With the rapid growth of the diversity and versatility of display devices which all come in different aspect ratios and resolutions

the content-aware image resizing has become one of the hot research fields in image processing. The main objective of such a technique is to preserve the image features when changing its size. The most content-aware image resizing methods have two basic steps: content significance recognition and image resizing based on a significance map. Firstly

the classic methods of the significance recognition are surveyed.Secondly

the resizing technologies based on significance maps are summarized. According to resizing methods based on pixel level discrete operating

sub-pixel level continuous operation or combination of the discrete operating and continuous operation

it can be categorized into image resizing based on seam carving

image resizing based on warping or multi-operator resizing. Thirdly

the algorithm effect comparisons between classes are given and their suitable image types are presented. Finally

future directions are discussed.