HTML5学习记录-----canvas学习之鼠标选取放大图像
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内容图文
canvas鼠标选取放大 欢迎大家有好点建议可以提。js高级扣扣群：170798851 欢迎来交流学习
??? git项目地址：https://github.com/Jonavin/HTML5_Study
/**
* Created by wsf on 2014-11-23.
*/
;//分号为了保证代码合并时不出错
(function(win){
"use strict";
var doc = win.document,cvs = doc.querySelector("#canvas"),
selector = doc.getElementById("selector"),
restBtn = doc.getElementById("resetBtn"),
ctx = cvs.getContext("2d"),
img = new Image(),width = cvs.width,height = cvs.height,msdown = {},selectRect = {},dragging = false;
var _functions = {
//选取开始
selectStart : function(x,y) {
msdown.x = x;//鼠标按下横坐标
msdown.y = y;
selectRect.left = msdown.x;
selectRect.top = msdown.y;//
this.moveSelector();//移动选取框
this.showSelector();//显示选取框
dragging = true;//
},
//移动选取框
moveSelector: function () {
selector.style.top = selectRect.top + "px";
selector.style.left = selectRect.left + "px";
},
//显示选取框
showSelector:function(){
selector.style.display = "inline";
},
//展开选取框
selectorStretch:function(x,y){
selectRect.left = Math.min(x,msdown.x);
selectRect.top = Math.min(y,msdown.y);
selectRect.width = Math.abs(x - msdown.x);
selectRect.height = Math.abs(y-msdown.y);
this.moveSelector();//移动选取框
this.resizeSelector();//重设选取框
},
//重设选取框大小
resizeSelector:function(){
selector.style.width = selectRect.width + "px";
selector.style.height = selectRect.height + "px";
},
//重置选取框
resetSelector:function(){
selectRect = {top:0,left:0,width:0,height:0};
},
//选取结束
selectEnd:function(){
var _box = cvs.getBoundingClientRect();
try{
ctx.drawImage(cvs,selectRect.left-_box.left,selectRect.top-_box.top,selectRect.width,selectRect.height,0,0,width,height);
}catch (e){
}
this.resetSelector();
selector.style.width = 0;
selector.style.height = 0;
this.hideSelector();
dragging = false;
},
hideSelector:function(){
selector.style.display = "none";
}
}
cvs.onmousedown = function(e){
var x = e.clientX,y = e.clientY;
e.preventDefault();//阻止浏览器默认事件
_functions.selectStart.call(_functions,x,y);
}
win.onmousemove = function(e){
var x = e.clientX,y = e.clientY;
e.preventDefault();
if(dragging){
_functions.selectorStretch.call(_functions,x,y);
}
}
win.onmouseup = function(e){
e.preventDefault();
_functions.selectEnd.call(_functions);
}
img.onload = function(){
ctx.drawImage(img,0,0,width,height);
}
restBtn.onclick = function(e){
ctx.clearRect(0,0,width,height);
ctx.drawImage(img,0,0,width,height);
}
img.src = "img.jpg";
})(window);
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>鼠标选取canvas区域</title>
<style>
body{
background: rgba(100,145,250,0.3);
}
#canvas{
margin-left: 20px;
margin-bottom: 10px;
margin-right: 0;
border:thin solid #aaa;
padding: 0;
}
#controls{
margin:20px 0 20px 20px;
}
#selector{
position: absolute;
border:3px solid blue;
cursor: crosshair;
display: none;
}
</style>
</head>
<body>
<div id="controls">
<input type="button" id="resetBtn" value="重置"/>
</div>
<div id="selector"></div>
<canvas id="canvas" width="800" height="520">
不支持canvas
</canvas>
<script src="mouseSelect.js"></script>
</body>
</html>
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原文：http://javasam.iteye.com/blog/2159523
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