1. A method for retargeting an image, comprising: determining a total block structure energy of an input image content by a processing unit; determining a compressibility rate of said input image content based on said total block structure energy by said processing unit; determining an optimal scaling factor of said input image content by said processing unit; and warping said input image content by using a new coordinate matrices and uniformly scaling said input image content by said processing to output a target image resolution; wherein said compressibility rate (r x and r y ) of said input image content may be obtained by the following equations: r x = 1 W ⁢ ∑ x ⁢ max ⁢ { ( G max y ⁢ { G } _ - max y ⁢ { G ⁡ ( x , y ) } ) , 0 } r y = 1 H ⁢ ∑ y ⁢ max ⁢ { ( G max x ⁢ { G } _ - max x ⁢ { G ⁡ ( x , y ) } ) , 0 } wherein W is a width of said input image content and H is a height of said input image content, and G(x, y) is equal to G x ⁡ ( x , y ) 2 + G y ⁡ ( x , y ) 2 which denotes the intensity gradient magnitude at pixel (x, y), and G max x {G} and G max y {G} denote the averages of maximal intensity gradient values along x and y directions; wherein said optimal scaling factor (S x *, S y *) is obtained by S x * = β · S y S y * = β + 1 - ω · ( r x · β - β - 1 - r y ) / ( 1 + ω ) ⁢ ( β 2 + 1 ) wherein β is equal to W r ·H o /W o ·H r , and (S x , S y ) denotes a resizing factor wherein ω is a weight, wherein W r is a width of a retargeted image and H r is a height of said retargeted image, wherein W o is a width of a source image, and H o is a height of said source image.