The unique Resolution-Slider-Control that is displayed near the bottom of any selected image, shows whether the resolution of an image is sufficient for the selected printing size using a yellow, green, and red scale.
Printers will interpolate the data to fit any size print you want to make, but they will print at either 300 or 360 dpi. There is a range around those resolutions where the printer does its best job of interpolating that resolution. PrinTao indicates the optimum range with green. Once you get into the red zone, you’ll start to see pixelization and in the yellow zone, you might start seeing some unexpected, unwanted artifacts.