Method and apparatus for identifying regions of an image to be filtered during processing of the image

• US 8,989,493 B1
• Filed: 01/29/2013
• Issued: 03/24/2015
• Est. Priority Date: 02/06/2012
• Status: Expired due to Fees

• Current Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Huang, Ying
• Primary Examiner(s): Liu, Li
• Application Number:
  US13/752,657
• Time in Patent Office: 784 Days
• Field of Search: None
• US Class Current: 382/181
• CPC Class Codes: G06T 2207/10008 from scanner, fax or copier
• CPC Class Codes: G06T 2207/20021 Dividing image into blocks, subimages or windows
• CPC Class Codes: G06T 2207/30176 Document
• CPC Class Codes: G06T 5/00 Image enhancement or restoration

Abstract

Embodiments of the present disclosure include methods, apparatuses, and systems for identifying regions to be filtered during processing of an image. A map generator is configured to receive pixels of an image and to determine a map for the image. The map indicates a number of islands within blocks of pixels of the image, where individual ones of the islands include either a single dark pixel, or two or more contiguous dark pixels, bordered by light pixels and/or one or more edges of the blocks of pixels. An index generator sets, based at least on the number of islands within the individual ones of the blocks of pixels that correspond to regions of the scanned image, filter indices for the regions of the scanned image. An image filter component, based on the filter indices, filters the regions of the scanned image.

Claims

1. A system comprising:

at least one integrated circuit configured to;

receive pixels of an image;

divide the image into a plurality of blocks of pixels;

determine numbers of islands within each of the plurality of blocks of pixels of the image, wherein determining a particular number of islands within a particular block of the plurality of blocks includes identifying at least one of

a single dark pixel bordered by at least one of (i) a plurality of light pixels of the particular block and (ii) one or more edges of the particular block, or

two or more contiguous dark pixels bordered by at least one of (i) a plurality of light pixels of the particular block and (ii) one or more edges of the particular block;

determine categorizations of each of the plurality of blocks of pixels based on the numbers of islands within each of the plurality of blocks of pixels; and

set, based at least on the categorizations of each of the plurality of blocks of pixels, filter indices for regions of the image, each of the regions including different subsets of the plurality of blocks of pixels; and

filter based on the filter indices, the regions of the image.

2. The system of claim 1, wherein the integrated circuit is further configured to receive the image from an image capture component.

3. The system of claim 1, wherein the integrated circuit is further configured to, based on comparisons of values of the pixels of the particular block to a threshold value, wherein the threshold value is a function of a mean value of the pixels of the particular block, determine:

(i) which of the pixels within the particular block are dark pixels, and

(ii) which of the pixels within the particular block are light pixels.

4. The system of claim 3, wherein the threshold value is calculated by adding the mean value to a bias value.

5. The system of claim 1, wherein:

the integrated circuit is further configured to;

based on whether each of the plurality of blocks of pixels has more than a threshold number of islands, determine the categorizations.

6. The system of claim 1, wherein the integrated circuit is further configured to reduce a number of the regions within the image, based on one or more of (i) de-noising of the image or (ii) merging at least one of the regions within the image that is (A) less than a predetermined size and (B) surrounded by a larger surrounding region.

7. The system of claim 1, wherein the map integrated circuit is further configured to:

identify an area within the image that includes a first subset of the blocks of pixels, the first subset of the blocks of pixels being

(i) categorized as a first type of block based on corresponding numbers of islands within each of the first subset of blocks of pixels, and

(ii) bounded by a second subset of blocks of pixels that are categorized as being a second type of block based on corresponding numbers of islands within each of the second subset of blocks of pixels; and

wherein the area of the map contains no more than a predetermined number of blocks of pixels; and

set the first subset of the blocks to be the second type of block.

8. The system of claim 1, wherein the integrated circuit is further configured to:

identify a boundary area between at least two areas of the image; and

set a filter index gradient across the boundary area to transition from (A) sharpening a first region of the image to (B) smoothing a second region of the image.

9. The system of claim 1, wherein the integrated circuit is further configured to set

a smoothing filter index for a first block of pixels that has more than a threshold number of islands;

and

a sharpening filter index for a second block of pixels that has fewer than the threshold number of islands.

10. A method, comprising:

receiving pixels of an image;

dividing the image into a plurality of blocks of pixels;

determining numbers of islands within each of the plurality of blocks of pixels, wherein determining a particular number of islands within a particular block of the plurality of blocks includes identifying at least one of

a single dark pixel bordered by at least one of (i) a plurality of light pixels of the particular block or (ii) one or more edges of the particular block, or

two or more contiguous dark pixels bordered by at least one of (i) a plurality of light pixels of the particular block or (ii) one or more edges of the particular block;

determining categorizations of each of the plurality of blocks of pixels based on the numbers of islands within each of the plurality of blocks of pixels;

setting, based at least on the categorizations of each of the plurality of blocks of pixels, filter indices for regions of the image, each of the regions including different subsets of the plurality of blocks of pixels; and

filtering, based on the filter indices, the regions of the image.

11. The method of claim 10, further comprising:

determining which pixels of the particular block of pixels are dark pixels, and which pixels of the particular block of pixels are light pixels, based on a comparison of values of the pixels in the particular block of pixels to a threshold value, wherein the threshold value is determined at least in part based on a mean value of the pixels in the particular block of pixels.

12. The method of claim 11, wherein the threshold value is calculated by adding the mean value to a bias value.

13. The method of claim 10, wherein:

the determining the categorizations of each of the plurality of blocks of pixels is based on whether the numbers of islands within each of the plurality of blocks of pixels meets or exceeds a threshold number of islands.

14. The method of claim 10, wherein the setting the filter indices includes:

setting a smoothing filter index for a first block of pixels that includes at least a threshold number of islands; and

setting a sharpening filter index for a second block of pixels that includes less than the threshold number of islands.

15. The method of claim 14, further comprising:

identifying a boundary area between a first region of the image that includes the first block of pixels and a second region of the image that includes the second block of pixels; and

setting a filter gradient across the boundary area to transition from sharpening to smoothing.

16. The method of claim 10, further comprising:

identifying a portion of the image that includes a first region that (i) includes only blocks of pixels that are categorized as a first type, and (ii) is completely bounded by a second region that includes only blocks of pixels that are categorized as a second type; and

setting the first region to be the second type.