Vector representation of graphics has an advantage of being displayed at any size. When resolution of a bitmap image is changed, lack of a line segment arises. In addition, moire occurs when resolution of an image with halftone dots is resized. In this paper, we propose a new technique to convert the binary image with halftone dots into the vector representation. Resolution conversion of binary image can easily be performed without moire by continuous tone approximation of halftone dots. First, we separate the area of halftone dots and line drawings in the image. Next, a continuous tone approximation is applied to the area of halftone dots. Then, the conventional vectorization is applied to both continuous tone areas and line drawings. Finally these components are mixed and reconstructed. Our approach provides an efficient way of displaying cartoon like images at any size with limited amount of data.