PURPOSE: To speedily form a seal on which a line drawing of an image is provided, by constituting the titled device of an image processor which converts a gradated image of an inputted original into a line drawing indicating the profile of the image and outputs the line drawing, and a printer for printing the line drawing on a seal member by using a transfer ink.

CONSTITUTION: An original picture signal from a TV camera is inputted to a converting circuit 3a, in which it is converted into digital data on a picture element basis, and the data are stored into an image memory circuit 3b. The data are read by a computer circuit 3c on a picture element basis, the product of each value thus read and a value in a differentiating mask is added, and the result gives a differential value for a central point. After differentiation for the entire region of one screen is completed, the differentials for each picture element are sequentially read, and a binary coding processing is performed in which a differential greater than a predetermined threshold is assigned '1' while a differential smaller than the threshold is assigned '0'. Finally, a noise-removing processing for removing unnecessary data is performed to finish a line drawing as simple as possible. The result of the image processing is stored as digital information in the circuit 3b, and is sequentially read by the computer 3c to be printed on a seal member 6a by a printer 6.