How to Build an Image Resizer in C# | .NET WinForms Tutorial

Published 07/04/2026

Description

Stop guessing which part of your high-resolution photo will make a good website banner. Most modern photos are far too tall for the wide, short aspect ratios required by web headers, leading to awkward crops and lost detail. In this video, I build a custom .NET WinForms application that solves this problem by providing a precise image-to-banner resizer. We will implement a movable overlay window that allows you to visually select your viewport, ensuring you get the perfect crop every time before exporting your final result as a PNG or JPEG. Contents: 0:00 - Introduction 0:15 - Description 1:50 - The Result (Demo) 2:16 - V1 - Loading an Image 4:46 - V2 - Resizing the Image 8:27 - V3 - Implementing the Overlay Window 15:00 - V4 - Extracting and Exporting the Crop 17:31 - Conclusion What you’ll learn: Image Handling in WinForms: How to properly load and render large image files within a desktop UI. Programmatic Resizing: Techniques for scaling images down while maintaining quality. Custom Overlay Logic: Building a movable UI element to act as a visual cropping guide. Coordinate Extraction: How to calculate the selected area's coordinates to "clip" and save a new image file. This project is a perfect example of how to build focused, practical desktop utilities using C# and .NET to solve real-world content creation problems. #DotNet #WinForms #CSharp GitHub https://l.samayas.eu/f842mwXYCT Follow me on X: https://l.samayas.eu/jo3eaYEf3E?P=YT&V=108 Buy me a Coffee: https://l.samayas.eu/jX6xL7EWhd?P=YT&V=108 Studio Equipment Camera Sony Alpha ZV-E10 II: https://l.samayas.eu/k7y95TREl0?P=YT&V=108 Secondary Camera Obsbot Tail Air: https://l.samayas.eu/iFQu9WfmCw?P=YT&V=108 Elgato Prompter: https://l.samayas.eu/fHVrqqXtSc?P=YT&V=108 Microphone Rode Wireless GO II: https://l.samayas.eu/afBINjiBXN?P=YT&V=108