Image scanner and image scanning method

1. An image scanner comprising:

a platen on which a document is placed;

a cover unit on which a pattern is depicted;

a scanning unit that scans the document between the platen and the cover unit; and

an image processing unit that sets a threshold value using information on a transmitted pattern of the pattern, obtained through the document, and performs image processing based on the threshold value,

wherein the information on the transmitted pattern is a brightness of the transmitted pattern, and

wherein the image processing unit removes, from a result of the scan, an image appearing in a processing region having a brightness greater than or equal to the threshold value.

2. The image scanner according to claim 1 ,

wherein the image processing unit sets the threshold value to a brightness of the transmitted pattern.

3. The image scanner according to claim 1 ,

wherein the pattern of the cover unit includes a first pattern and a second pattern less dense than the first pattern, and

the image processing unit corrects a brightness of the processing region based on a brightness of a second transmitted pattern obtained from the result of the scan and corresponding to the second pattern.

4. The image scanner according to claim 3 ,

wherein the image processing unit converts the brightness of the processing region to the brightness of the second transmitted pattern.

5. The image scanner according to claim 3 ,

wherein the image processing unit does not correct the brightness of the processing region when a difference between a brightness of a first transmitted pattern and the brightness of the second transmitted pattern is less than or equal to a predetermined value, the first transmitted pattern obtained from the result of the scan and corresponding to the first pattern.

6. The image scanner according to claim 1 ,

wherein while the cover unit is disposed in a location corresponding to a scanning reference location to which a corner of the document is aligned, a location of the pattern depicted on the cover unit corresponds to the scanning reference location, and

the scanning unit scans the document while the cover unit is disposed in the location corresponding to the scanning reference location.

7. The image scanner according to claim 1 , further comprising:

a reference data memory in which reference data representing the pattern is stored in advance; and

a detection unit that uses the reference data to detect, in a scanned image obtained from the result of the scan, a specific region including the transmitted pattern,

wherein the image processing unit sets the threshold value based on a brightness of the specific region detected by the detection unit.

8. The image scanner according to claim 7 ,

wherein the detection unit detects an extending portion extending beyond an edge of the document by detecting a portion of the specific region having a brightness lower than a predetermined value, and excludes the extending portion from the specific region, and

the image processing unit removes the extending portion from the scanned image.

9. An image scanning method comprising:

scanning a first side of a document while a cover unit on which a first pattern is depicted is in contact with a second side of the document opposite the first side;

obtaining a brightness of a first transmitted pattern corresponding to the first pattern from a result of the scanning;

setting a threshold value based on the brightness of the first transmitted pattern; and

removing show-through appearing in a processing region having a brightness greater than or equal to the threshold value from the result of the scanning.

10. The image scanning method according to claim 9 ,

wherein the cover unit further depicts a second pattern less dense than the first pattern, and

the image scanning method further comprises:

obtaining a brightness of a second transmitted pattern corresponding to the second pattern from the result of the scanning; and

determining whether a difference between the brightness of the first transmitted pattern and the brightness of the second transmitted pattern is less than or equal to a predetermined value,

wherein the removing is not performed when the difference is less than or equal to the predetermined value.

11. An image scanner comprising:

a platen on which a document is placed;

a cover unit on which a marking is depicted;

a scanning unit that scans the document between the platen and the cover unit; and

an image processing unit that sets a threshold value using information on a transmitted marking of the marking, obtained through the document, and performs image processing based on the threshold value,

wherein the information on the transmitted marking is a brightness of the transmitted marking, and

wherein the image processing unit removes, from a result of the scan, an image appearing in a processing region having a brightness greater than or equal to the threshold value.

12. The image scanner according to claim 11 ,

wherein the image processing unit sets the threshold value to a brightness of the transmitted marking.

13. The image scanner according to claim 11 ,

wherein the marking of the cover unit includes a first marking and a second marking less dense than the first marking, and

the image processing unit corrects a brightness of the processing region based on a brightness of a second transmitted marking obtained from the result of the scan and corresponding to the second marking.

14. The image scanner according to claim 13 ,

wherein the image processing unit converts the brightness of the processing region to the brightness of the second transmitted marking.

15. The image scanner according to claim 13 ,

wherein the image processing unit does not correct the brightness of the processing region when a difference between a brightness of a first transmitted marking and the brightness of the second transmitted marking is less than or equal to a predetermined value, the first transmitted marking obtained from the result of the scan and corresponding to the first marking.

16. The image scanner according to claim 11 ,

wherein while the cover unit is disposed in a location corresponding to a scanning reference location to which a corner of the document is aligned, a location of the marking depicted on the cover unit corresponds to the scanning reference location, and

the scanning unit scans the document while the cover unit is disposed in the location corresponding to the scanning reference location.

17. The image scanner according to claim 11 , further comprising:

a reference data memory in which reference data representing the marking is stored in advance; and

a detection unit that uses the reference data to detect, in a scanned image obtained from the result of the scan, a specific region including the transmitted marking,

wherein the image processing unit sets the threshold value based on a brightness of the specific region detected by the detection unit.

18. The image scanner according to claim 17 ,

wherein the detection unit detects an extending portion extending beyond an edge of the document by detecting a portion of the specific region having a brightness lower than a predetermined value, and excludes the extending portion from the specific region, and

the image processing unit removes the extending portion from the scanned image.

19. An image scanning method comprising:

scanning a first side of a document while a cover unit on which a first marking is depicted is in contact with a second side of the document opposite the first side;

obtaining a brightness of a first transmitted marking corresponding to the first marking from a result of the scanning;

setting a threshold value based on the brightness of the first transmitted marking; and

removing show-through appearing in a processing region having a brightness greater than or equal to the threshold value from the result of the scanning.

20. The image scanning method according to claim 19 ,

wherein the cover unit further depicts a second marking less dense than the first marking, and

the image scanning method further comprises:

obtaining a brightness of a second transmitted marking corresponding to the second marking from the result of the scanning; and

determining whether a difference between the brightness of the first transmitted marking and the brightness of the second transmitted marking is less than or equal to a predetermined value,

wherein the removing is not performed when the difference is less than or equal to the predetermined value.