Abstract: A method and apparatus for processing a first (e.g. half-tone) image constituted by a second (e.g. continuous tone) image convolved with a periodic (screen) function, to produce the second image is described. The invention is particularly suited to handling digitally represented half-tone images. The apparatus comprises a microcomputer (17) for determining digital data defining a frequency filter characteristic adapted to suppress the frequency or frequencies of the periodic function. A fast Fourier transform circuit (11) transforms the image data into the frequency domain and a multiplier (12) multiplies the transformed data by the frequency characteristic stored in a store (13). The resultant multiplied data is inversely transformed back into the image of spatial domain by a fast Fourier transform circuit (14) to generate the second image.

Abstract: An output scanner exposure cylinder perforated to allow exposure film to be held on to the cylinder by vacuum comprises a metal substrate carrying a coating of cured black resin composition which has been machined to e.g., a thickness of 0.1 to 1.5 mm. The resin is usually an epoxy resin and is applied as a powder and cured by heating.