iConStruct is a free program that allows the user to transform any image into icons of the most varied sizes and formats. The program analyzes the image and creates masks to achieve the best possible result. With iConStruct you can configure several options to modify the images before saving them.
In addition, images can be imported in two ways: by dragging the image into the program (Drop Picture Files Here) or by clicking on File / Open, and the resolution of the icons can be 256x256, 128x128 and 16x16 pixels. When saving the icons, iConStruct can do it in BMP or PNG. (For now it does not work with ICO).
You can free download iConStruct 32, 64 bit and safe install the latest trial or new full version for Windows 10 from the official site.