我试图使用 HTML 5 画布创建一个示例绘画应用程序。然后我添加了一个按钮来重绘用户之前绘制的内容。我不确定我做错了什么，或者可能完全错了。当我多次单击重绘按钮时，它会通过绘制线条来生成一些神奇的动画。即使我每次都记录绘制图像的起点。
Demo: http://jsfiddle.net/BW57H/6/
重现步骤：
通过单击鼠标并将其拖动到矩形框上来绘制一些圆形或矩形或其他东西。然后单击 reset and redraw ，然后单击 redraw 几次，然后查看结果。
我不确定我做了什么。我没有读过很多关于 Canvas 的文章。但我很想知道这里发生了什么。谢谢。
html
<body>
<canvas id="paint" width="600px" height="300px"></canvas>
<div id="controls">
<button name="reset" id="reset">Reset</button>
<button name="redraw" id="redraw">Re-Draw</button>
</div>
</body>
css
#paint{
border: solid;
}
js
$(document).ready(function(){
var x, y, context, painter;
var xCounter = 0 , yCounter = 0;
var xarray = [];
var yarray = [];
function init(){
while(document.getElementById("paint") === undefined){
//do nothing
}
console.log("Loaded document now registering events for canvas");
var canvas = document.getElementById("paint");
context = canvas.getContext('2d');
painter = new Painter();
canvas.addEventListener('mousedown', capture, false);
canvas.addEventListener('mouseup', capture, false);
canvas.addEventListener('mousemove', capture, false);
document.getElementById("reset").addEventListener("click",function(){ clearCanvas(canvas);}, false);
document.getElementById("redraw").addEventListener("click", function(){
autoDraw();
}, false);
}
function clearCanvas(canvas){
context.save();
// Use the identity matrix while clearing the canvas
context.setTransform(1, 0, 0, 1, 0, 0);
context.clearRect(0, 0, canvas.width, canvas.height);
// Restore the transform
context.restore();
};
function capture(event){
if(event.which !== 1){
return;
}
x = event.layerX;
y = event.layerY;
switch(event.type){
case 'mousedown':
painter.startPaint(event);
break;
case 'mouseup':
painter.endPaint(event);
break;
case 'mousemove':
painter.paint(event);
break;
}
};
var Painter = function(){
var self = this;
self.paintStarted = false;
self.startPaint = function(event){
self.resetRecordingParams();
self.paintStarted = true;
context.beginPath();
context.moveTo(x,y);
self.record();
}
self.endPaint = function(event){
self.paintStarted = false;
self.record();
self.paint(event)
}
self.paint = function(event){
if(self.paintStarted){
context.lineTo(x,y);
context.stroke();
self.record();
}
}
self.record = function(){
xarray[xCounter++] = x;
yarray[yCounter++] = y;
}
self.resetRecordingParams = function(){
xarray = [];
yarray = [];
xCounter = 0;
yCounter= 0;
}
return self;
}
function autoDraw(){
context.beginPath();
console.log('starting at: '+xarray[0]+','+yarray[0]);
context.moveTo(xarray[0],yarray[0]);
for (var i = 0; i < xarray.length; i++) {
setTimeout(drawLineSlowly, 1000+(i*20), i);
};
}
function drawLineSlowly(i)
{
context.lineTo(xarray[i],yarray[i]);
context.stroke();
}
init();
});