Cambiar aspect ratio para fotos según pantalla

aspect-ratio

CGSize s = originalImage.size;
CGSize s2 = [UIScreen mainScreen].bounds.size;

CGSize s3 = CGSizeMake(roundf(s.width / s2.width), roundf(s.height/s2.height));
CGFloat factor = fmax(s3.width, s3.height);
        
// Divide the size by the greater of the vertical or horizontal shrinkage factor
s.width = roundf(s.width /factor);
s.height = roundf (s.height / factor);
        
UIImage *image = [self scaleImage:originalImage  ToSize:s];