Paul Abhisek, Sutradhar Tandra, Bhattacharya Paritosh, Maity Santi P
Appl Opt. 2020 Oct 1;59(28):9032-9041. doi: 10.1364/AO.395848.
Infrared (IR) images are basically low-contrast in nature; hence, it is essential to enhance the contrast of IR images to facilitate real-life applications. This work proposes a novel adaptive clip-limit-oriented bi-histogram equalization (bi-HE) method for enhancing IR images. HE methods are simple in implementation but often cause over-enhancement due to the presence of long spikes. To reduce long spikes, this work suggests to apply a log-power operation on the histogram, where the log operation reduces the long spikes, and power transformation regains the shape of the histogram. First, a histogram separation point is generated applying the mean of the multi-peaks of the input histogram. After that, an alteration in the input histogram is done using the log-power process. Subsequently, a clipping operation on the altered histogram followed by redistribution of the clipped portion is performed to restrict over-enhancement. Next, the modified histogram is sub-divided using the histogram separation point. Finally, the modified sub-histograms are equalized independently. Simulation results show that the suggested method effectively improves the contrast of IR images. Visual quality evaluations and quantitative assessment demonstrate that the suggested method outperforms the state-of-the-art algorithms.
红外（IR）图像本质上基本是低对比度的；因此，增强红外图像的对比度以促进实际应用至关重要。这项工作提出了一种新颖的面向自适应裁剪限制的双直方图均衡化（bi-HE）方法来增强红外图像。直方图均衡化（HE）方法实现简单，但由于存在长尖峰往往会导致过度增强。为了减少长尖峰，这项工作建议对直方图应用对数幂运算，其中对数运算减少长尖峰，幂变换恢复直方图的形状。首先，利用输入直方图多峰的均值生成一个直方图分离点。之后，使用对数幂过程对输入直方图进行改变。随后，对改变后的直方图进行裁剪操作，然后对裁剪部分进行重新分配以限制过度增强。接下来，使用直方图分离点对修改后的直方图进行细分。最后，对修改后的子直方图分别进行均衡化。仿真结果表明，所提出的方法有效地提高了红外图像的对比度。视觉质量评估和定量评估表明，所提出的方法优于现有算法。
