Brightness Preserving Image Contrast Enhancement Using Spatially Weighted Histogram Equalization
Chao Zuo, Qian Chen, Xiubao Sui, and Jianle Ren
Jiangsu Key Laboratory of Spectral Imaging & Intelligence Sense, Nanjing University of Science and Technology, China
Jiangsu Key Laboratory of Spectral Imaging & Intelligence Sense, Nanjing University of Science and Technology, China
Abstract: This paper presents a simple and effective method for
image contrast enhancement called spatially weighted histogram
equalization. Spatially weighted histogram not only considers the times
of each grey value appears in a certain image, but also takes the local
characteristics of each pixel into account. In the homogeneous region of
an image, the spatial weights of pixels tend to zero, whereas at the
edges of the image, this weights are very large. In order to maintain
the mean brightness of the original image, the grey level transformation
function calculated by spatial weighted histogram equalization is
modified, and the final result is given by mapping the original image
through this modified grey level transformation function. The
experimental results show that the proposed method has better
performance than the existing methods, and preserve the original
brightness quite well, so that it is possible to be utilized in consumer
electronic products.
Keywords: Image contrast enhancement, histogram equalization, brightness preserving enhancement, spatially weighted histogram.
Received July 14, 2011; accepted December 30, 2011