Image forming apparatus, control method of image forming apparatus, and storage medium

1. An image forming apparatus having a failure diagnosis function, the image forming apparatus comprising:

a generating unit configured to generate a halftone image by performing halftone processing for an input image;

an obtaining unit configured to obtain a scanned image of a printed material on which the halftone image is printed; and

an identification unit configured to identify a failure component of the image forming apparatus based on a difference between the scanned image and the input image, wherein

the generating unit generates the halftone image by representing a dot pattern of a halftone portion in a case where the input image is a test image for the failure diagnosis by a dot pattern whose frequency is relatively higher than that of a dot pattern that is applied to the halftone portion in a case where the input image is an image other than the test image.

2. The image forming apparatus according to claim 1 , wherein

the generating unit generates the halftone image by representing the dot pattern of the halftone portion in a case where the input image is the test image by a dot pattern that is applied to a text portion of a print image.

3. The image forming apparatus according to claim 1 , wherein

the generating unit generates the halftone image by representing the dot pattern of the halftone portion in a case where the input image is an image other than the test image by screen processing using a predetermined screen ruling that is applied to an image portion of a print image.

4. The image forming apparatus according to claim 1 , wherein

the generating unit generates the halftone image in a case where the input image is the test image by performing screen processing using a screen whose ruling is 212 lines or more or error diffusion processing with a resolution of 1,200 dpi or more.

5. The image forming apparatus according to claim 1 , comprising:

a setting unit configured to set a high-accuracy diagnosis mode for diagnosing the image forming apparatus with high accuracy, wherein

the generating unit generates the halftone image in a case where the input image is the test image on a condition that the high-accuracy diagnosis mode is set.

6. The image forming apparatus according to claim 1 , wherein

the generating unit generates the halftone image in a case where the input image is the test image on a condition that a defective portion in which density becomes low is extracted from the difference.

7. The image forming apparatus according to claim 1 , wherein

the identification unit extracts at least one of a color feature amount and a shape feature amount from the difference and identifies a failure component of the image forming apparatus based on the extracted color feature amount or the shape feature amount.

8. The image forming apparatus according to claim 1 , comprising:

a gamma correction unit configured to perform gamma correction for at least one of the test image and the scanned image in a case where the input image is the test image.

9. The image forming apparatus according to claim 8 , wherein

the gamma correction unit performs gamma correction by using a correction table in accordance with a screen type that is used for the halftone portion of the test image.

10. The image forming apparatus according to claim 1 , further comprising:

a suppression unit configured to suppress the occurrence of moire for the scanned image.

11. The image forming apparatus according to claim 10 , wherein

the suppression unit suppresses the occurrence of the moire by using a filter in accordance with a screen type that is used for the halftone portion of the test image.

12. The image forming apparatus according to claim 1 , further comprising:

an inspection unit configured to inspect a defect of the printed material based on a difference between the input image and the scanned image.

13. A control method of an image forming apparatus having a failure diagnosis function, the control method comprising:

a generation step of generating a halftone image by performing halftone processing for an input image;

an obtaining step of obtaining a scanned image of a printed material on which the halftone image is printed; and

an identification step of identifying a failure component of the image forming apparatus based on a difference between the scanned image and the input image, wherein

at the generation step, the halftone image is generated by representing a dot pattern of a halftone portion in a case where the input image is a test image for the failure diagnosis by a dot pattern whose frequency is relatively higher than that of a dot pattern that is applied to the halftone portion in a case where the input image is an image other than the test image.

14. A non-transitory computer readable storage medium storing a program for causing a computer to execute a control method of an image forming apparatus having a failure diagnosis function, the control method comprising:

a generation step of generating a halftone image by performing halftone processing for an input image;

an obtaining step of obtaining a scanned image of a printed material on which the halftone image is printed; and

an identification step of identifying a failure component of the image forming apparatus based on a difference between the scanned image and the input image, wherein

at the generation step, the halftone image is generated by representing a dot pattern of a halftone portion in a case where the input image is a test image for the failure diagnosis by a dot pattern whose frequency is relatively higher than that of a dot pattern that is applied to the halftone portion in a case where the input image is an image other than the test image.