roi | 易学教程

Select a static ROI on webcam video on python openCV

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问题 I need to selec a ROI (region of interest), or work area, on a live video from my webcam and take a snapshot of ONLY this work area or ROI, but I can't found how to do this. In this page https://www.learnopencv.com/how-to-select-a-bounding-box-roi-in-opencv-cpp-python/ have a code for draw a ROI but only with images, not a live video. import cv2 cam = cv2.VideoCapture(0) cam.set(cv2.CAP_PROP_FRAME_WIDTH, 1280) cam.set(cv2.CAP_PROP_FRAME_HEIGHT, 720) cv2.namedWindow("test") img_counter = 0

Select a static ROI on webcam video on python openCV

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Iterate over regions and take mean pixel value in OpenCV?

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问题 So Im basically trying to divide up a gray scale image (in this case 32x32) by resizing the initial image. Once the "regions" are divided up, I need to take the mean pixel value of each one and then add to a string a 1, 0, or X. For example: "Region (3, 19) has a mean value of 21 so that's a 1". I think I have most of the logic down but shouldn't, in theory, the output recreate the image in the form of 1s, 0s, and Xs? I feel like my math is wrong on the for loops maybe? Remember, all Im

What is the difference between cropping an image and applying an ROI (region of interest) on the image

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问题 I'm using opencv . Having a base image ( 640x640 ) I want to know if applying a rectangular white shape mask of (100x100), in another words, a ROI is more time consuming compared to cropping the image in the same rectangular shape (100x100). What I consider as being a ROI mask = np.zeros_like(original_image) shape = np.array([[a,b,c,d]]) cv2.fillPoly(mask, shape, (255,255,255)) cv2.bitwise_and(original_image, mask) The way of cropping cropped = original_image[x:y, z:t] I want to apply a

How to capture mouse movement for the whole window in opencv python?

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问题 I know and have seen tons of documentations explaining about how to capture mouse movement within a given window using mouseclick events in opencv. What I want to know is that if is there a way to capture mouse movements (x,y co-ordinates) for the entire screen of my system. Any link, documentation or code snippet will be really helpful to proceed me with the same. 回答1: Depending on your OS, you can do that with pyautogui like this: #!/usr/bin/env python3 import time import pyautogui for i in

F-RCN论文阅读及难点解析

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论文名称：《 R-FCN：object detection via region-based fully convolutional networks 》论文下载：http://papers.nips.cc/paper/6465-r-fcn-object-detection-via-region-based-fully-convolutional-networks.pdf 论文代码：https://github.com/daijifeng001/r-fcn 一、概述： 1、R-FCN创新点： R-FCN要解决的根本问题是Faster R-CNN检测速度慢的问题。Faster R-CNN速度慢是因为ROI层后的结构对不同的proposal是不共享的，试想下如果有300个proposal，ROI后的全连接网络就要计算300次，耗时惊人。所以本文作者把ROI后的结构往前挪来提升速度，但光是挪动下还不行，ROI在conv5后会引起上节提到的平移可变性问题，必须通过其他方法加强结构的平移可变性，Position-sensitive score map因此而生。归纳如下：（1）提出Position-sensitive score maps来解决目标检测的位置敏感性问题；（2）充分利用全卷积网络来减少总体计算量，提升速度比Faster-RCNN快2.5-20倍； 2、R

opencv：截取 ROI 区域

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Rect roi; roi.x = 100; roi.y = 100; roi.width = 250; roi.height = 200; // 截取 ROI 区域 // 这种方式改变 sub，原图也会改变 Mat sub = src(roi); // 如果想要不影响原图，可以使用 clone，或者copyTo Mat sub2 = src(roi).clone(); rectangle(src, roi, Scalar(0, 255, 255), 1, 8); imshow("roi", sub); imshow("src roi", src); 来源： https://www.cnblogs.com/wbyixx/p/12244352.html

RTB撕开黑盒子 Part 3: Beyond Surplus

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在本文中，我将解释如果要对整个推广计划最大化利润，决定是否应该出价的应该是期望回本率 (ROI) ，而不是期望利润，这与我们以前介绍的有所不同。在 Datacratic ，我们已经在 2012 年底切到了基于 ROI 的策略。 Too Little of a Good Thing 推广计划的全部利润可以表达为：通过这个公式，看起来似乎是最大化每个竞价的期望利润，就是最大化整个推广计划的。但事实上不是，因为它有一个约束条件：所有的消耗加起来要等于预算。如果要最大化期望利润，是要每个请求需要更高的出价，那么你的竞价次数就会少，结果就是你可能整体的利润下降了。然而这并不意味着你应该在期望利润低时竞价，我的意思是你应该去权衡利润和消耗。这个问题在很久之前就被经济学者注意到了，我们要使用的衡量标准是 ROI ，它是计算投资回报率。如果你将每个请求都视为一次投资，你的反馈控制系统会告诉你现在是超速消耗或是次速消耗，你可以提高或是降低最小期望 ROI 阈值。你通过这个阈值决定是否竞价，而不是用最小期望利润阈值。在金融领域，这个阈值称为最低可接受的回报率 (minimum acceptable rate of return (MARR)) 或门槛收益率 (Hurdle Rate) 。 A Thought Experiment 下面是一个假设的实验，我们通过它来说明基于 ROI

get Original image from ROI image in opencv

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问题 is it possible to get back original image from image ROI? for example say we have cv::Mat image = imread("image.jpg", 0); cv::Mat imageROI = image(0, 0, 100, 100); myFunction(imageROI); and in myFunction I want to work with original image. is there any way to convert imageROI to original image when we don't access the original image? 回答1: Just incase anybody looks at this question you can actually do this cv::Mat mat = ... cv::Size size; cv::Point offset; // find original image size, and get

Giving specific values to pixels in some selected region

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问题 I'm trying to do the following in MATLAB : Select some region of interest Give the pixels in that region the value 1 for instance I'm not sure, would imfreehand be a starting point here for selecting the region of interest. What then? How can this be done in MATLAB ? Thanks. 回答1: Here is a short sample. Since you mentioned imfreehand , I included that but depending on what type of ROI you want to create, impoly or imrect may do a better job: img = im2double(imread('cameraman.tif')); imshow