Digital image processing apparatus

• US 5,079,624 A
• Filed: 08/25/1989
• Issued: 01/07/1992
• Est. Priority Date: 09/02/1988
• Status: Expired due to Term

• Current Assignee: Fuji Xerox Company Limited (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Xerox Company Limited (Fujifilm Holdings Corporation)
• Inventors: Yamaguchi, Kenichi, Sasuga, Kazuyasu
• Primary Examiner(s): Ng, Jin F.
• Assistant Examiner(s): Grant, III, Jerome
• Application Number:
  US07/398,441
• Time in Patent Office: 865 Days
• Field of Search: 358/401, 358/429, 358/447, 358/448, 358/452, 358/453, 358/454, 358/455, 358/456, 358/457, 358/458, 358/462, 358/463, 358/464, 358/75
• US Class Current: 358/530
• CPC Class Codes: H04N 1/58 Edge or detail enhancement; Noise or error suppression, e.g. colour misregistration correction H04N1/62 takes precedence
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence

Abstract

A digital image processing apparatus which receives color-separation signals of a picture represented in terms of gradation and converts the color-separation signals into binary signals of on and off, comprises a toner signal conversion and adjustment means for adjusting the density of a plurality of the color-separation signals to produce a plurality of gradation toner signals representing a density of or an amount of toner of process colors, producing india ink, and extracting gradation toner signals of development process color; a process toner signal processing means for applying processes for Moire prevention and edge emphasis to the gradiation toner signals to convert into binary toner signal of on and off; a region picture control means for producing control information for each of a plurality of regions to control the toner signals conversion and adjustment means and the process toner signal processing means; and an edit control means having a plurality of edit regions and edit information for controlling the graduation toner signals in the edit regions in accordance with the edit information.

Claims

1. A digital image processing apparatus in which color-separation signals of a picture represented in terms of gradation are converted into binary signals, said apparatus comprising:

END conversion means for converting color-separation signals into color signals which are gray-balanced;

color masking means for applying color masking process to the gray-balanced color signals provided by said END conversion means to produce first-order gradation toner signals;

background-color removing and black tone producing means for removing background-colors and for producing black tone in response to the first-order gradation signals provided by said color masking means to produce second-order gradation toner signals; and

process toner signal processing means for applying processes for Moire prevention and edge emphasis to the second-order gradation toner signals provided by said background-color removing and black tone producing means to produce binary toner signals.

2. A digital image processing apparatus according to claim 1, wherein said process toner signal processing means is provided with a reduction/enlargement processing unit having a ping pong buffer for storing two lines into which said gradation toner signals are written on a line basis and from which said gradation toner signals are read on a line basis to thereby perform a reduction and an enlargement process.

3. A digital image processing apparatus according to claim 2, wherein said digital image processing apparatus is arranged such that reading of one line of said ping pong buffer is executed at a time when writing to the other line of said ping pong buffer is executed.

4. A digital image processing apparatus according to claim 1, wherein said process toner signal processing means is provided with a screen generator for converting said gradation toner signals into binary toner signals of on and off by comparing said gradation toner signals with a threshold matrix, and thereafter performing an error diffusion process.

5. A digital image processing apparatus according to claim 4, wherein said digital image processing apparatus is arranged to select by a region signal a combination of said threshold matrix and an ON/OFF operation of said error diffusion process.

6. A digital image processing apparatus according to claim 4, wherein said threshold matrix is formed by subdividing a pixel.

7. A digital image processing apparatus according to claim 4, wherein said threshold matrix is formed so as to have a plurality of growing nuclei.

8. A digital image processing apparatus according to claim 4, wherein said threshold matrix has a submatrix construction formed of a plurality of unit matrices, and wherein a plurality of growing nuclei are disposed in said submatrix.

9. A digital image processing apparatus according to claim 1, wherein said background-color removing and black tone producing unit detects a maximum value and a minimum value of said first-order gradation toner signals to produce an adjustment value in accordance with a difference between the maximum and minimum values as a value of the black tone, and determines a background-color removal value in accordance with the black tone value.

10. A digital image processing apparatus according to claim 9, wherein said adjustment value and said background-color removal value are determined using approximation through mathematical operation and using conversion tables.

11. A digital image processing apparatus according to claim 1, further comprising region image control means for producing control information for each of a plurality of regions in an image to control said color masking means, background-color removing and black tone producing means and process toner signal processing means.

12. A digital image processing apparatus according to claim 11, wherein said region image control means is arranged to output color mode information including color conversion and full color and picture mode information including photograph and characters as said control information.

13. A digital image processing apparatus according to claim 11, wherein said region image control means is arranged to produce said control information in accordance with a priority level between said plurality of edit regions.

14. A digital image processing apparatus according to claim 1, further comprising edit control means for controlling said first-order gradation toner signals or said second-order gradation toner signals in accordance with edit information.

15. A digital image processing apparatus according to claim 14, wherein said edit control means has a specified region and edit information of said specified region and controls a gradation toner signal of said specified region with said edit information.

16. A digital image processing apparatus according to claim 14, wherein said edit contol means produces edit commands for picture elements on the basis of said edit information to perform edit control of said gradation toner signals.

17. A digital image processing apparatus according to claim 14, wherein said edit control means is provided with a plurality of control patterns which are selectively controlled by said edit commands.

18. A digital image processing apparatus according to claim 1, wherein said END conversion means is provided with a color conversion processing unit for converting a specified color of a square which is specified and contolled by a region processing information producing means before background-color removal.

19. A digital image processing apparatus according to claim 18, wherein said region processing information producing means, and said color conversion processing unit are constructed on a circuit board.

20. A digital image processing apparatus according to claim 1, wherein said process toner signal processing means is provided with an edge detection and frame erasure unit for detecting a document size from said first-order gradation toner signals before background-color removal and for removing gradation outside the document.

21. A digital image processing apparatus according to claim 1, wherein said process toner signal processing means is provided with a digital filtering circuit for detecting hue to decide for each gradation toner signal if edge emphasis and edge damping is required, thereby controlling a level of edge emphasis.

22. A digital image processing apparatus according to claim 1, wherein said process toner signal processing means is provided with a tone correction control unit for causing said gradation toner signals to be subjected to processes including density adjustment, contrast emphasis, negative/positive inversion, and color balance adjustment.