Combine two UIImages

To add two UIImages together you need to make use of Graphics Context.

1. - (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage *)image2 {  
2.     UIGraphicsBeginImageContext(image1.size);  
3.   
4.     // Draw image1  
5.     [image1 drawInRect:CGRectMake(0, 0, image1.size.width, image1.size.height)];  
6.   
7.     // Draw image2  
8.     [image2 drawInRect:CGRectMake(0, 0, image2.size.width, image2.size.height)];  
9.   
10.     UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();  
11.   
12.     UIGraphicsEndImageContext();  
13.   
14.     return resultingImage;  
15. }  

Create a UIImage from a part of another UIImage

This requires a round-trip to Core Graphics land:

1. - (UIImage *)imageFromImage:(UIImage *)image inRect:(CGRect)rect {  
2.     CGImageRef sourceImageRef = [image CGImage];  
3.     CGImageRef newImageRef = CGImageCreateWithImageInRect(sourceImageRef, rect);  
4.     UIImage *newImage = [UIImage imageWithCGImage:newImageRef];  
5.     CGImageRelease(newImageRef);  
6.     return newImage;  
7. }  

Save UIImage to Photo Album

This is just a one-liner:

1. UIImageWriteToSavedPhotosAlbum(image, self, @selector(imageSavedToPhotosAlbum: didFinishSavingWithError: contextInfo:), context);  

And to know if the save was successful:

1. - (void)imageSavedToPhotosAlbum:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo {  
2.     NSString *message;  
3.     NSString *title;  
4.     if (!error) {  
5.         title = NSLocalizedString(@"SaveSuccessTitle", @"");  
6.         message = NSLocalizedString(@"SaveSuccessMessage", @"");  
7.     } else {  
8.         title = NSLocalizedString(@"SaveFailedTitle", @"");  
9.         message = [error description];  
10.     }  
11.     UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title  
12.                                                     message:message  
13.                                                    delegate:nil  
14.                                           cancelButtonTitle:NSLocalizedString(@"ButtonOK", @"")  
15.                                           otherButtonTitles:nil];  
16.     [alert show];  
17.     [alert release];  
18. }