Rotate UIImage instance (90 degree as an e.g. here).

ky_uiimage_rotation.m

UIImage * image = ...

// Redraw image with rotation
CGSize originalSize = image.size;
CGSize finalSize = CGSizeMake(originalSize.height, originalSize.width);
UIGraphicsBeginImageContext(finalSize);
    
CGContextRef context = UIGraphicsGetCurrentContext();
    
CGAffineTransform transform = CGAffineTransformIdentity;
transform = CGAffineTransformTranslate(transform, originalSize.width * .5f, originalSize.height * .5f);
transform = CGAffineTransformRotate(transform, 90.f * M_PI / 180.f);
// -1.f here means fliping matrix vertical
transform = CGAffineTransformScale(transform, 1.f, -1.f);
CGContextConcatCTM(context, transform);

CGContextTranslateCTM(context, -finalSize.width * .5f, -finalSize.height * .5f);
CGContextDrawImage(context, (CGRect){CGPointZero, originalSize}, image.CGImage);
    
UIImage * rotatedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
    
return rotatedImage;

Note, don't forget this step

transform = CGAffineTransformScale(transform, 1.f, -1.f);

otherwise, the final image will be up side down.