APPARATUS FOR AND METHOD OF PROCESSING DOCUMENT IMAGE

• US 20150163376A1
• Filed: 12/05/2014
• Published: 06/11/2015
• Est. Priority Date: 12/06/2013
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: PAN, Pan, HE, Yuan, SUN, Jun
• Granted Patent: US 9,294,655 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04N 1/4072 dependent on the contents of the original
• CPC Class Codes: H04N 2201/0458 Additional arrangements for improving or optimising scanning resolution or quality

Abstract

An apparatus for and a method of processing a document image are provided. The apparatus comprises: an estimation unit for estimating a brightness image from the document image; and a correction unit for correcting the brightness image by using brightness values of at least a part of edge pixels which lie on or in the adjacency of edges of the brightness image in parallel with x direction, wherein directions of neighboring two edges of the brightness image are set to be x, y directions respectively, and wherein compared with x direction, brightness values of pixels of the brightness image change relatively slightly or do not change along y direction; wherein the correction unit performs interpolation on a straight line extending along y direction by using the brightness values of the edge pixels on the straight line, thereby correcting brightness values of other pixels on the straight line.

Claims

1. An apparatus for processing a document image, comprising:

an estimation unit to estimate a brightness image from the document image; and

a correction unit to correct the brightness image by using brightness values of at least a part of edge pixels which lie one of on and in an adjacency of edges of the brightness image in parallel with an x direction, wherein directions of two neighboring edges of the brightness image are set to be x, y directions respectively, and wherein as compared with the x direction, brightness values of pixels of the brightness image change one of relatively slightly and do not change along the y direction;

wherein the correction unit performs interpolation on a straight line extending along the y direction by using the brightness values of the edge pixels on the straight line to correct brightness values of other pixels on the straight line.

2. The apparatus for processing a document image according to claim 1, further comprising a modification unit to determine a position where a jump occurs in the brightness values of the edge pixels, and to modify a brightness value at the position where the jump occurs.

3. The apparatus for processing a document image according to claim 1, further comprising a modification unit to modify brightness values of the edge pixels at a position where a large hole previously existed, when the estimation unit estimates the brightness image in a hole-filling manner.

4. The apparatus for processing a document image according to claim 3, wherein, the modification unit is configured to one of:

perform the modification according to brightness values of edge pixels on an opposite side and having x coordinates closer to the x coordinates of pixels at positions to be modified;

perform the modification according to brightness values of pixels in a normalized symmetry with pixels at positions to be modified across a designated x coordinate point; and

perform the modification according to brightness values of the edge pixels on an opposite side and having x coordinates closer to the x coordinates of the pixels in the normalized symmetry with the pixels at the positions to be modified across the designated x coordinate point.

5. The apparatus for processing a document image according to claim 3, wherein, the modification unit is configured to perform the modification by using brightness values at positions, on brightness images of document images having adjacent numbers of pages, which have coordinates closer to the coordinates of the positions to be modified, if there are brightness images of other document images which are collected in batches.

11. The apparatus for processing a document image according to claim 2, wherein, the modification unit is configured to one of:

perform the modification according to brightness values of edge pixels on an opposite side and having x coordinates closer to the x coordinates of pixels at positions to be modified;

perform the modification according to brightness values of pixels in normalized symmetry with pixels at positions to be modified across a designated x coordinate point; and

perform the modification according to brightness values of the edge pixels on the opposite side and having x coordinates closer to the x coordinates of the pixels in normalized symmetry with the pixels at the positions to be modified across the designated x coordinate point.

12. The apparatus for processing a document image according to claim 2, wherein, the modification unit is configured to perform the modification by using brightness values at positions, on brightness images of document images having adjacent numbers of pages, which have coordinates closer to the coordinates of the positions to be modified, if there are brightness images of other document images which are collected in batches.

6. An apparatus for processing a document image, comprising:

an estimation unit to estimate a brightness image from the document image; and

a correction unit to correct brightness values of unreliable pixels in the brightness image;

wherein, if directions of two neighboring edges of the brightness image are set to be x, y directions respectively, and as compared with the x direction, brightness values of pixels of the brightness image along the y direction change one of relatively slightly and do not change, the correction unit is configured to one of;

perform the correction by using brightness values of the pixels at positions in a normalized symmetry with the unreliable pixels across a designated x coordinate point;

perform the correction by using brightness values at other positions having x coordinates closer to the x coordinates of the unreliable pixels; and

perform the correction by using brightness values at other positions having x coordinates closer to those of the positions in the normalized symmetry with the unreliable pixels across the designated x coordinate point.

7. The apparatus for processing a document image according to claim 6, further comprising a determination unit to determine the unreliable pixels;

wherein, the determination unit is configured to determine, as a position where the unreliable pixels lie, a position on the brightness image which corresponds to a filled large hole, if the estimation unit estimates the brightness image in a hole-filling manner.

8. The apparatus for processing a document image according to claim 6, further comprising a determination unit to determine the unreliable pixels;

the determination unit being configured to, when a jump occurs, one of on a brightness curve and on an entire brightness curved surface presented by the brightness image, determine a position where the jump occurs as the position where the unreliable pixels lie.

9. A method of processing a document image, comprising:

estimating a brightness image from the document image; and

setting directions of two neighboring edges of the brightness image to be x, y directions respectively, wherein as compared with the x direction, brightness values of pixels of the brightness image along the y direction change one of relatively slightly and do not change, the method further comprising;

correcting the brightness image by using brightness values of at least a part of edge pixels which lie one of on and in an adjacency of edges of the brightness image in parallel with the x direction;

wherein, an interpolation is performed on a straight line extending along the y direction by using the brightness values of the edge pixels on the straight line to correct brightness values of other pixels on the straight line.

10. A method of processing a document image, comprising:

estimating a brightness image from the document image; and

setting directions of two neighboring edges of the brightness image to be x, y directions respectively, wherein as compared with the x direction, brightness values of pixels of the brightness image along the y direction change one of relatively slightly and do not change, the method further comprising;

performing a correction on brightness values of unreliable pixels in the brightness image, wherein, one of;

the correction is performed by using brightness values of the pixels at positions in a normalized symmetry with the unreliable pixels across a designated x coordinate point;

the correction is performed by using brightness values at other positions having x coordinates closer to the x coordinates of the unreliable pixels; and

the correction is performed by using brightness values at other positions having x coordinates closer to the x coordinates of the positions in normalized symmetry with the unreliable pixels across the designated x coordinate point.

13. A non-transitory computer readable medium performing the method of claim 10.