Computer graphics technology can enhance or transform the display effect of ordinary 2D and 3D images, and has important application value in digital painting, so this paper explores the application of this technology in digital painting. The Kirsch edge detection algorithm is utilized for boundary extraction and USM sharpening of the image. The vector length is generated for line integral convolution operation, the pencil strokes with high texture quality are generated by the improved LIC algorithm, and finally the resultant image of LIC is merged with the resultant image after contour extraction. The quality analysis experiment verifies that the pencil texture generated by this paper’s algorithm has better stroke clarity and texture than the pencil texture realized by LIC and Photoshop methods. This paper’s algorithm takes 0.09788s, 0.255s and 1.32s to process 240*360, 320*480 and 960*1024 sized pencil images respectively, which is less time-consuming than the LIC algorithm. The analyzed results reflect that the pencil texture generation algorithm proposed in this paper has good performance effects and can enhance the realism of digital painting.