Please help me find an Apple programming document
I am working on CoreGraphics image clipping part of a project. 

It was late night yesterday and I was reading a bunch of Apple documents all at the same time. Among those, one particular page looked really promising to me. The page had a beetle and star-shaped path and demonstrated how to clip an image with the shape. I thought I bookmarked the page and went to bad.

When I wake up today, I cannot find the bookmark so start digging my browser history, google, and anywhere I can look into. No use at all after 6 hours. 

Can anyone please help me to find the document again?
Please help me find an Apple programming document
===

I am working on CoreGraphics image clipping part of a project. 

It was late night yesterday and I was reading a bunch of Apple documents all at the same time. Among those, one particular page looked really promising to me. The page had a beetle and star-shaped path and demonstrated how to clip an image with the shape. I thought I bookmarked the page and went to bad.

When I wake up today, I cannot find the bookmark so start digging my browser history, google, and anywhere I can look into. No use at all after 6 hours. 

Can anyone please help me to find the document again?