https://play.google.com/store/apps/details?id=jp.ne.ibis.ibispaintx.appGonna reply with a solution here, because this page is the top google search result for 'transparent icons android'. At least for me. And there's a lot of outdated or badly explained solutions out there.
This was easier than I thought, and can be done on an unrooted phone. The only downside is it's not a simple menu option, you have to basically edit the icons one by one on your phone or PC, and then replace them individually from your home screen.
(Step 0) - I use NovaLauncher. I know these instructions work for it. I think they also work for other launchers, but I'm not sure which ones. The key feature is, Nova Launcher lets you choose an icon from your photo gallery. If you don't have that feature, and really want transparent icons, you'll want to install Nova or some other compatible launcher first.
1. Install
ThemeX from the google play store. It's an old app (not updated since 2014) but as of 2021 it's still there, and still works on stock Android 10, on my Note 9.
2. From ThemeX, you will see your installed icon packs. Tap any of them, and its icons will be displayed. Tap the one you want to make transparent (you can tap more than one to select multiple), and then tap the Save (floppy disk) icon at the top. This will save the icon as a PNG, in a particular folder (something like
storage/emulated/0/themex/iconpack.ddt/icons/ )
3. To change the icon's transparency, you can use either a computer app like Photoshop, or a phone app. If you use a computer app, you will need to transfer the saved PNG's from the previous step to your computer. If you want to do it on your phone, the app "Ibis Paint" can do it. Tap "My Gallery", then the + button at the bottom left to start a new project, then "Import Picture" at the top. Browse to your saved icon. The app may ask if you want to do the line drawing filter, but we'll skip that, click "cancel". On the main screen, click the layers button (at the bottom, looks like stacked squares with "1" on top). Some layers stuff will pop up, at the bottom is a transparency slider. Put it at whatever percentage you want. If you're unsure, try 50%. Now click the back button twice, and an option will appear to save. Choose "Save as transparent PNG".
4. If you're doing this on your PC, you may be wondering if you want 8-bit or 16-bit for the icon. 8-bit is fine. When you transfer the PNG back to your phone, you can save it anywhere, just make sure it's easy to find the folder later.
5. Go to your home screen, with the icon you're trying to change. Long press that icon. A menu will appear, click "Edit" (pencil icon). You'll get a large preview of the icon with some options. Tap the preview. You'll be offered some options to change the icon. This is how the options screen looks:
On those horizontal bars, you can see the first option is the default theme. The second option is the one we want, called "Gallery Apps". Tap this, and then you'll be able to browse to your custom icon. The launcher lets you choose how you browse for it... you can use the Gallery App (so you'll get a preview of the icons) or you can choose whatever file explorer you have installed. Navigate to the folder where you saved the transparent icon.
6. After choosing the icon, you get a preview that you can crop. Tap "Done" at the top. Your icon has been changed. Note that with the latest version of Nova Launcher (still in beta as of this post) there's an annoying "reshape" option that is checked by default. It shrinks the icon and puts a non-transparent shaped background behind it. Just uncheck "reshape" and you'll get what you wanted, a full-sized icon with the transparent effect.
You'll have to repeat this for all your icons, one by one. I think the only shortcut is, you can select multiple icons in ThemeX to extract at the same time.
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