calculate new image size before CGContextRotateCTM

Greetings!

This question is rather mathematical, with the iphone SDK/quartz as example:

I am rotating an image using CGContextRotateCTM:

• Create a new context with the size of the source image
• rotate source image and draw it in context
• pass context to new rotated image.

This works fine, but the image is cut off at the edges, because it doesn't fit into the source image size. I would like to resize the context/the resulting image so that the entire rotated image is visible.

What algorithm could I use to calculate the needed size of the context befor开发者_运维知识库e I start the rotation?

Thank you very much in advance.

For anyone passing by: This post answers my problem:

Calculate Bounding box coordinates from a rotated rectangle, Picture inside

Thanks, m