The High Efficiency Image File (HEIF) or High Efficiency Image Coding(HEIC) image format that Apple uses by default in its iOS devices is good at storing images in a smaller file with better image quality. The problem is sometimes you need to use the image in a website or program that only accepts JPEG images. There are some programs that will convert them but you have to install it and trust that it is not spyware or worse.
This is where this tool comes to help. It is open source, uses .NET Core 3.1 and the Microsoft Windows.Storage and Windows.Graphics.Imaging API's to convert the images.
You also need to install the HEVC codec from the Microsoft Store for this to work.