Riso Kagaku Corporation

Ikuo Noguchi

Noboru Inamine

Syouji Kurita

A stencil making apparatus thermo-sensitively perforates a stencil sheet by a thermal print head. The apparatus includes a controlling device for driving contiguous N pieces of heat generating elements of the thermal print head while shifting respectively heat generating timings at every 1/N of a period of one line of main scanning in perforating inputted image data of the one line of the main scanning.

Stencil making apparatus

An image is processed by using an error diffusion method of propagating density distribution errors in pixels around a pixel to be noted. A method includes the steps of calculating thresholds (Th.sub.1, Th.sub.2) of densities corresponding to the area ratio between the pixels; selecting a pixel to be noted (f) which are different in the area ratio from each other; calculating errors (E) produced in the peripheral pixels according to the distances from the peripheral pixels to the noted pixel and areas of the individual peripheral pixels; adding the propagated errors to a density of the noted pixel so as to make a rearrangement (f') on the density of the noted pixel; comparing the rearranged density of the noted pixel with the thresholds to obtain a corresponding level (G) represented in a binary form, and obtaining density distribution errors (e).

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Ibaraki-ken, Japan

Ikuo Noguchi