Default [Q] issue with 9.png stretchings

Hi all, I'm facing an issue trying to theme a 9.png. The stock 9.png doesn't have any "1px black line" anywhere, but the file ext is *.9.png
So I themed it using photoshop CC, and then save it. Just replace the pic into the apk, then move it to phone..and when i open the apk with this 9.png, it doesn't fit/stretch right on the app. I also tried to save it (using photoshop) as web file, png-24 but happened to me the same. But the most curious thing is that when you move again the stock original png wich has no "1px black border" anywhere, it fits ok. So I don't have any idea what could it be.

Please can anyone help me?? thanks in advance!

I didn't download the 9 patcher, but I think it's gonna make the same (or am I wrong?)