如何修剪UIImageView中的透明空间？

Question

I have an app that can drag images anywhere in the view but my problem is that when the other image is behind to the other there is no way to move directly the image behind than moving the above image. I found only trimming UIImage but it will display still in UIImageView as rectangle. I would like to trim the white space so I can click directly behind images.

How can I trip UIImageView transparent space?

Answer 1

You can create a bitmap and then examine each pixel. You will find code to do this here. Once you know the exact dimensions you can use a Quartz CGImageRef function to extract out a smaller image from the larger one.

That said, you can add a gesture recognizer and use say double tap as a signal to move an image to the bottom of the view stack. I believe this is a much better solution if I were to use your app.