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Questions tagged [opticalflow]

Optical flow or optic flow is the pattern of apparent motion of objects, surfaces, and edges in a visual scene caused by the relative motion between an observer (an eye or a camera) and the scene.

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What is the difference between sparse and dense optical flow?

Lots of resources say that there are two types optical flow algorithms. And Lucas-Kanade is a sparse technique, but I can't find the meanings of sparse and dense? Can some one tell me what is the difference between dense and sparse optical flow?
Yücel Ceylan
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What is endpoint error between optical flows?

I've seen endpoint error (EPE) used as a metric for determining how close a flow estimation is to a ground truth flow, but I have a few questions about it and was hoping someone could enlighten me: What does it actually represent? How do you…
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Optical flow ignore sparse motions

We're actually working on an image analysis project where we need to identify the objects disappeared/appeared in a scene. Here are 2 images, one captured before an action has been made by the surgeon and the other afterwards.…
Maystro
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Fast, very lightweight algorithm for camera motion detection?

I'm working on an augmented reality app for iPhone that involves a very processor-intensive object recognition algorithm (pushing the CPU at 100% it can get through maybe 5 frames per second), and in an effort to both save battery power and make the…
Ertebolle
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OpenCV warping image based on calcOpticalFlowFarneback

I'm trying to perform a complex warp of an image using Dense Optical Flow. I am trying to warp the second image into roughly the same shape as the first image. cv::Mat flow; cv::calcOpticalFlowFarneback( mGrayFrame1, mGrayFrame2, flow, 0.5, 3, 15,…
Goz
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Lucas Kanade python numpy implementation uses enormous amount of memory

I was working on Optical Flow script using Lucas Kanade method, as University project. While it works well, there is something I can't figure out. It uses few MB of memory at start, but that amount increases rapidly every second. By the time it…
mpiekarz
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Image stabilization library Objective-C / C / C++?

is there a decent image stabilization library (something around optical flow) out there that can give me a 3 dimensional transformation matrix to stabilize with? I just want to stabilize a 10 frame sequence. A library with an Objective-C wrapper…
Geri Borbás
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simple case of optical flow

General: I'm hoping that the use-case I'm about to describe is a simple case of an optical flow problem and since I don't have much knowledge on the subject, I was wondering if anyone has any suggestions on how I can approach solving my…
Myx
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How to warp the later frame to previous frame using optical flow image

I just have two images,one is the current frame,the other is the optical flow image which calculated by other manners. The current frame is: The optical flow image is: My question is how to calculate the previous frame using the two images? I…
huoyan
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What is output from OpenCV's Dense optical flow (Farneback) function? How can this be used to build an optical flow map in Python?

I am trying to use the output of Opencv's dense optical flow function to draw a quiver plot of the motion vectors but have not been able to find what the function actually outputs. Here is the code: import cv2 import numpy as np cap =…
James Mallett
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How to grab video frames in Qt?

I am new to Qt, I only know the basics: create interfaces and connect slots. In a few words, my knowledge is not deep at all. I need to open a video file and capture all of its frames to get the R, G, B channels and, later on, process optical flow…
Leonardo Lanchas
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Visualize Optical Flow with color model

I've implemented a dense optical flow algorithm and I want to visualize it with following color model (color denotes direction of flow at some point, intensity denotes length of displacement vector) I've implemented a dirty version of the…
Daiver
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Unknown output of OpenCV's calcOpticalFlowFarneback

I've been wondering what the optical flow matrix, that calcOpticalFlowFarneback function of OpenCV returns, tells. If I compute this Python line: flow = cv2.calcOpticalFlowFarneback(cv2.UMat(prvs),cv2.UMat(next), None, 0.5, 3, 15, 3, 5, 1.2, 0) I…
user2229358
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How does KLT work in OpenCV?

I am curious about the logic behind KLT in openCV. From what I have known so far, the images sent to find optical flow in OpenCV is firstly converted to grayscale. What I am curious is that, when running the algorithm, we need set of features for…
ra bes
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How to do smooth frame interpolation and extrapolation using OpenCV?

My source data files are weather radar images captured every 15 minutes. I'm trying to make a smooth interpolation of intermediate frames and I'm trying to extrapolate the motion onwards from the last measurement. So far, my method has been to…
MrBronson
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