I: Using Apktool 2.0.0
I: Checking whether sources has changed...
I: Smaling smali folder into classes.dex...
I: Checking whether resources has changed...
I: Building resources...
libpng error: Not a PNG file
ERROR: Failure processing PNG image E:\XXX\XXX\XXX\apktool2.2\.\xxxx\res\XXX\
XXX.png
libpng error: Not a PNG file
ERROR: Failure processing PNG image E:\XXX\XXX\XXX\apktool2.2\.\xxxx\res\XXX\
XXX.png
libpng error: Not a PNG file
ERROR: Failure processing PNG image E:\XXX\XXX\XXX\apktool2.2\.\xxx\res\XXX\
XXX.png

这里只需要利用windows自带图片编辑工具另存为PNG图片然后替换就行了