em | 易学教程

CSS style - percentage vs em vs px? [closed]

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问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 6 years ago . After reading several articles on the web I´m a bit confused about when to use percent , em or px for div´s , input´s , font´s , buttons and so on... For the site I´m working on we wan´t to add a responsive design, and from what I understand from different articles than percent is the way to go for elements and

Using fractional em's in CSS's font-size property

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问题 Say, I have the following CSS rule defined: .className { font-size:0.89em; } My question is, how "deep" into fractions can I go while specifying 'em's for browsers actually to support it and for the font size to be rendered differently for a small fractional change in the em's value? 回答1: JohnB is right. We're still rendering in pixels whatever the size unit we use, and small changes in ems will not change the displayed size: For example, for text originally displaying at a height of 20px*,

算法4第6章碰撞检测实现

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碰撞检测采用事件驱动模型来模拟小球的运动及碰撞，首先预测所有的碰撞事件，按碰撞时间存入优先队列，碰撞发生时重新计算发生碰撞的小球的速度，方向，重新预测该小球可能发生的的碰撞事件存入优先队列同时定义一个重复的事件存入优先队列，用来模拟时钟及重绘每个小球的位置。遍历优先队列模型小球的运动和碰撞，示意图如下： public class CollisionSystem { private static final double HZ = 0.5; // number of redraw events per clock tick private MinPQ<Event> pq; // the priority queue private double t = 0.0; // simulation clock time private Particle[] particles; // the array of particles /** * Initializes a system with the specified collection of particles. * The individual particles will be mutated during the simulation. * * @param particles the array of particles

算法4第6章后缀数组讲解

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最长重复子字符串/后缀数组给定字符串怎样找到它的最长重复子字符串，如字符串atobeornottobe，最长重复子字符串是tobe 使用一般的方法速度很慢，时间复杂度是O(N^2),而使用后缀数组可以巧妙而高效的解决此问题。首先找出字符的所有后缀字符串组成后缀字符串数组，对数组进行排序，然后遍历数组，最长重复子字符串就在相邻的两个后缀字符串中如字符串tobeornottobe，后缀字符串是atobeornottobe,tobeornottobe,obeornottobe,beornottobe,eornottobe,ornottobe,rnottobe，nottobe，ottobe，ttobe,tobe,obe,be,e 排序后就是 atobeornottobe be beornottobe e eornottobe nottobe obeornottobe ornottobe ottobe rnottobe ttobe tobe tobeornottobe 该算法在一般情况下时间复杂度是O(NlogN),代码如下 public class LongestRepeatedSubstring { // Do not instantiate. private LongestRepeatedSubstring() { } /** * Returns the longest

Python网络爬虫案例（二）——爬取招聘信息网站

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利用Python，爬取 51job 上面有关于 IT行业的招聘信息　　版权声明：未经博主授权，内容严禁分享转载　　案例代码： # __author : "J" # date : 2018-03-07 import urllib.request import re import pymysql connection = pymysql.connect(host='127.0.0.1', port=3306, user='root', password='******', db='51job', charset='utf8') cursor = connection.cursor() num = 0 textnum = 1 while num < 18: num += 1 # 51job IT行业招聘网址需要翻页，大约800多条数据 request = urllib.request.Request( "http://search.51job.com/list/120000,000000,0100,32,9,99,%2B,2," + str( num) + ".html?lang=c&stype=1&postchannel=0000&workyear=99&cotype=99&degreefrom=99&jobterm=99&companysize=99&lonlat=0%2C0

What is the em font-size unit? How much is it in pixels?

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I want to know what the em unit is, and how much 1em is when converted to pixels ( px ). I also read somewhere about some IE bug, to overcome which body font-size should be set to something, but couldn't follow much. Can somebody explain that in detail? Despite what you may read elsewhere, there is no direct relationship between em and px. As one of the links states: the "em" value is based on the width of the uppercase M So it's going to be different for every font. A narrow font might have the same height (in px) as an extended font, but the em size will be different. EDIT three years later:

面试碰到的部分问题

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1.em、rem、px的区别 https://www.runoob.com/w3cnote/px-em-rem-different.html 1、概念 px：绝对单位，页面按精确像素展示。 em：相对单位，基准点为父节点字体的大小，如果自身定义了font-size按自身来计算（浏览器默认字体是16px），整个页面内1em不是一个固定的值。 rem：相对单位，可理解为”root em”, 相对根节点html的字体大小来计算，CSS3新加属性，chrome/firefox/IE9+支持。 2、特点 PX特点： 1. IE无法调整那些使用px作为单位的字体大小； 2. 国外的大部分网站能够调整的原因在于其使用了em或rem作为字体单位； 3. Firefox能够调整px和em，rem，但是96%以上的中国网民使用IE浏览器(或内核)。 EM特点： 1. em的值并不是固定的； 2. em会继承父级元素的字体大小。 rem特点： rem是CSS3新增的一个相对单位（root em，根em），这个单位引起了广泛关注。区别在于使用rem为元素设定字体大小时，仍然是相对大小，但相对的只是HTML根元素。这个单位可谓集相对大小和绝对大小的优点于一身，通过它既可以做到只修改根元素就成比例地调整所有字体大小，又可以避免字体大小逐层复合的连锁反应。目前，除了IE8及更早版本外

Any suggestions for how I can plot mixEM type data using ggplot2

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I have a sample of 1m records obtained from my original data. (For your reference, you may use this dummy data that may generate approximately similar distribution b <- data.frame(matrix(rnorm(2000000, mean=c(8,17), sd=2))) c <- b[sample(nrow(b), 1000000), ] ) I believed the histogram to be a mixture of two log-normal distributions and I tried to fit the summed distributions using EM algorithm using the following code: install.packages("mixtools") lib(mixtools) #line below returns EM output of type mixEM[] for mixture of normal distributions c1 <- normalmixEM(c, lambda=NULL, mu=NULL, sigma

web爬虫讲解—urllib库爬虫—基础使用—超时设置—自动模拟http请求

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利用python系统自带的urllib库写简单爬虫 urlopen()获取一个URL的html源码 read()读出html源码内容 decode(“utf-8”)将字节转化成字符串 #!/usr/bin/env python # -*- coding:utf-8 -*- import urllib.request html = urllib.request.urlopen('http://edu.51cto.com/course/8360.html').read().decode("utf-8") print(html) <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <meta name="csrf-param" content="_csrf"> <meta name="csrf-token" content="X1pZZnpKWnQAIGkLFisPFT4jLlJNIWMHHWM6HBBnbiwPbz4/LH1pWQ=="> 正则获取页面指定内容 #!/usr/bin/env python # -*- coding:utf-8 -*- import urllib.request

unit —— em / rem / vh / vw

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html,body{margin:0; padding:0; font-size:14px; } /*em 继承父元素的字体大小，来变大或变小，多层嵌套字体变化*/ .em, .em > .em-son, .em > .em-son > .em-grandson {font-size: 1.2em;} /*rem 继承根节点元素的字体大小，来变大或变小，多层嵌套字体不变化*/ .rem, .rem > .rem-son, .rem > .rem-son > .rem-grandson {font-size: 1.2rem;} /*rem 也可作为固定长度单位设置宽高等*/ .rem-box { width:10rem; height: 10rem; line-height:5rem; text-align: center; color: #fff; background: #d60b3b; } /*vh,vw 屏幕可见区域的高度，宽度的1%*/ .vhvw-box { width:50vw; height: 100vh; line-height:25vh; text-align: center; color: #fff; background: #d60b3b; } <body> <h1>em 继承父元素的字体大小，来变大或变小，多层嵌套字体变化</h1> <div class=

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