Auto white balance adjusting method and auto white balance adjusting system

An auto white balance adjusting system comprising:

• an image capturing device configured to acquire an image;
• a memory configured to save data;
• an output device configured to output an image with an adjusted white balance;
• and
• a processor coupled to the image capturing device, the memory, and the output device and configured to control the image capturing device, the memory, and the output device;
• wherein after the image capturing device acquires the image, the processor determines a local white pixel area according to a first color temperature curve and a first brightness range of a first color space saved in the memory, the processor determines a global white pixel area according to the first color temperature curve and a second brightness range of the first color space saved in the memory, the processor selects a plurality of pixels of an image according to the local white pixel area for generating a local average color value of the first color space, the local average color value corresponds to the local white pixel area, the processor selects a plurality of pixels of the image according to the global white pixel area for generating a global average color value of the first color space, the global average color value corresponds to the global white pixel area, the processor converts the local average color value of the first color space into three primary color gains of a second color space, the processor generates three primary color target gains according to the three primary color gains and a second color temperature curve of the second color space, the processor adjusts a white balance of the image frame by frame to meet the three primary color target gains according to the local average color value of the first color space and the three primary color gains of the second color space, the processor controls the output device for outputting the image with the adjusted white balance, and the first color space and the second color space are different.