struct CGAffineTransform { CGFloat a, b, c, d; CGFloat tx, ty; };

The property of transform of UIView has not been understood very well, and there are no experts to explain it.

CGAffineTransform is actually a matrix

| a, b, 0 | | c, d, 0 | | tx, ty, 1 |a={1,1} b={1,2} c={2,1} d={2,2} tx={3,1} ty={3,2}

This matrix is used to mark the changes of this View, which can be rotation, scaling and translation.

In other words, the coordinates of View are {x,y}, and the changed coordinates are {x’,y’}. | a, b, 0 | {x',y',1}={x,y,1} x | c, d, 0 | | tx, ty, 1 |http://developer.apple.com/library/io …This is an official document. There are many ways to easily create this matrix.