1. A real-time cloud image system, comprising: at least a frontend device generating an instruction message and a ROI (Region of Interest) message; and a backend system coupled to the frontend device, the backend system having at least a raw image, wherein the raw image has a plurality of images of different resolutions, each of the images and the raw image are composed of a plurality of tiles; wherein the ROI message corresponds to a region of interest respectively within each of the images and the raw image, the backend system according to the instruction message and the ROI message selectively provides a grouping of the tiles within the region of interest of the raw image or one of the images to the frontend device.