JP3318586B2 - Generating edge-enhanced image - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing method for obtaining a good edge-enhanced image using an image scanner.

[0002]

2. Description of the Related Art A method of generating an edge-enhanced image of a multivalued image according to the prior art will be described with reference to a flowchart of FIG. The edge of the multi-valued image (step S101) is uniformly enhanced using a differential filter (step S102) (step S103) to obtain an edge-enhanced image (step S104).

[0003]

However, when an edge-enhanced image is obtained from a multivalued image using the conventional technique,
A good image could not be obtained because the edge was applied uniformly.

[0004]

In the method of generating an edge-enhanced image according to the present invention, a multi-valued image read by an image scanner is edge-enhanced by a differentiation method based on Laplacian 8, and amplified and amplified by a sealing function.
Correct and generate an edge enhanced image.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a copying machine, contrast enhancement is generally used together with automatic contrast correction and differentiation. For this reason, in a portion having a high contrast, noise having a large luminance difference is removed, and a figure in a portion having a low contrast can be read to some extent. However, the image obtained by the copying machine is an image close to a binarized image. For example, the image information decreases when the setting is “thin” to obtain a good image, and the information amount increases when the setting is “dark”. Noise is increased as a whole, such as blackening of characters and the like. In a general copying machine, the optical system has large distortion in both the main scanning direction and the sub-scanning direction. On the other hand, when the image is read with an image scanner at 256 gradations of black and white, unless the driver software for reading is particularly processed, no correction of contrast or the like is performed, and a "dirty" image having more noise than a copier is obtained. However, this is because the copier expresses data with a large amount of information, such as 256 gradations of monochrome, while the image becomes close to a binary image. That is, if correction such as differential emphasis is performed on the data read by the image scanner, an image with a quality higher than that of a copier can be obtained.
Further, it is possible to acquire a sophisticated image with less distortion of the optical system as compared with a general copying machine.

First, the edge of a multi-valued image read by an image scanner is emphasized by using a differentiation method based on "Laplacian 8". That is, in a 3 × 3 matrix,
Edge emphasis is performed by adopting the largest difference in luminance between the central portion and the peripheral portion, which is the pixel, as the differential value of the pixel. Furthermore, since an image having low luminance and low contrast is obtained as it is, “amplification” and “correction” are performed by the sealing function.

The amplification / correction by the sealing function will be described with reference to FIG. FIG. 1 is an explanatory diagram showing the relationship between the differential value and the luminance. When the differential value is set in the X-axis direction and the luminance is set in the Y-axis direction, the normal input relationship is directly proportional (FIG. 1A). When luminance is amplified without correcting an image having low luminance and low contrast, the luminance is uniformly amplified. That is, the relationship between the differential value and the luminance is directly proportional to the proportional constant increased (not shown). As a result, an image can be obtained in which the brightness and contrast can be corrected but the edges are applied uniformly. Therefore, in the “amplification / correction by the ceiling function” according to the present invention, the maximum value (C _MAX ) of the luminance obtained in the normal input relationship is set as the ceiling value (the maximum limit value), and the luminance is amplified (FIG. 1 ( b)). By setting the ceiling value when amplifying the luminance and amplifying the luminance in this manner, it is possible to generate a good edge-enhanced image.

A method for generating an edge-enhanced image of a multivalued image according to the present invention will be described with reference to the flowchart of FIG. The multi-valued image read using the image scanner (Step S1) is amplified using a differentiation method based on Laplacian 8 (Step S2), while enhancing and correcting the edges of the image (Step S3) using a sealing function (Step S3). S4) An edge enhanced image is obtained (step S5).

[0009]

As described above, in the method for generating an edge-enhanced image according to the present invention, the edge of a multivalued image read by an image scanner is enhanced using a differential filter, and the edge is amplified and corrected by a sealing function. Generate an enhanced image. Therefore, an elaborate image with less distortion of the optical system can be obtained as compared with a general copier, and an image with a quality higher than that of a copier can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of amplification and correction by a sealing function.

FIG. 2 is a flowchart showing a method for generating an edge-enhanced image of a multi-value image according to the present invention;

FIG. 3 is a flowchart showing a method of generating an edge-enhanced image of a multivalued image according to the related art.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Ishikawa 1-9-9 Motohongocho, Hachioji-shi, Tokyo Inside Chuo Denshi Co., Ltd. (72) Inventor Mitsuhiro Aoki 1-9-9 Motohongocho, Hachioji-shi, Tokyo No. 9 Inside Chuo Denshi Co., Ltd. (72) Inventor Koki Ito 1-9-9 Motohongo-cho, Hachioji-shi, Tokyo Chuo Denshi Co., Ltd. (56) References JP-A-7-123248 (JP, A) JP-A-7-66977 (JP, A) JP-A-6-169400 (JP, A) JP-A-61-109262 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1 / 40-1/409

Claims (1)

(57) [Claims] 1. An image processing method for acquiring a good edge-enhanced image using an image scanner, wherein a multi-valued image read by the image scanner is enhanced by a differentiation method using a Laplacian 8 and an edge is amplified by a sealing function. A method of generating an edge-enhanced image, which is characterized by performing correction.