[c#] Create thumbnail image

This is the code I'm using. Also works for .NET Core > 2.0 using System.Drawing.Common NuGet.

https://www.nuget.org/packages/System.Drawing.Common/

using System;
using System.Drawing;

class Program
{
    static void Main()
    {
        const string input = "C:\\background1.png";
        const string output = "C:\\thumbnail.png";

        // Load image.
        Image image = Image.FromFile(input);

        // Compute thumbnail size.
        Size thumbnailSize = GetThumbnailSize(image);

        // Get thumbnail.
        Image thumbnail = image.GetThumbnailImage(thumbnailSize.Width,
            thumbnailSize.Height, null, IntPtr.Zero);

        // Save thumbnail.
        thumbnail.Save(output);
    }

    static Size GetThumbnailSize(Image original)
    {
        // Maximum size of any dimension.
        const int maxPixels = 40;

        // Width and height.
        int originalWidth = original.Width;
        int originalHeight = original.Height;

        // Return original size if image is smaller than maxPixels
        if (originalWidth <= maxPixels || originalHeight <= maxPixels)
        {
            return new Size(originalWidth, originalHeight);
        }   

        // Compute best factor to scale entire image based on larger dimension.
        double factor;
        if (originalWidth > originalHeight)
        {
            factor = (double)maxPixels / originalWidth;
        }
        else
        {
            factor = (double)maxPixels / originalHeight;
        }

        // Return thumbnail size.
        return new Size((int)(originalWidth * factor), (int)(originalHeight * factor));
    }
}

Source:

https://www.dotnetperls.com/getthumbnailimage

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