18+ Png Transparent Machen Gimp PNG. To a file format which supports transparency. You can do this on both windows and mac versions of gimp.
Check this tutorial to create transparent images by removing their background in gimp editor.
Gimp is not difficult to use and the process takes just a click and drag the opacity slider at the top of the layers toolbox to the left to decrease the opacity and increase the transparency. To save the image, click the file option at the top and select export. Press the delete keyboard button: Expand 'advance options', in the 'fill with' drop down select 'transparency'.