As imaging devices have been rapidly developed, it is very convenient to obtain natural images at all times and places. As a step further, generating the visual effect of artistic paintings from natural images has become an attractive image processing task, such as pencil drawing generation. However, current pencil drawing generation methods mainly concentrate on simulating the pencil-drawing patterns, while neglecting the complex illumination variations of an image. Therefore, various unsatisfying effects can be inevitably introduced, in turn weakening the quality of the generated pencil drawing patterns. To address this problem, we present a novel pencil drawing generation method based on Retinex decomposition. A mixed-norm Retinex image decomposition model is firstly proposed, which decomposes an image into an illumination layer and a reflectance layer. Then, with the obtained layers, the pencil line layer and tone layer are produced based on our simple but effective models, respectively. In experiments, the results show that our method consistently generates high-quality pencil drawing patterns from images with different illumination conditions. For example, as for the images with low light or back light, our method still ensures the visual quality of the obtained pencil drawings.

随着成像装置的迅速发展，在任何时间和任何地方获得自然图像是非常方便的。作为进一步的步骤，从自然图像产生艺术绘画的视觉效果已经成为有吸引力的图像处理任务，例如铅笔素描的产生。然而，当前的铅笔图生成方法主要集中在模拟铅笔画图案上，而忽略了图像的复杂照明变化。因此，不可避免地会引入各种不令人满意的效果，从而削弱了所产生的铅笔画图案的质量。为了解决这个问题，我们提出了一种基于Retinex分解的新颖铅笔图生成方法。首先提出了混合范数的Retinex图像分解模型，它将图像分解为照明层和反射层。然后，使用获得的图层，分别基于我们简单但有效的模型来生成铅笔线条图层和色调图层。在实验中，结果表明，我们的方法从具有不同照明条件的图像中始终生成高质量的铅笔画图案。例如，对于弱光或逆光的图像，我们的方法仍然可以确保获得的铅笔图的视觉质量。