Exporting Charts from Excel Documents to PNG Images with a Specific DPI Resolution Using SpreadProcessing and PdfProcessing

Updated on Jun 5, 2026

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 (for example, 300 DPI).

Solution

The SpreadProcessing library does not yet support exporting charts directly from Excel files to images. As an alternative, use 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

1. Extract the chart data from the Excel file using SpreadProcessing.
2. Rebuild the chart using a UI component, such as RadChartView from the Telerik UI for WinForms or WPF suites.
3. 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 control chart resolution and save the chart as a PNG image during the export process.

Sample Implementation for Exporting Charts as PNG with 300 DPI

csharp

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 together with the SpreadProcessing PDF export features. Charts saved as PNG images can then be adjusted for resolution.

Applying the Custom Renderer

csharp

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));
}

Recreating the chart with RadChartView may require extra effort if the charts are highly customized or complex.

See Also

• SpreadProcessing PDF Export
• Exporting spreadsheets with charts to PDF using RadSpreadProcessing and WinForms RadChartView