<!doctype html>
<html>
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type" />
<title>javascript canvas畫圖實例</title>
<meta http-equiv="X-UA-Compatible" content="IE=7" />
<meta name="keywords" content="" />
<meta name="description" content="" />
<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>
<div class="fa">
<div class="top">
<div id="color">
請選擇畫筆顏色：
<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="" />
</div>
<div class="font" id="font">
請選擇畫筆的寬度：
<input type="button" value="細" />
<input type="button" value="中" class="grea"/>
<input type="button" value="粗" />
</div>
<div>
<span id="error">如果有錯誤，請使用橡皮擦：</span>
<input id="eraser" style="width:60px;font-size:14px;"type="button" value="橡皮擦" />
</div>
<input id="clear" type="button" value="清除畫布" style="width:80px;"/>
<input id="revocation" type="button" value="撤銷" style="width:80px;"/>
<input id="imgurl" type="button" value="導出圖片路徑" style="width:80px;"/>
</div>
<canvas id="canvas" width="740" height="420">您的瀏覽器不支持 canvas 標籤</canvas>
<div id="div1"></div>
</div>
<div id="html">
</div>
<script>
(function(){
var paint={
init:function()
{
this.load();
},
load:function()
{
this.x=[];//記錄鼠標移動是的X座標
this.y=[];//記錄鼠標移動是的Y座標
this.clickDrag=[];
this.lock=false;//鼠標移動前，判斷鼠標是否按下
this.isEraser=false;
//this.Timer=null;//橡皮擦啓動計時器
//this.radius=5;
this.storageColor="#000000";
this.eraserRadius=15;//擦除半徑值
this.color=["#000000","#FF0000","#80FF00","#00FFFF","#808080","#FF8000","#408080","#8000FF","#CCCC00"];//畫筆顏色值
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("您的瀏覽器不支持 canvas 標籤");
return;
}
this.cxt=this.canvas.getContext('2d');
this.cxt.lineJoin = "round";//context.lineJoin - 指定兩條線段的連接方式
this.cxt.lineWidth = 5;//線條的寬度
this.iptClear=this.$("clear");
this.revocation=this.$("revocation");
this.imgurl=this.$("imgurl");//圖片路徑按鈕
this.w=this.canvas.width;//取畫布的寬
this.h=this.canvas.height;//取畫布的高
this.touch =("createTouch" in document);//判定是否爲手持設備
this.StartEvent = this.touch ? "touchstart" : "mousedown";//支持觸摸式使用相應的事件替代
this.MoveEvent = this.touch ? "touchmove" : "mousemove";
this.EndEvent = this.touch ? "touchend" : "mouseup";
this.bind();
},
bind:function()
{
var t=this;
/*清除畫布*/
this.iptClear.οnclick=function()
{
t.clear();
};
/*鼠標按下事件，記錄鼠標位置，並繪製，解鎖lock，打開mousemove事件*/
this.canvas['on'+t.StartEvent]=function(e)
{
var touch=t.touch ? e.touches[0] : e;
var _x=touch.clientX - touch.target.offsetLeft;//鼠標在畫布上的x座標，以畫布左上角爲起點
var _y=touch.clientY - touch.target.offsetTop;//鼠標在畫布上的y座標，以畫布左上角爲起點
if(t.isEraser)
{
/*
t.cxt.globalCompositeOperation = "destination-out";
t.cxt.beginPath();
t.cxt.arc(_x, _y,t.eraserRadius, 0, Math.PI * 2);
t.cxt.strokeStyle = "rgba(250,250,250,0)";
t.cxt.fill();
t.cxt.globalCompositeOperation = "source-over";
*/
t.resetEraser(_x,_y,touch);
}else
{
t.movePoint(_x,_y);//記錄鼠標位置
t.drawPoint();//繪製路線
}
t.lock=true;
};
/*鼠標移動事件*/
this.canvas['on'+t.MoveEvent]=function(e)
{
var touch=t.touch ? e.touches[0] : e;
if(t.lock)//t.lock爲true則執行
{
var _x=touch.clientX - touch.target.offsetLeft;//鼠標在畫布上的x座標，以畫布左上角爲起點
var _y=touch.clientY - touch.target.offsetTop;//鼠標在畫布上的y座標，以畫布左上角爲起點
if(t.isEraser)
{
//if(t.Timer)clearInterval(t.Timer);
//t.Timer=setInterval(function(){
t.resetEraser(_x,_y,touch);
//},10);
}
else
{
t.movePoint(_x,_y,true);//記錄鼠標位置
t.drawPoint();//繪製路線
}
}
};
this.canvas['on'+t.EndEvent]=function(e)
{
/*重置數據*/
t.lock=false;
t.x=[];
t.y=[];
t.clickDrag=[];
clearInterval(t.Timer);
t.Timer=null;
};
this.revocation.οnclick=function()
{
t.redraw();
};
this.changeColor();
this.imgurl.οnclick=function()
{
t.getUrl();
};
/*橡皮擦*/
this.$("eraser").οnclick=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)
{
/*將鼠標座標添加到各自對應的數組裏*/
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++)//循環數組
{
this.cxt.beginPath();//context.beginPath() , 準備繪製一條路徑
if(this.clickDrag[i] && i){//當是拖動而且i!=0時，從上一個點開始畫線。
this.cxt.moveTo(this.x[i-1], this.y[i-1]);//context.moveTo(x, y) , 新開一個路徑，並指定路徑的起點
}else{
this.cxt.moveTo(this.x[i]-1, this.y[i]);
}
this.cxt.lineTo(this.x[i], this.y[i]);//context.lineTo(x, y) , 將當前點與指定的點用一條筆直的路徑連接起來
this.cxt.closePath();//context.closePath() , 如果當前路徑是打開的則關閉它
this.cxt.stroke();//context.stroke() , 繪製當前路徑
}
},
clear:function()
{
this.cxt.clearRect(0, 0, this.w, this.h);//清除畫布，左上角爲起點
},
redraw:function()
{
/*撤銷*/
this.cxt.restore();
},
preventDefault:function(e){
/*阻止默認*/
var touch=this.touch ? e.touches[0] : e;
if(this.touch)touch.preventDefault();
else window.event.returnValue = false;
},
changeColor:function()
{
/*爲按鈕添加事件*/
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].οnclick=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="如果有錯誤，請使用橡皮擦：";
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].οnclick=function()
{
t.changeBackground(this.index);
t.cxt.lineWidth = t.fontWeight[this.index];
t.$("error").style.color="#000";
t.$("error").innerHTML="如果有錯誤，請使用橡皮擦：";
t.isEraser=false;
t.cxt.strokeStyle = t.storageColor;
}
}
},
changeBackground:function(num)
{
/*添加畫筆粗細的提示背景顏色切換，灰色爲當前*/
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 默認,相交部分由後繪製圖形的填充(顏色,漸變,紋理)覆蓋,全部瀏覽器通過*/
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>
</body>
<html>
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type" />
<title>javascript canvas畫圖實例</title>
<meta http-equiv="X-UA-Compatible" content="IE=7" />
<meta name="keywords" content="" />
<meta name="description" content="" />
<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>
<div class="fa">
<div class="top">
<div id="color">
請選擇畫筆顏色：
<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="" />
</div>
<div class="font" id="font">
請選擇畫筆的寬度：
<input type="button" value="細" />
<input type="button" value="中" class="grea"/>
<input type="button" value="粗" />
</div>
<div>
<span id="error">如果有錯誤，請使用橡皮擦：</span>
<input id="eraser" style="width:60px;font-size:14px;"type="button" value="橡皮擦" />
</div>
<input id="clear" type="button" value="清除畫布" style="width:80px;"/>
<input id="revocation" type="button" value="撤銷" style="width:80px;"/>
<input id="imgurl" type="button" value="導出圖片路徑" style="width:80px;"/>
</div>
<canvas id="canvas" width="740" height="420">您的瀏覽器不支持 canvas 標籤</canvas>
<div id="div1"></div>
</div>
<div id="html">
</div>
<script>
(function(){
var paint={
init:function()
{
this.load();
},
load:function()
{
this.x=[];//記錄鼠標移動是的X座標
this.y=[];//記錄鼠標移動是的Y座標
this.clickDrag=[];
this.lock=false;//鼠標移動前，判斷鼠標是否按下
this.isEraser=false;
//this.Timer=null;//橡皮擦啓動計時器
//this.radius=5;
this.storageColor="#000000";
this.eraserRadius=15;//擦除半徑值
this.color=["#000000","#FF0000","#80FF00","#00FFFF","#808080","#FF8000","#408080","#8000FF","#CCCC00"];//畫筆顏色值
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("您的瀏覽器不支持 canvas 標籤");
return;
}
this.cxt=this.canvas.getContext('2d');
this.cxt.lineJoin = "round";//context.lineJoin - 指定兩條線段的連接方式
this.cxt.lineWidth = 5;//線條的寬度
this.iptClear=this.$("clear");
this.revocation=this.$("revocation");
this.imgurl=this.$("imgurl");//圖片路徑按鈕
this.w=this.canvas.width;//取畫布的寬
this.h=this.canvas.height;//取畫布的高
this.touch =("createTouch" in document);//判定是否爲手持設備
this.StartEvent = this.touch ? "touchstart" : "mousedown";//支持觸摸式使用相應的事件替代
this.MoveEvent = this.touch ? "touchmove" : "mousemove";
this.EndEvent = this.touch ? "touchend" : "mouseup";
this.bind();
},
bind:function()
{
var t=this;
/*清除畫布*/
this.iptClear.οnclick=function()
{
t.clear();
};
/*鼠標按下事件，記錄鼠標位置，並繪製，解鎖lock，打開mousemove事件*/
this.canvas['on'+t.StartEvent]=function(e)
{
var touch=t.touch ? e.touches[0] : e;
var _x=touch.clientX - touch.target.offsetLeft;//鼠標在畫布上的x座標，以畫布左上角爲起點
var _y=touch.clientY - touch.target.offsetTop;//鼠標在畫布上的y座標，以畫布左上角爲起點
if(t.isEraser)
{
/*
t.cxt.globalCompositeOperation = "destination-out";
t.cxt.beginPath();
t.cxt.arc(_x, _y,t.eraserRadius, 0, Math.PI * 2);
t.cxt.strokeStyle = "rgba(250,250,250,0)";
t.cxt.fill();
t.cxt.globalCompositeOperation = "source-over";
*/
t.resetEraser(_x,_y,touch);
}else
{
t.movePoint(_x,_y);//記錄鼠標位置
t.drawPoint();//繪製路線
}
t.lock=true;
};
/*鼠標移動事件*/
this.canvas['on'+t.MoveEvent]=function(e)
{
var touch=t.touch ? e.touches[0] : e;
if(t.lock)//t.lock爲true則執行
{
var _x=touch.clientX - touch.target.offsetLeft;//鼠標在畫布上的x座標，以畫布左上角爲起點
var _y=touch.clientY - touch.target.offsetTop;//鼠標在畫布上的y座標，以畫布左上角爲起點
if(t.isEraser)
{
//if(t.Timer)clearInterval(t.Timer);
//t.Timer=setInterval(function(){
t.resetEraser(_x,_y,touch);
//},10);
}
else
{
t.movePoint(_x,_y,true);//記錄鼠標位置
t.drawPoint();//繪製路線
}
}
};
this.canvas['on'+t.EndEvent]=function(e)
{
/*重置數據*/
t.lock=false;
t.x=[];
t.y=[];
t.clickDrag=[];
clearInterval(t.Timer);
t.Timer=null;
};
this.revocation.οnclick=function()
{
t.redraw();
};
this.changeColor();
this.imgurl.οnclick=function()
{
t.getUrl();
};
/*橡皮擦*/
this.$("eraser").οnclick=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)
{
/*將鼠標座標添加到各自對應的數組裏*/
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++)//循環數組
{
this.cxt.beginPath();//context.beginPath() , 準備繪製一條路徑
if(this.clickDrag[i] && i){//當是拖動而且i!=0時，從上一個點開始畫線。
this.cxt.moveTo(this.x[i-1], this.y[i-1]);//context.moveTo(x, y) , 新開一個路徑，並指定路徑的起點
}else{
this.cxt.moveTo(this.x[i]-1, this.y[i]);
}
this.cxt.lineTo(this.x[i], this.y[i]);//context.lineTo(x, y) , 將當前點與指定的點用一條筆直的路徑連接起來
this.cxt.closePath();//context.closePath() , 如果當前路徑是打開的則關閉它
this.cxt.stroke();//context.stroke() , 繪製當前路徑
}
},
clear:function()
{
this.cxt.clearRect(0, 0, this.w, this.h);//清除畫布，左上角爲起點
},
redraw:function()
{
/*撤銷*/
this.cxt.restore();
},
preventDefault:function(e){
/*阻止默認*/
var touch=this.touch ? e.touches[0] : e;
if(this.touch)touch.preventDefault();
else window.event.returnValue = false;
},
changeColor:function()
{
/*爲按鈕添加事件*/
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].οnclick=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="如果有錯誤，請使用橡皮擦：";
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].οnclick=function()
{
t.changeBackground(this.index);
t.cxt.lineWidth = t.fontWeight[this.index];
t.$("error").style.color="#000";
t.$("error").innerHTML="如果有錯誤，請使用橡皮擦：";
t.isEraser=false;
t.cxt.strokeStyle = t.storageColor;
}
}
},
changeBackground:function(num)
{
/*添加畫筆粗細的提示背景顏色切換，灰色爲當前*/
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 默認,相交部分由後繪製圖形的填充(顏色,漸變,紋理)覆蓋,全部瀏覽器通過*/
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>
</body>
</html>
轉自:http://www.bcty365.com/content-62-6-1.html
據網上的說法是ie8不支持canvas, 在ie9和ie10才添加了對canvas的支持。有說法ie8能採用excanvas_r3能模擬解決但效率不高，沒試驗出來。
此例子在firefox,Google Chrome,360瀏覽器裏都能執行
