The image distance is taken to be positive for which kind of image?

1. Sign conventions distinguish the two image types. 2. A real image can be projected on a screen. 3. The image distance is taken to be positive for a real image. 4. It is negative for a virtual image. _Source: OpenStax College Physics for AP Courses 2e (CC BY 4.0), Ch 25 'Geometric Optics', sections 25.1-25.7_