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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.

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1answer
87 views

Estimating exterior camera parameters by matching lines using least square estimations (Lowe, 1991)

I'm new to computer vision and graphics. I want to estimate exterior camera parameters using non-linear least square estimation as suggested by "Lowe, David G. "Fitting parameterized three-dimensional ...
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0answers
27 views

Kalman Filter - Gaussian representation

I'm trying to understand well the kalman filter, as a result i'm having this question : Why do we represent noise with a Gaussian ? what does this really mean intuitively ?
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418 views

How can l extract characters withe same bounding box size?

l have a set of images which represent a sequence of characters. l'm wonderning whether OpenCV can segments and crop each character from the image with same bounding box size. My numbers are not ...
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0answers
69 views

Shot boundary detection using SVM's

I'm trying to do shot boundary detection using SVM's. I'm differentiating between 3 shots, cut, fade and dissolve + (normal frames). I had used two features, shannon's entropy and variance, it gave ...
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1answer
342 views

Can you detect circles only using the hough line transform?

I'm not talking about the Hough Circle Transform (where you replace the representing eqns, hence the parameters with a 3D set) but a Hough Line Transform. My solution to this: A hough line transform ...
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1answer
241 views

How to use Principal component Analysis(PCA) to extract feature from images [closed]

How can use principal component Analysis to extract feature from image that is been acquired by the camera?
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1answer
958 views

Why do we need 4 points for homography but 7/8 points for fundamental matrix calculation?

Sorry if this is a trivial question but I could not find a suitable answer elsewhere. I recently learned about homography and fundamental matrices in a CV class. I understand how these matrices are ...
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0answers
724 views

Fourier Mellin Transform

I start developing Analytical Fourier Mellin transform for image recognition using the invariant described in this paper "Robust and Efficient Fourier–Mellin Transform Approximations for Gray-Level ...
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2answers
450 views

How does Jpeg encoding affect the final file size of 24BPP RGB and 8BPP grayscale image?

The reason I'd like to know this is because of a file size problem. I am trying to reduce an image's file size from converting it from TIFF to JPEG. A user challenge me that he notice a RGB TIFF image ...
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1answer
305 views

Finding the four corners of each quadrilateral shapes in an image

I am working on some image processing application using Matlab. The image after segmentation will look (more or less) like the figure below. Now I want to find the four corners of each shape to crop ...
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2answers
3k views

Opencv color segmentation of traffic signs: HSV ranges

I am working on a project to detect and recognize signs in images from the LISA Traffic Sign Dataset. Since the images are very noisy (in regard to background) I am trying to segment the signs based ...
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2answers
447 views

How to reliably detect the state (opened or closed) of sliding doors from a statically-positioned video stream

I have a mounted (static) camera that has a view of a set of sliding doors. Since doors are rectangular in nature, and they don't have many degrees of freedom, this seems like a problem that should ...
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1answer
196 views

What does photon noise mean in digital image processing or computer vision?

From this link: Photon noise, also known as Poisson noise, is a basic form of uncertainty associated with the measurement of light, inherent to the quantized nature of light and the independence of ...
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0answers
41 views

How to derive the probability (as follows) according to the sum and product rules

How to derive the formulation by the sum and products? $$p(t|\mathbf{x},\mathcal{D})=\sum_{i=1}^{L}p(t|\mathbf{x},\mathcal{M}_i, \mathcal{D})p(\mathcal{M}_i | \mathcal{D})$$
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1answer
49 views

library for computing differential signatures from 2D planar curves

For one of the lectures on 2D planar differential geometry in the series "Image and Video Processing: From Mars to Hollywood With a Stop at The Hospital", the lecturer discusses differential ...
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1answer
540 views

Hand tracking, state of the art

I am looking for a framework for extracting hand region from the video feed from the webcam(analogous to Viola Jones HAAR detection of face). This region of interest will serve as input for a CNN for ...
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1answer
1k views

How can I track detected objects from frame to frame

I want to track people's faces in a video stream (like a security camera), but I am running into a problem. I was using a Haar classifier to find the faces and sending the detected faces to a system ...
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1answer
121 views

image reconstruction using a set of kernels

I try to be brief. For what I understood Convolutional Neural Network CNN for style-transfer extract/learn the main features of source Image. I think these features basically are Kernels (of different ...
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2answers
489 views

Why is scale space (DoG) needed to detect scale invariant features?

I would have a theoretical question, about the detector part of the SIFT algorithm, which as it is explained by D. Lowe in his paper, used the DoG to detect keypoints in an input image. Problem ...
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1answer
639 views

Two-View 3D reconstruction using the sparse Levenberg–Marquardt algorithm

I have trouble implementing the Levenberg-Marguardt algorithm as described in the book Multi View Geometry in Computer Vision. To be more specific I have trouble calculating the partial derivatives ...
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0answers
239 views

Image warpping in Matlab

While reading about the Object detection from the R-CNN paper. I have confusion in understanding about the warpping the image regions. The input to the CNN is 227x227 and the image regions would be ...
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0answers
164 views

Angle in orientation assignment in SIFT

I'm going through the Scale-invariant feature transform (SIFT) in this paper: Distinctive Image Features from Scale-Invariant Keypoints, David G. Lowe, 2004. Currently I'm stuck in orientation ...
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1answer
379 views

Is image annotation a hard AI problem? [closed]

From Wikipedia "In the field of artificial intelligence, the most difficult problems are informally known as AI-complete or AI-hard, implying that the difficulty of these computational problems is ...
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1answer
79 views

what is $1/f$ property of the visual world?

I was watching a talk by Edward H. Adelson on the perception of materials and surfaces. He mentions a $1/f$ property of the visual world. He says: low frequencies are prevalent than high ...
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0answers
196 views

how to show HSV is better choice for my work than RGB colour space

I am using HSV for object detection work. For the report I have to write why I am using HSV colour space instead of RGB colour space. I am trying to show this different by fitting the distribution for ...
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2answers
579 views

Techniques for detecting small blobs in noisy images

I am trying to write a program that uses computer vision techniques to detect (and track) tiny blobs in a stream of very noisy images. My data is of two types: one set of images are not so noisy, ...
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2answers
607 views

Segmentation of warped text lines

I am trying to segment warped text lines found in photos taken from a page of a book (from the camera of a smartphone). This is meant as a preprocessing step before running OCR on them. I have found ...
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0answers
356 views

Segmentation and edge linking

I am trying to implement segmentation on an image. after a difference of Gaussians Process and applying weights to my edges I want to go through edge linking by local processing. I have seen this ...
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1answer
603 views

what is difference between structure image and texture image

I am working in Computer Vision. One thing is confusing me, the difference between structure image and texture image. Both are looking same. but i read few papers, which showing that both are ...
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1answer
61 views

Understanding Active Contour results - Williams and Shah 1992

I have implemented a version of Williams and Shah's 1992 active contour algorithm, which uses the energy function: Ej = alpha * Econtj + beta * Ecurvj + gamma * Eimagej where j is a N8 neighbor of a ...
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1answer
105 views

Image reconstruction using Irradiation

I am a bit confused as to how to go about this. I have a surface [x,y,z] given by: ...
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1answer
160 views

Is image processing impacted by the lens or sensor size of the camera?

We want to configure a system for detecting and tracking basketball shots made. We have control over the cameras, so we can choose anything from a smartphone to a GoPro. Assume the scene is a typical ...
3
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1answer
646 views

Multi-scale in Object detection?

I want to ask about MultiScale Object Detection. For the multiscale, if we have an original image do I need to zoom-in at different scales in the image at a particular point or zoom-out at different ...
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2answers
144 views

How does viola jones algorithm cope up with a test image size which is very different to training image sizes?

To my understanding Viola jones algorithm is a combination of weak classifiers built on training imageset. Lets say we have training images of 24x24 and algorithm selected 100 haar features and built ...
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1answer
34 views

What is the performace of Bag of words under scale and rotation changes?

How does Bag of words perform under scale and rotation changes? Are scale and rotation the only metrics or are there any other metrics checked for evaluation of general computer vision method?
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1answer
727 views

Image processing: Image recognition and classification on fish

I need to identify the type of fish caught from fish images. How can I locate anchor points/landmark points to extract features from the image? Namely, I want to locate eye position, dorsal and ...
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1answer
63 views

Face detection in videos [closed]

I have to detect faces in videos using machine learning methods like SVM, I have to build it from scratch not using any inbuilt face detectors.My time limit is like 15hours from now.Can I get any ...
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1answer
648 views

Backprojection of 2D image on 3D model

I am trying to implement the paper "Face Reconstruction in the Wild". In that I use a template 3D model and rotate it to align it with the orientation of the face in the 2D image. Now I want to ...
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2answers
277 views

How can we combine 2D image with 3D image for the same sense?

We have 3D point cloud data captured by a laser scanner and need to register it with 2D images to get further information. In our case, the 2D image and 3D points are not overlapping and therefore we ...
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1answer
2k views

Difference between optical flow field and motion field?

I have been trying to understand the various confusing definitions of optical flow field and motion flow field but cannot wrap my head around it. Some authors use the term interchangeably other give ...
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3answers
830 views

Calculating Hamming distance effectively: a fast approach

Let us say that we have a database of 5000 entries. Each entry is a 32 point discrete signal (min. amplitude: 0 and max. amplitude: 10 (signal value ranging only in integers)) i.e. each discrete point ...
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2answers
403 views

Kalman filter for tracking obstacles

I'm developing a Computer Vision project in Matlab as an aid to visually impaired people. The setup would be a stereo pair of cameras which the blind person would carry. Using this stereo information, ...
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2answers
327 views

Backgammon checkers and dice detection

first of all thanks for reading, and sorry for such a generic question. If it is off topic for your forum i would be thankful if someone could point me to a place where i can find an answer. I am ...
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0answers
71 views

What are the classification methods available for face recognition watchlist screening? [closed]

My intention is to develop a method that only able to recognize a target among the non-target (unknown people) groups. What algorithm/method can I go through to build this type of classifier. It is ...
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0answers
79 views

Extrinsic Camera Parameters without introducing control points?

I am new to the field of Camera Calibration. We have successfully calibrated our camera through classic method (using checkerboard etc). I recently realized there is a field of research for Automatic ...
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2answers
623 views

Comparison between watershed and grabcut

I know that watershed and grabcut algorithms are both common tools for image segmentation. They both seem to rely on predefined markers to form something like a source-sink system and then uses the ...
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3answers
148 views

Can I use standard computer vision techniques for images taken in the NIR spectral range?

I'm relatively new in Computer Vision and I need some advice with respect to the general possibilities and shortcomings of images taken in the near infrared (NIR) range. I passed a great deal of time ...
2
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1answer
5k views

When is a network called end-to-end training?

In machine learning, we often see the expression "end-to-end" learning (or training). However, I do not know that it means. When is a network called end-to-end training? How to recognize a network is ...
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1answer
122 views

How to get Harris corners that are present in watershed segmented Bitwise image(road part)?

This is Harris corner image of test image: This is Bitwise watershed segmented image: I want to get that Harris corners which will be in segmented part of image(road part).
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133 views

Gabor Filter implemetation in frequency domain with three different filter central frequencies and 4 orintations

I am trying to construct a Gabor filter with 3 different central frequencies and 4 different orientation. But for a particular frequency, for all the orientation I am getting the same response, I don'...