Image matting is one of the most common image processing techniques, because it is often necessary to extract the desired foreground object from the original image and then to composite the extracted foreground with the another background. Over the years, there have been lots of commercial image processing tools or softwares which can support the human beings this function, such as photoshop, photoimpact and so on. However, it seems not very easy to use these tools, especially for most beginners who are not familiar with them. Moreover, these softwares usually require payments from the users. In view of the above issues, a multifunctional image keying system which can provide two main functions: image composition and image matting for free and without complicated operations is proposed in this paper. The proposed system is mainly implemented by utilizing the closed form matting method and the trimap which the users simply and roughly provide, thus it can make the users achieve the purpose of performing the operations of the image matting and composite easily and quickly.