Image Quality Enhancement for Low Backlight TFT-LCD Displays

Pei-Shan Tsai, Chia-Kai Liang, and Homer H. Chen

2007 IEEE International Conference on Image Processing

pdf, slides

Contact e-mail: liangck at gmail dot com

Abstract

Reducing LCD backlight can save power consumption of a portable device, but it also decreases the contrast and brightness of the images. Previous approaches adjust the backlight level frame by frame to reach a specified image quality level but do not optimize it. On the contrary, the proposed method adjusts the backlight to meet the target power level while maintaining the image quality. This is achieved by incorporating brightness compensation and local contrast enhancement depending on the given backlight level. Experimental results show that the proposed algorithm outperforms previous methods.

Results

The number next to the image represents the backlight factor of the mobile device. Move over these numbers to see the difference between the original images and the enhanced ones using our method. Also a comparsion with a previous method is provided. (It takes few minutes to load the images)

 
Original
[Chang et al. 2004]
Proposed

80%
80%
80%
60%
60%
60%
40%
40%
40%
20%
20%
20%
     
Original
[Chang et al. 2004]
Proposed

80%
80%
80%
60%
60%
60%
40%
40%
40%
20%
20%
20%
     
Original
[Chang et al. 2004]
Enhanced

80%
80%
80%
60%
60%
60%
40%
40%
40%
20%
20%
20%
     

Reference

W.-C. Cheng, Y. Hou, and M. Pedram, Power minimization in a backlit TFT-LCD display by concurrent brightness and contrast scaling, in Proc. Conf. on Design, Automation and Test in Europe, pp. 10252-10259, Feb 2004.

Trivia

This is not yet another tone mapping algorithm. The goal of this work is different: using minimal computation to enhance the image (not hdr image) quality when the mobile device is out of battery. Also the algorithm is designed to be mapped to hardware (ASIC or DSP) easily.

Last update: May 3, 2007, Chia-Kai Liang