I found out how to replace an app icon on my LG G3 and wanted to add one that has a transparent background.
I created one on my PC in Photoshop and saved it as a PNG. But when I copied it to the phone it changes the background to black
What launcher are you using? I have found that transparent icons are not supported on all launchers. I use Apex, and have no issues. Download Droidicon and search for transparent.
Could it be how I am copying the file?
I just dragged it over to the phone using windows explorer into a folder on my SD card. On the PC the icon transparency is fine
I am using the standard launcher that came with the phone. I know it supports transparency since some of the app icons do have transparency. For example the Contact Lens Management app that I use has a circular Iris as its icon and the areas around it is transparent
I use the stock launcher as well and have just updated my lg_dockmenu_ic_allapps.png icon to a perfectly transparent one. Restarted and it's working great. See below for the file I used (proper size):