用html5绘制折线图的实例代码_html5教程技巧

canvas>

(function (){

window.addEventListener("load", function(){

var data = [100,-1000,0,700];

// 获取上下文

var a_canvas = document.getElementById('a_canvas');

var context = a_canvas.getContext("2d");

// 绘制背景

var gradient = context.createLinearGradient(0,0,0,300);

// gradient.addColorStop(0,"#e0e0e0");

//gradient.addColorStop(1,"#ffffff");

context.fillStyle = gradient;

context.fillRect(0,0,a_canvas.width,a_canvas.height);

// 描绘边框

var grid_cols = data.length + 1;

var grid_rows = 4;

var cell_height = a_canvas.height / grid_rows;

var cell_width = a_canvas.width / grid_cols;

context.lineWidth = 1;

context.strokeStyle = "#a0a0a0";

// 结束边框描绘

context.beginPath();

// 准备画横线

/*for (var col = 0; col <= grid_cols; col++) {

var x = col * cell_width;

context.moveTo(x,0);

context.lineTo(x,a_canvas.height);

}

// 准备画竖线

for(var row = 0; row <= grid_rows; row++){

var y = row * cell_height;

context.moveTo(0,y);

context.lineTo(a_canvas.width, y);

}*/

//划横线

context.moveTo(0,a_canvas.height/2);

context.lineTo(a_canvas.width,a_canvas.height/2);

//画竖线

context.moveTo(0,0);

context.lineTo(0,a_canvas.height);

context.lineWidth = 1;

context.strokeStyle = "#c0c0c0";

context.stroke();

var max_v =0;

for(var i = 0; i

var d=0;

if(data[i]<0)

{dd=d-data[i];

}

else{d=data[i];};

if (d > max_v) { max_v =d};

}

max_vmax_v = max_v * 1.1;

// 将数据换算为坐标

var points = [];

for( var i=0; i < data.length; i++){

var v= data[i];

var px = cell_width *　(i +1);

var py = a_canvas.height/2 - a_canvas.height*(v / max_v)/2;

points.push({"x":px,"y":py});

}

// 绘制折现

context.beginPath();

context.moveTo(points[0].x, points[0].y);

for(var i= 1; i< points.length; i++){

context.lineTo(points[i].x,points[i].y);

}

context.lineWidth = 2;

context.strokeStyle = "#8BA9FF";

context.stroke();

//绘制坐标图形

for(var i in points){

var p = points[i];

context.beginPath();

context.arc(p.x,p.y,4,0,2*Math.PI);

//实心圆

/*

context.fillStyle = "#000";*/

//空心圆

context.strokeStyle = "#000";

context.stroke();

context.fillStyle="white";

context.fill();

}

//添加文字

for(var i in points)

{ var p = points[i];

context.beginPath();

context.fillStyle="black";

context.fillText(data[i], p.x + 1, p.y - 15);

}

},false);

})();

script>

html>

运行结果如下：

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