How to Convert Excel to Thumbnail Image in C#

When working with document preview features or content libraries, thumbnail images provide a quick visual reference without loading the entire file. This tutorial demonstrates how to create thumbnail images from Excel files using Aspose.Cells for .NET.

Why Use Thumbnails?

Create preview cards for document galleries
Build visual dashboards of spreadsheet reports
Add lightweight visuals to search or file management tools

Step-by-Step Guide

Step 1: Install Aspose.Cells

dotnet add package Aspose.Cells

Step 2: Load the Workbook

Workbook workbook = new Workbook("FinanceReport.xlsx");
Worksheet sheet = workbook.Worksheets[0];

Step 3: Configure Thumbnail Rendering Options

ImageOrPrintOptions options = new ImageOrPrintOptions
{
    ImageType = ImageType.Png,
    HorizontalResolution = 96,
    VerticalResolution = 96,
    OnePagePerSheet = true
};

Step 4: Render the First Worksheet to an Image

SheetRender renderer = new SheetRender(sheet, options);
renderer.ToImage(0, "preview_temp.png");

Step 5: Resize Image to Thumbnail Dimensions (Optional)

You can use a graphics library (e.g., System.Drawing) to resize the image:

using System.Drawing;

Bitmap original = new Bitmap("preview_temp.png");
Bitmap thumbnail = new Bitmap(original, new Size(160, 120));
thumbnail.Save("thumbnail.png");

Step 6: Use the Thumbnail Image

Now you have a lightweight thumbnail suitable for previews.

Complete Example Code

using System;
using System.Drawing;
using Aspose.Cells;
using Aspose.Cells.Rendering;

class Program
{
    static void Main()
    {
        // Load Excel file
        Workbook workbook = new Workbook("FinanceReport.xlsx");
        Worksheet sheet = workbook.Worksheets[0];

        // Configure low-resolution options
        ImageOrPrintOptions options = new ImageOrPrintOptions
        {
            ImageType = ImageType.Png,
            HorizontalResolution = 96,
            VerticalResolution = 96,
            OnePagePerSheet = true
        };

        // Render full sheet as a temporary image
        SheetRender renderer = new SheetRender(sheet, options);
        renderer.ToImage(0, "preview_temp.png");

        // Resize to thumbnail
        using (Bitmap original = new Bitmap("preview_temp.png"))
        {
            Bitmap thumbnail = new Bitmap(original, new Size(160, 120));
            thumbnail.Save("thumbnail.png");
        }

        Console.WriteLine("Thumbnail image created from Excel worksheet.");
    }
}

Best Practices

Recommendation	Purpose
Use `OnePagePerSheet = true`	Prevent multi-page splitting in image
Lower resolution	Optimizes for faster thumbnail generation
Resize image after rendering	More control over scaling and quality