US 9,813,592 B2
Image forming apparatus, storage medium, and color conversion method
Yuka Miyanaga, Osaka (JP)
Assigned to KYOCERA Document Solutions Inc., Osaka (JP)
Filed by KYOCERA Document Solutions Inc., Osaka (JP)
Filed on Sep. 19, 2016, as Appl. No. 15/268,770.
Claims priority of application No. 2015-188074 (JP), filed on Sep. 25, 2015.
Prior Publication US 2017/0094129 A1, Mar. 30, 2017
Int. Cl. H04N 1/60 (2006.01)
CPC H04N 1/6055 (2013.01) [H04N 1/6008 (2013.01); H04N 1/6019 (2013.01); H04N 1/6027 (2013.01); H04N 2201/0039 (2013.01); H04N 2201/0094 (2013.01)] 5 Claims
OG exemplary drawing
 
1. An image forming apparatus that prints an image, the image forming apparatus comprising:
a central processing unit (CPU); and
a storage section that stores a color conversion program, a color conversion table for printing the image by the image forming apparatus, and a display color conversion table for displaying the image by a computer, wherein
through execution of the color conversion program, the CPU functions as:
a representative color acquisition section that acquires a first representative color and a second representative color of the image; and
a color adjustment section that adjusts a reproduced color, of a color included in the image, obtained with reference to the color conversion table, wherein
the representative color acquisition section
generates a data string including all RGB values that can be included in the image and respective frequencies of all the RGB values that can be included in the image,
sequentially executes, on each of all pixels included in the image, processing for incrementing, by 1, a frequency of a RGB value of the pixel in the data string,
deletes any RGB value with a frequency of 0 and the frequency of the RGB value with the frequency of 0 from the data string,
assigns RGB values included in the data string with respective area IDs, the area IDs each being identification information attached to an individual region of a plurality of regions obtained by dividing an RGB color space,
collects frequencies of the respective area IDs in the data string,
sorts the data string in descending order based on the collected frequencies,
registers an area ID with a highest frequency among the collected frequencies as a first area ID of the first representative color,
acquires a second area ID that has a highest frequency among the collected frequencies next to the first area ID,
determines whether or not a region to which the second area ID is attached and a region to which the first area ID is attached are close to each other,
when it is determined that the region to which the second area ID is attached and the region to which the first area ID is attached are not close to each other, registers the second area ID as an area ID of the second representative color,
acquires a first RGB value of the first representative color by way of averaging RGB values attached with the first area ID by multiplying the RGB values attached with the first area ID by respective frequencies corresponding to the RGB values attached with the first area ID, and
acquires a second RGB value of the second representative color by way of averaging RGB values attached with the second area ID by multiplying the RGB values attached with the second area ID by respective frequencies corresponding to the RGB values attached with the second area ID,
the color adjustment section
acquires, from the storage section, the color conversion table and the display color conversion table,
copies the color conversion table to generate an adjustment color conversion table,
acquires a first point of a reproduced color, of the first RGB value of the first representative color in a LAB color space, obtained with reference to the color conversion table,
acquires a second point of a reproduced color, of the first RGB value of the target first representative color in the LAB color space, obtained with reference to the display color conversion table,
determines whether or not the first point is located in a region sandwiched between a “Red” hue plane and a “Red+Green” hue plane,
when it is determined that the first point is not located in the region sandwiched between the “Red” hue plane and the “Red+Green” hue plane, calculates, on a hue plane where the first point is located, a third point at which a straight line passing through the first point and the second point intersects with an outer frame of a region of color reproduction with reference to the display color conversion table,
determines whether or not the second point is included in a region of color reproduction by the image forming apparatus,
when it is determined that the second point is included in the region of color reproduction by the image forming apparatus, adjusts the adjustment color conversion table in a manner such as to move the first point to the second point,
adjusts the adjustment color conversion table in a manner such as to move a point near the first point towards the third point,
acquires a fourth point of a reproduced color, of the second RGB value of the second representative color in the LAB color space, obtained with reference to the color conversion table,
acquires a fifth point of a reproduced color, of the second RGB value of the target second representative color in the LAB color space, obtained with reference to the display color conversion table,
determines whether or not the fourth point is located in a region sandwiched between the “Red” hue plane and the “Red+Green” hue plane,
when it is determined that the fourth point is not located in the region sandwiched between the “Red” hue plane and the “Red+Green” hue plane, calculates, on a hue plane where the fourth point is located, a sixth point at which a straight line passing through the fourth point and the fifth point intersects with the outer frame of the region of color reproduction with reference to the display color conversion table,
determines whether or not the fifth point is included in the region of color reproduction by the image forming apparatus,
when it is determined that the fifth point is included in the region of color reproduction by the image forming apparatus, adjusts the adjustment color conversion table in a manner such as to move the fourth point to the fifth point,
adjusts the adjustment color conversion table in a manner such as to move a point near the fourth point towards the sixth point,
converts the RGB values of all the pixels included in the image into Lab values with reference to the adjustment color conversion table, and
converts the Lab values into CMYK values with reference to the color conversion table.