Merging two images of different size with rotate and zoom - ios

Question

I'm facing the following problem : I have to merge two images bottomImg and topImg to create a new image C as a result of the merging.
I already know how to merge two images but in this case my goal is a little bit different.
top image may be zoomed and rotated.
I have follow this answer. But in this solution top image is cut while i rotate. simulator
actual stored image is document like
I have try this code
_parentViewGIf for bottomImg and for _ivGIF for topImg
- (UIImage *)mergeImage:(UIImage *)bottomImg withImage:(UIImage *)topImg {
float width=bottomImg.size.width*_ivGIF.frame.size.width/_parentViewGIf.frame.size.width;
float height=bottomImg.size.width*_ivGIF.frame.size.height/_parentViewGIf.frame.size.width;
UIImage * scaledTopImg = [self imageByScalingProportionallyWithImage:topImg ToSize:CGSizeMake(bottomImg.size.width, bottomImg.size.height)];
UIGraphicsBeginImageContext(scaledTopImg.size);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(ctx, scaledTopImg.size.height * 0.5, scaledTopImg.size.height * 0.5);
CGFloat angle = atan2(_ivGIF.transform.a, _ivGIF.transform.b);
CGContextRotateCTM(ctx, angle);
[scaledTopImg drawInRect:CGRectMake(- scaledTopImg.size.width * 0.5f, -(scaledTopImg.size.height * 0.5f), scaledTopImg.size.width , scaledTopImg.size.height )];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
float x=bottomImg.size.width*_ivGIF.frame.origin.x/_parentViewGIf.frame.size.width;
float y=bottomImg.size.width*_ivGIF.frame.origin.y/_parentViewGIf.frame.size.width;
UIGraphicsBeginImageContext(bottomImg.size);
[bottomImg drawInRect:CGRectMake(0, 0, bottomImg.size.width, bottomImg.size.height)];
[newImage drawInRect:CGRectMake(0, 0, newImage.size.width, newImage.size.height)];
UIImage *newImage2 = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage2;
}
Thanks in advance for any help or suggestion