Implement a graffiti board with adjustable brush color/thickness/eraser based on javascript html5 canvas-JS Tutorial-php.cn

js html5 The graffiti drawing board special effects implemented by canvas can adjust the brush color | thickness | eraser, and can save the graffiti effect as image encoding. It is very suitable for learning HTML5 canvas. A browser that supports HTML5 must be used to see the effect.
<!doctype html> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<title>javascript结合html5 canvas实现的涂鸦板</title> 
<meta name="Copyright" content="JavaScript分享网 //m.sbmmt.com/" /> 
<meta name="description" content="javascript结合html5 canvas实现的涂鸦板,JavaScript分享网，js脚本，网页特效，网页模板，png图标，矢量图下载" /> 
<meta content="JavaScript,分享,JavaScript代码,Ajax,jQuery,网页模板,PNG图标，矢量图" name="keywords" /> 
</head> 
<body> 
<style> 
*{margin:0;padding:0;} 
.fa{width:740px;margin:0 auto;} 
.top{margin:20px 0;} 
.top input{width:25px;height:25px;border:1px solid #fff;border-radius:4px;background:#ddd;} 
.top .i1{background:#000000;} 
.top .i2{background:#FF0000;} 
.top .i3{background:#80FF00;} 
.top .i4{background:#00FFFF;} 
.top .i5{background:#808080;} 
.top .i6{background:#FF8000;} 
.top .i7{background:#408080;} 
.top .i8{background:#8000FF;} 
.top .i9{background:#CCCC00;} 
#canvas{background:#eee;cursor:default;} 
.font input{font-size:14px;} 
.top .grea{background:#aaa;} 
</style> 
</head> 
<body> 
<p class="fa"> 
<p class="top"> 
<p id="color"> 
请选择画笔颜色： 
<input class="i1" type="button" value="" /> 
<input class="i2" type="button" value="" /> 
<input class="i3" type="button" value="" /> 
<input class="i4" type="button" value="" /> 
<input class="i5" type="button" value="" /> 
<input class="i6" type="button" value="" /> 
<input class="i7" type="button" value="" /> 
<input class="i8" type="button" value="" /> 
<input class="i9" type="button" value="" /> 
</p> 
<p class="font" id="font"> 
请选择画笔的宽度： 
<input type="button" value="细" /> 
<input type="button" value="中" class="grea"/> 
<input type="button" value="粗" /> 
</p> 
<p> 
<span id="error">如果有错误，请使用橡皮擦：</span> 
<input id="eraser" style="width:60px;font-size:14px;"type="button" value="橡皮擦" /> 
</p> 
<input id="clear" type="button" value="清除画布" style="width:80px;"/> 
<input id="revocation" type="button" value="撤销" style="width:80px;"/> 
<input id="imgurl" type="button" value="导出图片路径" style="width:80px;"/> 
</p> 
<canvas id="canvas" width="740" height="420">您的浏览器不支持 canvas 标签</canvas> 
<p id="p1"></p> 
</p> 
<p id="html"> 
</p> 
<script> 
(function(){ 
var paint={ 
init:function() 
{ 
this.load(); 
}, 
load:function() 
{ 
this.x=[];//记录鼠标移动是的X坐标 
this.y=[];//记录鼠标移动是的Y坐标 
this.clickDrag=[]; 
this.lock=false;//鼠标移动前，判断鼠标是否按下 
this.isEraser=false; 
//this.Timer=null;//橡皮擦启动计时器 
//this.radius=5; 
this.storageColor="#000000"; 
this.eraserRadius=15;//擦除半径值 
this.color=["#000000","#FF0000","#80FF00","#00FFFF","#808080","#FF8000","#408080","#8000FF","#CCCC00"];//画笔颜色值 
this.fontWeight=[2,5,8]; 
this.$=function(id){return typeof id=="string"?document.getElementById(id):id;}; 
this.canvas=this.$("canvas"); 
if (this.canvas.getContext) { 
} else { 
alert("您的浏览器不支持 canvas 标签"); 
return; 
} 
this.cxt=this.canvas.getContext(&#39;2d&#39;); 
this.cxt.lineJoin = "round";//context.lineJoin - 指定两条线段的连接方式 
this.cxt.lineWidth = 5;//线条的宽度 
this.iptClear=this.$("clear"); 
this.revocation=this.$("revocation"); 
this.imgurl=this.$("imgurl");//图片路径按钮 
this.w=this.canvas.width;//取画布的宽 
this.h=this.canvas.height;//取画布的高 
this.touch =("createTouch" in document);//判定是否为手持设备 
this.StartEvent = this.touch ? "touchstart" : "mousedown";//支持触摸式使用相应的事件替代 
this.MoveEvent = this.touch ? "touchmove" : "mousemove"; 
this.EndEvent = this.touch ? "touchend" : "mouseup"; 
this.bind(); 
}, 
bind:function() 
{ 
var t=this; 
/*清除画布*/ 
this.iptClear.onclick=function() 
{ 
t.clear(); 
}; 
/*鼠标按下事件，记录鼠标位置，并绘制，解锁lock，打开mousemove事件*/ 
this.canvas[&#39;on&#39;+t.StartEvent]=function(e) 
{ 
var touch=t.touch ? e.touches[0] : e; 
var _x=touch.clientX - touch.target.offsetLeft;//鼠标在画布上的x坐标，以画布左上角为起点 
var _y=touch.clientY - touch.target.offsetTop;//鼠标在画布上的y坐标，以画布左上角为起点 
if(t.isEraser) 
{ 
/* 
t.cxt.globalCompositeOperation = "destination-out"; 
t.cxt.beginPath(); 
t.cxt.arc(_x, _y,t.eraserRadius, 0, Math.PI * 2); 
t.cxt.strokeStyle = "rgba(250,250,250,0)"; 
t.cxt.fill(); 
t.cxt.globalCompositeOperation = "source-over"; 
*/ 
t.resetEraser(_x,_y,touch); 
}else 
{ 
t.movePoint(_x,_y);//记录鼠标位置 
t.drawPoint();//绘制路线 
} 
t.lock=true; 
}; 
/*鼠标移动事件*/ 
this.canvas[&#39;on&#39;+t.MoveEvent]=function(e) 
{ 
var touch=t.touch ? e.touches[0] : e; 
if(t.lock)//t.lock为true则执行 
{ 
var _x=touch.clientX - touch.target.offsetLeft;//鼠标在画布上的x坐标，以画布左上角为起点 
var _y=touch.clientY - touch.target.offsetTop;//鼠标在画布上的y坐标，以画布左上角为起点 
if(t.isEraser) 
{ 
//if(t.Timer)clearInterval(t.Timer); 
//t.Timer=setInterval(function(){ 
t.resetEraser(_x,_y,touch); 
//},10); 
} 
else 
{ 
t.movePoint(_x,_y,true);//记录鼠标位置 
t.drawPoint();//绘制路线 
} 
} 
}; 
this.canvas[&#39;on&#39;+t.EndEvent]=function(e) 
{ 
/*重置数据*/ 
t.lock=false; 
t.x=[]; 
t.y=[]; 
t.clickDrag=[]; 
clearInterval(t.Timer); 
t.Timer=null; 
}; 
this.revocation.onclick=function() 
{ 
t.redraw(); 
}; 
this.changeColor(); 
this.imgurl.onclick=function() 
{ 
t.getUrl(); 
}; 
/*橡皮擦*/ 
this.$("eraser").onclick=function(e) 
{ 
t.isEraser=true; 
t.$("error").style.color="red"; 
t.$("error").innerHTML="您已使用橡皮擦！"; 
}; 
}, 
movePoint:function(x,y,dragging) 
{ 
/*将鼠标坐标添加到各自对应的数组里*/ 
this.x.push(x); 
this.y.push(y); 
this.clickDrag.push(y); 
}, 
drawPoint:function(x,y,radius) 
{ 
for(var i=0; i < this.x.length; i++)//循环数组 
{ 
this.cxt.beginPath();//context.beginPath() , 准备绘制一条路径 
if(this.clickDrag[i] && i){//当是拖动而且i!=0时，从上一个点开始画线。 
this.cxt.moveTo(this.x[i-1], this.y[i-1]);//context.moveTo(x, y) , 新开一个路径，并指定路径的起点 
}else{ 
this.cxt.moveTo(this.x[i]-1, this.y[i]); 
} 
this.cxt.lineTo(this.x[i], this.y[i]);//context.lineTo(x, y) , 将当前点与指定的点用一条笔直的路径连接起来 
this.cxt.closePath();//context.closePath() , 如果当前路径是打开的则关闭它 
this.cxt.stroke();//context.stroke() , 绘制当前路径 
} 
}, 
clear:function() 
{ 
this.cxt.clearRect(0, 0, this.w, this.h);//清除画布，左上角为起点 
}, 
redraw:function() 
{ 
/*撤销*/ 
this.cxt.restore(); 
}, 
preventDefault:function(e){ 
/*阻止默认*/ 
var touch=this.touch ? e.touches[0] : e; 
if(this.touch)touch.preventDefault(); 
else window.event.returnValue = false; 
}, 
changeColor:function() 
{ 
/*为按钮添加事件*/ 
var t=this,iptNum=this.$("color").getElementsByTagName("input"),fontIptNum=this.$("font").getElementsByTagName("input"); 
for(var i=0,l=iptNum.length;i<l;i++) 
{ 
iptNum[i].index=i; 
iptNum[i].onclick=function() 
{ 
t.cxt.save(); 
t.cxt.strokeStyle = t.color[this.index]; 
t.storageColor=t.color[this.index]; 
t.$("error").style.color="#000"; 
t.$("error").innerHTML="如果有错误，请使用橡皮擦："; 
t.cxt.strokeStyle = t.storageColor; 
t.isEraser=false; 
} 
} 
for(var i=0,l=fontIptNum.length;i<l;i++) 
{ 
t.cxt.save(); 
fontIptNum[i].index=i; 
fontIptNum[i].onclick=function() 
{ 
t.changeBackground(this.index); 
t.cxt.lineWidth = t.fontWeight[this.index]; 
t.$("error").style.color="#000"; 
t.$("error").innerHTML="如果有错误，请使用橡皮擦："; 
t.isEraser=false; 
t.cxt.strokeStyle = t.storageColor; 
} 
} 
}, 
changeBackground:function(num) 
{ 
/*添加画笔粗细的提示背景颜色切换，灰色为当前*/ 
var fontIptNum=this.$("font").getElementsByTagName("input"); 
for(var j=0,m=fontIptNum.length;j<m;j++) 
{ 
fontIptNum[j].className=""; 
if(j==num) fontIptNum[j].className="grea"; 
} 
}, 
getUrl:function() 
{ 
this.$("html").innerHTML=this.canvas.toDataURL(); 
}, 
resetEraser:function(_x,_y,touch) 
{ 
/*使用橡皮擦-提醒*/ 
var t=this; 
//this.cxt.lineWidth = 30; 
/*source-over 默认,相交部分由后绘制图形的填充(颜色,渐变,纹理)覆盖,全部浏览器通过*/ 
t.cxt.globalCompositeOperation = "destination-out"; 
t.cxt.beginPath(); 
t.cxt.arc(_x, _y, t.eraserRadius, 0, Math.PI * 2); 
t.cxt.strokeStyle = "rgba(250,250,250,0)"; 
t.cxt.fill(); 
t.cxt.globalCompositeOperation = "source-over" 
} 
}; 
paint.init(); 
})(); 
</script> 
<p style="clear:both"></p> 
</body> 
</html>
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