日期:2014-05-17 浏览次数:20847 次
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<html>
<head>
<script type="text/javascript">
//var cxt=document.getElementById(drawplane).getContext("2d");
function plot(canvasid,fun,x1,x2,y1,y2){
var cvs=document.getElementById(canvasid);
var cxt=cvs.getContext('2d');
var cvs_width=cvs.width;
var x_width=x2-x1;
var x_to_cvs_rate=cvs_width/x_width;
var cvs_height=cvs.height;
var y_height=y2-y1;
var y_to_cvs_rate=cvs_height/y_height;
//function cvs_to_x(left){
//cvs_left
//}
//初始化绘图
var cvs_top=0;
var y=0;
var cvs_left0=x1*x_to_cvs_rate;
var cvs_left1=x2*x_to_cvs_rate;
cxt.translate(-cvs_left0,cvs_height/2);
cxt.scale(1,-1);
var cvs_left0=x1*x_to_cvs_rate;
var cvs_left1=x2*x_to_cvs_rate;
for(var cvs_left=cvs_left0;cvs_left<=cvs_left1;cvs_left++){
//计算
x=cvs_left/x_to_cvs_rate;
y=fun(x);
cvs_top=y*y_to_cvs_rate;
//绘图
cxt.lineTo(cvs_left,cvs_top);
}
cxt.stroke();
}
function init(){
plot("drawplane",Math.abs,-10,10,-1,1);
}
window.onload=init;
</script>
</head>
<body>
<canvas id="drawplane" style="border:solid 1px red"></canvas>
</body>
</html>
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