1. An image descriptive method comprises: (a) obtaining an image, wherein the image having a plurality of pixels; (b) determining a starting point in the image; (c) sampling the plurality of pixels from the starting point along a trajectory of a former spiral aggregation with a former angle in the image, and arranging the plurality of pixels on the trajectory to form a former spiral aggregation; (d) forming a latter spiral aggregation with a latter angle after increasing an angle variation in the former angle, and sampling the plurality of pixels form the starting point along the trajectory of the latter spiral aggregation, and arranging the plurality of pixels on the trajectory to form a latter spiral aggregation; (e) deciding a frequency of the increased variance for repeatedly performing the step (d) for obtaining a plurality of the latter spiral aggregation, wherein the plurality of pixels correspond to a value; and (f) arranging the former spiral aggregation and the latter spiral aggregation form a spiral aggregation map, and recording the value of each the plurality of pixels.