<!-- <!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：
