Working with Images in C# (.NET): Libraries, Tools, and Examples

Working with Images in C# (.NET): Library Overview and Practical Examples

Image processing is a common task in modern C# (.NET) applications. Whether it's uploading a user avatar, creating thumbnails, adding watermarks, or converting formats — .NET offers several powerful solutions. In this article, we will review the main libraries, their capabilities, and write real code examples.

1. Standard Library: System.Drawing.Common

Historically the first and most well-known is System.Drawing.Common. It provides access to GDI+ (Graphics Device Interface) on Windows. However, it has important limitations:

• Works only on Windows (for .NET Core/.NET 5+ the System.Drawing.Common package is required, but support on Linux/macOS is limited).
• Not optimized for high-load web services (memory leaks if used incorrectly).
• Does not support modern formats (WebP, AVIF) out of the box.

Example of loading and resizing an image:

using System.Drawing;using System.Drawing.Imaging;

public static void ResizeImage(string sourcePath, string destPath, int newWidth, int newHeight){    using (var image = Image.FromFile(sourcePath))    using (var resized = new Bitmap(newWidth, newHeight))    using (var graphics = Graphics.FromImage(resized))    {        graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;        graphics.DrawImage(image, 0, 0, newWidth, newHeight);        resized.Save(destPath, ImageFormat.Jpeg);    }}

This code loads the source image, creates a new Bitmap with the specified dimensions, and draws the source onto it with high quality. Suitable for simple tasks.

2. Modern Cross-Platform Library: ImageSharp (SixLabors)

ImageSharp is a fully managed library for .NET that does not depend on GDI+. It works on Windows, Linux, and macOS. Key advantages:

• Pure C# code, no native dependencies.
• Support for WebP, PNG, JPEG, BMP, GIF, TIFF.
• Built-in filters, rotations, cropping, resizing.
• High performance and security for web applications.

Installation: dotnet add package SixLabors.ImageSharp

Example of resizing and saving to WebP:

using SixLabors.ImageSharp;using SixLabors.ImageSharp.Processing;using SixLabors.ImageSharp.Formats.Webp;

public static void ResizeToWebp(string input, string output, int width, int height){    using (var image = Image.Load(input))    {        image.Mutate(x => x.Resize(width, height));        var encoder = new WebpEncoder { Quality = 80 };        image.Save(output, encoder);    }}

Note: the Mutate method applies changes to the image itself (without creating a copy), saving memory.

3. Graphics Engine: SkiaSharp

SkiaSharp is a wrapper around the Skia library (used in Chrome, Android, Flutter). It provides maximum flexibility and performance, especially for complex 2D graphics.

• Cross-platform (Windows, Linux, macOS, mobile platforms).
• Hardware acceleration support (GPU).
• Rich set of tools: paths, brushes, shaders, masks.

Example of adding a watermark:

using SkiaSharp;

public static void AddWatermark(string imagePath, string watermarkText, string outputPath){    using (var input = SKBitmap.Decode(imagePath))    using (var canvas = new SKCanvas(input))    using (var paint = new SKPaint    {        Color = SKColors.White.WithAlpha(128),        TextSize =