How to crop an image with a selectable area in swift 4 or later?

The simple solution is to just render the image view within a particular CGRect:

func snapshot(in imageView: UIImageView, rect: CGRect) -> UIImage {
    return UIGraphicsImageRenderer(bounds: rect).image { _ in
        imageView.drawHierarchy(in: imageView.bounds, afterScreenUpdates: true)
    }
}

The limitation of that approach is that if the image is a considerably higher resolution than the image view could render (as is often the case when we use “aspect scale fit”), you’ll lose this additional precision.

If you want to preserve the resolution, you should convert the CGRect to coordinates with the image, in this case, assuming “aspect scale fit” (namely, centered and scaled so the whole image is shown):

func snapshot(in imageView: UIImageView, rect: CGRect) -> UIImage {
    assert(imageView.contentMode == .scaleAspectFit)

    let image = imageView.image!

    // figure out what the scale is

    let imageRatio = imageView.bounds.width / imageView.bounds.height
    let imageViewRatio = image.size.width / image.size.height

    let scale: CGFloat
    if imageRatio > imageViewRatio {
        scale = image.size.height / imageView.bounds.height
    } else {
        scale = image.size.width / imageView.bounds.width
    }

    // convert the `rect` into coordinates within the image, itself

    let size = rect.size * scale
    let origin = CGPoint(x: image.size.width  / 2 - (imageView.bounds.midX - rect.minX) * scale,
                         y: image.size.height / 2 - (imageView.bounds.midY - rect.minY) * scale)
    let scaledRect = CGRect(origin: origin, size: size)

    // now render the image and grab the appropriate rectangle within
    // the image’s coordinate system

    let format = UIGraphicsImageRendererFormat()
    format.scale = image.scale
    format.opaque = false

    return UIGraphicsImageRenderer(bounds: scaledRect, format: format).image { _ in
        image.draw(at: .zero)
    }
}

Using this extension:

extension CGSize {
    static func * (lhs: CGSize, rhs: CGFloat) -> CGSize {
        return CGSize(width: lhs.width * rhs, height: lhs.height * rhs)
    }
}

That yields:

If I understand your question correctly there are two parts to your question:

1. An adjustable rectangle area over the image
2. Crop an UIImage

Break your google query and search for solution based on the above questions separately.

Or probably take help or use something like this:

iOS-Image-Crop-View