Original tone mapped image by Camera {x=big, c=1.8}:

Histogram of the tone mapped image:

Image statistics of the tone-mapped image:

Median percentile of the lightness (CIE L*a*b*): 49.4453
Mean of the chroma value (CIE L*a*b*): 15.981
Image produced by the generic tone mapping operator:
(evalution of the fit via PSNR: PSNR = 35.2485dB)

Fitted tone curve of the generic tone mapping operator,
compared to the luminance compression done by the tone mapping operator:

Fitted parameters of the generic tmo:

Exposure: 0.32684
Contrast: 1.5757
Low midtone range: 1.5979
High midtone range: 0.84784
Saturation: 0.74954
Frequencies: 0.609, 0.979, 1.015, 0.992, 0.996