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

• US 5,485,534 A
• Filed: 06/25/1993
• Issued: 01/16/1996
• 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): Boudreau, Leo H.
• Assistant Examiner(s): Johns, Andrew W.
• Application Number:
  US08/081,153
• Time in Patent Office: 935 Days
• Field of Search: 382/22, 382/54, 382/263, 382/264, 382/266, 382/275, 358/37, 358/166, 358/447, 358/463
• 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. An image sharpness emphasis apparatus comprising:

means for generating a sharp signal which is representative of an image, a line memory output unit, coupled to said generating means, which receives said sharp signal to output an unsharp signal and a matrix signal, an edge detecting filter coupled to said line memory output unit for detecting locations of edges on said image based on said sharp signal, a multiplication accumulating means which multiplies said matrix signal by the output of said edge detecting filter, which represents locations of edges on said image, so as to be accumulated, a subtracting means which calculates a difference signal between said sharp signal and said unsharp signal, a look-up table to be accessed based on the output value of said multiplication accumulating means, a multiplication means for effecting multiplications between said difference signal, a sharpness coefficient and a function output of said look-up table, and an adder for adding up said sharp signal and the output of said multiplication means so as to be outputted.

2. An image sharpness emphasis apparatus as claimed in claim 1, wherein there are provided a plurality of said edge detecting filters and said multiplication accumulating means for the plural directions, and said look-up table is to be accessed by adding up the resultants of the multiplicated accumulation of said each direction.

3. An apparatus for emphasizing sharpness in a picture signal comprising:

(a) picture generating means for generating a picture signal representing an orignal image;

(b) a memory and output device coupled to said picture generating means for storing said picture signal, and for outputting a matrix signal, having said picture signal as central data, and an unsharp signal, having peripheral data of said picture signal;

(c) detecting means for detecting edge levels of said matrix signal;

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

(e) emphasizing means for emphasizing sharpness in said picture signal in accordance with said weighted signal and said unsharp signal.

4. The apparatus for emphasizing sharpness in claim 3, wherein said detecting means further comprises a plurality of edge detecting filters for detecting said edges of said matrix signal for different scanning directions and accumulating means for respectively multiplying and accumulating said matrix signal with said edge detecting filters so as to thereby generate a plurality of edge level signal of said matrix signal.

5. The apparatus for emphasizing sharpness in claim 3, wherein said detecting means comprises a plurality of filters each for detecting an edge of said picture signal in a different scanning direction.

6. The apparatus for emphasizing sharpness in claim 3, wherein said picture signal is a pixel of said original image, said matrix signal is an N by N matrix having said pixel as a central point, and said unsharp signal is an average value of an N by N matrix containing pixels of said original image that surround said picture signal.

7. The apparatus for emphasizing sharpness recited in claim 3, wherein said emphasizing means further comprises:

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

multiplication means for producing a product signal representative of a product of said difference signal and weighted signal;

adder means for producing an addition signal representative of an addition of said picture signal and said product signal.