MKMapView zoom to show all annotations in frame - ios

Question

I have a full screen map, and I want to zoom to a level where all annotations are visible on the map, but only in the content area of the app, as specified by this image:
As you can see, the map fills the entire screen, however, there are rectangles overlayed on the top and bottom which cover the map. The content area is the part that's bright green. Given an array of annotations, I want to be able to zoom the map so that all are visible within that green content area, and not within the actual frame of the map.
I'm using this (category) method here which does the default task of zooming to fit in the frame of the map. But I'm getting stuck on how to modify this to factor in only the content area:
- (void)zoomToShowAnnotations:(NSArray *)annotations extraPaddingMultiplier:(CGFloat)multiplier
{
CLLocationCoordinate2D topLeftCoord;
topLeftCoord.latitude = -90;
topLeftCoord.longitude = 180;
CLLocationCoordinate2D bottomRightCoord;
bottomRightCoord.latitude = 90;
bottomRightCoord.longitude = -180;
for(id<MKAnnotation> annotation in annotations)
{
topLeftCoord.longitude = fmin(topLeftCoord.longitude, annotation.coordinate.longitude);
topLeftCoord.latitude = fmax(topLeftCoord.latitude, annotation.coordinate.latitude);
bottomRightCoord.longitude = fmax(bottomRightCoord.longitude, annotation.coordinate.longitude);
bottomRightCoord.latitude = fmin(bottomRightCoord.latitude, annotation.coordinate.latitude);
}
MKCoordinateRegion region;
region.center.latitude = topLeftCoord.latitude - (topLeftCoord.latitude - bottomRightCoord.latitude) * 0.5;
region.center.longitude = topLeftCoord.longitude + (bottomRightCoord.longitude - topLeftCoord.longitude) * 0.5;
region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * (multiplier != 0 ? multiplier : 1); // Add a little extra space on the sides
region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * (multiplier != 0 ? multiplier : 1); // Add a little extra space on the sides
[self setRegion:region animated:YES];
}

Answer 1

According to documentation this method should to the job.
// Position the map such that the provided array of annotations are all visible to the fullest extent possible.
#available(iOS 7.0, *)
open func showAnnotations(_ annotations: [MKAnnotation], animated: Bool)
You'll have to set an array of your annotations and put it in the function like this
let annotation = MKPointAnnotation()
annotation.coordinate = CLLocationCoordinate2D(latitude: 11.12, longitude: 12.11)
mapView.addAnnotation(annotation)
mapView.showAnnotations([annotation], animated: true)

Answer 2

This is just a list of steps, no actual code or anything.
Compute the aspect ratio of the region you have found.
If the aspect ratio is relatively wider than (or equal to) your desired ratio, go to step 5.
Construct a new region fitting your existing region and whose aspect ratio matches your desired ratio (expand the width).
Construct a new region fitting your expanded region within the screen (expand the height).
Party down.