How to set resolution for Chart during server-side export ?

Chart does not have built-in support to customize the resolution of exported image. But it is possible to customize the resolution of exported image in server-side.

Follow the below steps to increase the resolution of exported chart in server-side

1. Calculate the scaling factor for required DPI
2. Draw the scaled chart
3. Export the scaled chart to server and re-scale the chart to its original size

   JS / Client-side
    
       function exportChart(e) {
           var chart = $("#chartPieTopWorst").ejChart("instance");            
               
           //Calculate the scalefactor
           var devicePixelRatio = window.devicePixelRatio || 1,                
               dpi = 300,
               scaleFactor = dpi / (96 * devicePixelRatio),                
               width, height;
                           
           var type = chart.model.exportSettings.type;
           chart.model.exportSettings.mode = "server";
               
           //Scale the chart based on required DPI
           width = parseFloat(chart.model.size.width);
           height = parseFloat(chart.model.size.height);
           chart.model.size.width = (width * scaleFactor).toString();
           chart.model.size.height = (height * scaleFactor).toString();            
           chart.model.series[0].marker.dataLabel.font.size = (parseFloat(chart.model.series[0].marker.dataLabel.font.size) * scaleFactor) + "px";
           chart.redraw();
               
           //Export the chart to server
           chart.export();
    
           //Rescale the chart to its actual size
           chart.model.size.width = width.toString();
           chart.model.size.height = height.toString();            
           chart.model.series[0].marker.dataLabel.font.size = parseFloat(chart.model.series[0].marker.dataLabel.font.size) / scaleFactor + "px";
                           
           chart.redraw();
       }
    
   

4. In server-side, use the Bitmap.SetResolution method to customize the resolution of exported image.

C# / Server-side    
 
//Server side method for chart exporting
    protected void ExportChart(object sender, Syncfusion.JavaScript.Web.ChartEventArgs e)
    {            
        string DataURL = e.Arguments["Data"].ToString();         
 
        DataURL = DataURL.Remove(0, DataURL.IndexOf(',') + 1);
        MemoryStream stream = new MemoryStream(Convert.FromBase64String(DataURL));
 
        //Bitmap with 96 dpi resolution
        Bitmap img = (Bitmap)Bitmap.FromStream(stream);
 
        int dpi = 300;
        //Bitmap with custom resolution
        Bitmap bmp = new Bitmap(img.Width, img.Height);
 
        //Set required resolution before drawing in PDF
        bmp.SetResolution(dpi, dpi);
        using (Graphics g = Graphics.FromImage(bmp))
        {
            //Draw chart with high quality in new resolution
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
            g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
 
            g.Clear(Color.White);
            g.DrawImage(img, new Rectangle(0, 0, bmp.Width, bmp.Height), new Rectangle(0, 0,img.Width, img.Height), GraphicsUnit.Pixel);
        }
 
        //Save the bitmap in server
        //If needed it can be transferred to client for download
        bmp.Save("Chart.png");
            
        //Dispose bitmap and streams
        bmp.Dispose();
        img.Dispose();
                        
        stream.Dispose();
    }

Sample link: ChartExportDemo