Inverse Sigmoid-Based X-Ray Image Enhancement

Jaepil Ko, Won-Kee Hong
2016 Indian Journal of Science and Technology  
Objectives: The retinex algorithm efficiently recovers image details in the dark regions. That is mainly due to the separation of illumination and reflection in images as well as the logarithm that is similar to the human vision system. However, it fails to recover details in bright regions. This paper proposes a modified approach introducing a new logarithm formula to obtain contrast improvements in both dark and bright regions. Methods/Statistical analysis: The proposed method suggests using
more » ... he inverse-sigmoid function instead of the log function in the retinex processing as a tone mapping. Findings: In our experimental results on X-ray images, the comparison results clearly demonstrated that our method is superior to the conventional method in the view point of recovering bright regions. Another advantage of our method is that it can be easily extended by adopting the improved frameworks for the retinex algorithms. Improvements/Applications: The proposed method can be used for X-ray image enhancement. Figure 6. Example of the LHE with different window sizes 15 (1st and 3rd column) and 25 (2nd and 4th column).
doi:10.17485/ijst/2015/v8i1/108372 fatcat:flmu5gpxsnbabitxwxjhbwmnty