Image forming apparatus, method of controlling the same, and storage medium

1. An image forming apparatus comprising:

a printer unit that prints an image on a sheet using a line head in which a plurality of light emitting devices are arranged;

a storage that stores information regarding light amounts corresponding to the light emitting devices of the line head;

a memory that stores instructions; and

a processor that executes the instructions stored in the memory to:

generate a mask pattern based on the information regarding the light amounts obtained from the storage and a target light amount, and

execute mask processing on halftone image data that is in positional correspondence with the light emitting devices using the generated mask pattern.

2. The image forming apparatus according to claim 1 , wherein, if the information regarding the light amounts is larger than the target light amount, the processor, in generation of the mask pattern, obtains light amount decrease rates for bringing the information regarding the light amounts close to the target light amount, obtains masking ratios by referencing a table that stores masking ratios corresponding to the light amount decrease rates, and generates the mask pattern using the obtained masking ratios and a threshold matrix for generating a mask pattern.

3. The image forming apparatus according to claim 2 , wherein the processor, in the generation of the mask pattern, generates the mask pattern by shifting, in a main scanning direction, a main scanning position at which the threshold matrix is to be applied, with respect to a width of the threshold matrix in a sub-scanning direction.

4. The image forming apparatus according to claim 3 , wherein the width of the threshold matrix in the sub-scanning direction and an amount of the shift are mutually prime.

5. The image forming apparatus according to claim 2 , wherein the processor, in executing the mask processing, executes, at main scanning positions corresponding to the respective light emitting devices, mask processing for thinning out pixels corresponding to the light amount decrease rates from among pixels corresponding to the width of the threshold matrix in a sub-scanning direction.

6. The image forming apparatus according to claim 1 , wherein the processor executes the instructions stored in the memory further to:

correct gradation of image data, and

execute halftone processing on multi-value image data whose gradation has been corrected,

wherein the halftone image data is generated by the halftone processing.

7. The image forming apparatus according to claim 6 , wherein the processor, in the halftone processing, converts a resolution of the image data whose gradation has been corrected into a resolution corresponding to an arrangement of the light emitting devices of the line head.

8. The image forming apparatus according to claim 1 , wherein the processor, in executing the mask processing, executes the mask processing at a resolution higher than the resolution corresponding to the arrangement of the light emitting devices of the line head, and

wherein the processor executes the instructions stored in the memory further to:

return image data that has undergone the mask processing to the resolution corresponding to the arrangement of the light emitting devices of the line head.

9. The image forming apparatus according to claim 2 , wherein the mask pattern and the threshold matrix represent a pattern having a blue noise characteristic.

10. A method of controlling an image forming apparatus that includes a line head in which a plurality of light emitting devices are arranged and a memory that stores information regarding light amounts corresponding to the light emitting devices of the line head, and forms an image using the line head, the method comprising:

generating a mask pattern based on the information regarding the light amounts obtained from the memory and a target light amount, and

executing mask processing on halftone image data that is in positional correspondence with the light emitting devices using the mask pattern generated in the generating.

11. A non-transitory computer-readable storage medium storing a program for causing a processor to execute a method of controlling an image forming apparatus that includes a line head in which a plurality of light emitting devices are arranged and a memory that stores information regarding light amounts corresponding to the light emitting devices of the line head, and forms an image using the line head, the method comprising:

generating a mask pattern based on the information regarding the light amounts obtained from the memory and a target light amount, and

executing mask processing on halftone image data that is in positional correspondence with the light emitting devices using the mask pattern generated in the generating.