# Patent

## Title
System and method for filtering noise in an image

## Abstract

A method for filtering noise in an image filters noise pixels in a discrepant block between a current image and a background image firstly, and further filter each small block whose area is less than a preset value from the discrepant block. The method further calculates a total area of each big block whose area is greater than or equal to the preset value from the discrepant block, and adds the current image to a background list of the current image if the total area is less than another preset value.

## Background
BACKGROUND
1. Technical Field
Embodiments of the present disclosure relate to image processing technology, and particularly to a system and method for filtering noise in an image.
2. Description of Related Art
Noise may be filtered from an image using a number of known methods. One such method filters pixels in the image whose difference value of red, green, and blue (RGB) is less than a preset value. Another method sharpens the image firstly, then, filters the pixels in the sharpened image whose difference value of RGB is less than the preset value. However, the above-mentioned two methods cannot filter the noise in the image efficiently. Therefore, prompt and accurate method of filtering noise in an image is desired.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of one embodiment of a computer comprising a system for filtering noise in an image.
FIG. 2 is a flowchart of one embodiment of a method for filtering noise in an image.
FIGS. 3A-3C are schematic diagrams of one embodiment of calculating a discrepant block between a current image and a background image.



DETAILED DESCRIPTION
All of the processes described below may be embodied in, and fully automated via, functional code modules executed by one or more general purpose computers or processors. The code modules may be stored in any type of readable medium or other storage device. Some or all of the methods may alternatively be embodied in specialized hardware. Depending on the embodiment, the readable medium may be a hard disk drive, a compact disc, a digital video disc, or a tape drive.
FIG. 1 is a block diagram of one embodiment of a computer 2 comprising a noise filtering system 21. In one embodiment, the noise filtering system 21 may be used to filter noise from an image by first filtering noise pixels in a discrepant block (refers to FIG. 3) between a current image and a background image, and then filter each small block whose area is less than a preset value from the discrepant block. A total area of each big block whose area is greater than or equal to the preset value is obtained from the discrepant block, and the current image is added to a background list of the current image if the total area is less than another preset value. In one embodiment, the background list is a data structure (e.g., a queue) for storing the background image, and the discrepant block is an array of one or more pixels connected together. A detailed description will be given in the following paragraphs.
In one embodiment, the computer 2 is electronically connected to a display device 1, an image obtaining device 3, and an input device 4. Depending on the embodiment, the display device 1 may be a liquid crystal display (LCD) or a cathode ray tube (CRT) display, for example.
The computer 2 further includes a storage device 20 for storing information, such as image data 22 captured by the image obtaining device 3. In one embodiment, the image obtaining device 3 may be an Internet Protocol (IP) Camera.
The input device 4 may be used to manually edit a displayed image of an image data 22 on the display device 1. In one embodiment, the input device 4 may be a keyboard.
In one embodiment, the noise filtering system 21 includes an obtaining module 210, a calculating module 211, a filtering module 212, and an adding module 213. In one embodiment, the modules 210-213 comprise one or more computerized instructions that are stored in the storage device 20. A processor 23 of the computer 2 executes the computerized instructions to implement one or more operations of the computer 2.
The obtaining module 210 obtains a current image and a background image from the storage device 20. In one embodiment, the current image and the background image are automatically acquired by the image obtaining device 3 (e.g., the IP Camera).
The calculating module 211 determines if a background list of the current image is null, and calculates a discrepant block between the current image and the background image if the background list is not null. As an image comprises a plurality of blocks, the block in the current image may be different from the block in the background image, and the different block between the current image and the background image is regarded as a discrepant block. An example of the discrepant block between the current image and the background image is shown in FIGS. 3A-3C. Referring to FIGS. 3A-3C, FIG. 3A represents a current image, FIG. 3B represents a background image, and FIG. 3C represents a discrepant block between FIG. 3A and FIG. 3B.
The filtering module 212 filters each pixel of the discrepant block whose difference value of red, green, and blue (RGB) is less than a first preset value from the discrepant block. In one embodiment, the difference value of RGB of each pixel in the discrepant block refers to a difference value between an RGB value of the pixel and an RGB value of a corresponding pixel in the background image. Supposing the first preset value is twenty four, the filtering module 212 filters each pixel whose difference value of RGB is less than twenty four from the discrepant block. In other embodiment, the filtering module 212 can filter each pixel whose difference value of YCbCr or other suitable difference value is less than a corresponding preset value from the discrepant block. In YCbCr, Y is the brightness (luma), Cb is blue minus luma (B-Y), and Cr is red minus luma (R-Y).
The filtering module 212 filters each small block of the discrepant block whose area is less than a second preset value from the discrepant block. In one embodiment, the second preset value is 40 pixels.
The calculating module 211 calculates a total area of each big block of the discrepant block whose area is greater than or equal to the second preset value from the discrepant block, and determines if the total area is less than a third preset value. In one embodiment, the third preset value is 200 pixels.
The adding module 213 adds the current image to the background list if the background list is null, or adds the current image being filtered to the background list if the total area is less than the third preset value.
The obtaining module 210 further obtains a next current image and a next background image from the storage device 20 if the total area is greater than or equal to the third preset value. Thus, the next current image can be filtered by modules 211-213.
In other embodiment, the obtaining module 210 may first sharpen the current image after the current image is obtained from the storage device 20.
FIG. 2 is a flowchart of one embodiment of a method for filtering noise in an image. Depending on the embodiment, additional blocks may be added, others removed, and the ordering of the blocks may be changed.
In block S1, the obtaining module 210 obtains a current image and a background image from the storage device 20.
In block S2, the calculating module 211 determines if a background list of the current image is null. The procedure goes to block S8 directly if the background list is null, or the procedure goes to block S3 if the background list is not null.
In block S3, the calculating module 211 calculates a discrepant block between the current image and the background image.
In block S4, the filtering module 212 filters each pixel of the discrepant block whose difference value of red, green, and blue (RGB) is less than a first preset value from the discrepant block. In one embodiment, the difference value of RGB of each pixel in the discrepant block refers to a difference value between an RGB value of the pixel and an RGB value of a corresponding pixel in the background image.
In block S5, the filtering module 212 filters each small block of the discrepant block whose area is less than a second preset value from the discrepant block. In one embodiment, the second preset value is 40 pixels.
In block S6, the calculating module 211 calculates a total area of each big block of the discrepant block whose area is greater than or equal to the second preset value from the discrepant block.
In block S7, the calculating module 211 determines if the total area is less than a third preset value, and the procedure goes to block S8 if the total area is less than the third preset value, or the procedure returns to block S1 if the total area is greater than or equal to the third preset value.
In block S8, the adding module 213 adds the current image to the background list if the background list is null, or adds the current image being filtered to the background list if the total area is less than the third preset value.
In other embodiment, the method further includes a following block before S1: the obtaining module 210 sharpens the current image after the current image is obtained from the storage device 20.
It should be emphasized that the above-described embodiments of the present disclosure, particularly, any embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiment(s) of the disclosure without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present disclosure and protected by the following claims.

## Claims

1. A computer-implemented method for filtering noise in an image using a computer comprising a processor, the method comprising execution of the steps comprising:
(a) obtaining a current image and a background image captured by an image obtaining device from a storage device using the processor;
(b) adding the current image to a background list of the current image if the background list is null using the processor;
(c) calculating a discrepant block between the current image and the background image if the background list is not null using the processor;
(d) filtering each pixel of the discrepant block whose difference value of red, green, and blue (RGB) is less than a first preset value from the discrepant block using the processor;
(e) filtering each small block of the discrepant block whose area is less than a second preset value from the discrepant block using the processor;
(f) calculating a total area of each big block of the discrepant block whose area is greater than or equal to the second preset value from the discrepant block using the processor, and determining if the total area is less than a third preset value; and
(g) adding the current image being filtered to the background list if the total area is less than the third preset value using the processor, or returning to block (a) if the total area is greater than or equal to the third preset value.

2. The method according to claim 1, wherein the background list is a data structure for storing the background image.

3. The method according to claim 1, wherein the difference value of RGB of each pixel in the discrepant block refers to a difference value between an RGB value of the pixel and an RGB value of a corresponding pixel in the background image.

4. The method according to claim 1, wherein the discrepant block refers to an array of one or more pixels connected together.

5. The method according to claim 1, further comprising: sharpening the current image after the current image is obtained from the storage device.

6. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed by a processor of a computer, cause the processor to perform a method for filtering noise in an image, the method comprising:
(a) obtaining a current image and a background image captured by an image obtaining device from a storage device;
(b) adding the current image to a background list of the current image if the background list is null;
(c) calculating a discrepant block between the current image and the background image if the background list is not null;
(d) filtering each pixel of the discrepant block whose difference value of red, green, and blue (RGB) is less than a first preset value from the discrepant block;
(e) filtering each small block of the discrepant block whose area is less than a second preset value from the discrepant block;
(f) calculating a total area of each big block of the discrepant block whose area is greater than or equal to the second preset value from the discrepant block, and determining if the total area is less than a third preset value; and
(g) adding the current image being filtered to the background list if the total area is less than the third preset value, or returning to block (a) if the total area is greater than or equal to the third preset value.

7. The non-transitory computer-readable storage medium according to claim 6, wherein the background list is a data structure for storing the background image.

8. The non-transitory computer-readable storage medium according to claim 6, wherein the difference value of RGB of each pixel in the discrepant block refers to a difference value between an RGB value of the pixel and an RGB value of a corresponding pixel in the background image.

9. The non-transitory computer-readable storage medium according to claim 6, wherein the discrepant block refers to an array of one or more pixels connected together.

10. The non-transitory computer-readable storage medium according to claim 6, further comprising: sharpening the current image after the current image is obtained from the storage device.

11. The non-transitory computer-readable storage medium according to claim 6, wherein the medium is selected from the group consisting of a hard disk drive, a compact disc, a digital video disc, and a tape drive.

12. A computer, comprising:
a storage device;
at least one processor; and
one or more modules that are stored in the storage device and executed by the at least one processor, the one or more modules comprising:
an obtaining module operable to obtain a current image and a background image captured by an image obtaining device from the storage device;
a calculating module operable to determine if a background list of the current image is null, and calculate a discrepant block between the current image and the background image if the background list is not null;
an adding module operable to add the current image to the background list if the background list is null;
a filtering module operable to filter each pixel of the discrepant block whose difference value of red, green, and blue (RGB) is less than a first preset value from the discrepant block;
the filtering module further operable to filter each small block of the discrepant block whose area is less than a second preset value from the discrepant block;
the calculating module further operable to calculate a total area of each big block of the discrepant block whose area is greater than or equal to the second preset value from the discrepant block, and determine if the total area is less than a third preset value; and
the adding module further operable to add the current image being filtered to the background list if the total area is less than the third preset value.

13. The computer according to claim 12, wherein the background list is a data structure for storing the background image.

14. The computer according to claim 12, wherein the difference value of RGB of each pixel in the discrepant block refers to a difference value between an RGB value of the pixel and an RGB value of a corresponding pixel in the background image.

15. The computer according to claim 12, wherein the discrepant block refers to an array of one or more pixels connected together.

16. The computer according to claim 12, wherein the obtaining module further operable to sharpening the current image after the current image is obtained from the storage device.