1. A computer-implemented method for processing an input image recorded by a surveillance camera, in which the input image shows a three-dimensional scene in which a distance between the surveillance camera and objects in the three-dimensional scene is referred to as an object distance, and in which a resolution of the input image is reduced to realize a resolution-reduced image of the three-dimensional scene, the method comprising the steps of: in an off-line process, generating reduction parameters in advance that include information about perspective distortion of the three-dimensional scene; and using a computer, processing the input image and the off-line generated reduction parameters to implement a resolution reduction in the input image with consideration of the perspective distortion information of the three-dimensional scene; and wherein said resolution reduction in the resolution reduced image includes reducing resolution of regions in the input image that represent regions in the three-dimensional scene having great object distance to a lesser extent than that of regions in the input image that represent regions in the three-dimensional scene having a small object distance, thereby realizing the resolution-reduced image.