IMAGE PROCESSING DEVICE, IMAGE FORMING APPARATUS, IMAGE PROCESSING METHOD, AND PROGRAM

• US 20090154800A1
• Filed: 12/04/2008
• Published: 06/18/2009
• Est. Priority Date: 12/04/2007
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Momose, Kiyoharu, Tsukui, Shinobu, Maki, Yoichiro, Kojima, Shoji
• Granted Patent: US 8,280,159 B2
• Time in Patent Office: Days
• US Class Current: 382/165
• CPC Class Codes: H04N 19/117 Filters, e.g. for pre-processing or post-processing sub-band filter banks H04N19/635
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock

Abstract

An image processing device that processes input image data includes: an image dividing unit that divides the input image data into a plurality of blocks; an image type determining unit that determines the type of the input image data for every block on the basis of the number of edge elements included in the block; a frequency component conversion unit that converts color components of the input image data into frequency components for every block; and an image compression unit that compresses corresponding image data for every block by specifying unnecessary components of the converted frequency components of the image data on the basis of the determined type of the image data and suppressing or removing the specified unnecessary components.

Claims

1. An image processing method for compressing an image, the method comprising:

receiving input image data, the image data including color components;

dividing the input image data into a plurality of blocks, each block including edge elements;

determining type of the input image data for each block based on a number of edge elements of each block; and

compressing each block based on the type of input image data, wherein compressing includes converting the color components into frequency components, identifying unnecessary frequency components, and suppressing or removing unnecessary frequency components.

2. The method of claim 1, wherein determining the type of the input image data includes counting edge elements to calculate monochrome edge elements and color edge elements, and comparing the sum of monochrome edge elements and color edge elements to a predetermined value.

3. The method of claim 1, wherein the blocks are derived from text, and compressing includes a text adjustment operation which determines directions of edge components through a pattern matching operation and removes unnecessary frequency components based on directions of edge components.

4. The method of claim 3, wherein the text is determined to be monochrome text, and only brightness components of the color components are converted into frequency components for each monochrome text block.

5. The method of claim 1, wherein the blocks are derived from blank data, and compressing includes a blank adjustment operation which replaces the color components with fixed data.

6. The method of claim 5, wherein blank data includes pixels which are white.

7. The method of claim 1, wherein converting the color components into frequency components is performed by applying a discrete cosine transform to each color component which converts the color components into discrete cosine coefficients.

8. The method of claim 7, wherein suppressing or removing unnecessary frequency components is performed by applying image adjustment coefficients to the discrete cosine coefficients.

9. The method of claim 8, wherein each unnecessary frequency component is identified by comparing an absolute value of a discrete cosine coefficient with a product of a predetermined frequency coefficient and a variation width of a respective color component.

10. The method of claim 9, wherein an unnecessary frequency component has an absolute value of a discrete cosine coefficient which is less than or equal to the product of the predetermined frequency coefficient and the variation width.

11. An image processing device for compressing an image, the device comprising:

a bus; and

a main controller coupled to the bus, the main controller for storing and executing a method comprising;

receiving input image data, the image data including color components;

dividing the input image data into a plurality of blocks, each block including edge elements;

determining a type of the input image data for each block based on a number of edge elements of each block; and

compressing each block based on the type of input image data, wherein compressing includes converting the color components into frequency components, identifying unnecessary frequency components, and suppressing or removing unnecessary frequency components.

12. The device of claim 11, wherein determining the type of the input image data includes counting edge elements to calculate monochrome edge elements and color edge elements, and comparing the sum of monochrome edge elements and color edge elements to a predetermined value.

13. The device of claim 11, wherein the blocks are derived from text, and compressing includes a text adjustment operation which determines directions of edge components through a pattern matching operation and removes unnecessary frequency components based on directions of edge components.

14. The device of claim 13, wherein the text is determined to be monochrome text, and only brightness components of the color components are converted into frequency components for each monochrome text derived block.

15. The device of claim 11, wherein the blocks are derived from blank data, and compressing includes a blank adjustment operation which replaces the color components with fixed data.

16. The device of claim 15, wherein blank data includes pixels which are white.

17. The device of claim 11, wherein converting the color components into frequency components is performed by applying a discrete cosine transform to each color component which converts the color components into discrete cosine coefficients.

18. The device of claim 11, wherein suppressing or removing unnecessary frequency components is performed by applying image adjustment coefficients to the discrete cosine coefficients.

19. The device of claim 18, wherein each unnecessary frequency component is identified by comparing an absolute value of a discrete cosine coefficient with a product of a predetermined frequency coefficient and a variation width of a respective color component.

20. The device of claim 19, wherein an unnecessary frequency component has an absolute value of a discrete cosine coefficient which is less than or equal to the product of the predetermined frequency coefficient and the variation width.