Could not create writeable, case-sensitive, disk image on El Capitan

Hi all,

This is my first time posting, so pls bear with me if this seems like a dumb question.

I've been trying to create a case-sensitive (journaled) HFS+ disk image on my MacBook (early 2015 model. OSX El Capitan 10.11.2).

The purpose is for building Android AOSP (according to AOSP site, case-sensitive file-system is required).

But so far, I have not been able to successfully create a desired image (case-sensitive AND writeable).

With "Disk Utility", I was able to create a writeable image (i.e. when mounted, the file-system is read/write) but non-case-sensitive.

Why is "Disk Utility" unable to do this since it even provides an option for "Case-sensitive Journaled HFS+"?

Then I tried using "hdiutil create" command line tool (according to some online search results), which was able to create case-sensitive but read-only images (i.e. when mounted, file-system is read-only).

I have tried with different combinations of "-format" & "-fs" options, but nothing seems to work so far.

Using "hdiutil convert" also does not help.

Any advice is much appreciated.

Thanks in advance!