中文摘要：

针对红外图像信噪比小的特点，提出一种基于Prewitt算子的改进方向中值滤波（IDMF，Improved Directional Median Filter）去噪算法，通过Prewitt算子计算目标背景过渡区域（TBA, TargetandBackground Area）的梯度方向，以此找到对应的轮廓方向，在轮廓方向上进行中值滤波，在滤除噪声的同时可以较好地保留图像细节.同时，针对红外图像的灰度分布集中且对比度小的特点，提出了一种局部对比度增强和全局对比度增强相结合的增强算法.首先采用Roberts交叉梯度算子进行局部对比度增强，再通过分段非线性变换函数进行全局对比度增强．实验结果验证了该方法的有效性．

英文摘要：

The SNR（SignaltoNoise） of infrared image is generally very low, In this point, a new denoising algorithm based on Prewitt operator, named IDMF（Improved Directional Median Filter） is proposed. First, the Prewitt operator is used to calculate the gradient direction of TBA（TargetandBackground Area） and the corresponding contour direction is calculated. Second, the median filter is applied to remove the noise in this direction and the detail information can be farthest preserved. Meanwhile, considering the low overall gray distribution of the infrared image and its low contrast, a new contrast enhancement algorithm combined of a partial contrast enhancement and overall contrast enhancement is proposed. The Roberts cross gradient operator is used to achieve the partial enhancement and the piecewise nonlinear function is introduced to the overall contrast enhancement. Experimental results show that our method is effective.