C# Create thumbnail image

This post shows you How to create a thumbnail image in C# .NET. You can use the c# code below to get thumbnail from file.

public Image CreateThumbnailImage(string fileName, int width = 64, int height = 88)
{
    Image image = Image.FromFile(fileName);
    Image thumb = image.GetThumbnailImage(width, height, () => false, IntPtr.Zero);
    image.Dispose();
    return thumb;
}

The c# example above will help you convert an image to thumbnail image, then return an image object.

If you want to save an image to file, you can modify your code as shown below.

string fileName = "your image file"
int width = 150;
int height = 150;
Image image = Image.FromFile(fileName);
Image thumb = image.GetThumbnailImage(width, height, ()=>false, IntPtr.Zero);
thumb.Save(Path.ChangeExtension(fileName, "thumb"));

Or you can use the GetThumbnailImage method in System.Drawing.dll, System.Drawing.Common.dll

The GetThumbnailImage method works well when the requested thumbnail image has a size of about 120 x 120 pixels.

If you request a large thumbnail image (for example: 300 x 300) from an Image that has an embedded thumbnail, there could be a noticeable loss of quality in the thumbnail image.

It might be better to scale the main image (instead of scaling the embedded thumbnail) by calling the DrawImage method.