Image signal processing apparatus

An image signal processing apparatus comprising:

• binarizing means for binarizing a multi-level input pixel signal;
• converting means for converting an output signal of the binarizing means, which corresponds to a pixel of interest, into one of a signal of at least two successive black dots and a signal of at least two successive white dots;
• calculating means for deriving a difference between an output signal of the converting means and the input pixel signal, and for generating corrective data on the basis of the derived difference;
• and
• correcting means for correcting the input pixel signal, which corresponds to pixels near a pixel of interest, in accordance with the corrective data.

An image signal processing apparatus comprising:

• correcting means for correcting a multi-level input pixel signal in accordance with corrective data;
• binarizing means for binarizing an output signal of the correcting means into a corresponding binary pixel signal;
• reducing means for thinning out pixels in the binary pixel signal and thereby reducing the binary pixel signal;
• and
• calculating means for deriving a difference between the binary pixel signal and the output signal of the correcting means, and for generating the corrective data on the basis of the derived difference;
• wherein the calculating means comprises means for excluding the pixels, which are thinned out by the reducing means, from generating the corrective data to enable the correcting by the correcting means to be done only on pixels which are not thinned out by the reducing means.

An image signal processing apparatus comprising:

• correcting means for correcting a multi-level input pixel signal in accordance with corrective data;
• binarizing means for binarizing an output signal of the correcting means into a corresponding binary pixel signal;
• reducing means for thinning out pixels in the binary pixel signal and thereby reducing the binary pixel signal;
• and
• calculating means for deriving a difference between the binary pixel signal and the output signal of the correcting means to generate error data;
• processing means for multiplying the error data of pixels near a pixel of interest by predetermined weight coefficients to generate weighted error data respectively, and for generating the corrective data on the basis of the weighted error data;
• wherein the processing means comprises means for excluding the pixels, which are thinned out by the reducing means, from generating the corrective data to enable the correcting by the correcting means to be done only on pixels which are not thinned out by the reducing means.

An image signal processing apparatus comprising:

• correcting means for correcting input image data in accordance with first corrective data;
• binarizing means for binarizing an output signal of the correcting means;
• subtracting means for calculating a difference between an output signal of the binarizing means and the output signal of the corrective means;
• memory means for memorizing binary values of already-processed pixels, which are represented by the output signal of the binarizing means, near a currently-processed pixel;
• first corrective-quantity determining means for determining second corrective data on the basis of the binary values of the already-processed pixels which are memorized by the memory means, the second corrective data depending on a difference between a theoretical dot size and an actual dot size in a recording system;
• second corrective-quantity determining means for adding an output signal of the first corrective-quantity determining means and an output signal of the subtracting means to generate the first corrective data;
• receiving means for receiving a signal representing whether or not the input image signal is effective;
• and
• feeding means for feeding an output signal of the second corrective-quantity determining means to the correcting means as the first corrective data when the signal received by the receiving means represents that the input image signal is effective.

An image signal processing apparatus comprising:

• an edge emphasizing filter for multiplying a pixel of interest and pixels adjoining the pixel of interest of an input multi-level image signal by first predetermined coefficients, and for calculating a filter correction value equal to a sum thereof;
• correcting means for calculating and processing the filter correction value;
• binarizing means for binarizing an output signal of the correcting means;
• a subtraction circuit for calculating a subtraction value between an output signal of the binarizing means and the output signal of the correcting means;
• and
• correction value calculating means for multiplying subtraction values of pixels adjoining a pixel to be binarized which are already outputted from the subtraction circuit by second predetermined coefficients, and for outputting resultants to the correcting means.

An image signal processing apparatus comprising:

• an edge emphasizing filter for multiplying a pixel of interest and pixels adjoining the pixel of interest of an input multi-level image signal by predetermined coefficients, and for calculating a filter correction value equal to a sum thereof;
• a dither pattern generating circuit for outputting a signal in synchronism with the input image signal;
• and
• a binarizing comparator for comparing a dither pattern outputted from the dither pattern generating circuit and the filter correction value to determine a binary level of the pixel of interest.

An image signal processing apparatus comprising:

• an edge emphasizing filter for multiplying a pixel of interest and pixels adjoining the pixel of interest of an input multi-level image signal by predetermined coefficients, and for calculating a filter correction value equal to a sum thereof;
• a dither pattern generating circuit for outputting a signal in synchronism with the input image signal;
• an adder for adding a dither pattern outputted from the dither pattern generating circuit and the filter correction value;
• and
• binarizing means for binarizing an output signal of the adder.

An image signal processing apparatus comprising:

• an edge emphasizing filter for multiplying a pixel of interest and pixels adjoining the pixel of interest of an input multi-level image signal by predetermined coefficients, and for calculating a filter correction value equal to a sum thereof;
• a dither pattern generating circuit for outputting a signal in synchronism with the input image signal;
• an adder for adding a dither pattern outputted from the dither pattern generating circuit and the filter correction value being an output signal of the edge emphasizing filter;
• and
• means for outputting information of whether a carry bit of the adder is present or absent as a binary value.

An image signal processing apparatus comprising:

• an edge emphasizing filter including means for inputting a positive value "A" and a negative value "-B" as filter coefficients to emphasize edges in an image, means for using the input value "A" as filter coefficients of pixels adjoining a pixel of interest in main and sub scanning directions, means for using the input value "-B" as filter coefficients of pixels adjoining the pixel of interest in inclined directions, means for using a value "1+4B-4A" as a filter coefficient of the pixel of interest, means for multiplying the pixel of interest and the pixels adjoining the pixel of interest of an input multi-level image signal by the filter coefficients respectively, and means for outputting a sum thereof as a filter correction value;
• correcting means for calculating and processing the filter correction value;
• binarizing means for binarizing an output signal of the correcting means;
• a subtraction circuit for calculating a subtraction value between an output signal of the binarizing means and the output signal of the correcting means;
• and
• correction value calculating means for multiplying subtraction values of pixels adjoining a pixel to be binarized which are already outputted from the subtraction circuit by predetermined coefficients, and for outputting resultants to the correcting means.

An image signal processing apparatus comprising:

• an edge emphasizing filter including means for inputting a positive value "A" and a negative value "-B" as filter coefficients to emphasize edges in an image, means for using the input value "A" as filter coefficients of pixels adjoining a pixel of interest in main and sub scanning directions, means for using the input value "-B" as filter coefficients of pixels adjoining the pixel of interest in inclined directions, means for using a value "1+4B-4A" as a filter coefficient of the pixel of interest, means for multiplying the pixel of interest and the pixels adjoining the pixel of interest of an input multi-level image signal by the filter coefficients respectively, and means for outputting a sum thereof as a filter correction value;
• a dither pattern generating circuit for outputting a signal in synchronism with the input image signal;
• and
• a binarizing comparator for comparing a dither pattern outputted from the dither pattern generating circuit and the filter correction value to determine a binary level of the pixel of interest.

An image signal processing apparatus comprising:

• an edge emphasizing filter including means for inputting a positive value "A" and a negative value "-B" as filter coefficients to emphasize edges in an image, means for using the input value "A" as filter coefficients of pixels adjoining a pixel of interest in main and sub scanning directions, means for using the input value "-B" as filter coefficients of pixels adjoining the pixel of interest in inclined directions, means for using a value "1+4B-4A" as a filter coefficient of the pixel of interest, means for multiplying the pixel of interest and the pixels adjoining the pixel of interest of an input multi-level image signal by the filter coefficients respectively, and means for outputting a sum thereof as a filter correction value;
• a dither pattern generating circuit for outputting a signal in synchronism with the input image signal;
• an adder for adding a dither pattern outputted from the dither pattern generating circuit and the filter correction value;
• and
• binarizing means for binarizing an output signal of the adder.

An image signal processing apparatus comprising:

• correcting means for correcting input image data in accordance with a corrective value;
• binarizing means for binarizing an output signal of the correcting means;
• subtracting means for calculating a difference value between an output signal of the binarizing means and the output signal of the correcting means;
• memory means for memorizing difference values outputted from the subtracting means as error values corresponding to a pixel of interest and pixels adjoining the pixel of interest;
• and
• calculating means for reading out the error values corresponding to the pixels adjoining the pixel of interest from the memory means, for multiplying the readout error values by predetermined coefficients respectively, and for calculating a sum thereof and outputting an error correction value to the correcting means, the error correction value being equal to the sum.

An image signal processing apparatus comprising:

• correcting means for correcting input image data in accordance with a corrective value;
• binarizing means for binarizing an output sign of the correcting means;
• subtracting means for calculating a difference value between an output signal of the binarizing means and the output signal of the correcting means;
• error distributing means for making difference values outputted from the subtracting means into correspondence with a pixel of interest and pixels adjoining the pixel of interest, for multiplying the difference values by predetermined coefficients to generate errors respectively, and for outputting the errors for the respective pixels adjoining the pixel of interest;
• and
• calculating means for sequentially correcting and adding an output signal of the error distributing means in correspondence with the respective pixels adjoining the pixel of interest to generate an error correction value, and for outputting the error correction value to the correcting means.