JPS62171275A - Image area separating device - Google Patents

Abstract

PURPOSE:To separate the dot area and the line drawing area even when a dot photograph with unknown line number and angle and a line picture exist in mixture by converting an input picture signal into a binary picture signal and discriminating whether an area is a dot photograph area or a line drawing area depending on the presence of white or black level closed area of the signal in a prescribed area and storing the result of discrimination of the dot photograph area with priority. CONSTITUTION:An input picture signal is converted into a binary picture signal at a fixed threshold level by a binarization circuit 11 and a closed area detection circuit 12 discriminates 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, and in case of existence, logic 1 is outputted as the existence of the closed area an in case of nonexistence not, logic 0 is outputted. A write circuit 13 receives the output of the detection circuit 12 to write the result of closed area detection in the corresponding location of a built-in picture memory. The write is applied to logic 1 with priority at the write. The result of write is outputted from a terminal 102.

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.

When inputting this halftone photograph using a facsimile, moiré may occur. A binary output formula that can suppress the occurrence of moire is also known, but if you use a special binary output formula to suppress the occurrence of moire, it will cause unnecessary cuts in thin lines and around the lines in line drawings. Nottuchi sometimes appeared. For this reason, several devices for separating the halftone photographic area and the line drawing area have been proposed in order to separate the two and apply a binary output formula 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; The present invention is characterized by comprising 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. An image area separation device is obtained.

(Principle of the Invention) Halftone photography expresses gradation information using the areas of minute white 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. Finally, 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 determined based on whether or not the area of interest is surrounded by the same color, white or black, and there are pixels in the area of interest that have a different color from the surrounding pixels. 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.

(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 a device that implements the present invention. The image signal input from the terminal 101 is sent to the binarization circuit 1.
It is converted into a binary image signal with a fixed threshold of 1. 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. , outputs 1, otherwise outputs 0.

The writing circuit 13 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 image memory. During this writing, writing is performed so that 1 has priority. The written 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. 4 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 the figure are ignored. A binary image signal is supplied from a terminal 201. 1 pixel delay element 22A.

22B and 22C output the pixel value corresponding to A3 in FIG.
RY read-only memory). ROM23A
determines whether all pixels in A3 are white, black, or a mixture of both. In the same way, one pixel delay element 22H, 2
The contents of 2L and 22P, that is, the part A4 in Figure 4 is RO.
M23F, 22Q.

The contents of 22R and 228, that is, the A1 part, are stored in ROM23.
E, delay element 21A, 2 with 4 pixels less than 1 line
The output of 1B and 21C, that is, the A2 part is stored in ROM23.
It is judged as H.

The output of each ROM is AI again in ROM24A,
A2゜A3. It is determined whether all of A4 is white, black, or a mixture of both. Next, Al in FIG. 4, A2.
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 ROM2
At 3B, it is determined whether all the colors are white, black, or a mixture of both. Similarly, the ROM 23C has one-pixel delay elements 22I and 22J.

The contents of 22 are determined, and the ROM 23D determines the contents of 1-pixel delay elements 22M, 22N, and 220. These determination results are again determined in the ROM 24B as to whether all are white, black, or a mixture of both. ROM24A and ROM24
The output of B is 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 region if all the outputs of ROM24A are white and the outputs of ROM24B are all black or a mixture of white and black, and if all the outputs of ROM24A are black and the outputs of ROM24B are all black. This is the case when the color is all white or a mixture of white and black. In the end, if there are pixels of a different color from the surrounding area within an area surrounded by the same color, Sarel determines that there is a closed area. ROM23G ROM
25B C It is determined whether there is a closed region in the case of 3×3 pixels shown in FIG.

The outputs of ROM 25A and ROM 25B are logically ORed by OR gate 26 and output to terminal 202.

FIG. 3 is a block diagram of the write circuit 13. terminal 3
01 is always supplied with O, and the terminal 302 is supplied with the output of the closed area detection circuit 12. Delay elements 31A to 31D with 4 pixels less than 1 line and 1 pixel delay element 32
The image area separation result is stored in the image memory consisting of A to 32T, but the information that the area of interest is a halftone area is written with priority by the logical OR gate. This result is output from terminal 303.

In the above explanation, both the closed area determination in the closed area detection circuit and the priority determination in the write circuit are 5.
Although an example has been described in which processing is performed in units of ×5 pixels, the unit of processing is not limited to this size. Further, the unit of processing may be changed between the closed area detection circuit and the writing circuit.

(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 areas and line drawing areas can be effectively separated. 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, and Fig. 4 is a case where the area of interest is 5 x 5 pixels. FIG. 5 is a block diagram showing the positional relationship between peripheral pixels and internal pixels in the case of 3×3 pixels. In the figure, 11...Binarization circuit with fixed threshold, 12
...Closed area detection circuit, 13...Writing circuit, 2LA, 21B, 21C, 21D...Delay element with 4 pixels less than 1 line, 22A, 22B, 22C, 22D, 22E, 2
2F, 22G, 22H, 22I, 22J. 22, 22L, 22M, 22N, 220.2
2P, 22Q, 22R, 228, 22T, . 1 pixel delay element, 23A, 23B, 23C, 23D, 23E, 2
3F, 23G, 23H...ROM (read-only memory), 24A, 24B...ROM (read-only memory), 26...Logic OR gate, 31A, 31B, 31C, 31D...4 from 1 line Delay element with fewer pixels, 32A, 32B, 32C, 32D, 32E, 3
2F, 32G, 32H, 32I, 32J. 32, 32L, 32M, 32N, 320.3
2P, 32Q, 32R, 32S, 32T, . 1 pixel delay element, 33A, 33B, 33C, 33D, 33E, 3
3F, 33G, 33H, 33I. 33J, 33, 33L, 33M, 33N,
330.33P, 33Q, 33R, 338°33T
, 33U, 33V, 33W, 33X, 33Y
-・Logic OR gate \"-++--' Figure 1 Figure 4 Figure 5 Whistle ';]

Claims (2)

[Claims] (1) In 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, a means for converting the input image signal into a binary image signal; and a means for converting the input image signal into a binary image signal; means for determining whether a predetermined region is a halftone photographic region or a line drawing region according to the presence or absence of a white or black closed region within the predetermined region; 1. An image area separation device comprising: storage means for storing a result indicating that the area is a line drawing area with priority over a result indicating that the area is a line drawing area. (2) The means for determining whether the predetermined area is a halftone photographic area or a line drawing area is to set a rectangle as the predetermined area, and to determine whether the predetermined area is a halftone photographic area or a line drawing area, and to determine whether the predetermined area is a halftone photographic area or a line drawing area. The image according to claim (1), characterized in that the image is a means for determining whether the area is a halftone photograph area or a line drawing area depending on the presence or absence of a closed area surrounded by the image. area separation device.