Question

I am creating a drawing app and have run into a problem. I have an array of curves; each curve keeps an array of points, and each point keeps its color, thickness, and coords.

When I drawRect: is called, I redraw all the curves from this array. The problem is that this array is getting huge, and the app slows down.

My idea is to, at the end of each redrawing, save the current context as an image, free the curves array, and at the next redraw, use that image as the background. Ultimately, I don’t need the curves array at all, just an array of the curves in progress. Is this possible? Or maybe there is another way to do it?

Answer 1

You can render the corresponding layer of your view as image to update in on the next iteration. Sure it is better in this case to use UIImageView as yourViewToSaveAsImage. In this case you could get this process even easier…

UIView *view = yourViewToSaveAsImage;

UIGraphicsBeginImageContext(view.bounds.size);
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();