JPH0588333A - Opaque method - Google Patents

Abstract

PURPOSE:To make a plate (opaque) easily, speedily, and precisely by detecting an unnecessary part such as a pinhole by a decision processing method and shielding the unnecessary part from light. CONSTITUTION:An original picture to be inspected is read, line by line, in order by a scanning read means 7 such as a line sensor, image parts 3 and non-image parts 4 are decided in picture element units by a connecting method, and decided picture elements ate outputted together to an opaque device 51. The opaque device 51 shields the non-image parts 4 of a film for plate making or photosensitive paper from light by a light shield device 54 such as a thermal transfer printing device according to input image information. Thus, unnecessary parts of the plate making film such as a pinhole are detected by the decision processing method which can set a necessary margin nearby an original image and shielded from the light. Consequently, opaque processing is performed easily, speedily, and precisely and the operation can be done by an unskilled person.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a necessary light transmitting portion or a reflecting portion or an unnecessary portion (non-image portion) which is an image portion in a plate-making film or printing paper,
The present invention relates to an operating method for providing a light-shielding layer by instructing the light-shielding means to cover all or part other than an image portion or unnecessary portions.

[0002]

2. Description of the Related Art In the work of plate making for printing, the work of shielding unnecessary light transmitting portions or reflecting portions (defective portions) caused by stains on the base plate due to the glue used, stains on the exposure device, etc. , Or the work of dividing the drawing lines by color. In these works, first, the image portion and the defective portion are discriminated and the drawing portion and the non-drawing portion are discriminated (discrimination processing). It is necessary to perform a light-shielding operation (light-shielding process) to shield the defective portion and the image area. However, as a light-shielding method for a plate-making film or printing paper, a mask sheet utilization method and a correction liquid application method are known. In the method of using a mask sheet, a peelable red layer or the like formed on a polyethylene terephthalate film is shielded from light by cutting or the like. However, most of the shading work by this method is manual work.

On the other hand, the correction liquid coating method uses a light shielding liquid (correction liquid) in which a vehicle contains a light shielding agent such as carbon black. This method is superior to the mask sheet using method in that the applied light-shielding layer is thin. This correction liquid application method has a drawback that it is difficult to perform light-shielding work in a fine portion due to the application work with a writing brush, time-consuming manual work, and labor-intensive work as the light-shielding work.

Almost all means for shielding unnecessary light-transmitting or reflecting portions of conventional plate-making films or printing papers must be done by the hands of workers, and the improvements studied so far have not been improved. However, most of them are limited to measures for strengthening the light-shielding film and applying it to only a part.

Further, looking at the detection of an unnecessary portion such as a plate-making film or a printing paper, there are problems such as detection by the human eye, time is required, and the skill of the operator. Unnecessary parts are generally pinholes or wires. At present, not only are these unnecessary portions large in number, but much effort is required for detection.

From the point of view of detecting an unnecessary light transmitting portion or a reflecting portion in a plate-making film or photographic printing paper, there is a printed matter inspection device or a printed circuit board inspection device, but these devices are used as inspection samples. The sample is stored in the device by the electronic (electrical) storage means, and the sample image input from the actual product or the TV camera etc. is held in the device, and the constituent images are sequentially scanned or sampled by an appropriate method. The purpose is achieved by comparing and verifying with the sample.

[0007]

As these devices, for example, JP-A-60-250957 and JP-A-60-25 are available.
No. 0958, No. 61-12341, No. 61-1234
3 and 61-12345, etc.
Although these have the advantage that inspection or information setting for inspection can be performed quickly and stably and the production of printed matter can be rationalized, unnecessary light transmission parts or reflection parts of plate-making film or photographic paper etc. For detection, there is no inspection sample, that is, the inspection sample cannot be used because it is the blockboard. In other words, there is a demand for a device that shields unnecessary portions from light without requiring a standard sample.

Further, JP-A-62-275265,
An apparatus for automating the make operation such as Japanese Patent Laid-Open No. 63-23552 is also under study, but it is an apparatus for which an inspection sample is required or for the purpose of improving the conventional correction liquid coating operation. However, it cannot be said that the device is automated or simplified.

In consideration of the drawbacks of the conventional method, the present invention is a method effective for plate making work for shielding unnecessary light transmitting portions or reflecting portions of a plate making film or printing paper, and the like. An object of the present invention is to provide a highly efficient method or device capable of automating or mechanizing discrimination work and light-shielding work in the work without opening the original image part in the output with low resolution. Is.

Incidentally, Japanese Patent Laid-Open No. 2-87145 discloses an embodiment of an apparatus capable of automating an make operation.

[0011]

To solve this problem, the operating method of the present invention comprises: (A) image scanning / reading means for converting a plate-making film or photographic paper on which an image is formed into pixels. Sequential reading is performed for each line that is a column, (B) Binary data of 0 or 1 for each pixel of the read predetermined number of lines is stored in a line memory, and (C) The predetermined number of stored lines On the other hand, the target pixel and a small number of pixels surrounding the target pixel are divided into small areas for determination, and each pixel is shifted in the main scanning direction, and the predetermined small area is set in advance in the small area for determination. If more than one data is present in a concatenated manner, or if the data of the pixel including the target pixel and corresponding to the preset discrimination pattern is all "1", the target pixel is set to the image part. If not, or if not connected or target When the prime is 0, it is determined to be a non-image portion such as noise, and (D) When the target pixel is determined to be an image portion, a mask including the target pixel and a pixel group of a predetermined pattern around the target pixel. Area is set, and the pixels in the mask area are treated as necessary image areas. (E) While shifting the target pixel by one pixel in the main scanning direction, The discrimination mask area setting operation is repeated, and the above (C) is performed for all the pixels on the (F) line.
After performing the operations (1) to (D), one new line is shifted in the sub-scanning direction, and the operations (C) to (D) are sequentially repeated again for the new one line.
(G) The image area or the non-image area is discriminated by outputting or processing the pattern of the mask area set in the step (D) directly or after temporarily holding it in the output memory, and A light-shielding layer is formed by a light-shielding device on a portion of the plate-making film or photographic paper that is not the image portion subjected to the discrimination processing.

[0012]

[Function] The original image to be inspected is scanned by a line sensor, etc.
The reading means sequentially reads each line, the image portion and the non-image portion are discriminated for each pixel by the concatenation method, and the discriminated pixels are bundled and output to the opaque device. Based on the input pixel information, the opaque device shields the non-image portion of the plate-making film or the printing paper with a light-shielding device such as a thermal transfer printing device.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation method of the present invention will be described below with reference to the drawings.

First, a method of discriminating an image portion or a non-image portion used in the operating method of the present invention will be described.

In FIG. 1, 1 is an original image, and the original image 1 has an image portion 3 and a non-image portion 4 on a base portion 2. In the case of this example, the image part 3 is the character "AR", and the non-image part 4 has three (4a, b, 4c), and this image part is caused by, for example, film defects or stains on the plate mount. It is generated and is a target of discrimination with respect to the image portion 3 and a target of light shielding. An example of the discrimination device used for the discrimination is shown in a block diagram in FIG.

That is, the discriminating device 5 is an optical system 6, an image reading / scanning means 7, a line memory-8, and an output memory.
12 and a processor 13. The processor 13 processes the signal input from each memory and outputs a control signal to the operating device 51. Since the image reading / scanning means 7 uses a line sensor as a typical example for the sake of description, it is hereinafter referred to as a line sensor 7.

Returning to FIG. 1 again, the line sensor 7 reads the image data of the original image 1 line by line (see FIG. 1).
(A)). Here, a line is a pixel row in the main scanning direction, and reference numeral 15 in FIG. 1 indicates a line.

Each pixel 10 on the target line is evaluated by the following method. That is, first, a predetermined number of adjacent lines (7 in the column shown in FIG.
The binarized data of (line) is stored in the line memory 8 (FIG. 1 (b)). A small evaluation area 16 (hereinafter referred to as an evaluation window 16) including a target image and a plurality of pixels around the target image is set. In the case of this embodiment, the pixel group is a 7 × 7 matrix (see FIG. 1 (s)). The evaluation window 16 evaluates the target pixel 10a by the connection method (FIG. 1C). That is, line memory
The pixel whose image data on 8 is positive is the target pixel 10a.
, The target pixel is recognized as an image and an evaluation result of “positive” is given. If not, consider it as non-image part or noise,
The evaluation result "negative" is given. A mask area consisting of a predetermined pattern (for example, a rectangular pixel group of m × n pixels including the target pixel in the center in FIG. 1 (u), etc.) is set around the target pixel which is evaluated as “positive”. However, all the pixels in this area are regarded as the necessary drawing line or the area in the vicinity thereof, and the evaluation result “positive” is given. The evaluation result in (1) is stored in an output memory that has a one-to-one correspondence with pixels other than the line memory. At this time, the logical sum of each corresponding pixel is stored in the portion where the already-evaluated pixel and the area overlap (FIG. 1D). The evaluation window 16 is shifted by one pixel in the main scanning direction, and the same evaluation (to) is applied to the pixel adjacent to the target pixel.
I do. When all the pixels on the target line have been evaluated by repeating the operations from to, the line sensor 7 reads the image data of the new line and stores the image data in the line memory.
8 and store. At this time, the oldest line data that has already been evaluated is erased from the line memory 8 (FIG. 1 (t)). Using the line data newly added to the line memory, the same processing is performed for the line adjacent to the above-mentioned target line (FIG. 1 (e)).

Finally, the positive portion of the output memory 12 is regarded as an image, and the negative portion is judged as a non-image portion or noise, and is referred to in the following processing (operation such as operation).

The flowcharts of the above processing are shown in FIGS. FIG. 2 is a flowchart showing the process of reading the original image 1 and inputting it to the line memory.
FIG. 6 is a flow chart showing a procedure of calculation processing and mask area setting for image discrimination by the connection method.

A binarized image read by the line sensor 7 in the process of FIG. 1B is shown in FIG.
It is evaluated in the process of (b). FIG. 4B shows an image temporarily stored in the output memory 12 after the mask area is set in the subsequent process. As shown,
The output memory 12 stores an image in which fine noise such as pinholes found in the original image is removed and a margin is provided around the image by the mask area. This image is input to the operation device 51.

Next, the operation device will be described. Figure 6
Further, in FIG. 7, reference numeral 51 is an operating device. Operation
The device 51 includes a transport device 52, a detection device 53, and a light blocking device 5.
4. The peeling device 55 is provided. The peeling device 55 includes a peeling angle adjusting device 56.

The carrier device 52 comprises three roller pairs 62, 6
3, 64 are arranged along the path 67 of the object 61. The roller pairs 62, 63, 64 are each a roller 65 driven by a driving means such as a pulse motor, and the rollers 65, 63, 64.
The roller 65 and an opposing roller 66 that forms a nip and conveys an object. However, the transport device 52 is not limited to the pulse motor as the drive source of the roller pairs 62, 63, 64, but may be a motor drive utilizing a rotary encoder.

The detection device 53 has an exposure device 68. The exposure device 68 is located on one side of the path 67 of the object 61, and on the opposite side of the path 67 of the object 61, a mirror for changing the optical path.
71 and the line sensor 7 are located, and the light emitted from the exposure device 68 passes through the object 61, and then the optical path changing mirror 7
It is arranged so as to be incident on the line sensor 7 after being reflected by 1 and changing the optical path.

Examples of the object 61 such as a plate-making film according to the present invention include a negative or positive monochrome or color film, a printing paper, a blockboard, etc. in addition to the plate-making film.

The exposure device 68 may be any means capable of performing exposure with desired accuracy and obtaining information by the exposure. For example, a slit is provided between the light source and the object, or exposure is performed from the light source. The light is exposed by exposing the sharp to have a desired width. The exposure device 68 is not particularly limited as long as it can emit light that can be received by the line sensor, and for example, an LED array, a tungsten lamp, a fluorescent lamp, a xenon lamp or the like can be used.

As the line sensor 7, various commonly used ones can be used. For example, a CCD contact type image sensor, a CCD camera, a photo multiplayer, a photoconductive image pickup tube represented by a vidicon, a photodiode, a phototransistor, a solar cell and the like can be used.

Upon detection by the line sensor 7, it is possible to use a lens system that is appropriately enlarged or reduced, if necessary, so that the detection ability can be improved and the apparatus can be simplified. Thus, the resolving power of the line sensor, that is, the degree of detection of a necessary portion can be variously set depending on the combination with the lens system used. Detection of pixels such as a plate-making film may be performed by using a plurality of line sensors, or by using a single or a plurality of line sensors and moving to receive transmitted light or reflected light. The operation of the line sensor 7 is controlled by the detection controller. The output of the line sensor 7 is input to the line memory 8 of the discriminating device 5 described above. Discrimination device 5
Is output to the controller 74. The control device 74 includes an arithmetic device 75 (CPU), a storage device 76, and an auxiliary storage device 7.
7 and an input device 78.

The storage device 76 and the auxiliary storage device 77 store the information obtained from the discriminating device 5 in a desired area of the object, and may be any writable and readable memory. As the arithmetic unit (CPU) 75,
A computer can be used.

Further, the storage device 76 stores at the timing of the discriminating device 5 and the like, and reads it at the timing of the light shielding device.
Further, the data read out from the storage device 76 at the timing of the shading device is converted into, for example, a head control signal of a thermal printer, which is an example of the shading device, and the pulse width is controlled to control the thermal head. Perform temperature control. The input device 78 is not particularly limited as long as it can input the pixel size, but a keyboard or the like can be used. The detection of the image portion or the unnecessary portion of the object is performed by the above-described discrimination processing method.

As the shading device 54, a thermal transfer printer 81 for shading based on position information can be used. As shown in FIG. 7, the thermal transfer printer 81 has a thermal head 82 and a thermal transfer body 83 as main components, and the thermal transfer printer 81 is based on the position information.
The thermal head 82 is instructed to form the light shielding layer 97. That is, according to the position information, the thermal head 82 provides the light-shielding layer 97 composed of the light-shielding material on the object 61 from the thermal transfer member 83 carrying the light-shielding material. 8
4 is an unwinding roller for supplying the thermal transfer member 83,
Reference numeral 85 is a winding roll for winding the used thermal transfer member 83.
It shows La. The roller 86 is a constituent member of the transport device 52 and also serves as a platen of the thermal transfer printer 81.

As the heat-sensitive transfer member 83, a transfer material containing a pigment or dye and a heat-melting film forming material and capable of heat transfer at about 50 to 130 ° C. is provided on a support. The pigment or dye satisfies the light-shielding condition in an exposure operation which is a post-process using a plate-making film or printing paper. As the heat-meltable film forming material,
There is wax or other material.

Unwinding roller 84 and winding roller 85
A path 90 of the heat-sensitive transfer body 83 is formed between them and a back tension roller 87, a heat-sensitive transfer printer 81, and a conveyance roller pair 88 are arranged along the path 90.

The thermal transfer printer 81 has a holder 91, and a thermal head mounting frame 92 is rotatably mounted on the holder 91 by a shaft 93.

A thermal head 82 is fixed to the tip of the thermal head mounting frame 92. Also the holder 9
1, a thermal head pressing spring 94 is attached, and the thermal head pressing spring 94 presses the thermal head 82 toward the platen roller 86. A cam follower 95 is attached to the holder 91, and the cam follower 95 is in contact with the cam 96. Therefore, the holder 91 is oscillated and displaced according to the rotation angle of the cam 96, and the platen roll is moved.
It approaches or separates from La 86.

The object 61 and the heat-sensitive transfer member 83 are supplied to the inlet side of the platen roller 86 and overlapped with each other, and the thermal head 82 is heated by the position information, and the thermal head 82 heat-melts the thermal transfer material. Thermal transfer body 8
3, the heat-sensitive transfer material is transferred to a portion other than the detected image portion of the object 61 or an unnecessary portion to form the light shielding layer 97. The light-shielding layer preferably has necessary resistance in a work environment that the plate-making film or the like receives after being transferred or applied to an unnecessary portion of the plate-making film or the like, and a light-shielding layer that suits each work environment is selected. be able to. At the exit side of the platen roller 86, the object 6 is removed by the peeling device 98.
1 and the thermal transfer member 83 are separated.

The peeling device 98 is a film guide roller 91.
And a transfer member guide roller 102. The film guide roller 91 guides the object 61 to determine its traveling direction, and the transfer member guide roller 102 guides the heat-sensitive transfer member 83. Determine its progress. However, in this embodiment, the platen roller 86 also serves as the film guide roller 91.

Platen roller 86 (film guide roller
Object 91 and thermal transfer member 83 on the exit side of
The angle θ between and is the peeling angle, and this angle θ is the operation angle.
As mentioned above, it affects the quality of the black circle. The peeling angle θ is adjusted by the peeling angle adjusting device 56. The peeling angle adjusting device 56 has a long hole 103 in a holder 91, and a shaft 104 of a transfer body guide roller 102 is displaceably fitted in the long hole 103 so as to fix the shaft 104 in the longitudinal direction of the long hole 103. By selecting the position, the position of the transfer member guide roller 102 is changed, and thus the isolation angle θ can be adjusted.

In addition, the peeling angle can be adjusted by varying the position of the roller in contact with the object, varying the position of the roller in contact with the heat-sensitive transfer material, or both. Etc. Regarding the adjustment of the peeling angle, it is necessary that the angle can be adjusted within the range of 10 to 90 °, preferably 20 to 60 °. As the adjustment stage, for example, adjustment can be made every 1 degree, every 5 degrees, every 10 degrees. By this angle adjustment, it becomes possible to deal with a change in the type of the thermal transfer material, a change in the type of the target object, and the like with one device.

After the transfer using the heat-sensitive transfer member 83 is performed, the conductive roller 115 which is an example of the static electricity removing means.
The static electricity of the target object 61 is removed by bringing the target object 61 into contact with the target object at a conveyance speed. The roller pair 62 has an inlet side and an outlet side, and a thermal transfer printer 81.
Detectors 112, 113, 114 are disposed on the entrance side of the. The detectors 112, 113, 114 detect the object 61 in the path 67, and a means for blocking the light by the object by a combination of a small light source and a phototransistor, a means for operating the microswitch by touching the object, Alternatively, the object is means for actuating the microswitch by pushing up the roller.

The operation of the opaque device thus constructed is as follows. Object 61 which is a plate-making film
Is inserted into the inlet 111 of the operating apparatus 1. When it is inserted, the detector 112 detects the object 61, and the conveyance by the conveyance device 2 is started. Note that the drive for carrying can be always operated after the power is turned on, but preferably the carrying is started from the insertion of the object 61.
The conveyed object 61 is detected by the detector 113 and generates a signal which serves as a reference for determining the position of the object 61 necessary for the subsequent operation. Although the two detectors 112 and 113 are used here, it is also possible to use one detector also as one. The detection by the detector 113 has a function for positioning. That is, the detection start information can be a reference for position information by the next exposure, light reception, and detection. It should be noted that a mark indicating the reference position provided in advance on the object may be used.

The object 61 being conveyed is exposed by the exposure device 68 of the detection device 53. Exposure device 6
Reference numeral 8 includes an illumination light source and a slit.

Light from the object 61 (in FIG. 5, transmitted light is shown, but it may be reflected light) is incident on the line sensor 7. The object 61 that has passed through the exposure device 68 is detected by a detector 114 provided in front of the light shielding device 54. This detection also serves as a reference for determining the light blocking position.

Information from the detection by the detector 113 serves as a reference, and the position of the detected image information can be automatically set based on this reference from the transport distance or the transport speed.
That is, the distance from the start point by the detector 113 can also be obtained, and this position information is stored and combined with the coordinate information of the object 61 from the detector, and the light shielding device 54
The light can be shielded without being pre-positioned. By the detection by the detector 114 provided in front of the light shielding device 54, it is possible to automatically process from the reference information and the detected position information. In addition,
The distance between the detector 113 and the exposure location, and the detector 1
The distance between 14 and the shading device 54 does not necessarily have to be the same. These calculations and processes are performed by the calculation device 75 and stored in the storage device 76 and the auxiliary storage device 77. That is, the exposure device 68 operates according to the size input from the input device 78 to the arithmetic device 75, and further, based on the detection pitch, an instruction from the detection controller 73 via the arithmetic device 75. The image information of the object 61, which is the information from the detection device 53, is sequentially stored in the storage device 76 under the control of the arithmetic device 75. In the device according to the present invention, the arithmetic device 75 is not always essential, and in some cases, the arithmetic device 75 may not be provided.

Next, the object 61 reaching the light shielding device 54 is superposed on the heat-sensitive transfer body 83 by the platen roller 86.
At this time, the holder 91 is displaced by the operation of the cam 96 (displaced in the counterclockwise direction in FIG. 5), and the elastic pressing force of the thermal head pressing spring 94 acts to actuate the thermal head 8.
2 is pressed against the platen roller 86 to sandwich the heat-sensitive transfer body 83 and the object 61 which are overlaid. The thermal head 82 is arranged at a right angle to the carrying direction, and the thermal head 92 is heated by the result of the logical product of the positional information of both the auxiliary storage device 77 and the object 61, and the transfer body is melted by heat. A light-shielding layer is formed on the detected unnecessary portion on the object 61.

After the formation of the light-shielding layer is completed, the heat-sensitive transfer member 83 and the object 61 which are overlaid are sent out from the light-shielding device 54 and enter the peeling device 55. In the peeling device 55, the object 6
1 is guided by the film guide roller 101 toward the roller pair 64, while the thermal transfer member 83 is guided by the transfer member guide roller 102 toward the take-up roller 85.
In this way, the object 61 and the thermal transfer member 83 are guided in the directions different from each other by the peeling angle θ, so that the two are peeled off. When adjusting the peeling angle, the shaft 104 is moved in the longitudinal direction of the long hole 103 formed in the holder 91 to change the position of the heat-sensitive transfer member guide roller 102. As a result, the transport direction of the thermal transfer member 83 changes, and the peeling angle changes.

[0047]

According to the operation method of the present invention, an unnecessary portion such as a pinhole in a plate-making film or the like is detected by a discrimination processing method capable of setting a necessary margin near the original image. Focusing on the fact that this unnecessary portion should be shielded from light, compared to the conventional mask sheet use method or correction liquid coating method, simple, quick and accurate plate making (operation
You can do it even if you don't have to be an expert.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing a determination process.

FIG. 2 is a flowchart showing image reading / input.

FIG. 3 is a flowchart showing a calculation process by a concatenation method.

FIG. 4 is an explanatory diagram showing contents of each memory in the discrimination processing device.

FIG. 5 is a block diagram showing a discrimination processing device.

FIG. 6 is a schematic side sectional view of the operating device.

FIG. 7 is an enlarged side view illustrating a thermal transfer portion.

[Explanation of symbols]

 1 original image 2 ground part 3 image part 4 (4a, 4b, 4c) non-image part 5 discriminating device 6 optical system 7 image reading / scanning means (line sensor) 8 line memory-10 pixels 10a target pixel 12 output memory-13 Processor 15 Line 16 Evaluation window 51 Operation device 52 Conveyor device 53 Detection device 54 Shading device 55 Peeling device 56 Peeling angle adjusting device 61 Object 62, 63, 64 Roller pair 65 Roller 66 Opposing roller 67 Path 68 Exposure device 71 Optical path changing mirror 74 Control device 75 Computing device (CPU) 76 Storage device 77 Auxiliary storage device 78 Input device 81 Thermal transfer printer 82 Thermal head 83 Thermal transfer body 84 Unwinding roller 85 Rewinding Roller 86 Platen Roller 87 Back Tension Roller 88 Transport Roller Pair 90 Route 9 1 Holder 92 Thermal Head Mounting Frame 93 Shaft 94 Thermal Head Pressing Spring 95 Cam Follower 96 Cam 97 Light-Shielding Layer 98 Peeling Device 101 Film Guide Roller 102 Transfer Body Guide Roller 103 Long Hole 104 Shaft 111 Inlet 112 , 113, 114 Detector 115 Conductive roller

Claims (1)

[Claims] 1. (A) A plate-making film or photographic paper on which an image is formed by an image scanning / reading unit is sequentially read for each line that is a pixel row, and (B) a predetermined number of read lines. Binary data of 0 or 1 for each pixel is stored in a line memory, and (C) for a predetermined number of stored lines, a small area for discrimination consisting of a target pixel and a predetermined number of pixels around it. If there is a predetermined number or more of 1 data connected in advance in the small area for discrimination, the target pixel is divided, or the target pixel is divided. Including If the data of the pixels corresponding to the preset discrimination pattern are all "1", the target pixel is discriminated from the image part, or if it is not connected or the target pixel is 0, noise is generated. And the non-image part such as If it is determined to be an image part, a mask area consisting of the target pixel and a pixel group of a predetermined pattern around it is set, and the pixels in the mask area are treated as necessary image areas. , (E) while shifting the target pixel by one pixel in the main scanning direction,
The determination mask area setting work of (D) is repeated, and (F)
When the operations (C) to (D) are performed on all the pixels on the line, the new one line is shifted in the sub-scanning direction, and the new one line is again subjected to the (C).
~ Repeating the operations of (D) in sequence, and (G) outputting or processing the pattern of the mask area set in the step (D) directly or temporarily after holding it in the output memory. An image method for discriminating an image portion or a non-image portion by the method described above, and forming a light-shielding layer with a light-shielding device on a portion of the plate-making film or printing paper which is not the image-treated portion.