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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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320 views

How should someone start to learn machine learning and computer vision for mobile applications? [closed]

I am very interested in learning Machine Learning and Computer Vision for mobile apps, for iOS and Android. But I have no clue or even a slight idea on how to even begin. I know this is heavy on math ...
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1answer
117 views

Super resolution methods

I am working on the project where my goal is to create SR image from 25 LR images that are precisely shifted by 0.2px (both in horizontal and vertical direction ). I also know that the captured object ...
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1answer
846 views

How to choose the most appropriate color space for a computer vision application?

A lot of image processing techniques used in computer vision consist (among other things) in switching from RGB to another color space (HSV, YUV, LMS...) : color transfer, visual tracking... It seems ...
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1answer
138 views

Are the HOG features of the images good enough to do image classification alone? Why are their variances low?

I've also asked this question here:https://cs.stackexchange.com/questions/77884/are-the-hog-features-of-the-images-good-enough-to-do-image-classification-alone I've been working on classifying human ...
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1answer
341 views

Difference between Generalized Hough Transform and Cross-correlation Feature Matching

I've been taking the Udacity Computer Vision Course, and one thing that has confused me so far is how the Generalized Hough Transform is any different from feature matching on an edge image using ...
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4answers
366 views

Palm Pilot Graffiti

I have been completely unable to find details on the underlying model that is used for the Palm Pilot Graffiti handwriting recognition. Given the computing power available for handheld PDA technology, ...
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1answer
115 views

Pinhole camera model from houdini parameters

From a simulation with Houdini software I retrieved these parameters: Camera position: -0.675839, 33.5945, 0.0318854 Camera Rotation: 0.0318854, 92.4693, 0.1 Focal Length: 52.5172 mm Image size: 1920 ...
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0answers
185 views

stones' detection in jewel image

The project I am doing is to detect stones in an image of a jewel, so as to get the idea of the deduction to be made in the gross weight of the jewel. I have done image-segmentation in the HSV color ...
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0answers
555 views

Correct Fish Eye camera Radial Distortion and blurry effect at the image edges

There are a lot of questions regarding this topic ,but I am trying to get a more clear picture from these questions. I am trying to calibrate a fish eye camera and I am using OpenCV omnidir class ...
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0answers
382 views

What are the drawbacks of Harris corner detector? [closed]

What are drawbacks of Harris corner detection when trying to match features in a stereo pair? I notice that whenever I use Harris corner detector to match features, images with strong occluded areas ...
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1answer
89 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
28 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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0answers
444 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
81 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
412 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
258 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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2answers
1k 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
799 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
499 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
344 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
4k 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 ...
4
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2answers
505 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 ...
2
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1answer
209 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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1answer
50 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
587 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
2k 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
127 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
584 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
658 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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1answer
401 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
80 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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2answers
604 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
743 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
395 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
667 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
67 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
107 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
163 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 ...
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1answer
686 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
152 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
35 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
745 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
64 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
715 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
329 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
911 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
413 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
380 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
72 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 ...