JPH052978B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for extracting a specific image from a document and making a plate.

When creating a printing plate, a so-called cutting operation (opaque operation) is performed in which only a certain image is left and the other parts are deleted, so the part of the image that should be left is transparent and the other parts are not. By making a mask plate that does not allow light to pass through, and overlaying this mask plate and a made printing plate (film plate) on an unexposed film plate and printing, a printing plate in which only the specific image exists is created. It is being created.

However, such conventional technology requires a large number of steps, and most of the steps require manual labor, making the work complicated and inefficient.Furthermore, the opaque work requires considerable experience. It is necessary to train skilled personnel to carry out this work.

On the other hand, using a large-scale computer system,
So-called layout scanners with editing and correction functions have been developed and put into practical use in recent years, and by using such layout scanner systems, it is possible to extract and output only specific images and delete other images. However, since it requires a large-scale computer, the entire system is large-scale and expensive.

The present invention has been made in view of the prior art, and its purpose is to provide a method for extracting and making a plate of only a specific image, which can minimize manual work, and has no other purpose. The object of the present invention is to provide a method for extracting only a specific image and making a plate, which can shorten the working time, and a further object is to provide a method for extracting only a specific image and making a plate, which does not require large-scale equipment. Another object of the present invention is to provide a method for extracting only a specific image and making a plate by which the specific image can be extracted accurately.

This invention, which was made to achieve the above object, utilizes a scanner system and a coordinate reading device, and focuses on the fact that density data becomes discontinuous at the contour line of an image, causing a density jump phenomenon. It was done by

The present invention will be described in detail below with reference to embodiments of the drawings.

FIG. 1 shows one model of a manuscript having an image to be extracted, FIG. 2 is an enlarged view of the image part to be extracted in FIG. 1, and FIG. 3 shows a plate-making method according to the present invention. FIG. 4 is a flowchart showing the processing procedure performed by the computer shown in FIG. 3. FIG.

In Figure 1, 1 is a manuscript, and this manuscript 1
may be a transparent original such as a photographic film, or a reflective original such as a painting, photographic paper, or general printed matter, and there is a tree 2 corresponding to the image to be extracted mixed with other images in the original. .

Such a document 1 is attached to an input section of a color scanner (electronic color separation machine) commonly used in the printing field. The general configuration of the input section of a color scanner is as shown in FIG. 2, which includes a rotating drum (not shown) on which the original 1 is mounted, a light source 12 that illuminates the original 1 in spots, and light reflected from the original 1. Or, use a half mirror, difroid mirror, etc. to convert the transmitted light into 3
By separating and passing through a color separation filter, R,
It consists of light receiving sections 13, 14, and 15, which are composed of photoelectric converters such as photodiodes and photomultipliers that receive light separated into three colors of G and B, and the irradiation position is set with respect to the rotating drum. By relatively moving in the axial direction of the rotating drum, the original 1
can scan the entire surface.

R, G, and B are output from the light receiving sections 13, 14, and 15, respectively.
An electrical signal of a size corresponding to the amount of received light separated into three colors is output, and the amplifiers 16, 17, 1
8 and samplers 19, 20, 21
The signals are sampled at an appropriate sampling frequency, and further converted into digital signals by A/D converters 22, 23, and 24, and sent to the computer 11. As a result, R, G, and
This means that the concentration of B has been detected. Note that the density in this case refers not only to the actual density obtained by taking the logarithm of the ratio of the amount of incident light to the amount of transmitted or reflected light, but also to the ratio of the actual amount of light received to the reference amount of light received at the light receiving section. It also includes broad concepts such as

On the other hand, 31 is a coordinate reading device, in which the original 1 is mounted on the original placing table 32, the cursor 33 is moved to the point where the coordinates of the original 1 are to be read, the cursor is positioned at that point, and an input button (not shown) is pressed. ), the X coordinate and Y coordinate of that point can be read by the X coordinate detector 34 and Y coordinate detector 35. The coordinate reading device may be of a type in which magnetically sensitive lines are arranged in a grid pattern in the X and Y directions under the surface of the document table 32, and read the X and Y coordinates by sensing the magnetic lines of force from the cursor 33, or a cursor. 33 is supported by the X rail and Y rail, and the cursor 33 and the
The most common method is to detect the amount of rail movement using a rotary encoder, etc. and read the coordinate values.
The present invention is not limited to these, and any coordinate reading device can be used.

The coordinate values from the X coordinate detector 34 and the Y coordinate detector 35 are digitized by A/D converters 36 and 37 and input to the computer 11.

Such a coordinate reading device 31 reads the coordinates of a plurality of points 3 along the outline of an image to be extracted from a document mounted on a document table 32, as shown in FIG. It is preferable that this point be as close as possible to the contour line and be a point that shows the characteristics of the contour line.

A rotation detector 25 detects the rotation of the rotating drum, and operates to generate one pulse for each rotation of the rotating drum. Scan line number generator 2
Reference numeral 6 is used to send a scanning line number, which is incremented by 1 every time a pulse is received from the rotation detector 25 using the scanning start signal as a trigger, to the computer 11. The density data and their scanning line numbers are sequentially stored in the storage device 41.

On the other hand, a plurality of points 3 ₁ from the coordinate reading device 31,
The coordinates of 3 ₂ , . . . , 3 _l are also stored in other areas of the storage device 41.

Here, it is easy to associate the above coordinate data with the scanning line number and density data from the scanner; for example, by setting the relationship between the coordinate system and the address where the density data is stored in advance. For example, by specifying the coordinates, the address where the density data of that point is stored can be determined, and therefore the density data of that point and the included scanning line number can be retrieved.

The output circuit 51 corresponds to the output section of the scanner,
Density signals for each color are input from the computer 11 for only image 2, which has been cut out through image processing by a computer, which will be described later. In response to this signal, a matrix circuit converts the R, G, and B color signals into Y, M, and C. Convert it to a color signal, adjust the density range and contrast (tone correction), and perform further color correction (masking). After masking is completed, the BK (black) signal is calculated from the Y, M, and C signals. It serves to control each of the exposure lamps 52, 53, 54, and 55 based on the four color signals thus obtained, and a rotating drum (not shown). The photosensitive film attached to the exposure lamps 52, 53,
By exposing at 54 and 55, it is possible to obtain a film plate in which only image 2 is made into a plate and images in other areas are removed.

Next, image clipping processing performed by the computer 11 will be explained.

As described above, the storage device 41 stores raster data, which is density data from the scanner, and coordinate data from the coordinate reading device 31.

As shown in FIG. 4, the coordinates of points 3 ₁ , 3 ₂ , ..., 3 _l read along the contour are stored in a memory 4.
1 to the buffer in the computer 11 and sequentially read them (step 61). The scanning line number n and density data addresses i and j corresponding to these coordinates are determined from the above relationship (step 6).
2) The obtained scanning line number n and address information (i, j) are temporarily stored in a register (step 64). The address information obtained here is particularly referred to as a reference address because it should serve as a reference for finding the contour line. Such processing is performed on the coordinates of all points stored in the buffer, and the scanning line number and reference address where the density data is stored corresponding to each coordinate are calculated.

At this point, the points 3 _{1 and 3} read by the coordinate reader are
This means that we have been able to find the scanning line numbers and reference addresses for 3 ₂ , ..., 3 _l , but the reference addresses for other scanning lines are not known yet, and we will find them in the next step. .

That is, in step 65, the coordinate reading points 3 ₁ and 3 ₂ are first read.
reads each scanning line number and reference address, and calculates the reference addresses of all the scanning lines existing between these scanning lines from the reference addresses of points ₃₁ and ₃₂ by, for example, linear approximation (step 66). The obtained reference address is stored in the storage device 41 along with the scanning line number.
(Step 67). Perform these operations at points 3 ₂ and 3 ₃ , points 3 ₃ and 3 ₄ , ..., points 3 _l-1 and 3 _l , point 3 _l
and _3.1 , to find the reference addresses for all the scanning lines scanning the image 2 to be cropped. Therefore, the reference address stores the density data of a point located near the outline of the image to be cut out for each scanning line.

After such processing is completed, processing is performed to extract the outline of the image to be cut out sequentially starting from the first scanning line.

In step 70, it is checked whether or not a reference address exists in each scanning line sequentially starting from the first scanning line. If the reference address does not exist, the process jumps to step 70 and the next scanning line number is determined. If the reference address is set and a reference address exists in that scanning line, the density data of each pixel in that scanning line is read from the storage device 41 into the computer 11 (step 71).

Next, the reference addresses i, j in this scanning line
The density data of the reference address is compared with the density data of the address next to the reference address (step 73), and in step 75, the density data of the reference address is compared with the density data of the address immediately before the reference address, and these data are compared. If either of the differences obtained from the two comparisons exceeds the set value, a density jump has occurred, and it can be determined that there has been an image switch. Either one is selected as the address of the contour line and stored in the register along with the scanning line number.

On the other hand, if there is no density jump, m=0 when comparing the density of reference addresses i and j with the addresses before and after them, so steps 78 to 80 are equivalent to steps 73 to 75. Therefore, only one is added to m, and in steps 73 and 74, the density of the address next to the reference addresses i and j is compared with the density of the addresses before and after it, and the comparison is performed. If there is no density jump as a result, in steps 78 and 79, the density of that address is compared with the density of the addresses before and after the reference addresses i and j, and the density difference is determined as a result of the comparison. If the value exceeds the set value, it means that a density jump point has occurred, and one of the addresses where a density jump was observed is stored in a register as a contour address along with a scanning line number (step 82). As a result of the comparison, if the density difference is less than the set value, it is assumed that there is no density jump, and the same density comparison as described above is continued using addresses that are further shifted forward or backward by one from the reference addresses i and j.

By sequentially performing such operations on each scanning line, address information indicating the outline of the image 2 to be extracted is accumulated in the register.

Therefore, in the case of this embodiment, based on the contour line address required when outputting density data for each scanning line at the time of output (during exposure), two If it is assumed that only the density data of the addresses sandwiched between the contour line addresses is outputted, and the density data of the other addresses are not outputted, the output circuit 51 outputs the image 2.
Only the density data of
By exposing the plate-making film in steps 3, 54, and 55, only a specific image can be extracted and plate-made.

Note that the density data for comparison may be for any of the colors R, G, and B, and the processing procedure by the computer is not limited to the flowchart shown in this example. , various possible changes in detail are included as embodiments of the invention.

Further, although the present invention relates to a plate-making method, it can also be applied to a technique for determining the outline of an image in a document. In this case, it is not necessary to use a scanner for plate making as shown in the example, and it is possible to use a simpler scanner system that can obtain scanning line numbers and monochromatic density data as raster data. .

As described in detail above, according to the present invention, when extracting a partial image of a document and making a plate, the coordinates of a plurality of points along the outline of the image from the coordinate reading device and the scanning line from the scanner are obtained. The contour line is extracted from the density data for each scan line based on the phenomenon that the density data becomes discontinuous at the contour line of the image and a jump in density can be seen. By selectively outputting the density data, you can print only a specific image.
Compared to conventionally known methods, this method makes maximum use of existing equipment and allows work to be performed simply, efficiently, and accurately.

[Brief explanation of the drawing]

The drawings show one embodiment of the invention,
FIG. 1 is an explanatory diagram showing one model of a document having an image to be extracted, FIG. 2 is an explanatory diagram showing an enlarged image portion of FIG. 1 to be extracted, and FIG. 4 is a system configuration diagram for implementing the method, and FIG. 4 is a flowchart showing the processing procedure by the computer in FIG. 3. 1... Original, 2... Image to be extracted, 3 ₁ ,
3 ₂ , ..., 3 _l ... Point near contour, 11 ... Computer, 31 ... Coordinate reading device, 41 ... Storage device, 51 ... Output circuit.

Claims (1)

[Claims] 1 Obtain the density data of the image of the original by scanning the original and store it in a storage device, extract the original from the original, read the position coordinates of a plurality of points along the outline of the image to be made, and further perform the steps described above. For each scanning line between the plurality of points, identify points near the plurality of points, read the position coordinates, find the address of the storage device corresponding to the read coordinates, and use this address as a reference for each scanning line. Detects the density jump point of the density data and detects the outline of the image to be extracted.
A method for extracting and making a plate for a specific image, which is characterized by outputting only the density data of the image to be extracted using this contour line as a boundary line.