Canvas 实现进度条展示统计数据示例

梦里梦外; 2024-02-20 12:37 44阅读 0赞

canvas可以画柱状图，如下就是一个例子，主要用到了lineWidth，beginPath，lineCap等知识点。

### 效果图 ###

![在这里插入图片描述][6585907df5444518aaf5ad2387109395.gif_pic_center]

### 源代码 ###

<!DOCTYPE Html>
    <html>
    <head>
        <title>Line Chart Demo</title>
        <meta http-equiv="Content-Type" content="text/html;charset=UTF-8"/>
    </head>
    <body>
        <header>预约挂号人数（<span id="hosUnitDiv"></span>）</header>
        <canvas id="canvas2">您的浏览器不支持canvas，请换高版本的浏览器！</canvas>
        <script type="text/javascript" >
    	/*进度条图*/
    var progressChart = {
        
      // 绘制chart
      drawChart: function(canvas2, data, padding, marginRight, ygap, bgLineColor, scaleColor) {
        
        this.canID2 = document.getElementById("canvas2");
        this.content2 = this.canID2.getContext("2d");
        // this.canID2.width = 400;
        var canRealWidth = this.canID2.width - marginRight; // 图像真实的宽度 （距离右边canvas有一定的距离
        var dataMax = this.getArrayMax(data);  // 数据中最大的值
        var unit = this.getUnitByDataMax(dataMax); // 单位
        var xlimt = this.getXLimtByNewData(dataMax / (unit.number)); // x轴刻度 array
        var xgap = (canRealWidth - padding) / (xlimt.length - 1); // x轴刻度间距
        var newData = this.getNewDataByUnit(data, unit.number);
        var ymove = 5; // 整图y轴，向下移动 解决0的时候，显示不全问题
        this.canID2.height = ygap * (data.length) + ymove * 4;
        // 绘制x轴刻度
        for(var i=0; i<xlimt.length; i++) {
        
          // console.log(i*xgap + padding);
          this.content2.fillStyle = scaleColor;
          // this.content2.textAlign = "left";
          // if语句解决最后一个刻度，靠图像右端对齐问题
          if(i === xlimt.length -1) {
        
            this.content2.fillText(xlimt[i],i*xgap + padding - 16, ygap*data.length + ygap);
          } else {
        
            this.content2.fillText(xlimt[i],i*xgap + padding, ygap*data.length + ygap);
          }
        }
        for(var i=0; i<data.length; i++) {
        
          // 画横线
          this.content2.lineWidth=8;
          this.content2.strokeStyle=bgLineColor;// 笔触颜色
          this.content2.beginPath();
          this.content2.moveTo(padding, ygap*i + ymove);
          this.content2.lineTo(canRealWidth, ygap*i + ymove);
          this.content2.lineCap = 'round';
          this.content2.stroke();
          this.content2.closePath();
          // y轴刻度
          this.content2.fillStyle = scaleColor;
          this.content2.textAlign = "left";//y轴文字靠右写
          // this.content2.textBaseline = "middle";//文字的中心线的调整
          this.content2.font = '12px PingFang HK';  
          this.content2.fillText(data[i].y, 0, ygap*i + 10);
    
          // 画真实数据线
          /* 画有渐变色线 */
          this.content2.beginPath();
          var linear_gradient = this.content2.createLinearGradient(0,0, canRealWidth,50);
          linear_gradient.addColorStop(0, '#5c80cd');
          linear_gradient.addColorStop(1, '#ac92d3');
          this.content2.strokeStyle = linear_gradient;
          this.content2.lineJoin = 'round';
          this.content2.lineWidth = 8;
          this.content2.strokeRect(padding, ygap*i + ymove, newData[i].x * (canRealWidth - padding) / xlimt[xlimt.length - 1], 0);
        }
        return unit;
      },
      // 根据x轴最大的数据 判断单位 params: 原始数据中最大的值
      getUnitByDataMax: function(maxData) {
        
        if(maxData > 1000 && maxData <= 10000) {
        
          return unit = {
        text: '百人', number: 100};
        } else if(maxData > 10000) {
        
          return unit = {
        text: '千人', number: 1000};
        }
      },
      // 获取x轴刻度 params：原始数据通过单位处理后的数据 的最大值
      getXLimtByNewData: function(handleByUnitNewdataMax) {
        
        if (handleByUnitNewdataMax > 0 && handleByUnitNewdataMax <= 50) {
        
          return xlimt = [0, 10, 20, 30, 40, 50];
        } else {
        
          return xlimt = [0, 20, 40, 60 ,80, 100];
        }
      },
      // 根据单位处理原始数据，获取到新的数据
      getNewDataByUnit: function(data, unit) {
        
        var canvas2NewData = [];
        // var canvas2NewData = canvas2Data.map(function(item) {
        
        //   item.x = item.x /unit;
        // }); ??? 为什么map不可以
        for (var i = 0; i < canvas2Data.length; i++) {
        
          canvas2NewData[i] = {
        y: canvas2Data[i].y, x:canvas2Data[i].x / unit};
        };
        return canvas2NewData;
      },
      // 获取x轴 最大值 
      getArrayMax: function(array) {
        
        return array.reduce(function(prev, next) {
        
          if (prev.x > next.x) {
         return prev.x;} else {
        return next.x};
        });
      }
    }
    	</script>
        <script>
          /*进度条图*/
          var canvas2Data = [
            {
        x:520, y:'1月'},
            {
        x:1000, y:'2月'},
            {
        x:600, y:'3月'},
            {
        x:2100, y:'4月'},
            {
        x:3400, y:'5月'},
            {
        x:3600, y:'6月'},
            {
        x:4000, y:'7月'},
            {
        x:6000, y:'8月'},
            {
        x:7000, y:'9月'},
            {
        x:9000, y:'10月'}
          ];
    
          var hosUnit = progressChart.drawChart(canvas2, canvas2Data, 30, 10, 13, '#bcc0c7', '#fff');
          document.getElementById('hosUnitDiv').innerText = hosUnit.text;  
        </script>
    </body>
    </html>

[6585907df5444518aaf5ad2387109395.gif_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/20/b487a5f8852c4f3ea0b3408ae7fd668c.png