问题
Right now this code will only rotate my image 90 degrees. I can not figure out how to rotate it 270 degrees.
transform = transform.rotated(by: CGFloat(Double.pi))
回答1:
Start with some basic math.
360° = 2π. 180° = π. 90° = π/2. 270° = 3π/2.
This means your posted code is rotating 180 degrees.
Use Double.pi/2 for 90° and 3*Double.pi/2 for 270°.
来源：https://stackoverflow.com/questions/43619944/how-to-get-image-orientation-to-rotate-270-degrees-swift3