Electronic gravure engraving apparatus including photo tone and character/solid tone processing

An apparatus for making a press plate for gravure printing by an electronic engraving process comprising:

• a picture input unit for inputting a manuscript picture as a set of pixels having a density value,
• an engraving unit including a stylus for engraving cells corresponding to said respective pixels on a plate, a drive device for vibrating said stylus, and a scanning mechanism for scanning said stylus onto said plate,
• picture area designation means for designating a photo tone area having a gentle tone and a character/solid tone area where characters or solid patterns without tone are arranged on said manuscript picture,
• photo tone processing means for converting a density value of a pixel in said photo tone area into a cell width value indicating a size of a cell to be engraved and delivering said cell width value to said engraving unit to thereby engrave a cell of the indicated size,
• character/solid tone processing means for converting a density value of a pixel in said character/solid tone area into a cell width value indicating a size of a cell to be engraved and delivering said cell width value to said engraving unit to thereby engrave a cell of the indicated size, and
• signal distribution means for distributing density values in said photo tone area of the inputted pixels to said photo tone processing means and density values in said character/solid tone area of the inputted pixels to said character/solid tone processing means,
• wherein said photo tone processing means delivers a cell width value that increases linearly with an increase in a distributed density value in a substantial range of density values, and
• wherein said character/solid tone processing means delivers a cell width value indicating that a cell is not to be engraved when a distributed density value is lower than a first density value (indicative of a minimum density value for a cell engraving), a maximum cell width value indicating that a cell of the maximum size is to be engraved when a distributed density value is higher than a second density value (indicative of a minimum density value for the engraving of maximum sized cells), and a cell width value increasing from said minimum cell width value to said maximum cell width value with an increase in the density value when a distributed density value is between said first and second density values.