用html5绘制折线图的实例代码_html5教程技巧

百变鹏仔 2个月前 (10-18) #H5教程

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用html5绘制折线图的实例代码_html5教程技巧

<html>    <canvas id="a_canvas" width="1000" height="700">canvas>    <script>                            (function (){                 window.addEventListener("load", function(){                   var data = [100,-1000,0,700];                   // 获取上下文              var a_canvas = document.getElementById(&#39;a_canvas&#39;);              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<data.length; 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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