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用html5绘制折线图的实例代码_html5教程技巧

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2017-03-30 14:30:124347browse

用html5绘制折线图的实例代码_html5教程技巧

  1. <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:

1007.jpg

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