Halftone image recording apparatus combining error scattering and multi-level tone conversion techniques

Claim 2

An image recording apparatus comprising: adding means for outputting a dither-processed signal by superposing on each two-dimensionally distributed m×n pixel group of an input image signal representative of tones m×n adjusting levels on a pixel-by-pixel basis; error correcting means for outputting an error scattered image signal by applying to said dither-processed signal a correction matching a signal level error between an input and an output of a pixel whose recording level has already been determined; multi-level converting means for converting said error scattered image signal into a multi-level tone recording signal by using at least two threshold levels; and recording means for recording an image represented by said tone recording signal.

Claim 3

An apparatus as claimed in claim 1, further comprising: tone detecting means responsive to the input image signal for determining whether an image represented by said input image signal is a tone image area or a two-level image area; and dither-process adjusting means for feeding to said adding means dither-process adjusting levels assigned to tone image processing when said tone detecting means detects a tone image area or dither-process adjusting levels assigned to two-level image processing when said tone detecting means has detected a two-level image area.

Claim 4

An apparatus as claimed in claim 1, further comprising: tone detecting means responsive to the input image signal for determining whether an image represented by said input image signal is a tone image area or a two-level image area; selecting means for selecting sharpness of an output image; and multi-level threshold value setting means for feeding to said adding means and said multi-level converting means, respectively, dither-process adjusting values and multi-level threshold values which are associated with determination by said tone detecting means and selection by said selecting means.

Claim 5

An image recording apparatus comprising: error correcting means for outputing an error scattered image signal by applying to an input image signal representative of tones a correction matching a signal level error between an input and an output of a pixel whose recording level has already been determined; dither/multi-level converting means for converting said error scattered image signal into a tone recording signal by processing each group of two dimensionally distributed m×n pixels of said image signal by corresponding threshold values of at least two threshold value groups each comprising m×n threshold values; and recording means for recording an image represented by said tone recording signal.

Claim 6

An image recording apparatus comprising: error correcting means for outputing an error scattered image signal by applying to an input image signal representative of tones a correction matching a signal level error between an input and an output of a pixel whose recording level has already been determined; dither/multi-level converting means for converting said error scattered image signal into a tone recording signal by processing each group of two dimensionally distributed m×n pixels of said image signal by corresponding threshold values of at least two threshold value groups each comprising m×n threshold values; and recording means for recording an image represented by said tone recording signal.

Claim 7

An apparatus as claimed in claim 4, further comprising: tone detecting means for determining whether an image represented by the input image signal is a tone image area or a two-level image area; and dither-process adjusting means for feeding to said dither/multi-level converting means a threshold value group assigned to tone image processing when said detecting means has detected a tone image area or a threshold value group assigned to two-level image processing when said detecting means has detected a two-level image area.

Claim 8

An apparatus as claimed in claim 4, further comprising: selecting means responsive to the input image signal for selecting sharpness of an output image; and multi-level threshold setting means for feeding to said multi-level converting means a threshold value group associated with determination by said tone detecting means and selection by said selecting means.

Claim 9

An image recording apparatus comprising: error correcting means for outputting an error scattered image signal by applying to an input image signal representative of tones a correction matching a signal level error between an input and an output of a pixel whose recording level has already been determined; multi-level converting means for converting said error scattered image signal into a multi-level tone recording signal by comparing said error scattered image signal with a plurality of threshold values having a distance which is smaller than a distance of recording levels; and recording means for recording an image represented by said multi-level tone recording signal.

Claim 10

An image recording apparatus comprising: error correcting means for outputting an error scattered image signal by applying to an input image signal representative of tones a correction matching a signal level error between an input and an output of a pixel whose recording level has already been determined; multi-level converting means for converting said error scattered image signal into a multi-level tone recording signal by comparing said error scattered image signal with a plurality of threshold values having a distance which is smaller than a distance of recording levels; and recording means for recording an image represented by said multi-level tone recording signal.

Claim 11

An imge recording apparatus comprisin: error correcting means for outputting an error scattered image signal in response to an input image signal representative of tones; multi-level converting means for converting said error scattered image signal into a multi-level tone recoding signal by using at least two threshold values; tone detecting means responsive to the input image signal for determining whether an image represented by said input image signal is a tone image area or a two-level image area; selecting means for selecting sharpness of an output image; multi-level threshold setting means for feeding to said multi-level converting means threshold values associated with determination by said tone detecting means and selection by said selecting means; and recording means for recording an image represented by said multi-level tone recording signal.

Claim 12

An imge recording apparatus comprisin: error correcting means for outputting an error scattered image signal in response to an input image signal representative of tones; multi-level converting means for converting said error scattered image signal into a multi-level tone recoding signal by using at least two threshold values; tone detecting means responsive to the input image signal for determining whether an image represented by said input image signal is a tone image area or a two-level image area; selecting means for selecting sharpness of an output image; multi-level threshold setting means for feeding to said multi-level converting means threshold values associated with determination by said tone detecting means and selection by said selecting means; and recording means for recording an image represented by said multi-level tone recording signal.