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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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191 views

How Can PCA Be Used in Image Analysis [closed]

I am still a not how PCA can be used in image analysis and where is it is mostly used. For example how can PCA be used in order to differentiate between different faces? Can you please mention other ...
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1answer
88 views

Good Metric for Spatial Resolution

I am trying to filter crawled images with their image quality. By 'high quality' I mean high resolution, not aesthetic score or perceptual score. However I found that some images have very high pixel ...
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2answers
664 views

Camera measurement of heart rate - frequency bias towards 50 bpm (0.83 Hz)?

I am trying to develop a RGB camera-based non-contact measurement of heart rate using principles of remote photoplethysmography. I want to be able to measure a range of heart rates I have been looking ...
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1answer
696 views

Block normalization of histogram of oriented gradient

I am a beginner in image processing. I have some questions regarding HOG. https://www.learnopencv.com/histogram-of-oriented-gradients/ From this website, it mentioned that each element inside the ...
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1answer
3k views

Line Detection with OpenCV and Python [closed]

Why do we get less amount of lines then desired in line detection using HoughLines tranformation from OpenCV? How could we improve this method and get all the lines appearing in the image? I would ...
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1answer
2k views

Calculating distance between two blobs in a binary image in microns

I have a monochrome CCD camera with resolution 960 X 1280 and can give up-to 15 fps I am working on python opencv. I want to track the distance between two rectangular blobs in binary images in real ...
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1answer
486 views

Edge detection in low contrast images

I have some images which have some objects of my interest. The objects have very low contrast w.r.t. background and I would like to detect the edges of these objects in these low-contrast images. Any ...
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1answer
39 views

How to choose good features for my machine vision application? [closed]

I am trying to create an application (with OpenCV3) that can distinguish sidewalks from streets by a real-time camera that is embedded in a glass. I have 3 question about this project: Which features ...
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1answer
278 views

Pattern matching methods: Based on Area and Based on features

Good morning, I'm new to image processing and I'm currently working on a project for pattern matching and OCR more specifically. In the state of art I've found the matching process can be classified ...
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1answer
25 views

Are there paper about black box testing of optic flow algorithms?

Do papers exist about comparisons of the resulting optic flow and its precision compared to the used optic flow method? I would like to find paper that dealt with this topic in some way and had ...
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1answer
281 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
51 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
85 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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1answer
85 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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2answers
191 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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2answers
391 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
144 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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1answer
66 views

Detecting objects in real world video feed?

I have an image which consists on an object in a plain black background. This is the reference image of the object. Now, My task is to take a webcam and obtain the video feed and I have to detect if ...
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1answer
22 views

looking for simplified version of motion capture for simplified situation where objects are solid and have no joint (no internal degree of freedom)

The whole question is about a simplified algorithm for tracking a single solid object which has no joint, with assumption that i have full control on adding some markers in real world to it. For ...
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3answers
715 views

How to filter objects on basis of orientation of regionprops

I am trying to detect straight vertical lines in an image. I used vertical edge detection and then I tried to check which objects has the ...
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1answer
87 views

Finding crosses and their orientation on a given image

I want to recognize table structure from some arbitrary photo image and store it in some formal notation (Let it be HTML table notation). For example I have this blurry image as input: After ...
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1answer
2k views

How do I understand Fourier descriptors more visually and intuitively?

I read the book Image Processing, Vision and Machine Vision and find the concept Fourier descriptors hard to understand, although literally its derivation is somewhat reasonable. Can anyone give me a ...
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2answers
207 views

Beginner Question: Extracting Features for Image Classification

I'm a Python programmer, but a beginner to image processing :) Apologies if this isn't a suitable question for the forum, happy to rewrite or move. I want to create a supervised classifier to ...
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1answer
77 views

How can I use a trained model to generate related images?

Suppose I have a data set of a large number of related images and I extract HOG features and train it using SVM Classifier or KNN Classifier. How can I use this model to generate a new image which is ...
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1answer
406 views

Extracting DCT coefficients from H.264/AVC bitstream

Is it possible to extract DCT coefficients from H.264/AVC bitstream without doing a full-decoding of the video? There are a lot of papers on compressed domain video processing which are based on the ...
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1answer
96 views

Object detection using several images

how do people combine different information (e.g., RGB and depth image or RGB and thermal image) to make their object detection algorithms better? If the single modality images A and B are perfectly ...
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1answer
156 views

Converting blobs to circles

I have this binary image with some blobs of random sizes. I would like to convert the blobs into circles of uniform diameter. it doesn't really matter what diameter but they need to be circles and ...
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1answer
92 views

Understanding Eigenface Face Recognition Algorithm Notations

I have been reading the paper from Matthew A. Tusk and Alex Pentland https://www.cs.ucsb.edu/~mturk/Papers/mturk-CVPR91.pdf I got stuck in this part. I have a couple of questions. Assume my images ...
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1answer
61 views

neural network for 3D pictures

I'm wondering if they are some state-of-art algorithms to apply the convolutional neural network approach to 3D pictures, eg. input is no longer a grid of pixels, but voxels. My objective is to ...
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1answer
8k views

Difference between cv::subtract and operator - in cv::Mat OpenCV

What's the difference between cv::subtract and operator - in OpenCV? Mat original = imread...; Mat smoothed, difference, result; smoothed - original image ...
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2answers
406 views

Identification of a given barcode as either 1 D or 2 D

I am working on an algorithm (in MATLAB) to identify/classify a given bar code (image) as 1 D or 2 D. I have considered using the contrast of THE IMAGE matrix as a parameter or using the FFT of the ...
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1answer
4k views

Lane detection and tracking using B-snake?

I am truly sorry if my question sounds little bit stupid, but I am getting stuck at this part for a long time. I am currently working for my final year project of lane detection for curved road using ...
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1answer
303 views

How to plot ROC curve for weka multilayerperceptron?

I am working on an image classification project I use multilayerperceptron,how do I plot ROC curve.I use weka's perceptron.
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1answer
202 views

How to Linearise an Input Image before applying Color Correction?

I'm doing color correction on Raw images taken from Camera directly. I want to make my Camera reproduce same colors as my Target camera. Here are the steps I'm following: Take Target Color values ...
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1answer
172 views

Why is the backprojection of the Middlesbury depth map “cone shaped”?

I wrote some come to backproject depth maps. Testing it with the Middlebury cone set, I get: First of all it has noise, which I shouldn't get from the ground truth, but more importantly it seems like ...
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1answer
871 views

How do I implement LIBSVM for multiclass classification using java?

I am currently working on an image classification project ,where i need to use bag of features model with libsvm(HIK kernel) for classification.I have extracted sift feature and created a visual ...
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1answer
95 views

What does one call this method of grid fitting?

The input space has artefacts that are already in a grid-like layout: I'd like to be able to fit/draw a grid over the artefacts so as to separate them, preferably with lines on average mid-way ...
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1answer
5k views

Circle detection opencv

I Would like an explanation of the parameters for opencv's HoughCircles function. I'm new to image processing in general and I have recently started using opencv. ...
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1answer
726 views

Why do eigenvectors specify the direction of fastest and slowest changes in the image

I'm reading Szeliski's Computer Vision:Algorithms and Applications. On page 212-213, corner detector is discussed. I can understand upto equation 4.8. From then on, I don't understand how come ...
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1answer
2k views

AGAST vs FAST evaluation

In ~2006 the FAST corner detector was introduced. One of it characteristics is that you have to train a decision tree from some test image in order to learn the types of corners present and relevant ...
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1answer
2k views

Skeleton from distance map

Can anyone give some tips how to obtain Skeleton from distance map? I already managed to obtain skeleton using erased method (e.g. zhang suen) but it's time consuming because it's an iterative method ...
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1answer
110 views

Classifying animated GIFs as animation or film

Is there any known way of differentiating between frames of real footage and animated content? It seems like there's probably range of colors more likely to appear in a histogram for real footage, or ...
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1answer
89 views

Separate sub-figures!

Any idea on separating multi-panel figures? There are 2 different sub-figures connected each other. Thanks!
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2answers
173 views

Floating point Descriptor evaluation

I have come up with a new descriptor(floating point). I want to evaluate this descriptor against SIFT, GLOH, etc etc. I am using the K. Mikolajczyk, C. Schmid, approach. The method is described in ...
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1answer
119 views

How to choose the number of codewords in bag of words model

In the bag of words model, generally is it better to have more codewords or less? For example, if I have 1000 x 20 raw features, then what would be good value for codebooks? I am thinking of smaller ...
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1answer
174 views

Adding measuruments noises to kalman filter

I'm implementing navigation system for my robot. There are two ways to get data from it: odometry(encoders from motors) and camera. Both of information sources can give me estimate of robot's position....
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1answer
77 views

need general resource about image matching

i'm working on image matching mainly SIFT and SURF for my thesis. i read Moravec's and harris corner detectors and understand them quiet well in my own opinion.A COMBINED CORNER AND EDGE DETECTOR[1] ...
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1answer
2k views

Computer Vision Libraries for PHP

Are there any computer vision libraries in PHP, or any server-side programming languages? If not, maybe we can make a list of some -already implemented- methods (Viola Jones face detector, landmark ...
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1answer
176 views

(Rough) camera calibration of manipulated images

Coming from a photogrammetry background, I am quite familiar with camera calibration, and the common assumptions that are used for crowd-sourced images (i.e. center point in the middle of the image, ...
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1answer
558 views

How to make filters?

I am trying to make filters like sepia filter in my app like other photo editing applications , till now I don't have any idea about it , Can any one help me out ...