Converting .jpg images to .icon format.
Converting JPEG Images directly to Icon Images (.jpg to .icon conversion) should be possible using one of several icon editing tools capable of importing .jpg images, such as Axialis WorkShop, Adobe Illustrator or IcoFX.
You will most likely be exporting your final icon image as an .ico file.
Alternatively, you can try one of many available online graphics conversion tools.
A powerful vector graphics editor from Adobe
A cross-platform icon making software
A professional icon and cursor editor
Icon creator and editor for Mac