The original text contains a symbol error in Equation 6.

[HaoyuCao]

According to the text, $\lambda$ is used for compressing the HDR luminance map to a proper range, i.e., the process of compressing $Y$ to $Y_c$. My understanding is that $Y_c$ has not been obtained yet when calculating the adaptive $\lambda$, so it is not possible to compute the histogram of $Y_c$. Perhaps the correct notation should be $Y \rightarrow Y_c$?

[HaoyuCao]

I misunderstood the calculation process of Equation (6), the orginal version is correct.
Anyway, thanks a lot for the codes.