Star.m

    UIImage *im = [UIImage imageNamed:@"8n2ty.jpg"];
    UIImageView *iv = [[UIImageView alloc] initWithImage:im];
    [self.view addSubview:iv];

    CGFloat w = im.size.width / 2.;
    CGFloat h = im.size.height / 2.;
    UIImage *q1, *q2, *q3, *q4;
    CGRect r1 = CGRectMake(0, 0, w, h);
    CGRect r2 = CGRectMake(w, 0, w, h);
    CGRect r3 = CGRectMake(0, h, w, h);
    CGRect r4 = CGRectMake(w, h, w, h);
    
    CGImageRef imageRef = CGImageCreateWithImageInRect([im CGImage], r1);
    q1 = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);

    imageRef = CGImageCreateWithImageInRect([im CGImage], r2);
    q2 = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);

    imageRef = CGImageCreateWithImageInRect([im CGImage], r3);
    q3 = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);

    imageRef = CGImageCreateWithImageInRect([im CGImage], r4);
    q4 = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    
    CGContextRef context = CGBitmapContextCreate(nil, 2 * w, 2 * h, 8, 8,
                                                 CGColorSpaceCreateDeviceRGB(), CGImageGetBitmapInfo(im.CGImage));
    
    CGContextDrawImage(context, r1, q1.CGImage);
    CGContextDrawImage(context, r2, q2.CGImage);
    CGContextDrawImage(context, r3, q3.CGImage);
    CGContextDrawImage(context, r4, q4.CGImage);
    
    CGImageRef mergeResult  = CGBitmapContextCreateImage(context);
    UIImage *mergedImage = [[UIImage alloc] initWithCGImage:mergeResult];
    CGContextRelease(context);
    CGImageRelease(mergeResult);
    
    
    UIImageView *mergedIV = [[UIImageView alloc] initWithImage:mergedImage];
    mergedIV.frame = CGRectMake(0, iv.frame.origin.y + 2 * iv.frame.size.height, 2 * w, 2 * h);
    [self.view addSubview:mergedIV];