js method of drawing circles and rectangles_javascript skills
The example in this article describes how to draw circles and rectangles in js. Share it with everyone for your reference. The details are as follows:
JS is used here to draw circles and rectangles, and it supports selecting the background color of graphics. At the same time, you can set the options of rounded rectangle, radius, perfect circle, rectangle, and square. Maybe you don't need these graphics, but it is important for you to learn how to draw graphics in JavaScript. This is the core of the expression.
The operation effect is as shown below:
The specific code is as follows:
<!doctype html>
<html>
<head>
<title>js来绘制圆形和矩形</title>
<style>
*{margin:0; padding:0;}
#div{position:absolute; background:#ccc;}
.sel{ margin:30px auto; width:960px; overflow:hidden}
li{ list-style:none; float:left; width:60px; height:20px;}
#colors{ width:500px; float:left}
.selColor{ float:left}
#radius{ width:40px; height:20px;}
.red{background:red;}
.yellow{background:yellow;}
.blue{background:blue;}
.pink{background:pink;}
.black{background:black;}
.orange{background:orange;}
.green{ background:green;}
.xz{ width:340px; float:right;}
#canvas{ width:960px; height:500px; border:1px solid #ccc; margin:0 auto}
</style>
<script>
function $Id(id)
{
return document.getElementById(id);
}
window.onload=function(){
var oCanvas=$Id('canvas');
var oRoud=$Id('roud');
var oRadius=$Id('radius');
var oCir=$Id('circle');
var oSqu=$Id('squ');
var oColors=$Id('colors');
var aColors=oColors.getElementsByTagName('li');
var color='red';
var aInputs=document.getElementsByTagName('input');
var xz='roud';
var arr=[];
for(var i=0;i<aInputs.length;i++)
{
if(aInputs[i].type=='checkbox')
{
arr.push(aInputs[i]);
}
}
for(var i=0;i<arr.length;i++)
{
arr[i].onclick=function()
{
if(!this.checked)
{
this.checked=false;
}
else
{
for(var j=0;j<arr.length;j++)
{
arr[j].checked=false;
}
this.checked=true;
xz=this.value;
}
}
}
//选择颜色
for(var i=0;i<aColors.length;i++)
{
aColors[i].onclick=function()
{
color=this.className;
}
}
oCanvas.onmousedown=function(ev)
{
if(oCanvas.setCapture)
{
oCanvas.setCapture();
}
for(var i=0;i<arr.length;i++)
{
if(arr[i].checked)
{
arr[i].checked=true;
xz= arr[i].value;
}
}
var oEv=ev||window.event;
var disX=oEv.clientX;
var disY=oEv.clientY;
var oR=document.createElement('div');
oR.id="div";
oR.style.top=disY+'px';
oR.style.left=disX+'px';
oR.style.backgroundColor=color;
document.body.appendChild(oR);
document.onmousemove=function(ev)
{
var oEv=ev||window.event;
var x=oEv.clientX;
var y=oEv.clientY;
if(x<oCanvas.offsetLeft)
{
x=oCanvas.offsetLeft;
}
else if(x>oCanvas.offsetLeft+oCanvas.offsetWidth)
{
x=oCanvas.offsetLeft+oCanvas.offsetWidth
}
if(y<oCanvas.offsetTop)
{
y=oCanvas.offsetTop;
}
else if(y>oCanvas.offsetTop+oCanvas.offsetHeight)
{
y=oCanvas.offsetTop+oCanvas.offsetHeight
}
oR.style.width=Math.abs(x-disX)+'px';
oR.style.top=Math.min(disY,y)+'px';
oR.style.left=Math.min(disX,x)+'px';
switch(xz)
{
case 'roud':
oR.style.height=Math.abs(y-disY)+'px';
oR.style.borderRadius=oRadius.value+'px';
break;
case 'circle':
oR.style.height=Math.min(Math.abs(x-disX),Math.abs(y-disY))+'px';
oR.style.width=Math.min(Math.abs(x-disX),Math.abs(y-disY))+'px';
oR.style.borderRadius=(Math.min(Math.abs(x-disX),Math.abs(y-disY)))/2+'px';
break;
case 'squ':
oR.style.height=Math.abs(y-disY)+'px';
break;
case 'square':
oR.style.height=Math.min(Math.abs(x-disX),Math.abs(y-disY))+'px';
oR.style.width=Math.min(Math.abs(x-disX),Math.abs(y-disY))+'px';
}
}
document.onmouseup=function()
{
document.onmousemove=null;
document.onmouseout=null;
if(oCanvas.releaseCapture)
{
oCanvas.releaseCapture();
}
}
return false;
}
}
</script>
</head>
<body>
<div class="sel">
<span class="selColor">请选择一种颜色</span>
<ul id="colors">
<li value="red" class="red"></li>
<li value="yellow" class="yellow"></li>
<li value="blue" class="blue"></li>
<li value="pink" class="pink"></li>
<li value="black" class="black"></li>
<li value="orange" class="orange"></li>
<li value="green" class="green"></li>
</ul>
<p class="xz">
<input type="checkbox" value="roud" id="roud" />圆角矩形
<label>半径</label><input type="text" value="" id="radius" />
<input type="checkbox" id="circle" value="circle" />正圆
<input type="checkbox" id="squ" value="squ" />矩形
<input type="checkbox" id="square" value="square" />正方形
</p>
</div>
<div id="canvas">
</div>
</body>
</html>
I hope this article will be helpful to everyone’s JavaScript programming design.
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