At the beginning, I need to explain some knowledge about color space.

The raw RGB is linear, but the sRGB value generated by camera is nonlinear value.

So, the whole process of the color calibration is:

1. Using ColorChecker to compute the gamma of the sRGB value.

2. Do gamma correction (that will transform sRGB to linear RGB)

3. Find the linear mapping matrix to transform linear RGB to true XYZ values.

4. Transform XYZ to LAB. (The XYZ and LAB are camera independent)

Color Calibration using ColorChecker