Quartz2D how to save the current context and then draw over it?

Question

I'm trying to draw using Quartz2D and but i'm finding the drawing to lag a lot right after a few dots. Therefore I am wondering how can I cache the current context into a bmp or a jpg or a layer and then draw onto the layer again to make the drawing smoother. Which way is the best way to do it? Thanks!

Answer 1

IIRC, Quartz2D uses a painting model to render content, and once you draw something you can't interact with it at all, so I don't see why caching the current context would do anything to help.

However, if you want to cache your current context, the code looks something like this:

// Begin image context
UIGraphicsBeginImageContext(view.bounds.size);

[view.layer renderInContext:UIGraphicsGetCurrentContext()];
CGImageRef screenshotRef = CGBitmapContextCreateImage(UIGraphicsGetCurrentContext());
UIImage *screenshot = [[UIImage alloc] initWithCGImage:screenshotRef];

// End image context
UIGraphicsEndImageContext();
// Release CGImage
CGImageRelease(screenshotRef);

return screenshot;