**Tao Zhang, Wenli Du, Hao Wang \*, Qin Zeng and Long Fan**

School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China;

zhangtao@tju.edu.cn (T.Z.); duwenli0210@tju.edu.cn (W.D.); zengqin@tju.edu.cn (Q.Z.); fl0228@tju.edu.cn (L.F.)

**\*** Correspondence: wanghao47@tju.edu.cn

Received: 9 February 2020; Accepted: 2 March 2020; Published: 6 March 2020

**Abstract:** Local dimming technology focuses on improving the contrast ratio of the displayed images for a great visual perception. It consists of backlight extraction and pixel compensation. Considering a single existing backlight extraction algorithm can hardly adapt to images with diverse characteristics and rich details, we propose a stronger adaptive local dimming method with details preservation in this paper. This method, combining the advantages of some existing methods and introducing the combination of the subjective evaluation and the objective evaluation, obtains a stronger adaptation compared with others. Besides, to offset the luminance reduction caused in the backlight extraction process, we improve the bi-histogram equalization algorithm and propose a new pixel compensation method. To preserve image details, the Retinex theory is adopted to separate details. Experimental results demonstrate the effect of the proposed method on contrast ratio improvement and details preservation.

**Keywords:** local dimming; retinex theory; bi-histogram equalization; contrast ratio; details preservation
