Method of generating gradation-corrected image data, method of generating gradation-corrected halftone dot percentage data, method of generating gradation-corrected threshold data, image output apparatus, and method of calculating amount of exposure

A method of generating gradation-corrected halftone dot percentage data for use in recording a halftone-dot image on a recording medium based on input gradation image data by converting the input gradation image data into gradation-corrected halftone dot percentage data depending on conditions of an output machine, comparing the gradation-corrected halftone dot percentage data with threshold data to produce binary data, and thereafter scanning the recording medium in the output machine with a light beam modulated by the binary data, comprising the steps of:

• calculating an amount-of-exposure distribution to be imparted to said recording medium based on conditions of said output machine including a shape of halftone recording dots corresponding to input gradations to be recorded on the recording medium and specification details of said light beam;
• calculating a density distribution of an image to be recorded on said recording medium from the calculated amount-of-exposure distribution and characteristics of density with respect to an amount of exposure of said recording medium;
• calculating output halftone-dot percentage data to be actually recorded on said recording medium based on the calculated density distribution;
• generating a characteristic curve of the calculated output halftone-dot percentage data with respect to said input gradations;
• generating a gradation corrective curve based on said characteristic curve;
• and
• converting said input gradation image data into the gradation-corrected halftone-dot percentage data according to said gradation corrective curve.

A method of generating gradation-corrected threshold data for use in recording a halftone-dot image on a recording medium based on input gradation image data by comparing the input gradation image data with gradation-corrected threshold data depending on conditions of an output machine to produce binary data, and thereafter scanning the recording medium in the output machine with a light beam modulated by the binary data, comprising the steps of:

• comparing input gradation data required to reproduce a full range of optical densities for the image on the recording medium with uncorrected threshold data to produce threshold correcting binary data;
• calculating an amount-of-exposure distribution to be imparted to said recording medium based on conditions of said output machine including a shape of halftone recording dots to be recorded on the recording medium, produced based on the threshold correcting binary data, and specification details of said light beam;
• calculating a density distribution of an image to be recorded on said recording medium from the calculated amount-of-exposure distribution and characteristics of density with respect to an amount of exposure of said recording medium;
• calculating output halftone-dot percentage data to be actually recorded on said recording medium based on the calculated density distribution;
• generating a characteristic curve of the calculated output halftone-dot percentage data with respect to said uncorrected threshold data;
• generating a gradation corrective curve based on said characteristic curve;
• and
• generating the gradation-corrected threshold data by correcting a threshold of the uncorrected threshold data according to said gradation corrective curve.

An image output apparatus comprising:

• a halftone attribute specifying unit for specifying attributes of a halftone-dot image to be outputted;
• a calculating unit for calculating gradation correcting data based on the specified attributes, threshold data corresponding thereto, output machine information, and recording medium information;
• a gradating corrector for correcting supplied gradation image data with said gradation correcting data to output corrected gradation image data;
• a binary signal processor for comparing the corrected gradation image data with said threshold data to generate binary data;
• and
• an output machine for scanning said recording medium with a light beam based on said binary data to record a halftone-dot image on the recording medium;
• said calculating unit comprising means for calculating an amount-of-exposure distribution to be imparted to said recording medium based on a shape of halftone recording dots as said attributes to be recorded on the recording medium, specification details of said light beam as said output machine information, and said threshold data, calculating a density distribution of an image to be recorded on said recording medium from the calculated amount-of-exposure distribution and characteristics of density with respect to an amount of exposure of said recording medium, calculating halftone-dot percentage data to be actually recorded on said recording medium based on the calculated density distribution, generating a characteristic curve of the calculated output halftone-dot percentage data with respect to said threshold data, generating a gradation corrective curve based on said characteristic curve, and generating the gradation correcting threshold data for correcting the gradations of the gradation image data according to said gradation corrective curve.

An image output apparatus comprising:

• a halftone attribute specifying unit for specifying attributes of a halftone-dot image to be outputted;
• a storage unit for storing gradation correcting data calculated based on the specified attributes, threshold data corresponding thereto, output machine information, and recording medium information;
• a gradation corrector for correcting supplied gradation image data with said gradation correcting data read from said storage unit to output corrected gradation image data;
• a binary signal generator for comparing said corrected gradation image data with threshold data to generate binary data;
• and
• an output machine for scanning a recording medium with a light beam based on said binary data to record a halftone-dot image on the recording medium;
• wherein said gradation correcting data stored in said storage unit is produced by calculating an amount-of-exposure distribution to be imparted to said recording medium based on a shape of halftone recording dots as said attributes to be recorded on the recording medium, specification details of said light beam as said output machine information, and said threshold data, calculating a density distribution of an image to be recorded on said recording medium from the calculated amount-of-exposure distribution and characteristics of density with respect to an amount of exposure of said recording medium, calculating halftone-dot percentage data to be actually recorded on said recording medium based on the calculated density distribution, generating a characteristic curve of the calculated output halftone-dot percentage data with respect to said threshold data, generating a gradation corrective curve based on said characteristic curve, and using said gradation corrective curve said gradation correcting data.

An image output apparatus comprising:

• a halftone attribute specifying unit for specifying attributes of a halftone-dot image to be outputted;
• a calculating unit for calculating gradation-corrected threshold data based on the specified attributes, uncorrected threshold data corresponding thereto, output machine information, and recording medium information;
• a binary signal generator for comparing supplied image data with said gradation-corrected threshold data to generate binary data;
• and
• an output machine for scanning a recording medium with a light beam based on said binary data to record a halftone-dot image on the recording medium;
• said calculating unit comprising means for calculating an amount-of-exposure distribution to be imparted to said recording medium based on a shape of halftone recording dots as said attributes to be recorded on the recording medium, and specification details of said light beam as said output machine information, calculating a density distribution of an image to be recorded on said recording medium from the calculated amount-of-exposure distribution and characteristics of density with respect to an amount of exposure of said recording medium, calculating halftone-dot percentage data to be actually recorded on said recording medium based on the calculated density distribution, generating a characteristic curve of the calculated output halftone-dot percentage data with respect to said uncorrected threshold data, generating a gradation corrective curve based on said characteristic curve, and generating the gradation-corrected threshold data from the uncorrected threshold data according to said gradation corrective curve.

An image output apparatus comprising:

• a halftone attribute specifying unit for specifying attributes of a halftone-dot image to be outputted;
• a storage unit for storing gradation-corrected threshold data calculated based on the specified attributes, uncorrected threshold data corresponding thereto, output machine information, and recording medium information;
• a binary signal generator for comparing supplied threshold image data with said gradation-corrected threshold data read from said storage unit to generate binary data;
• and
• an output machine for scanning a recording medium with a light beam based on said binary data to record a halftone-dot image on the recording medium;
• wherein said gradation-corrected threshold data stored in said storage unit is produced by calculating an amount-of-exposure distribution to be imparted to said recording medium based on a shape of halftone recording dots as said attributes to be recorded on the recording medium, and specification details of said light beam as said output machine information, calculating a density distribution of an image to be recorded on said recording medium from the calculated amount-of-exposure distribution and characteristics of density with respect to an amount of exposure of said recording medium, calculating halftone-dot percentage data to be actually recorded on said recording medium based on the calculated density distribution, generating a characteristic curve of the calculated output halftone-dot percentage data with respect to said threshold data, generating a gradation corrective curve based on said characteristic curve, and generating said gradation-corrected threshold data by correcting a threshold of the uncorrected threshold data according to said gradation corrective curve.

An image output apparatus comprising:

• a halftone attribute specifying unit for specifying attributes of a halftone-dot image to be outputted;
• a threshold data storage unit for outputting threshold data corresponding to the specified attributes;
• an output condition specifying unit for specifying an item from output machine information and recording medium information, at least one of which contains a plurality of items;
• a corrective characteristic storage unit for storing a plurality of corrective characteristics of gradation-corrected threshold data with respect to said threshold data based on the attributes specified by said halftone attribute specifying unit, threshold data corresponding thereto, and the item of the output machine information and recording medium information which is specified by said output condition specifying unit;
• a corrected threshold data generator for outputting gradation-corrected threshold data produced by correcting the threshold data supplied from said threshold data storage unit with the corrective characteristics stored in said corrective characteristic storage unit;
• a binary signal generator for comparing inputted gradation image data with said gradation-corrected threshold data to produce binary data;
• and
• an output machine for generating a halftone-dot image based on said binary data and outputting the halftone-dot image to a recording medium;
• wherein said corrective characteristics stored in said corrective characteristic storage unit are produced by calculating an amount-of-exposure distribution to be imparted to said recording medium based on a shape of halftone recording dots as said attributes to be recorded on the recording medium, and specification details of said light beam as said output machine information, calculating a density distribution of an image to be recorded on said recording medium from the calculated amount-of-exposure distribution and characteristics of density with respect to an amount of exposure of said recording medium, calculating halftone-dot percentage data to be actually recorded on said recording medium based on the calculated density distribution, generating a characteristic curve of the calculated output halftone-dot percentage data with respect to said threshold data, and generating the corrective characteristics based on said characteristic curve.