图像亮度精确控制的双直方图均衡算法

Bi-Histogram Equalization Algorithm with Precise Control of Image Brightness

针对传统的双直方图均衡算法(BBHE)不能精确实现图像亮度保持目标的问题,该文提出一种新的双直方图均衡算法。基于给定图像的灰度直方图,建立灰度阈值与输出图像亮度之间的对应关系;求解满足图像亮度要求的所有灰度阈值,从中选择一个最佳阈值用于图像的双直方图均衡处理,使输出图像与BBHE算法增强的图像之间具有最大直方图相似度。基于多种亮度图像的实验结果表明,BBHE算法的输出图像亮度与期望值之间相差-36.94%~8.85%,该算法将误差范围缩小到0.43%~2.56%,显著提高了双直方图均衡算法控制图像亮度目标的精确性,运行速度满足实时要求。

A novel bi-histogram equalization algorithm is proposed for keeping image brightness preservation. Based on the grayscale histogram of the given image, the corresponding relation between the grayscale threshold and the output brightness is established; all the thresholds are calculated to meet the requirements of the output brightness, then the best one is chosen for bi-histogram equalization so that the biggest histogram similarity exists between the output image and the result by the brightness preserving bi-histogram equalization （BBHE） method. Experimental results of several images with different brightness show that by using the proposed algorithm the margin of relative error between output brightness and expected value reaches 0.43%～2.56%, but only？36.94%～8.85% by using the BBHE method. We conclude that the proposed algorithm significantly improves the accuracy of brightness control target for bi-histogram equalization, and the operating speed meets real-time requirements.