使用html5的canvas和JavaScript创建一个绘图程序的示例代码

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<canvas id="canvasInAPerfectWorld" width="490" height="220"></canvas>

context = document.getElementById('canvasInAPerfectWorld').getContext("2d");

var clickX = new Array(); 
var clickY = new Array(); 
var clickDrag = new Array();//存储路径点 
var paint;//是否绘制，mousedown时置为true 
function addClick(x, y, dragging) 
{ 
 clickX.push(x); 
 clickY.push(y); 
 clickDrag.push(dragging); 
}

function redraw(){ 
 context.clearRect(0, 0, context.canvas.width, context.canvas.height); // 清除画布内容 
 context.strokeStyle = "#df4b26";//设置线条颜色 
 context.lineJoin = "round";//当两条线条交汇时，创建圆形边角 
 context.lineWidth = 5;//线条粗细 
 for(var i=0; i < clickX.length; i++) { 
 context.beginPath();//开始一条路径，或重置当前的路径 
 if(clickDrag[i] && i){ 
 context.moveTo(clickX[i-1], clickY[i-1]); 
 }else{ 
 context.moveTo(clickX[i]-1, clickY[i]); 
 } 
 context.lineTo(clickX[i], clickY[i]); 
 context.closePath(); 
 context.stroke();//绘制路径 
 } 
}

$('#canvas').mousedown(function(e){ 
 var mouseX = e.pageX - this.offsetLeft; 
 var mouseY = e.pageY - this.offsetTop; 
 paint = true; 
 addClick(e.pageX - this.offsetLeft, e.pageY - this.offsetTop); 
 redraw(); 
});

$('#canvas').mousemove(function(e){ 
 if(paint){ 
 addClick(e.pageX - this.offsetLeft, e.pageY - this.offsetTop, true); 
 redraw(); 
 } 
 });

$('#canvas').mouseup(function(e){ 
 paint = false; 
 });

$('#canvas').mouseleave(function(e){ 
 paint = false; 
});