CODEWITHSUNDEEP
iosios7mapkit
plaetzchen
plaetzchen

Reputation: 767

How to draw a MKPolyline on a MKMapSnapshot

In iOS 7 you can make static snapshots of a map using the MapKit framework. Very useful if you want to send someone an email with a location or something. The only thing that I am missing is: How can I draw an MKPolyline on that snapshot?

Upvotes: 0

Views: 1295

Answers (2)

Eric Schlichting
Eric Schlichting

Reputation: 96

I converted plaetzchen's answer to a swift 4 extension for MKMapSnapshot

import MapKit

extension MKMapSnapshot {

    func drawPolyline(_ polyline: MKPolyline, color: UIColor, lineWidth: CGFloat) -> UIImage {
        UIGraphicsBeginImageContext(self.image.size)
        let rectForImage = CGRect(x: 0, y: 0, width: self.image.size.width, height: self.image.size.height)

        // Draw map
        self.image.draw(in: rectForImage)

        var pointsToDraw = [CGPoint]()


        let points = polyline.points()
        var i = 0
        while (i < polyline.pointCount)  {
            let point = points[i]
            let pointCoord = MKCoordinateForMapPoint(point)
            let pointInSnapshot = self.point(for: pointCoord)
            pointsToDraw.append(pointInSnapshot)
            i += 1
        }

        let context = UIGraphicsGetCurrentContext()
        context!.setLineWidth(lineWidth)

        for point in pointsToDraw {
            if (point == pointsToDraw.first) {
                context!.move(to: point)
            } else {
                context!.addLine(to: point)
            }
        }

        context?.setStrokeColor(color.cgColor)
        context?.strokePath()

        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image!
    }
}

You invoke it like this: 

let image = mapSnapshot.drawPolyline(polyline, color: uiColor, lineWidth: 4)

Upvotes: 0

plaetzchen
plaetzchen

Reputation: 767

This is how:

- (UIImage *)drawRoute:(MKPolyline *)polyline onSnapshot:(MKMapSnapshot *)snapShot withColor:(UIColor *)lineColor {

UIGraphicsBeginImageContext(snapShot.image.size);
CGRect rectForImage = CGRectMake(0, 0, snapShot.image.size.width, snapShot.image.size.height);

// Draw map
[snapShot.image drawInRect:rectForImage];

// Get points in the snapshot from the snapshot
int lastPointIndex;
int firstPointIndex = 0;
BOOL isfirstPoint = NO;
NSMutableArray *pointsToDraw = [NSMutableArray array];
for (int i = 0; i < polyline.pointCount; i++){
    MKMapPoint point = polyline.points[i];
    CLLocationCoordinate2D pointCoord = MKCoordinateForMapPoint(point);
    CGPoint pointInSnapshot = [snapShot pointForCoordinate:pointCoord];
    if (CGRectContainsPoint(rectForImage, pointInSnapshot)) {
        [pointsToDraw addObject:[NSValue valueWithCGPoint:pointInSnapshot]];
        lastPointIndex = i;
        if (i == 0)
            firstPointIndex = YES;
        if (!isfirstPoint) {
            isfirstPoint = YES;
            firstPointIndex = i;
        }
    }
}

// Adding the first point on the outside too so we have a nice path
    if (lastPointIndex+1 <= polyline.pointCount {
    MKMapPoint point = polyline.points[lastPointIndex+1];
    CLLocationCoordinate2D pointCoord = MKCoordinateForMapPoint(point);
    CGPoint pointInSnapshot = [snapShot pointForCoordinate:pointCoord];
    [pointsToDraw addObject:[NSValue valueWithCGPoint:pointInSnapshot]];
}
// Adding the point before the first point in the map as well (if needed) to have nice path

if (firstPointIndex != 0) {
    MKMapPoint point = polyline.points[firstPointIndex-1];
    CLLocationCoordinate2D pointCoord = MKCoordinateForMapPoint(point);
    CGPoint pointInSnapshot = [snapShot pointForCoordinate:pointCoord];
    [pointsToDraw insertObject:[NSValue valueWithCGPoint:pointInSnapshot] atIndex:0];
}

// Draw that points
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 3.0);

for (NSValue *point in pointsToDraw){
    CGPoint pointToDraw = [point CGPointValue];
    if ([pointsToDraw indexOfObject:point] == 0){
        CGContextMoveToPoint(context, pointToDraw.x, pointToDraw.y);
    } else {
        CGContextAddLineToPoint(context, pointToDraw.x, pointToDraw.y);
    }
}
CGContextSetStrokeColorWithColor(context, [lineColor CGColor]);
CGContextStrokePath(context);

UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return resultingImage;
}

I know this is maybe not the best way to do, so if you have a nicer or faster way to do: Please share :)

Upvotes: 9

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