js 绘制数学函数
<!-- <!doctype html> --> <html lang="en"> <head> <meta charset="UTF-8"> <title>js绘制数学函数</title> </head> <body> <div id="main" style="border-bottom:solid red 0px;height:100%;width:100%"></div> </body> <script> function $(id){return document.getElementById(id)}; /* 绘图对象 绘图函数，比如画点，线，多边形，圆 绘图参数，比如背景颜色，画笔颜色 */ var Plot = { container : null , //画布 ox : 500 , //原点x oy : 300 , //原点y baseLineColor : 'black' , //坐标轴颜色 brushColor : 'red' , //画笔颜色 brushWeight : 1 , //画笔粗细 baseLineX : null , // baseLineX 和 baseLineY 用于坐标移位 baseLineY : null , //初始化方法 init : function(containerId , ox , oy , baseLineColor , brushColor , brushWeight ){ if($(containerId)){ Plot.container = $(containerId); }else{ alert('你必须制定一个区域作为画布！'); return; } if((typeof ox) == 'number'){ Plot.ox = ox ; } if((typeof oy)== 'number'){ Plot.oy = oy ; } Plot.baseLineColor = baseLineColor ; Plot.brushWeight = brushWeight ; Plot.brushColor = brushColor ; Plot.drawCoordinate(); }, //设置原点函数 setOPoint : function(ox,oy){ Plot.ox = ox ; Plot.oy = oy ; Plot.container.removeChild(Plot.baseLineX) ; Plot.container.removeChild(Plot.baseLineY) ; Plot.drawCoordinate(); }, //设置画笔粗细函数 setBrushWeight : function(weight){ Plot.brushWeight = weight ; }, setBrushColor : function(color){ Plot.brushColor = color ; }, // 画坐标轴 drawCoordinate : function(){ var baseLineX = document.createElement('div') ; baseLineX.style.position = 'absolute' ; baseLineX.style.left = 0 ; baseLineX.style.top = Plot.oy ; baseLineX.style.fontSize = '1px' ; baseLineX.style.height = '1px' ; baseLineX.style.width = '100%' ; baseLineX.style.overflow = 'hidden' ; baseLineX.style.backgroundColor = Plot.baseLineColor ; Plot.container.appendChild(baseLineX) ; Plot.baseLineX = baseLineX ; var baseLineY = document.createElement('div') ; baseLineY.style.position = 'absolute' ; baseLineY.style.left = Plot.ox ; baseLineY.style.top = 0 ; baseLineY.style.fontSize = '1px' ; baseLineY.style.height = '100%' ; baseLineY.style.width = '1px' ; baseLineY.style.overflow = 'hidden' ; baseLineY.style.backgroundColor = Plot.baseLineColor ; Plot.baseLineY = baseLineY ; Plot.container.appendChild(baseLineY) ; }, //清理画布 clean : function(){ Plot.container.innerHTML = '' ; Plot.drawCoordinate() ; }, //画点，相对原点 drawDot : function(x,y){ var dot = document.createElement('div') ; dot.style.left = Plot.ox + x + 'px' ; dot.style.top = Plot.oy - y + 'px' ; dot.style.height = Plot.brushWeight ; dot.style.width = Plot.brushWeight ; dot.style.position = 'absolute' ; dot.style.fontSize = '1px' ; dot.style.backgroundColor = Plot.brushColor ; dot.style.overflow = 'hidden' ; Plot.container.appendChild(dot) ; dot = null ; }, //sin函数，传入角度 sin : function(angle){ for(var i=0 ; i<angle ; i++){ Plot.drawDot(i,Math.sin(i/180*Math.PI)*100) ; } }, // cos函数，传入角度 cos : function(angle){ for(var i = 0 ; i < angle ; i++){ Plot.drawDot(i,Math.cos(i/180*Math.PI)*100) } }, //tan函数 tan : function(){ for(var i=0 ; i<720 ; i++){ if(Math.tan(i/180*Math.PI)*100>Plot.oy){ continue ; } Plot.drawDot(i,Math.tan(1/180*Math.PI)*50); } }, //画线 从 (x0,y0) 到 (x1,y1) line : function(x0,y0,x1,y1){ // 竖线 if((x1-x0)==0){ for(var i=((y1>y0)?y0:y1) ; i<((y1>y0)?y1:y0); i++ ){ Plot.drawDot(x1,i); }; return; }; //横线 if((y1-y0)==0){ for( var i=((x1>x0)?x0:x1); i<((x1>x0)?x1:x0); i++ ){ Plot.drawDot(i,y1); }; return; }; //斜线 //K=斜率，直线方程 y=kx + b; var k = (y1-y0)/(x1-x0) ; if(k<=1){ for(var i=((x1>x0) ? x0 : x1); i<((x1>x0) ? x1 : x0 );i++){ Plot.drawDot(i,k*i+y1-k*x1); }; }else{ for(var i=((y1>y0)?y0:y1) ; i<((y1>y0)?y1:y0) ; i++){ Plot.drawDot((i-y1+k*x1)/k,i) ; }; }; return; }, // 画圆，radius是半径，（xi,yi）为圆心 circle : function(radius,xi,yi){ if((typeof xi)=='undefined'){ xi = 0 ; }; if((typeof yi)=='undefined'){ yi = 0 ; }; // 以i为角度,从0到360 var i = 0 ; while(i<360){ var _x0 = Math.sin(i/180*Math.PI)*radius ; var _y0 = Math.cos(i/180*Math.PI)*radius ; var step = radius/100 ; // 使画出来的圆更圆润 if(1/step > 1){ step = 1 ; }else if(1/step < 0.2){ step = 0.2 ; }else{ step = 1/step ; }; Plot.drawDot(_x0+xi,_y0+yi) ; i = i + step ; } }, //画多边形 polygon : function(dots){ if(typeof dots == 'undefined'){ alert('你应该指定一些点画多边形') ; return ; }; if(dots.constructor != Array){ alert('你应该指定一些点画多边形') ; return ; }; for(var i = 0 ; i < dots.length-1 ; i++){ Plot.line(dots[i].x , dots[i].y , dots[i+1].x , dots[i+1].y); if(i ==1 && dots.length==2){break;} }; Plot.line(dots[0].x, dots[0].y, dots[dots.length-1].x, dots[dots.length-1].y); }, } </script> <!-- test --> <script> Plot.init('main',500, 500,'green','red',1); Plot.sin(720); Plot.setBrushWeight(3); // Plot.cos(720); // Plot.setBrushWeight(2); // Plot.circle(200,100,100); // Plot.setBrushColor('purple'); // Plot.circle(100,100,100); // Plot.setBrushColor('blue'); // Plot.circle(50,100,100); // var t = new Array(); // var dots = new Array(); // dots[0] = {x:-10,y:-10}; // dots[1] = {x:400,y:10}; // dots[2] = {x:400,y:300}; // dots[3] = {x:10,y:300}; // Plot.polygon(dots); </script> </html>
原理：就是用1px*1px的点来画线和面
注意：文件的头部<!doctype html>必须被注释掉
效果图：
