Before I write this blog, a really big thanks for this website: How to Make a Game Like Candy Crush: Part 1
Okay, a great news? When I want to search of the "Candy Crush source code", I found this blog, then I found some great materials: Smooth corner edges. Not much thing have to tell: These are the tiles:
No such thing: File:Tile 14.png
If you are using game maker, you can add it to your files. Remember, set "snap" to 20, and place corner/borders first then place the main board first.