Resizing image results in low resolution

So I am trying to use a specific PNG image for my map annotation. The original image is 761 x 761 and the resized annotation image that shows up in my app is all blurry and low-resolution-looking. Any idea why that is?

        chargerAnnotationImage = UIImage(named: "ChargerGreen")!
        let size = CGSize(width: 25, height: 25)
        UIGraphicsBeginImageContext(size)
        chargerAnnotationImage.drawInRect(CGRectMake(0, 0, size.width, size.height))
        let resizedImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return resizedImage 

Thank you!