1. A lumber grading system for providing a lumber cutting solution for a piece of lumber, comprising: a first camera adapted to take an image of rear and bottom sides of the piece of lumber; a second camera adapted to take an image of front and upper sides of the piece of lumber; a first video acquisition means connected to the first camera, for acquiring the image generated by the first camera; a second video acquisition means connected to the second camera, for acquiring the image generated by the second camera; a computer means connected to the first and second acquisition means, for performing an image processing of the images and generating the lumber cutting solution for the piece of lumber based on preset grade determination parameters, the image processing including a longitudinal division of the images of the piece of lumber into a number of consecutive zones based on predetermined lumber cutting positions, an attribution of respective grades to the zones based on an image analysis of the zones as a function of the preset grade determination parameters, and a solution search providing the lumber cutting solution as a function of the grades attributed to the zones; and a communication means connected to the computer means, for transmitting the lumber cutting solution.