Image processing apparatus and method of processing an image

1. An image processing apparatus, comprising:

a scanner configured to read a document into a document image by, for each line of the document,

reading the line of the document at a first resolution in a main scanning direction, and

reading the line of the document at a second resolution in a sub-scanning direction perpendicular to the main scanning direction; and

at least one processor configured to,

detect an inclination angle of the document image corresponding to inclination of the document associated with conveying the document through the scanner,

obtain a distortion angle of the document image based on the inclination angle associated with conveying the document through the scanner and a ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction, the distortion angle of the document image being an angle between a side of the document image and the sub-scanning direction that varies according to a read state and results in a distortion between the document and the document image representing same, and

correct the distortion of the document image using the distortion angle.

2. The image processing apparatus of claim 1 wherein the at least one processor further configured to correct inclination of the document image by rotating the document image using the inclination angle.

3. The image processing apparatus of claim 1 , further comprising:

a memory configured to store a plurality of distortion angle values each corresponding to one of multiple combinations of an inclination angle of the document image and a set of a first resolution for the main scanning direction and a second resolution for the sub-scanning direction,

wherein the at least one processor obtains the distortion angle by referring to the memory.

4. The image processing apparatus of claim 2 , further comprising,

a memory configured to store a plurality of distortion angle values each corresponding to one of multiple combinations of an inclination angle of the document image and a set of a first resolution for the main scanning direction and a second resolution for the sub-scanning direction,

wherein the at least one processor obtains the distortion angle by referring to the memory.

5. The image processing apparatus of claim 1 , wherein the at least one processor detects the inclination angle from image data corresponding to a number of lines of the image data obtained by the scanner, the number of lines being determined based on the ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction.

6. The image processing apparatus of claim 2 , wherein the at least one processor detects the inclination angle from image data corresponding to a number of lines of the image data obtained by the scanner, the number of lines being determined based on the ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction.

7. The image processing apparatus of claim 3 , wherein the at least one processor detects the inclination angle from image data corresponding to a number of lines of the image data obtained by the scanner, the number of lines being determined based on the ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction.

8. The image processing apparatus of claim 4 , wherein the at least one processor detects the inclination angle from image data corresponding to a number of lines of the image data obtained by the scanner, the number of lines being determined based on the ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction.

9. The image processing apparatus of claim 5 wherein the at least one processor determines the number of lines of the image data based at least on an allowable upper limit value of the inclination angle of the document to be read and the ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction.

10. A method of processing an image comprising:

reading, via a scanner, a document into a document image by, for each line of the document,

reading the line of the document at a first resolution in a main scanning direction, and

reading the line of the document at a second resolution in a sub-scanning direction perpendicular to the main scanning direction;

detecting an inclination angle of the document image corresponding to inclination of the document associated with conveying the document through the scanner;

obtaining a distortion angle of the document image based on the inclination angle associated with conveying the document through the scanner and a ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction, the distortion angle of the document image being an angle between a side of the document image and the sub-scanning direction that varies according to a read state and results in a distortion between the document and the document image representing same; and

correcting the distortion of the document image using the distortion angle.

11. The method of processing an image of claim 10 , further comprising:

correcting an inclination of the document image by rotating the document image using the inclination angle.

12. The method of claim 11 , wherein the correcting the distortion and the correcting the inclination are performed concurrently.

13. The method of processing an image of claim 10 , further comprising:

obtaining the distortion angle by referring to a memory storing distortion angle values each corresponding to one of multiple combinations of the inclination angle of the document image and a set of resolutions each for one of the main scanning direction and the sub-scanning direction.

14. The method of processing an image of claim 11 , further comprising:

obtaining the distortion angle by referring to a memory storing distortion angle values each corresponding to one of multiple combinations of the inclination angle of the document image and a set of resolutions each for one of the main scanning direction and the sub-scanning direction.

15. The method of processing an image of claim 10 , further comprising:

detecting the inclination angle from image data corresponding to a number of lines of the image data obtained by reading,

wherein the number of lines is based on the ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction.

16. The method of processing an image of claim 12 , further comprising:

detecting the inclination angle from image data corresponding to a number of lines of the image data obtained by reading,

wherein the number of lines is based on the ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction.

17. The method of processing an image of claim 13 , further comprising:

detecting the inclination angle from image data corresponding to a number of lines of the image data obtained by reading,

wherein the number of lines is based on the ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction.

18. The method of processing an image of claim 14 , further comprising:

detecting the inclination angle from image data corresponding to a number of lines of the image data obtained by reading,

wherein the number of lines is based on the ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction.

19. The method of processing an image of claim 15 , further comprising:

determining the number of lines of the image data based at least on an allowable upper limit value of the inclination angle of the document to be read and the ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction, the allowable upper limit value being set in advance.

20. A non-transitory recording medium storing a plurality of instructions which, when executed by one or more processors, cause the one or more processors to perform a method of processing an image, comprising:

reading, via a scanner, a document into a document image by, for each line of the document,

reading the line of the document at a first resolution in a main scanning direction, and

reading the line of the document at a second resolution in a sub-scanning direction perpendicular to the main scanning direction;

detecting an inclination angle of the document image corresponding to inclination of the document associated with conveying the document through the scanner;

obtaining a distortion angle of the document image based on the inclination angle associated with conveying the document through the scanner and a ratio between the first resolution of the main scanning direction and the second resolution of the sub-scanning direction, the distortion angle of the document image being an angle between a side of the document image and the sub-scanning direction that varies according to a read state and results in a distortion between the document and the document image representing same; and

correcting the distortion of the document image using the distortion angle.