Abstract: Algorithm of natural texture synthesis is an efficient and excellent synthesis
method based on sample images, especially applicable to natural plant. However, the problem of
candidate pixels going out of sample image borders is not solved ideally, which mainly causes the
obvious seams between two pixel blocks. This paper presents a modified algorithm of natural
texture synthesis. The pixels that cause invalid candidate points are all at the border of the sample
image, the pixel regions at the border of sample are replaced by the other pixel blocks within the
sample in our algorithm. The replacing one is of the same shape and size as the target one. Also
the pixel colors of a replaced region and the target one are well matched along an irregular line. In
synthesis process, the growth of a pixel block can turn to a replacing pixel block when touching
the boundary of the sample image, and thus the seams among texture blocks are obviously
reduced, and the output image quality is highly improved.

Key words: improvement, texture synthesis, sample image, image quilting