结合偏微分方程增强图像纹理及对比度

针对图像获取过程中外界光照的非均匀性会使图像存在阴影区和高亮区,从而丢失图像细节的问题,本文结合偏微分理论,提出了基于直方图均衡化的偏微分图像增强方法.该方法首先将图像变换到梯度域,通过梯度场的变换得到新的梯度函数；然后应用最小二乘原理,对梯度场中变换后的图像进行重建以增强图像的纹理细节,表现原本不清楚的细节信息.另外,针对光照的不均匀特性,结合直方图均衡化,提出反均衡变换来增强图像的亮度和对比度.提出的算法采用有限差分法将图像离散化,并与热方程相结合,其计算简单,运行速度快,具有较强的灵活性和较广的应用范围.采用Visiual C++编程,对于大小为512 pixel×512 pixel的图像的处理时间为35 ms,达到了视频实时增强显示要求.

Enhancement of image texture and contrast combined with partial differential equation

The non-uniform distribution of light illumination makes images show some shadow areas and highlight areas in the process of collecting images,which will lose a lot of image details.To solve this problem,this paper proposes a partial differential image enhancement method based on histogram equalization.First,this method transforms the image into a gradient domain,and the new gradient function is obtained through the gradient field transformation.Then,by using the least square principle to reconstruct the image from the gradient field,the textures and details of the image are enhanced and the unknown details are shown all.According to the non-uniform properties of light illumination,anti-balanced transformation is proposed by combining with the histogram equalization to adjust the brightness and contrast of the images.Furthermore,it uses the finite difference method to discrete the image.By combining with the heat equation,the method has characteristics of simple calculation,fast operation,stronger flexibility and wider applications.Based on programming by Visiual C++,its image processing time is 35 ms for an image with the size of 512 pixel×512 pixel,which meets the requirements of real-time image enhancement systems.