You can't move 9patch images between both types without converting them. If you try to unpack *.9.png file from apk and use it in sources of other app, then you will get error during build, cause *.9.png without borders are invalid at build time. And vice versa: if you replace *.9.png file in apk by png with borders, then this image won't be recognized as 9patch image - it will look weird and borders will be visible at runtime. 9patch binary chunk isn't recognized by image processing tools, so if you try to do anything with compiled 9patch image, then it's possible you will break its npTc chunk and image will look weird on a device. You can't use optipng on compiled 9patch image, also many image editors will break it even if you just open & save file without doing any changes.