Unfortunately, I couldn't find an official plugin repository for Paint.NET that hosts an "Alpha to 255" plugin. However, I can guide you through creating a simple plugin using the Paint.NET Effect Plugin SDK.

Paint.NET is a free image editing software for Windows that offers many of the features you'd find in more advanced image editing software like Adobe Photoshop.

The plugin you're looking for is a simple utility that allows you to set the alpha channel of an image to 255, effectively removing any transparency. This can be useful when working with images that have transparent backgrounds and you want to convert them to a solid background.

public class AlphaTo255Effect : Effect { public AlphaTo255Effect() { this.Name = "Alpha to 255"; this.Description = "Sets the alpha channel to 255"; }