Create a UIImage from two other UIImages on the iPhone

Question

Hi,

I'm trying to write an animation on the iPhone, without much success, getting crashes and nothing seems to work.

What I wanna do appears simple, create a UIImage, and draw part of another UIImage into it, I got a bit confused with the context and layers and stuff.

Could someone please explain how to write something like that (efficiently), with example code?

Answer 1

For the record, this turns out to be fairly straightforward - everything you need to know is somewhere in the example below:

+ (UIImage*) addStarToThumb:(UIImage*)thumb
{
   CGSize size = CGSizeMake(50, 50);
   UIGraphicsBeginImageContext(size);

   CGPoint thumbPoint = CGPointMake(0, 25 - thumb.size.height / 2);
   [thumb drawAtPoint:thumbPoint];

   static UIImage* starred = nil;
   if (starred == nil) {
       starred = [UIImage imageNamed:@"starred.png"];
   }

   CGPoint starredPoint = CGPointMake(0, 0);
   [starred drawAtPoint:starredPoint];

   UIImage* result = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();

   return result;
}