Abstract: An encryption method includes: recognizing any face included in an image; analyzing color(s) of the recognized face(s) and thereby determining skin-color(s) of person(s) included in the image; determining a skin-area using the determined skin-color(s); calculating a ratio of the area of the recognized face(s) to the determined skin-area, and determining whether the image required to be encrypted based upon the calculated ratio; and encrypting the image in response to the inputs of a user if the image is required to be encrypted.

Abstract: A computer alert system includes an image capture unit, an element detection unit, an autofocus unit, a calculation unit, a comparison unit and a warning unit. The image capture unit is capable of capturing a digital image of an object. The element detection unit is capable of detecting if a designated element of the object is in the captured digital image. The autofocus unit is capable of focusing on the designated element of the digital image. The calculation unit is capable of calculating a distance from the designated element of the object to the computer. The comparison unit is capable of determining if the calculated distance is acceptable. The alert unit capable of triggering an alert if the calculated distance is not acceptable. Furthermore, a computer alert method is employed by the computer alert system.