Apparatus and method for selectively processing a scanned image

Claim 3

The method of claim 1, wherein each of the horizontal and vertical pixel windows has a window span of three image pixels.

Claim 6

The method of claim 3, wherein the step (B) is performed by determining if the pixel value of the image pixel is different from that of at least one of the adjacent pixels by more than a predetermined value.

Claim 7

The method of claim 4, wherein the predetermined value is twenty while the pixel value of each image pixel of the scanned image can range from zero to two hundred fifty five.

Claim 8

The method of claim 3, wherein the step (D) further comprises the steps of (I) determining which one of the adjacent pixels and the image pixel has the median pixel value, wherein when the image pixel appears to belong to the scanned text image, the image pixel has the median pixel value; (II) subtracting an error value multiplied by a predetermined parameter from the median pixel value, wherein the error value is initially set at zero; (III) changing the pixel value of the image pixel to the subtracted median pixel value; (IV) updating the error value for a next image pixel by adding the difference between the original pixel value of the image pixel and the subtracted median pixel value to the error value.

Claim 9

The method of claim 6, wherein the predetermined parameter is selected from a range of a 0.2 to 0.4.

Claim 10

The method of claim 7, wherein the predetermined parameter is 0.25.

Claim 11

The method of claim 3, further comprising the steps of (E) determining if the scanned halftone image has at least one more unprocessed image pixel; (F) if the scanned halftone image is determined to have at least one more unprocessed image pixel, then returning to the step (B).

Claim 12

An image processing apparatus for a scanned image having a scanned halftone image and a scanned text image, comprising: (A) a modified median filter having a filter window that allows the modified median filter to pass through image pixels of the scanned text image substantially unchanged when the modified median filter minimizes moire pattern in the scanned halftone image such that the moire pattern is minimized without reducing the resolution of the scanned image, wherein the filter window is a cross-shaped filter window that has a horizontal pixel window and a vertical pixel window intersecting the horizontal pixel window.

Claim 13

An image processing apparatus for a scanned image having a scanned halftone image and a scanned text image, comprising: (A) a modified median filter having a filter window that allows the modified median filter to pass through image pixels of the scanned text image substantially unchanged when the modified median filter minimizes moire pattern in the scanned halftone image such that the moire pattern is minimized without reducing the resolution of the scanned image, wherein the filter window is a cross-shaped filter window that has a horizontal pixel window and a vertical pixel window intersecting the horizontal pixel window.

Claim 14

The image processing apparatus of claim 10, wherein each of the horizontal and vertical pixel windows has a window span of three image pixels.

Claim 15

The image processing apparatus of claim 10, wherein the modified median filter is a digital non-recursive filter.

Claim 16

The image processing apparatus of claim 10, wherein the modified median filter is a digital recursive filter.

Claim 17

An image processing apparatus for a scanned image having a scanned halftone image, a scanned text image, and a scanned continuous tone image, comprising: (A) a first set of instructions that define a cross-shaped filter window for a modified median filter, wherein the cross-shaped filter window allows the modified median filter to pass through image pixels of the scanned text image substantially unchanged while reducing moire pattern in the scanned halftone image; (B) a second set of instructions that determine if an image pixel of the scanned image appears to belong to the scanned continuous tone image; (C) a third set of instructions that pass through the image pixel unchanged if the image pixel appears to belong to the scanned continuous tone image; (D) a fourth set of instructions that send the image pixel and a number of adjacent pixels that fall within the cross-shaped filter window to the modified median filter if the image pixel does not appear to belong to the scanned continuous tone image such that moire pattern in the scanned halftone image is minimized without reducing the resolution of the scanned image.

Claim 18

An image processing apparatus for a scanned image having a scanned halftone image, a scanned text image, and a scanned continuous tone image, comprising: (A) a first set of instructions that define a cross-shaped filter window for a modified median filter, wherein the cross-shaped filter window allows the modified median filter to pass through image pixels of the scanned text image substantially unchanged while reducing moire pattern in the scanned halftone image; (B) a second set of instructions that determine if an image pixel of the scanned image appears to belong to the scanned continuous tone image; (C) a third set of instructions that pass through the image pixel unchanged if the image pixel appears to belong to the scanned continuous tone image; (D) a fourth set of instructions that send the image pixel and a number of adjacent pixels that fall within the cross-shaped filter window to the modified median filter if the image pixel does not appear to belong to the scanned continuous tone image such that moire pattern in the scanned halftone image is minimized without reducing the resolution of the scanned image.

Claim 19

The image processing apparatus of claim 14, wherein the second set of instructions determine if the image pixel appears to belong to the scanned continuous tone image by determining if the pixel value of the image pixel is different from that of at least one of the adjacent pixels by more than a predetermined value.

Claim 20

The image processing apparatus of claim 15, wherein the predetermined value is twenty while the pixel value of each image pixel of the scanned image can range from zero to two hundred fifty five.

Claim 21

The image processing apparatus of claim 14, wherein the fourth set of instructions further comprises (I) a first subset of instructions that determine which one of the adjacent pixels and the image pixel has the median pixel value, wherein when the image pixel belongs to the scanned text image, the image pixel has the median pixel value; (II) a second subset of instructions that subtract an error value multiplied by a predetermined parameter from the median pixel value, wherein the error value is initially set at zero; (III) a third subset of instructions that change the pixel value of the image pixel to the subtracted median pixel value; (IV) a fourth subset of instructions that update the error value for a next image pixel by adding the difference between the original pixel value of the image pixel and the subtracted median pixel value to the error value.

Claim 22

The image processing apparatus of claim 17, wherein the predetermined parameter is selected from a range of 0.2 to 0.4.

Claim 23

The image processing apparatus of claim 18, wherein the predetermined parameter is 0.25.

Claim 24

The image processing apparatus of claim 14, wherein the cross-shaped filter window has a horizontal pixel window and a vertical pixel window intersecting the horizontal pixel window, wherein each of the horizontal and vertical pixel windows has a window span of three image pixels.