Exporting Charts from Excel Documents to PNG Images with a Specific DPI Resolution Using SpreadProcessing and PdfProcessing
Environment
| Version | Product | Author |
|---|---|---|
| 2025.2.520 | RadSpreadProcessing & RadPdfProcessing | Desislava Yordanova |
Description
Learn how to extract the charts from Excel documents and save them as PNG files, while specifying the desired resolution (e.g. 300 DPI).
Solution
Exporting charts directly from Excel files to images is not yet supported by the SpreadProcessing library. As an alternative, you can benefit the export option to PDF format which allows you to plug into the chart rendering process, export the chart and handle the DPI settings
Suggested Workflow Using Charting Controls
- Extract the chart data from the Excel file using SpreadProcessing.
- Rebuild the chart using a UI component, such as RadChartView from the Telerik UI for WinForms or WPF suites.
- Export the chart as a PNG image with 300 DPI using RadChartView.
Alternative Approach: Exporting to PDF
Export the XLSX document to PDF format using SpreadProcessing. This method internally uses a chart renderer for rendering charts in the PDF. Implement a custom IPdfChartRenderer to manipulate chart resolution and save the chart as a PNG image in the ongoing export process.
Sample implementation for exporting charts as PNG with 300 DPI:
public class WinFormsPdfChartImageRenderer : IPdfChartRenderer
{
public void RenderChart(FixedContentEditor editor, FloatingChartShape chartShape)
{
string filePath = @"exportedChart.png";
// Set chart dimensions
System.Drawing.Size size = new System.Drawing.Size((int)(chartShape.Width), (int)(chartShape.Height + 10));
System.Drawing.Image chartImage = Telerik.WinForms.Controls.Spreadsheet.Layers.ChartModelToImageConverter.GetImageFromFloatingChartShape(chartShape, size);
using (var bmp = new Bitmap(chartImage))
{
// Set DPI to 300
bmp.SetResolution(300, 300);
// Save as PNG
bmp.Save(filePath, System.Drawing.Imaging.ImageFormat.Png);
}
using (FileStream fs = new FileStream(filePath, FileMode.Open))
{
editor.DrawImage(fs);
}
Process.Start(new ProcessStartInfo(filePath) { UseShellExecute = true });
}
}
To export charts to PNG, use the custom renderer in conjunction with SpreadProcessing’s PDF export functionalities. Charts saved as PNG images can then be adjusted for resolution.
Applying the custom renderer:
Telerik.Windows.Documents.Spreadsheet.Model.Workbook workbook;
IWorkbookFormatProvider formatProvider = new Telerik.Windows.Documents.Spreadsheet.FormatProviders.OpenXml.Xlsx.XlsxFormatProvider();
string fileName = "SampleFile.xlsx";
using (Stream inputStream = new FileStream(fileName, FileMode.Open))
{
workbook = formatProvider.Import(inputStream, TimeSpan.FromSeconds(10));
}
PdfFormatProvider pdfFormatProvider = new Telerik.Windows.Documents.Spreadsheet.FormatProviders.Pdf.PdfFormatProvider();
pdfFormatProvider.ExportSettings.ChartRenderer = new WinFormsPdfChartImageRenderer();
converter.PdfFormatProvider = pdfFormatProvider;
using (Stream output = File.OpenWrite("Sample.pdf"))
{
pdfFormatProvider.Export(workbook, output, TimeSpan.FromSeconds(10));
}
Note: Recreating the chart using RadChartView may require extra effort if the charts are highly customized or complex.