JPH03145278A - Image information encoding method - Google Patents

Abstract

PURPOSE:To improve the coding efficiency by decomposing a contour of a black picture into vectors, coding the picture, dividing one page of picture into plural small areas and applying coding the picture in the unit of small areas. CONSTITUTION:One page of original is divided into small areas of a prescribed size of rectangular shape, contours L1, L2 of a black level picture appearing in picture information are extracted in the unit of small areas, then kind information of plural vectors constituting the contour and coordinates of start points P1, P2 of the contour is used as coding information. Furthermore, coding information is arranged in response to the prescribed order of arrangement of the small areas to constitute the coding information by one page. Since the contours L1, L2 of the black level picture are decomposed into a vector and coded, the coding efficiency is excellent and since one page of picture is divided into plural small areas and coded in the unit of the small areas, then the kind of the vector required for coding is reduced and the code quantity is reduced. Thus, the coding efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image information encoding method for encoding and compressing image information obtained by raster scanning a document image.

[Prior Art] For example, as a method for encoding and compressing image information obtained by raster scanning a document image using a facsimile machine, etc.
For example, so-called one-dimensional encoding methods such as the MH encoding method, which is a standard encoding and compression method for Group 3 facsimile equipment, and so-called MR encoding methods, such as the MR encoding method that is an optional encoding and compression method for Group 3 facsimile equipment. A two-dimensional encoding method is used.

- Dimensional encoding method checks the consecutive number of black and white pixels (run length) from the scan start position line by line and converts it into variable length data, and two-dimensional encoding method is the standard. It encodes the state of black and white change between the reference line and the encoded line.

Usually, a two-dimensional encoding method has a higher encoding compression rate than a -dimensional encoding method.

[Problems to be Solved by the Invention] However, in such conventional methods, the encoding compression ratio is higher in the two-dimensional encoding method than in the -dimensional encoding method, but even so, the encoding efficiency is high. This caused the inconvenience of not having one.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for encoding image information with good encoding efficiency.

[Means for Solving the Problems] In the present invention, one page of a document is divided into rectangular small regions of a predetermined size, and the outline of a black image appearing in image information is extracted for each small region. A plurality of vectors forming the contour are detected, and the coordinates of the starting point of the contour and type information of the plurality of vectors forming the contour are used as encoded information. moreover.

Arranging the encoded information according to a predetermined arrangement order of the small areas,
This constitutes one page of encoded information.

[Operations] Therefore, since the outline of the black image is decomposed into vectors and encoded, the encoding efficiency is high. In addition, since the image of one page is divided into multiple small areas and encoded in units of small areas, it is possible to reduce the types of Baku1Hel required for encoding, and the code can be shortened. Encoding efficiency is further improved. Furthermore, the direction in which the outline of the black image is found in each small area is determined, and the coded information is arranged in the order in which the small areas are arranged to form one page of coded information.
Information for identifying each small area can be omitted, further improving encoding efficiency.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the encoding method of the present invention, first, as shown in FIG.
A document image for one page is divided into rectangular small regions of predetermined width and height, and the outline of a black image is extracted from each small region. In addition, in the same figure, identification codes (a, b) are attached to each small area for convenience.

For example, in a black image as shown in FIG. 2(a), an outer contour Ll and an inner contour L2 constituting the black image are extracted.

Once the contour has been extracted in this way, next, as shown in FIG. 3, from the reference point at the upper left corner of each small area, a pixel that is the starting point of the contour is searched for in the lower right direction.

As a result, for example, the pixel P1 becomes the starting point for the contour L1, and the pixel P2 becomes the starting point for the contour L2.

Then, the contour is traced in a fixed direction from the starting point, and the traced results are decomposed into a combination of a plurality of vectors. As a result, vectors forming each of the contours LL and L2 are detected, for example, as shown in FIG. 2(C).

In this way, when multiple vectors making up a contour are detected, for each contour, small area data is constructed consisting of a set of encoded data that includes the coordinates of the starting point and the types of vectors that continue from the starting point. do.

Then, the small area data obtained in this way is arranged in the order of the small areas as shown in FIG. 4, thereby configuring one page of encoded information.

Also, when decoding the original image information based on this one page's worth of encoded information, first, the first small area data is sequentially decoded from the beginning to restore the outline of the black image,
The original image is reconstructed by filling in the area surrounded by these outlines with black pixels.

At this time, at the boundary between one small area data and the next small area data, the direction from the coordinates of the starting point of the contour decoded immediately before to the coordinates of the starting point of the next small area data is Since the state does not follow the direction during encoding (see FIG. 5), when such a state is detected, it can be determined that it is a break in small area data.

Therefore, the encoded information can be appropriately decoded without adding identification information for identifying each small area data.

In addition, during encoding, the process of extracting contours, detecting the start point of contours, converting contours into vectors, converting vectors to contours during encoding, and converting the inner area surrounded by contours into black pixels. Since the filling process and the like are conventionally known, detailed explanation thereof will be omitted.

As explained above, in this embodiment, the document image is divided into a plurality of small regions, and the outline of the black image is extracted and vectorized for each small region, so the types of vectors used for encoding are Therefore, the number of bits of data representing the vector can be reduced, and the amount of data after encoding can be reduced.

Furthermore, since the number of bits of data representing the coordinates of the starting point of one contour can be reduced, the amount of encoded data can be further reduced.

According to experiments conducted by the inventor, the encoding method of the present invention reduces the amount of data after encoding by 20% compared to the conventional MR method.
It was possible to reduce the degree.

[Effects of the Invention] As described above, according to the present invention, since the outline of a black image is decomposed into vectors and encoded, the encoding efficiency is high.
In addition, since the image of one page is divided into multiple small areas and encoded in units of small areas, the number of types of vectors required for encoding can be reduced, and the code length for vectors can be shortened. As a result, encoding efficiency is further improved.

Furthermore, the direction in which to find the outline of the black image in each small area is determined, and the encoded information is arranged in the order of arrangement of the small areas.
Since the encoded information for each page is configured, information for identifying each small area can be omitted, and the encoding efficiency is further improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of a small area, Fig. 2 (a) is a schematic diagram showing an example of a black image, and Fig. 2 (b) is a schematic diagram showing an example of the outline of the black image in Fig. 2 (a). , the same figure (C) is the same figure (b)
) Figure 3 is a schematic diagram showing an example of the direction in which contours to be encoded are searched for. Figure 4 is a schematic diagram showing an example of encoded information for one page. 5A and 5B are schematic diagrams for explaining a method for determining the delimitation of small area data during decoding. Figure 2

Claims (2)

[Claims] (1) In an image information encoding method that encodes and compresses image information obtained by raster scanning a document image, one page of the document is divided into rectangular small regions of predetermined dimensions, and each small region is divided into extracts the outline of the black image that appears in the image information, detects multiple vectors that make up that outline,
A method for encoding image information, characterized in that the coordinates of the starting point of the contour and type information of a plurality of vectors constituting the contour are used as encoded information. (2) The encoded information is formed by finding an outline in a certain direction in each small area, and is arranged in a predetermined order of the small areas to form one page of encoded information. The method of encoding image information according to claim 1, characterized in that: