What is a,b value for black color.

[rsingh-aiborne]

what is ab value of black color

[Benitoite]

In CIELAB, the absence of light has no color; black is L*=0, a*=0, b*=0, notwithstanding any colorspace conversions.

[rsingh-aiborne]

I know that but, how to set the value of L?
! wanted to convert white wall into black

[junyanz]

The code will preserve the L channel by default and only predict ab channels. If you really want to change the L channel, you can modify this line.