Install etc1tool by entering the following commands in the terminal:
sudo apt update sudo apt install etc1tool
Description:
ETC1 conversion tool
etc1tool is a command line utility that lets you encode PNG images to the ETC1 compression standard and decode ETC1 compressed images back to PNG. It is part of the Android SDK for working with media files for game apps. The standard for the ETC1 texture format is here: http://www.khronos.org/registry/gles/extensions/OES/OES_compressed_ETC1_RGB8_texture.txt
Homepage: https://android.googlesource.com/platform/development
Version: 7.0.0+r33-1
Section: universe/devel