How can I get the number of rows in the image in Objective-C

How can I get the number of rows in the image in Objective-C

I have a TIFF image as an input to me, which I can transform to NSData,
CGImageRef, etc. So, from any of these objects, is there method present to
extract the number of rows present in the image. I need this information
for my project (in MAC OS X).
Also, I don't think that number of rows in the image would be the same as
height of the image.