Image forming apparatus capable of forming image on sheet with uneven surface, image forming condition adjustment method

An image forming condition adjustment method executed in an image forming apparatus including an image forming portion configured to form an image on a sheet, the image forming condition adjustment method comprising:

• a first acquisition step of acquiring a captured image of the sheet;
• a second acquisition step of acquiring a specific value that indicates a difference between a gradation value of a pixel that, among pixels included in the captured image acquired in the first acquisition step, corresponds to a higher part of an outer surface of the sheet, and a gradation value of a pixel that, among the pixels included in the captured image, corresponds to a lower part that is lower than the higher part;
• and
• an adjustment step of adjusting an image forming condition of the image forming portion based on the specific value acquired in the second acquisition step.

An image forming apparatus comprising:

• an image forming portion configured to form an image on a sheet using toners of colors C, M, and Y;
• a transfer processing portion configured to transfer, to the sheet, a specific toner image that includes a first toner layer of a first color formed on an image-carrying member and a second toner layer of a second color formed on the first toner layer, the first color being any one of the colors C, M, and Y, the second color being any one of the colors C, M, and Y and being different from the first color;
• a first acquisition processing portion configured to acquire a captured image of the sheet;
• a detection processing portion configured to detect a specific image that corresponds to the specific toner image included in the captured image acquired by the first acquisition processing portion;
• a second acquisition processing portion configured to acquire a skewness of a histogram of gradation values of a color mixture of the second color and a third color in the pixels included in the specific image detected by the detection processing portion, the third color being a color different from the first color and the second color among the colors C, M, and Y;
• and
• an adjustment processing portion configured to adjust the image forming condition of the image forming portion based on the skewness acquired by the second acquisition processing portion.

An image forming condition adjustment method executed in an image forming apparatus including an image forming portion configured to form an image on a sheet using toners of colors C, M, and Y, the image forming condition adjustment method comprising:

• a transfer step of transferring, to the sheet, a specific toner image that includes a first toner layer of a first color formed on an image-carrying member and a second toner layer of a second color formed on the first toner layer, the first color being any one of the colors C, M, and Y, the second color being any one of the colors C, M, and Y and being different from the first color;
• a first acquisition step of acquiring a captured image of the sheet;
• a detection step of detecting a specific image that corresponds to the specific toner image included in the captured image acquired in the first acquisition step;
• a second acquisition step of acquiring a skewness of a histogram of gradation values of a color mixture of the second color and a third color in the pixels included in the specific image detected in the detection step, the third color being a color different from the first color and the second color among the colors C, M, and Y;
• and
• an adjustment step of adjusting the image forming condition of the image forming portion based on the skewness acquired in the second acquisition step.