You can completely avoid manually doing the transforms and scaling yourself, as suggested by an0 in this answer here:
- (UIImage *)normalizedImage {
if (self.imageOrientation == UIImageOrientationUp) return self;
UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);
[self drawInRect:(CGRect){0, 0, self.size}];
UIImage *normalizedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return normalizedImage;
}
The documentation for the UIImage methods size and drawInRect explicitly states that they take into account orientation.