How to use the canvg function in canvg

const addSVG = (doc, paperData, svgData, pixelToMMFactor) => {
    let canvasElem = document.createElement('canvas')
    canvasElem.width  = svgData.size.width;
    canvasElem.height = svgData.size.height;

    canvg(canvasElem, svgData.svgAsText, {
        // ignoreClear: true,
        // ignoreDimensions: true,
        // scaleWidth: canvasElem.width  ,
        // scaleHeight: canvasElem.height  ,
        // forceRedraw: () => true
    });
    let imgData = canvasElem.toDataURL("image/jpeg", 1);

    doc.addImage(imgData, 'PNG',
        (svgData.size.left - paperData.containerOffsetX) * pixelToMMFactor,
        (svgData.size.top - paperData.containerOffsetY) * pixelToMMFactor,
        svgData.size.width  * pixelToMMFactor,
        svgData.size.height * pixelToMMFactor
    );
}

downloadImage() {
        console.log('-- downloadImage --');
        
        let svgText = ReactDOM.findDOMNode(this.svgDom).childNodes[0].outerHTML;
        canvg('canvas', svgText);
        let buffer = canvasBuffer(canvas, 'image/png');
        let imageName = path.join(downloadsFolder(), '/image.png');
        
        fs.writeFile(imageName, buffer, () => {
            console.log(imageName);

            this.setState({
                infoText: `Download file: ${imageName} successful.`
            });            
        });

    }

var style = createStyleElement(res);
                        var div = document.createElement('div');
                        chart.fire('beforeExportSVGNode');
                        var svg = chart.getSVG().cloneNode(true);
                        chart.fire('afterExportSVGNode');
                        div.appendChild(fixSVGForCanvgCompatibility(svg));
                        d3.select(svg)
                            .attr('version', 1.1)
                            .attr('xmlns', 'http://www.w3.org/2000/svg');
                        svg.insertBefore(style, svg.firstChild);
                        this._renderAdditionalInfo(svg, chart);
                        this._addBackground(svg, this._backgroundColor);
                        var canvas = document.createElement('canvas');
                        canvas.height = svg.getAttribute('height');
                        canvas.width = svg.getAttribute('width');
                            canvg(
                                canvas,
                                svg.parentNode.innerHTML,
                                {
                                    renderCallback: function (dom) {
                                        var domStr = (new XMLSerializer()).serializeToString(dom);
                                        var isError = (domStr.substring(0, 5).toLowerCase() === '

snipGraph($event) {
    const chart = this.getChartById(this.chartId);
    const svgString = chart.getSVG();
    const hiddenCanvas = document.getElementById(this.hiddenCanvasId);
    canvg(hiddenCanvas, svgString, { renderCallback: () => {
        const base64Image = hiddenCanvas.toDataURL('image/png');
        const imageObject = this.UtilService.getImageObjectFromBase64String(base64Image);
        this.NotebookService.addNote($event, imageObject);
      }
    });
  }

snipGraph($event) {
    const chart = $('#' + this.chartId).highcharts();
    const svgString = chart.getSVG();
    const hiddenCanvas = document.getElementById(this.hiddenCanvasId);
    canvg(hiddenCanvas, svgString, { renderCallback: () => {
        const base64Image = hiddenCanvas.toDataURL('image/png');
        const imageObject = this.UtilService.getImageObjectFromBase64String(base64Image);
        this.NotebookService.addNote($event, imageObject);
      }
    });
  }

arr.forEach((d, i) => {
                let htmlString = ReactDOMServer.renderToStaticMarkup(
                    
                );
                canvg(canv, htmlString);
                d.icon = canv.toDataURL("image/png");
            });
            this.setState({});

svgElem.each((index, node) => {
      let parentNode = node.parentNode
      let svg = node.outerHTML.trim()
      let canvas = document.createElement('canvas')
      canvg(canvas, svg)
      if (node.style.position) {
        canvas.style.position += node.style.position
        canvas.style.left += node.style.left
        canvas.style.top += node.style.top
      }
      nodesToRecover.push({
        parent: parentNode,
        child: node
      })
      parentNode.removeChild(node)
      nodesToRemove.push({
        parent: parentNode,
        child: canvas
      })
      parentNode.appendChild(canvas)
    })