日期:2014-05-17 浏览次数:20719 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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