html5绘制折线图

来源：互联网发布：8684公交软件下载编辑：程序博客网时间：2024/05/31 13:15
原文链接
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<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('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<data.length; i++){
              var d=0;
              if(data[i]<0)
              {d=d-data[i];
                  }
                  else{d=data[i];};
            if (d > max_v) { max_v =d};
          }
          max_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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