JPH02246579A - Dot distance and angle detector for dot picture - Google Patents

Abstract

PURPOSE:To discriminate the distance and the angle of an arbitrary dot by obtaining coordinates of the center of the dot from coordinates of a change point and obtaining the angle and the distance of the dot from these coordinates of the center. CONSTITUTION:A dot picture is read by an OCR 100, and a binary image is stored in a picture memory 202 of a distance and angle detector 200, and this binary image is scanned by a dot distance and angle detecting program 203. Coordinates of the center of the dot are obtained from obtained binary change point coordinates, and coordinates of the center of an adjacent dot closest to obtained coordinates of the center of the dot are obtained, and the distance and the angle between dots are obtained from coordinates of centers of these dots. Thus, the distance and the angle of an arbitrary dot are detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] This invention relates to a device for detecting halftone dot distances and angles from binarized halftone dot images.

For the purpose of detecting an arbitrary halftone dot distance angle, a changing point coordinate detecting means scans the image to obtain binary changing point coordinates, and a changing point coordinate detecting means detects a halftone dot from the coordinates obtained by the changing point coordinate detecting means. halftone dot center coordinate detection means for determining the center coordinates; and determining the center coordinates of adjacent halftone dots that are closest to the halftone dot center coordinates determined by the halftone dot center coordinate detection means;
The present invention is configured to include halftone dot distance and angle detection means for determining the distance and angle between halftone dots from the two halftone dot center coordinates.

[Industrial application field]

The present invention relates to halftone dot distance angle detection for data compression of halftone dot images.

[Prior Art] A newspaper CTS system stores image data captured by a scanner in a computer, processes the data according to publication conditions, and outputs the data when necessary. If this image data is handled without being compressed, the amount of data will be enormous. Further, problems arise in terms of image data transfer time and storage device capacity for storage.

Data compression of newspaper images has been conventionally performed.

A black and white halftone dot image of a newspaper image is one that forms a 90 degree angle with the horizontal line of the newspaper surface, assuming that the direction in which the center points of each halftone dot are short is the halftone dot direction of the halftone dot image (Fig. 6 (a)). ) forms a 45 degree angle (Figure 6(b)).

After the halftone image is disulphated, it is subjected to known adaptive predictive coding, and further data compression is performed by well-known Huffman coding. As the applied predictive coding, there is a halftone image coding method (Japanese Patent Publication No. 63-18384).

Now, in order to execute the adaptive predictive coding, it is necessary to know the halftone dot direction and distance of the halftone dot image.

``Conventional To determine the direction and distance of halftone dots, first, image data is scanned (FIGS. 7(a) and 7(b)). The results of the scanning are shown in FIG. As a result of scanning, several white pixels follow, followed by several black pixels, and the above-mentioned process is repeated.

The lengths of the white pixel and black pixel (the length of the white pixel and the length of 10 pixels) and the bare length of the above-mentioned pair are totaled, and the bare length with the highest frequency is calculated from the halftone dot period (the halftone dot center point of the newspaper page). Based on the obtained halftone period, it was determined whether the halftone direction was 90 degrees or 45 degrees by examining the correlation of regions shifted by half a period in both the X and Y directions. FIG. 9 shows a diagram explaining the above determination. FIG. 9(a) shows the area 130 and the area 1.
Examine 31 correlations. In addition, (b) shows the area 132 and area 1.
We are investigating 33 correlations.

[Problem to be solved by the invention]

In recent years, color halftone images have appeared in newspapers. The color halftone image is expressed by yellow, cyan, magenta, and black halftone dots. If the directions of the halftone dots of all four colors are in the same direction, there will be slight angle deviations during printing, resulting in moire fringes. In order to prevent the moire fringes, the dot directions of the four colors are printed in different directions.

For example, the halftone dot direction is yellow 5 cyan.

Magenta and black, 90 degrees, 45 degrees, and 15 degrees, respectively.

It's like 75 degrees. However, the angle differs depending on the newspaper company or printing company.

Therefore, in order to perform data compression of a color image, particularly data compression using adaptive predictive coding, a high data compression rate cannot be obtained unless the halftone dot angle and distance of each color are known.

Since the black and white halftone dot image has a halftone dot direction of 45 degrees or 90 degrees, the distance and angle of the halftone dots can be found by finding the bare length.

However, if the angle of the dot direction is shallow such as 15 degrees, the dot distance cannot be determined from the bare length. 1st
Figure 0 is a 15 degree halftone image.

The bare lengths of scanning line 140 and scanning line 141 end up being different. Therefore, 45 degrees.

Like a 90 degree halftone image, the length of the bare length cannot be set as the halftone period.

Therefore, in the present invention, angles are 90 degrees, 45 degrees, and 15 degrees.

It is an object of the present invention to provide an apparatus for determining halftone dot distances and angles of a color image having a plurality of halftone dot angles such as 75 degrees, and for determining arbitrary angles.

[Means to solve problems]

In order to achieve the above object, the present invention provides a changing point coordinate detecting means for determining binary changing point coordinates, a halftone dot center coordinate detecting means for determining the center coordinates of a halftone dot from the changing point coordinates, and A structure having halftone dot distance angle detection means for finding the center coordinates of the halftone dots that are closest to each halftone dot, and for finding the distance and angle between the halftone dots from the center coordinates of a certain halftone dot and the center coordinates that are closest to the center coordinates of the halftone dot. shall be.

[Effect]

The center coordinates of the halftone dot are determined by the halftone dot center coordinate detection means from the change point coordinates determined by the change point coordinate detection means. Next, the halftone dot angle and distance are determined from the center coordinates by the halftone dot distance angle detection means.

〔Example〕

1(a), (b), and (C) are flowcharts of the halftone dot distance angle detection program, in which 211 is a change point coordinate detection means, 212 is a halftone dot center coordinate detection means, and 213 is a halftone dot distance angle detection means. It is a means. FIG. 2 is a block diagram of a halftone image data compression device, in which a distance and angle detection device 200 detects the distance and angle of a binary image read by an OCR 100. Next, the adaptive predictive coding device 300 predictively codes each pixel, and then the image is sent to the data compression device 400.
The data is compressed by Huffman encoding and stored in the storage device 50.
Store as 0. FIG. 3 is a block diagram of the distance and angle detection device 200, in which the halftone dot distance and angle detection program 203 is activated by a microprocessor (hereinafter abbreviated as MPU) 201. FIGS. 4 and 5 are explanatory diagrams of the operation of distance and angle detection.

An embodiment of the present invention will be described below with reference to the drawings.

First, a halftone dot image that has been converted into a halftone dot for color printing of newspapers, etc. is read with a 0CR100, and a binary image of yellow, cyan, magenta, and each point is detected by a distance angle detection device 20.
0 in the image memory 202. The binary image is "0pa,"1'.

It is expressed as

The binary image stored in the image memory 202 is scanned by a dot distance angle detection program 203.

First, an initial value in the y-axis direction is determined (11).

Furthermore, an initial value in the X-axis direction is determined (12).

The initial values of (x, y) are determined by the image memory 2.
Rather than scanning all pixels within 02,
), this is to scan only a predetermined area. In this case, the coordinates are 41.

1 is added to X (13), and it is determined whether the value of X falls within a predetermined detection area (14).

If it is not a detection area, processing 13 is further executed.

Assume that the value of X is the detection area. The binary image is scanned in the X-axis direction as shown in Fig. 4, etc.).

Read the (x, y) coordinate values, detect the binary change point, and if the change point is from "0°° to "1°", perform process 17,
In the case of a change point from "l" to "0", process 18 is executed. In the process 17, the coordinates of the change point are changed to change point "0".
1°° memory (FIG. 3 2041). Also processing 1
On the day, the change point ° "lO" is stored in the memory 2042. The change point from “0゛° to “1゛” and “1°° to “0”
are stored in association.

Next, when X reaches a predetermined value, scanning in the X-axis direction is ended (19). If the process does not end, process 13 is executed again.

When it is finished, 1 is added to y (20), and the above y
If the value of is within the predetermined area (2021) and the X coordinate has not yet been completed (21), process 12 is executed again, otherwise the scanning is completed (21).

Next, change point °“01” memory 2041. Change point “1”
0" memory 2042, and find the distance between the change point of "1" from "O" and the change point of "1" to "0°" stored in correspondence (22). Between the change points If the distance is greater than or equal to a predetermined value, process 25 is executed. If it is less than the predetermined value, the midpoint between the change points is determined and stored in the midpoint coordinate memory 205 between change points. In other words, if one halftone dot is scanned multiple times as shown in FIG. Take out (24
). In FIG. 5(a), they are 05 and Oj.

When all change points have completed the above processes 22 to 24 (25
), the pairs of midpoints, that is, midpoints between change points within the same halftone dot, are associated with each other. That is, in the process 24, only the midpoint between the upper and lower changing points of the halftone dot is extracted, but since the upper and lower parts are not associated with each other within the same halftone dot, the X coordinate of the midpoint between the changing points is are almost the same and whose distance falls between a certain value and a certain value (26).

Next, the midpoint between the midpoints between the corresponding change points (
In FIG. 5(a), the midpoint between OL and Oj) is determined and stored in the pair center coordinate memory 206 with the coordinates of the midpoint as the center of the halftone dot (27).

When the above processes 26 and 27 are completed for all the midpoints between the change points (28), a certain halftone dot center coordinate stored in the pair center coordinate memory 206 is read, and the distance between the halftone dot center coordinate and the halftone dot center coordinate is read. Determine the halftone dot center coordinates that are close (29)
. As shown in FIG. 5(b), the center coordinate OI of the halftone dot 52 is closest to the center coordinate 0 of the halftone dot 51. Set the above two coordinates to 0. From the positional relationship (ΔX, Δy) of Ol, find the distance r and halftone dot angle atan (ΔX/Δy) (
(see FIG. 5(C)) and is stored in the distance and angle memory 207 (30).

When the above processing 29.30 is completed for all halftone dot centers (32L calculates the average distance and angle from the information stored in the distance angle memory 207, and uses the results as the halftone dot distance and halftone angle) (32).

Now, the obtained halftone dot distance and halftone dot angle are sent to the adaptive predictive encoding device 300, and adaptive predictive coding is performed according to the halftone dot distance and halftone angle.

The result is compressed by Huffman encoding or the like in the data compression device 400 and stored in the storage device 500.

The present invention has been described above according to examples. In the embodiment, the area to be scanned to obtain the dot distance and angle is not all areas of the binary image but some areas, but the invention is not limited to this.

As shown above, the present invention can be modified in various ways according to the gist of the present invention, and the present invention does not exclude them.

(Effects) Even if the dot distances and angles are not known in advance, the present invention allows all dot distances and angles to be determined, making it possible to compress color image data.

[Brief explanation of drawings]

Fig. 1 is a flowchart of the halftone distance angle detection program, Fig. 2 is a block diagram of the halftone image data compression device, Fig. 3 is a block diagram of the distance angle detection device, and Figs. 4 and 5 are distance angles. An explanatory diagram of the detection operation, Fig. 6 is an explanatory diagram of the halftone dot angle, and Fig. 7 is an explanatory diagram of the halftone dot angle.
8, 9, and 10 are explanatory diagrams of conventional halftone dot period detection. 201...MPU 202...Image memory 203...Dot distance angle detection program 100...
0CR 200... Distance angle detection device 300... Adaptive predictive coding device 400... Data compression device 500... Storage device
Diagram (b) #Ekyōji Nehihiroken Seven Angram J70-Chart Diagram 1
Data crimping of five fortune telling data ``ψL city - A eyes 2 wards 茅 times (C) net and distance koji burden 1 Kenshichi program's phrodite diagram ゛ 1 figure (σ) 17] - the angle ha

[Sai ◆ Σ wo Hiro 1] tbun entrustment to 4 @Konotoge hinoki ii motion accent usage error 4 Figure (α) (bλ (C) 'w** sword i 41st, yI Oi'pgimta early 5
Diagram 熠hawk carp, set-up, in-shaotsu, ki a1 (b) Conventional - Bingru, maro-ken, 1st order, Ming-Ko-Ko, 7 times 41 禾-稠r, Sururo-ke t7, Seimei-zu, Figure 5I-δ

Claims (2)

[Claims] (1) In a device for detecting halftone dot distances and angles from a binarized halftone dot image, a change point coordinate detection means (211) for scanning the image and obtaining binary change point coordinates; halftone dot center coordinate detection means (212) for determining the center coordinates of a halftone dot from the coordinates found by the change point coordinate detection means (211); and a certain halftone dot found by the halftone dot center coordinate detection means (212). halftone dot distance and angle detection means (213) for determining a halftone dot center coordinate different from the halftone dot center coordinate at a distance closest to the center coordinate, and calculating a distance and an angle between the halftone dots from the two halftone dot center coordinates; What is claimed is: 1. A halftone dot distance angle detection device for halftone dot images. (2) The halftone dot center coordinate detection means (212) determines center coordinates between change points on the same scanning line and the same halftone dot from the change point coordinates determined by the change point coordinate detection means (211), and The method is characterized in that, from the obtained center coordinates between the plurality of change points, the center coordinates of the center coordinates between the change points within the same halftone dot and located at the top and bottom of the halftone dot are taken as the center coordinates of the halftone dot. The halftone dot distance angle detection device for halftone dot images according to claim 1.