CGTransform3D and UIImage

Screen Shot 2013-03-14 at 5.35.21 PM

I spent several hours today (that I will never get back) attempting to force a view with a 3D transform to render properly into a UIImage as a favor for Aaron B. Long story short? Failed.

My most promising approach was this, where I attempted to read in an image pixel-by-pixel. Although it worked for the gross dimensions, the fine details were not properly read due to the z-axis rotation:

CGPoint p = [view.layer.superlayer convertPoint:refPoint toLayer:view.layer];

In the end, the lesson is this: 1. Don’t get distracted by Quartz stuff when you’re supposed to be writing a Quartz book. 2. Listen to Apple when it says, “Layers that use 3D transforms are not rendered”

On the bright side, I have marching ants working beautifully — integrated with CADisplayLink and a time interval you specify:  Marching Ants


  • UIGetScreenImage() was the only way I ever found to get an image of 3D rendered text. I spent whole days trying to find a way when I was working on Crawl Creator. (Originally it was going to output .gifs instead of full on .mp4 with audio)

    Cause, what’s a Star Wars crawl without it being in 3D?

    An idea just occurred to me though, what about doing it this way:

    • Iterate through subviews

    • Query for the transform for each subview

    • Render in context to produce an image for each subview

    • Using either GPUImage or CoreImage, apply the queried transform to the image rendered.

    • Now hide said subview.

    • Continue on your merry way, tracking each subview image, and position in it’s superview.

    • Finally, combine all of these rendered and transformed UIImages into one final UIImage.

    I’m going to try this out a bit later tonight I think.

  • Actually, GPUImage awesomely supports transforming a UIImage with a CATransform3D matrix, where as CoreImage wants CIVectors and the like, so I’m going to try to add this to the GPUImage project. I’ll keep you updated.

  • I’m reallllllly close. But for some reason the CIPerspectiveTransform filter’s extent is causing a crop on the conversion to a UIImage.