Abstract: In order to solve the problem that the existed texture smoothing methods can not maintain narrow structure while removing texture,a scale adaptive texture filtering algorithm based on semi-Gaussian gradient operator is proposed.Firstly,we design a semi-Gaussian gradient operator with texture suppressing and structure preserving characteristics.Its amplitude can distinguish structure from texture,and its direction represents the normal direction of the structure.Secondly,the optimal smoothing scale for each pixel is estimated based on the amplitude of the semi-Gaussian gradient,and the Gaussian filter is utilized to obtain a guidance image in which most of the texture are diminished.Finally,a filtering direction kernel based on the semi-Gaussian gradient direction is introduced to the bilateral filter,and a trilateral texture filtering algorithm based on the guidance image is put forward,which can effectively avoid the burr near the structure.Experimental results show that our algorithm can guarantee the structural integrity while flattening the texture,and show superior performance in maintaining the narrow structures and keeping the structures clean.