Method and apparatus for emphasizing sharpness of image by detecting the edge portions of the image

• US 5,602,942 A
• Filed: 04/06/1992
• Issued: 02/11/1997
• Est. Priority Date: 03/28/1990
• Status: Expired due to Term

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Takemoto, Fumito, Shimazaki, Osamu
• Primary Examiner(s): JOHNS, ANDREW W
• Application Number:
  US07/864,382
• Time in Patent Office: 1,772 Days
• Field of Search: 382/22, 382/54, 382/263, 382/264, 382/266, 382/275, 358/447, 358/37, 358/166, 358/463, 348/252
• US Class Current: 382/263
• CPC Class Codes: G06T 2207/10008 from scanner, fax or copier
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 5/75 Unsharp masking
• CPC Class Codes: G06T 7/12 Edge-based segmentation
• CPC Class Codes: H04N 1/4092 Edge or detail enhancement

Abstract

According to this invention, a sharpness emphasis is carried out by multiplying a sharpness emphasis signal of an original image by a function of a look-up table which is accessed based on an output from an edge detecting filter performing detections in accordance with only the edge portions of the original image. Since the edge detecting filter for detecting edges of the image is equipped in order to emphasize the sharpness only in the edge portions of the image, it is possible to prevent the image grains from being sharpness-emphasized. In addition, although the edge detecting filter may have a same size of a mask with that of the unsharpness mask, it is possible, if required, to modify freely both sizes of the masks, in order to perform a proper process in accordance with each image variation.

Claims

1. A method of emphasizing sharpness in a picture signal, said method comprising the steps of:

(a) generating a picture signal which represents an original image;

(b) storing said picture signal, and generating a matrix signal, having said picture signal as central data, and an unsharp signal, having peripheral data of said picture signal;

(c) detecting edge levels of said matrix signal;

(d) adjusting detected edges and generating an edge adjusting signal from a function stored in a look-up table, said edge adjusting signal being generated in accordance with said detected edge level; and

(e) emphasizing sharpness in said picture signal in accordance with said edge adjusted output signal and said unsharp signal.

2. The method of emphasizing sharpness recited in claim 1, wherein said detecting step (c) further comprises detecting said edges of said matrix signal for a plurality of different scanning directions and generating a plurality of edge level signals of said matrix signal.

3. The method of emphasizing sharpness recited in claim 2, wherein said detecting step is performed in a plurality of different scanning directions.

4. The method of emphasizing sharpness recited in claim 1, wherein said emphasizing step further comprises:

producing a difference signal representative of a difference between said picture signal and said unsharp signal;

producing a product signal representative of a product of said difference signal and said edge adjusted output signal;

producing an addition signal representative of an addition of said picture signal and said product signal.