer
1k views

How do I detect and rotate a square?

I have recently written code for detecting path colors in a 2D grid and printing the corresponding path costs and it works fine for me. Here's my code; I am currently new to OpenCV and know only C++ (...
2
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1answer
376 views

What is the triangulation angle?

I start to work in the field of computer vision and read a paper in which the author states "When suitable correspondences between salient image structures have been established, the 3D uncerntainty ...
3
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1answer
97 views

What is the name of this problem in Computer Vision?

My google skills have failed me during research for a college project. Our task is write a program that describes an image in spacial terms, e.g. "Cat on the left of a chair", or for a simple image "...
11
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3answers
13k views

What is the difference between the fundamental matrix and the essential matrix?

Could someone, in plain english, explain the distinction between the fundamental matrix and the essential matrix in multi-view computer vision? How are they different, and how can each be used in ...
1
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0answers
179 views

Computer vision training procedures: SVM/AdaBoost vs Neural Networks

With SVM, adaboost or similar alogrithms, image training sets must be cropped with specific constraints (keep image cropping ratio the same, have object tightly cropped, same resolution) In general, ...
2
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1answer
322 views

Can you determine rotation/camera calibration from series of images separated by pure rotation

I have a series of about 50 images, each separated by a small rotation and taken from the same camera. The images are feature-dense, and I can calculate a homography from image-to-image easily. My ...
2
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1answer
173 views

How to balance doing a literature review and just solving the problem yourself [closed]

I work for a company that has several projects involving computer vision. The literature rarely has papers on the exact problems we are solving. Furthermore, the state of the art in much of ...
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0answers
274 views

How to identify the z-ordering of objects in a computer vision or image processing scene?

Given that there is an image with objects in it, is there any method in computer vision to determine the z-ordering of objects. For an ideal image of three circles overlapping, I can determine that it ...
0
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1answer
412 views

Blob detection as Constraint satisfaction problem?

In image processing I have a black and white image which is represented by matrix {0,1}, I have to find blob (a region of connected pixels) in it. I'm confused, can this problem be reduced to ...
0
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0answers
453 views

Camera Matching Algorithm

I am trying to understand how camera matching (or match moving) works. I need to build a program that can move the camera in a way to match a 3D object to its projection on an image. For eg. if I had ...
1
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1answer
137 views

What is the significance of the following equation in computer vision?

Say I have a set of sample measurements of a one dimensional curve in the image plane $f(x)$. What is the purpose of minimizing the following functional $$E(S) = \int \left[\lambda(S''(x))^2 + (f(x) - ...
0
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0answers
151 views

Technique behind the way google earth overlaps polygons on top of pictures

What´s the technique behind the way google earth overlaps polygons on top of pictures(like the ones users assign to streets and houses) ? It seems to be aware of perspective, and I don´t remember ...
0
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0answers
255 views

Ways of object recognition in computer vision

In the field of computer vision, we talk a lot about this process of feature detection-description-matching as a way of recognizing objects. But on the other hand, there's also talks about object ...
2
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1answer
3k views

How to reconstruct the image from a neural network output?

I am trying to use the genetic algorithm to optimise a multi-layered neural network for image classification (i am using a subset of the MNIST handwritten digit data set as my initial dataset, but ...
-2
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1answer
90 views

from when do we have the field of computer vision? [closed]

when was the field of computer vision created and what are the disciplines that gave birth to it? I would appreciate it if you could give some web references that have the answer.
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0answers
120 views

General object recognition versus specific object recognition

I have a question about the difference between general object detectors and specific object detectors. By specific object detectors, I'm referring to classifiers/object recognizers that are built to ...
4
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1answer
1k views

Training and testing image sizes for classification in computer vision

When training a classifier for object detection using features extracted from images (eg HoG features), how important is it that the images used for training fed into the classifier in their natural ...
5
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1answer
619 views

Advantages of adaboost over gentleboost in applications, or vice versa?

I've been researching on AdaBoost and GentleBoost classifiers, but can't seem to find a clear answer to the question: What is Adaboost better at classifying in computer vision? What is GentleBoost ...
3
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1answer
2k views

Similarity between two geometric shapes

I have two shapes in a 2D space, not necessarily convex, and I'd like to compare how similar they are. How can I define a robust distance metric to measure their similarity, and how can I compute it? ...
6
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1answer
5k views

Does there exist a data compression algorithm that uses a large dataset distributed with the encoder/decoder?

If my goal were to compress say 10,000 images and I could include a dictionary or some sort of common database that the compressed data for each image would reference, could I use a large dictionary ...
1
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1answer
369 views

How to compute Gabor feature vector?

I'm working on semi automatic texture segmentation using level set and gabor feature vector described by Manjunath und Ma [1]. I consider their feature representation is better than others since I can ...
2
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4answers
693 views

Environment detection - How to detect “city” versus “landscape” background environment in computer vision?

I'm searching for computer vision or machine learning algorithms/methods that are used to classify or differentiate two outdoor environments. Given an image with vehicles, I need to be able to detect ...
3
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1answer
110 views

Environment requirement in training image dataset for classifier

I have a question about preparing the dataset of positive samples for a cascaded classifier that will be used for object detection. As positive samples, I have been given 3 sets of images: a set of ...