A low-complexity method of converting 2D images/videos into 3D ones includes the steps of identifying whether each pixel in one of the frames is an edge feature point; locating at least two vanishing lines in the frame according to the edge feature point; categorizing the frame into the one of close-up photographic feature, of landscape feature, and of vanishing-area feature; if the frame is identified to have the vanishing-area feature or the landscape feature to generate a GDM; and apply a modificatory procedure to the GDM to generate a final depth information map; if the frame is identified to have the close-up photographic feature, distinguish between a foreground object and a background information in the frame and define the depth of field to generate the final depth information map.