Image forming apparatus, image forming method, and storage medium storing program for forming image

1. An image forming apparatus comprising:

a screen processing part that performs a screen processing on image data;

a correction processing part that divides the image data subjected to the screen processing into a plurality of regions, determines a different correction parameter for each of the regions in response to a characteristic of the screen processing, and performs the correction processing;

an image formation part that forms an image based on the image data subjected to correction processing:

a distortion detection part to detect a distortion of an output image, the distortion of the image is generated in a transfer part or a fixing part; and

wherein the correction processing part determines a division number of the regions and the correction parameter as to cancel the distortion detected by the distortion detection part.

2. The image forming apparatus according to claim 1 , wherein the characteristic of the screen processing is at least one of a period and an angle of the screen processing, and

the correction processing part selects at least one of a correction period and a correction angle which does not interfere with the at least one of the period and the angle of the screen processing.

3. The image forming apparatus according to claim 2 , wherein the correction processing part performs a pixel operation for each line to perform the correction processing, and

determines a pixel arrangement parameter to make a pixel operation period different from the period of the screen processing.

4. The image forming apparatus according to claim 2 , wherein the correction processing part performs a pixel operation for each line to perform the correction processing, and

determines a pixel arrangement parameter to make a correction angle different from the angle of the screen processing.

5. The image forming apparatus according to claim 1 , wherein the plurality of regions are a plurality of band-shaped regions extending in a main scanning direction.

6. The image forming apparatus according to claim 1 , wherein the plurality of regions are a plurality of band-shaped regions extending in a sub-scanning direction.

7. The image forming apparatus according to claim 1 , wherein the correction processing part combines a plurality of correction processings with different correction parameters to perform the correction processing.

8. The image forming apparatus according to claim 7 , wherein the correction processing part combines reduction or enlargement of the regions and movement of the regions to perform the correction processing.

9. The image forming apparatus according to claim 8 , wherein the correction processing part displaces positions to be operated in adjacent regions from each other.

10. An image forming method comprising:

detecting distortion in an image outputted based on image data;

performing screen processing on the image data;

dividing the image data into a plurality of regions;

determining a pixel arrangement parameter corresponding to a characteristic of the screen processing for each region and a different correction amount corresponding to the detected distortion;

correcting the image data subjected to the screen processing using the pixel arrangement parameter and the different correction amount;

forming an image based on the corrected image data;

detecting a distortion of an output image with a distortion detection part, the distortion of the image is generated in a transfer part or a fixing part; and

determining a division number of the regions and the correction parameter with a correction processing part as to cancel the distortion detected by the distortion detection part.

11. A storage medium readable by a computer, the storage medium storing a program of instructions executable by the computer to perform a function for forming an image, the function comprising:

detecting distortion in an image outputted based on image data;

performing screen processing on the image data;

dividing the image data into a plurality of regions;

determining a pixel arrangement parameter corresponding to a characteristic of the screen processing for each region and a different correction amount corresponding to the detected distortion;

correcting the image data subjected to the screen processing using the pixel arrangement parameter and the different correction amount;

forming an image based on the corrected image data;

detecting a distortion of an output image with a distortion detection part, the distortion of the image is generated in a transfer part or a fixing part; and

determining a division number of the regions and the correction parameter with a correction processing part as to cancel the distortion detected by the distortion detection part.