According to Apple's Human Interface guidelines, transparency is not allowed in app icons.
There are a variety of ways to remove transparency from your app's icon.
- Open the image in Preview
- File > Duplicate (Command-Shift-S)
- File > Save (Command-S)
- In the save dialogue, deselect the "Alpha" checkbox
- Delete " copy" from filename (including the space)
- This will overwrite your original, if you want to keep the original, just leave "copy" in the name or name it something else.
- Save
- Click 'Replace' to confirm you want to overwrite the original (Only necessary if you are overwriting your original)
If you have many images to process you may want to use an open source program to remove alpha channels.
Find Alpha-Channel-Remover on GitHub here, and download it here
ImageMagick is a command line utility for editing images.
- Run
brew install imagemagick - Then run
convert <ORIGINAL_IMAGE_NAME>.png -background black -alpha remove -alpha off <OUTPUT_IMAGE_NAME>.png.
Once you've removed transparency from your app icon, rebuild your app.