1. A method for generating a pixel filtering boundary required by an auto white balance calibration, the method comprising: dividing a G/B-G/R color space into six color regions ( 301 ˜ 306 ) having different color component relationships with referring a specific color temperature reference point ( 210 ) as a center; respectively identifying six color boundaries ( 311 ˜ 316 ) in the six color regions ( 301 ˜ 306 ) by adopting a saturation calculating approach of a HSV color space to generate a specific hexagonal filtering boundary ( 310 ) corresponding to the specific color temperature reference point ( 210 ), so that each of the six color boundaries ( 311 ˜ 316 ) has a predetermined saturation difference (Sd) with the specific color temperature reference point ( 210 ); respectively identifying multiple hexagonal filtering boundaries ( 320 ˜ 360 ) corresponding to other color temperature reference points ( 220 ˜ 260 ) by adopting same approach utilized for generating the specific hexagonal filtering boundary ( 310 ); generating an enveloping boundary in the G/B-G/R color space based on the specific hexagonal filtering boundary ( 310 ) and the multiple hexagonal filtering boundaries ( 320 ˜ 360 ); and configuring the enveloping boundary as a pixel filtering boundary ( 500 ) to be used in the auto white balance calibration.