JPS62226770A - Image area separation device - Google Patents

Abstract

PURPOSE:To effectively separate a dot area and a line picture area by converting a signal into a binary picture signal so as to discriminate whether the signal is in the dot picture area or the line picture area depending on the presence of a white or a black closed area in a prescribed area. CONSTITUTION:A picture signal inputted from a terminal 101 is converted into a binary coding picture signal at a fixed threshold level by a binarycoding circuit 11. Then whether a black picture element surrounded by a white level or a white picture element surrounded by a black level exists in a noted area is discriminate by a closed area detection circuit 12. A write circuit 12 receives an output of the circuit 12 and writes the result of closed area detection to a position corresponding to the built-in 1st picture memory. The result is fed to a photographic area smearing circuit 14, the minute photographic area in the line picture area is changed forcibly into the line picture area and the result is outputted from a terminal l02.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apparatus for separating an image containing a mixture of halftone photographs and line drawings such as characters into a halftone photograph area and a line drawing area.

(Prior art and its problems) With the spread of facsimiles in recent years, there are increasing opportunities to transmit not only line drawings such as characters but also images such as printed photographs. When printing photographs, generally halftone photographs are often used.

If this halftone photograph is input from a facsimile, moiré may occur. When a special binarization force formula was used to suppress the occurrence of moiré, breaks in thin lines or unnecessary notches could appear around the lines in line drawings.

Therefore, several devices for separating the halftone photographic area and the line drawing area have been proposed in order to separate the two and apply binarization force formulas suitable for each. These methods detect patterns unique to halftone photographs and distinguish between the two.

However, these methods are not effective unless the unique patterns of halftone photographs are known in advance. Therefore, sufficient image area separation cannot be achieved for images in which various line numbers and angles are generated, and the desired goal cannot be achieved.

(Object of the Invention) The object of the present invention is to eliminate the above-mentioned disadvantages, and to perform image area separation that effectively separates the halftone dot area and the line drawing area even when halftone photographs and line drawings with unpredictable line counts and angles coexist. The goal is to provide equipment.

(Structure of the Invention) According to the present invention, there is provided a means for converting an input image signal into a binary image signal, and a means for converting an input image signal into a binary image signal; means for determining whether the area is a halftone photographic area or a line drawing area, and a storage means for storing the determination result with priority given to the result that the area is a halftone photographic area over the result that the area is a line drawing area;
There is obtained an image area separation device characterized in that it is equipped with means for reading out the image area separation results stored in the storage means and converting a minute halftone photographic area in a line drawing area into a line drawing area.

(Principle of the Invention) A halftone photograph expresses shading information using the area of minute mortar or black dots. Therefore, in the halftone photographic area, a characteristic repetition of white or black dots occurs. In the present invention, this dot, that is, black surrounded by white,
Alternatively, a white area surrounded by black is called a closed area, and the presence or absence of this closed area is used to determine whether or not it is a halftone photographic area. First, the input image is once binarized, and then if there is a closed area surrounded by white or black pixels within the set area, it is determined that it is a halftone dot area, otherwise it is determined that it is a line drawing area. to decide. Then, the judgment result is stored in memory. Since the binary image signal used here is only used to separate image areas, there is no problem even if moire occurs, so binarization using a fixed threshold may be used. Detection of a closed area is performed by surrounding the area of interest with the same color, white or black.
and? The determination is made based on whether or not there is a pixel of a different color from the surrounding pixels in the upper eye area. This judgment result is written in all reference areas, and is stored in the memory that stores the judgment result so that the result that it is a halftone photograph has priority over the previous result that it is a line drawing. Next, there may be characters in halftone photographs,
Since there are generally no very small photographs in a line drawing area, an operation is performed in which a minute halftone photograph area surrounded at both ends by line drawing areas is forcibly converted into a line drawing area.

(Example) The present invention will be described in detail below with reference to the drawings. 1st
The figure is a block diagram showing an example of the device of the present invention. An image signal inputted from a terminal 101 is converted into a binary image signal by a binarization circuit 11 using a fixed threshold. Next, the closed area detection circuit 12 determines whether or not there is a black pixel surrounded by white or a white pixel surrounded by black in the area of interest, and if there is, it is determined that a closed area exists. ,1
, otherwise output O. The writing circuit 12 receives the output of the closed area detection circuit 12 and writes the closed area detection result into the corresponding position of the built-in first image memory. OR so that 1 takes priority when writing this
Write using logic. The image area separation result obtained in this manner is supplied to the photo area filling circuit 14, and the separation result for a minute photo area in the line drawing area is forcibly changed to a line drawing area. The changed result is output from the terminal 102.

FIG. 2 shows a block diagram of the closed area detection circuit 12.

Here, for simplicity, the size of the region of interest used for detecting a closed region is set to 5×5 pixels, but it is also possible to increase the size to 7×7° or 9×9 pixels using almost the same circuit configuration.

FIG. 5 shows the positional relationship between peripheral pixels in the region of interest and pixels inside the region. In the figure, Al, A2. A3°A4 corresponds to the periphery, and B corresponds to the inside. The pixel values indicated by x in FIG. 5 are ignored. In FIG. 2, a binary image signal is supplied from a terminal 201. 1 pixel delay element 22A
, 22B, 22C correspond to A2 in Figure 5.
Outputs the WI raw value and stores it in ROM23A (READ ONLY
MEMORY (read-only memory).

The ROM 23A determines whether all pixels of A3 are white, black, or a mixture of both. In the same way, the contents of the one-pixel delay elements 22H, 22L, and 22P, that is, A4 in FIG.
The contents of 22Q, 22R, and 228, that is, the portion A1, are determined in the ROM 23E, and the outputs of the delay elements 21A, 21B, and 21C, which are 4 pixels less than one line, or the portion A2 are determined in the ROM 23H.

The output of each ROM is again ROM24A, Al,
A2. A3. It is determined whether all of A4 is white, black, or a mixture of both. Next, AI, A in Figure 5
2. A3. It is determined whether the part B surrounded by A4 is entirely white, black, or a mixture of both in the following manner. The outputs of the 1-pixel delay elements 22E, 22F, and 22G are judged by the ROM 23B as to whether they are all black, black, or a mixture of both. Similarly, the ROM 23C determines the contents of the 1-pixel delay elements 22I, 22J, and 22, and
ROM23D C 1 pixel delay element 22M, 22N,
220 to determine the content. These judgment results are R
The OM24B again determines whether all the images are white, black, or a mixture of both.

The outputs of the ROM 24A and ROM 24B are input to the ROM 25A, and it is determined whether or not there is a closed area. If there is a closed area, a value of 1 is output. It is determined that there is a closed area if the output of ROM24A is all white and if RO
If the output of M24B is all black or a mixture of white and black, and if the output of ROM24A is all black and RO
This is a case where the output of M24B is all white or a mixture of white and black. After all, if there are pixels of a color different from the surrounding area within an area surrounded by the same color, it is determined that there is a closed area. ROM23G and ROM25B are 3 shown in Figure 6.
Determine the existence of a closed region in the case of ×3 pixels. ROM2
The outputs of 5A and ROM25B are logically ORed by OR gate 26.
is taken and output to terminal 202.

FIG. 3 is a block diagram of the write circuit 13. terminal 3
0 is always supplied from terminal 01, and the output of the closed area detection circuit 12 is supplied from terminal 202. Delay elements 21A to 21D with 4 pixels less than 1 line and 1 pixel delay element 22
The image area separation result is stored in the image memory consisting of A to 22T, and the logical OR gates 33A to 33Y
The information that the area of interest is a halftone area is written with priority. This result is output from terminal 302.

FIG. 4 shows a block diagram of the photo area filling circuit 14. The image area separation result supplied from the terminal 302 is stored pixel by pixel in the 1-pixel delay elements 41A to 411, and the OR gate 43 stores the separation result delayed by 9 pixels as viewed from the terminal 302 and the separation result supplied to the terminal 302. is input. When both are logic 0, that is, in the line drawing area, the OR gate 43 outputs logic 0. This is fed to AND gates 42A to 42H to write whatever the contents of registers 41A to 41H are to a logic 0 into the next one pixel delay element. If both ends are line drawing areas, this operation
This corresponds to converting all pixels to a line drawing area. In other cases, the OR gate 43 outputs logic 1, so the AND gates 42A to 42H transmit the contents of the one-pixel delay element in the previous stage to the next stage as is. In this way, the photo area filling circuit 14 converts a minute photo area in a line drawing area into a line drawing area. Here, as an example, an area with a length less than 8 pixels in the main scanning direction was converted into a line drawing area as a minute photographic area, but it is also possible to fill in a wider area with the same configuration. If line memory is used, filling in the sub-scanning direction is also possible. The converted image area separation result is output from the terminal 102.

(Effects of the Invention) As described above, according to the image area separation device according to the present invention, even if halftone photographs and line drawings with unpredictable line counts and angles coexist, halftone photograph areas and line drawings can be effectively separated. Areas can be separated.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram of a closed area detection circuit, FIG. 3 is a block diagram of a writing circuit, FIG. 4 is a block diagram of a photographic area filling circuit, and FIG. Figure 5 is a diagram showing the positional relationship between surrounding pixels and internal pixels when the area of interest is 5 x 5 pixels, and Figure 6 is a 3 x 3
FIG. 7 is a diagram showing the positional relationship between peripheral pixels and internal pixels in the case of a pixel. In the figure, 11...Binarization circuit with fixed threshold, 12
...Closed area detection circuit, 13...Writing circuit, 14
... Photo area filling circuit, 21A, 21B,
21C, 21D...Delay elements with 4 pixels less than one line, 22A, 22B, 22C, 22D, 22E. 22F, 22G, 22H, 22I, 22J, 2
2, 22L, 22M, 22N, 220°22
P, 22Q, 22R, 228, 22T...1 pixel delay element, 23A. 23B, 23C, 23D, 23E, 23F, 2
3G, 23H...ROM (read-only memory)
, 24A, 24B...ROM (read-only memory), 25A, 25B...ROM (read-only memory), 26...Logic OR gate, 31A, 31
B, 31C, 31D...Delay elements with 4 pixels less than one line, 32A, 32B, 32C, 32D. 32E, 32F, 32G, 32H, 32I, 3
2J, 32, 32L, 32M, 32N. 320, 32P, 32Q, 32R, 328, 32T
・1 pixel delay element, 33A, 33B, 33C, 33
D, 33E, 33F, 33G, 33H, 33I
, 33J. 33, 33L, 33M, 33N, 330.3
3P, 33Q, 33R, 338, 33T. 33U, 33V, 33W, 33X, 33Y,,
-Logic OR'7'-), 41A. 41B, 41C, 41D, 41E, 41F, 41G
, 41H, 411...1 pixel delay element, 42A, 4
2B, 42C, 42D, 42E, 42F, 42
G, 42H... Theory 71 Mouth O 5 Ro O 6 Mouth piece 3 Diagram

Claims (1)

[Claims] A device for separating an image containing a mixture of halftone photographs and line drawings such as characters into a halftone photograph area and a line drawing area, comprising means for converting the input image signal into a binary image signal, and a predetermined area of the binary image signal. means for determining whether the predetermined area is a halftone photographic area or a line drawing area according to the presence or absence of a white or black closed area within the area; A storage means for storing a result indicating that it is a line drawing area with priority, and a means for reading out the image area separation result stored in the storage means and converting a minute halftone photograph area in the line drawing area into a line drawing area. An image area separation device characterized by: