Printing calibration processing apparatus, image forming apparatus, and printing calibration processing method

An image forming apparatus comprising:

• an image reading section configured to read a document image;
• an image forming section configured to receive image data read by the image reading section and print an image on a printing sheet;
• a test-image output section configured to output plural patches for gradation characteristic generation to the image forming section as a test image;
• a gradation-characteristic-data generating section configured to read, with the image reading section, images of a printed surface and a rear surface of a test chart obtained by printing the test image on a printing sheet with the image forming section and generate gradation characteristic data of the read printed surface and the read rear surface;
• a gradation-correction-date creating section configured to determine a correction value of maximum gradation on the basis of a gradation characteristic of the printed surface and a gradation characteristic of the rear surface generated by the gradation-characteristic-data generating section;
• a gradation-correction-data storing section configured to store the gradation correction data created by the gradation-correction-data creating section;
• a color-material-amount-conversion-data creating section configured to determine a maximum of a color material on the basis of the correction value of the maximum gradation determined by the gradation-correction-data creating section;
• a color-material-amount-conversion-data storing section configured to store a value of the maximum of the color material;
• a color-material-amount-limitation processing section configured to perform, concerning image data for printing, limitation processing for setting the maximum of the color material as an upper limit of a color material use amount using the value of the maximum of the color material stored in the color-material-amount-conversion-data storing section;
• and
• a gradation correcting section configured to apply gradation correction to the image data subjected to the limitation processing by the color-material-amount-limitation processing section using the gradation correction data stored in the gradation-correction-data storing section.

A printing calibration processing method comprising:

• outputting plural patches for gradation characteristic generation to an image forming section as a test image;
• reading images of a printed surface and a rear surface of a test chart obtained by printing the test image on a printing sheet with the image forming section and generating gradation characteristic data of the printed surface and the rear surface;
• determining a correction value of maximum gradation on the basis of a gradation characteristic of the generated printed surface and the gradation characteristic of the generated rear surface and creating gradation correction data;
• storing the created gradation correction data in a gradation-correction-data storing section;
• determining a maximum of a color material on the basis of the correction value of the maximum gradation;
• storing a value of the maximum of the color material in a color-material-conversion-data storing section;
• performing, concerning image data for printing, limitation processing for setting the maximum of the color material as an upper limit of a color material use amount using the value of the maximum of the color material stored in the color-material-amount-conversion-data storing section;
• and
• applying gradation correction to the image data subjected to the limitation processing using the gradation correction data stored in the gradation-correction-data storing section.