White Balance Principle(2)
In the previous article, we learned about the concept of color temperature, and we can expand it to discuss it. Simply put, the purpose of white balance correction is to adjust the color temperature so that the color looks like the human eye. The current algorithmic basis in white balance correction is the following two very important theories.
Gray world theory: This theory is very interesting. It is not so much about color science. I think it is more like a statistical category. It believes that the average value of the R, G, and B components of any image will tend to be balanced when there is enough color change (that is, the three values of RGB are equal, that is, they should be black and white gray type). This theory is widely used in global white balance. It is characterized by the ability to use more image information to make judgments, but it is a little weak when faced with a single color image.
These two theories correspond to the theoretical basis of adjusting the white balance of RGB and YCbCr in two color spaces: how to judge whether the white balance of a picture is accurate, and if it is not accurate, how to quantify the deviation value.