1

我正在尝试使用 Onclick 按钮将我的 chart.js 图表下载为 png，但我不知道我将如何实现这一点，我已经完成了这个答案React-chartjs-2 Donut chart export to png但是这对我来说还不是很清楚，因为我是 chart.js 的新手，不知道如何将这些变量与我的按钮连接起来。

import React from 'react';
import { Component, useRef } from 'react';
import { Bar } from 'react-chartjs-2';
import 'chartjs-plugin-datalabels';

const data = {
  labels: ['Finance & Business', 'Mining', 'Community Services', 'Electricity', 'Agriculture', 'Construction', 'Manufacture', "Trade & Tourism", "Transport & Logistics"],
  datasets: [
    {
      label: 'My First dataset',
      backgroundColor: ["#3283FC", "", "", "#00C0C8", "#C0BD00", "#3A46B1", "#00A150", "#FEB200", "#9302a1"],
      borderWidth: 1,
      hoverBackgroundColor: 'rgba(255,99,132,0.4)',
      hoverBorderColor: 'rgba(255,99,132,1)',
      data: [0.6, 0.0, 0.0, -0.1, -0.1, -0.3, -0.3, -0.6, -1.0],
    }
  ]
};


class StackedBar extends Component {

  render() {

    return (
      <div>
        <h2>Bar Example (custom size)</h2>
        <Bar

          data={data}
          options={{
            plugins: {
              datalabels: {
                display: true,
                color: '#fff'
              }
            },
            title: {
              display: true,
              text: 'Contribution Percentage',
              position: 'left'
            },
            maintainAspectRatio: true,
            scales: {
              xAxes: [{

                stacked: true,
                gridLines: {
                  borderDash: [2, 6],
                  color: "black"
                },
                scales: {
                }
              }],
              yAxes: [{
                ticks: {
                  beginAtZero: true,
                  steps: 0.5,
                  stepSize: 0.5,
                  max: 1.5,
                  min: -1.0

                },
              }]

            },

          }}
        />
      </div>
    );
  }
}
export default StackedBar;
4

2 回答 2

2

所以我安装了一个名为 FileSave.js 的插件 //

  1. npm 安装 npm i file-saver
  2. 导入插件 import { saveAs } from 'file-saver';
  3. 不仅仅是写这个 blob 函数
   class StackedBar extends Component {
   saveCanvas() {
       //save to png
       const canvasSave = document.getElementById('stackD');
       canvasSave.toBlob(function (blob) {
           saveAs(blob, "testing.png")
       })
   }

   render() {

       return (
           <div>
               <a onClick={this.saveCanvas}>Download as PNG</a>
      
               <Bar id="stackD" data={data} options={options} />
           </div>
       );
   }
}
export default StackedBar;
于 2020-10-16T09:08:36.417 回答
0

另一种选择是使用图表参考，然后使用 chart.js 的 toBase64Image 函数。将其保存为 base64，转换为 blob 并使用文件保护程序包保存为文件。

import { saveAs } from 'file-saver';

/**
 * @param b64Data
 * @param contentType
 * @param sliceSize
 * @returns {Blob}
 * @link https://stackoverflow.com/questions/16245767/creating-a-blob-from-a-base64-string-in-javascript
 */
const b64toBlob = (b64Data, contentType = '', sliceSize = 512) => {
  const byteCharacters = atob(b64Data);
  const byteArrays = [];

  for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
    const slice = byteCharacters.slice(offset, offset + sliceSize);

    const byteNumbers = new Array(slice.length);
    // eslint-disable-next-line no-plusplus
    for (let i = 0; i < slice.length; i += 1) {
      byteNumbers[i] = slice.charCodeAt(i);
    }

    const byteArray = new Uint8Array(byteNumbers);
    byteArrays.push(byteArray);
  }

  return new Blob(byteArrays, { type: contentType });
};

... in component
  const chartRef = useRef(null);
... in jsx...


<Button
   onClick={() => {
   const b64 = chartRef.current.toBase64Image().replace('data:image/png;base64,', '');
   const content = b64toBlob(b64);
   const file = new File([content], 'Revenue_chart.png', { type: 'image/png' });
   saveAs(file);
  }}
  >
    img
</Button>
<Line data={data} options={options} ref={chartRef} />
于 2021-05-28T04:02:16.773 回答