JP3313779B2 - Image processing apparatus and image processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and an image processing apparatus.
For example, the present invention relates to an image processing apparatus and an image processing method having a function of adding specific information to a reproduced image.

[0002]

2. Description of the Related Art In recent years, as the performance of color copying machines and color printers has been improved, the possibility of unauthorized use of the same has arisen. However, it has been almost impossible to specify which device has made the copy or limit the person who made the copy, based on the copied copy.

In order to prevent such illegal copying, studies have been made to identify such cases by a color copying machine or a color printer itself and to forcibly prohibit illegal copying. In this case, a circuit for determining a specific original is used in a color copying machine or a color printer, but since the number of image patterns that can be registered is limited in this circuit, it is not possible to register all types of specific originals. The disadvantage is that it is possible.

In a color copying machine or a color printer having an external interface, such a circuit for determining a specific document may not function. For example, if the image data on the external interface is data of three primary colors of red, green, and blue, each of which is simultaneously transmitted, the above-described determination circuit can operate. However, the image data on the external interface is cyan,
In the case of data specifications that match the individual characteristics of the printer, such as magenta, yellow, and black, there are a plurality of types of color reproducible combinations, which requires a plurality of types of image patterns for determining a specific document. Further, it is very difficult to determine even a specific document is detected, and the number of images of the specific document that can be determined is reduced. Further, when image data representing the components of each color is sent in a frame-sequential manner for each color, the image data must be stored in a memory for determination, which increases the cost of the apparatus, and this causes the identification There is also a disadvantage that a great deal of expense is required for determining the document.

Further, assuming that the above problem of the image data sent from the external interface has been solved, even if the number of specific documents to be targeted is limited to a recognizable number and the recognition is performed, the registration is not performed. It is impossible to avoid erroneously determining that a picture very similar to a specific original is a specific original or erroneously determining a dirty specific original as not a specific original.

As described above, it is important to add a means for detecting a specific document to the apparatus itself. However, since the detection capability of the specific document is limited, copying of a document which should not be copied is performed. In such a case, it is important to specify the copying machine that made the copy or the person who made the copy. Against this background, a technique for adding a copying machine or information capable of identifying a copied person to a document image has been studied. The technique uses an output color component (for example, yellow) that is least noticeable to human eyes among output color components (for example, magenta, cyan, yellow, and black) of a copying machine, and outputs an image signal of the output color component. (For example, by adding a constant value), a small number or code representing the serial number of the copying machine or the like is struck small and repeated at regular intervals.

[0007]

However, in the above technique, even though yellow is the least visible output color component, modulation of an image signal must be minimized. When using a machine for design purposes, it is troublesome to see patterns that are not in the manuscript.

Further, when copying an original, even if the original is of a uniform color, the image signal is not always uniform due to variations in the sensitivity of the CCD, but the host uses an external interface of the color copier. When printing out an image on a computer, it is possible to directly output CG (computer graphics), so that there is a sufficient uniform area at the image signal level. then,
When the yellow component is modulated, there is a disadvantage that the additional pattern becomes conspicuous particularly in a light gray or light blue uniform portion.

[0009] has been conventionally considered, and small cohesive unit pattern numbers and codes representing the additional information, the method of configuring the additional pattern repeating the unit pattern at regular intervals, just because the unit pattern is held together small It is easy to notice and human eyes can recognize regular patterns more easily than patterns in random arrangement. Therefore, it becomes more noticeable when unit patterns are arranged in a grid. Therefore, the degree of modulation of the image signal must be reduced, and additional information may not be read depending on a specific document.

Therefore, it is difficult to identify all output images when they are viewed with the naked eye, and to satisfy the condition of having the opposite direction that it can be reliably identified by a certain method in a copy such as a specific original document. It is necessary to consider various modulations and patterns. Therefore, an object of the present invention is to add information for identifying a copying machine or a person to a reproduced image of an original image when the information for identifying a device is added.
An object of the present invention is to provide an image processing apparatus and an image processing method capable of adding a pattern to be represented in a pattern that is as inconspicuous as possible.

Furthermore, there is a reality that the density of an output image is generally affected by the environment such as indoor temperature and humidity in a copying machine. Therefore, after the above processing (pattern addition) is performed, when the pattern is output, the pattern may be visible depending on the environment. Therefore, another object of the present invention is to operate an apparatus for an image signal without being affected by the environmental state of the apparatus.
An object of the present invention is to provide an image processing apparatus and an image processing method for adding a pattern representing information for identification so as to be difficult for a human eye to identify.

[0012]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, an image processing apparatus according to the present invention comprises: an addition unit (109) for adding a pattern representing information for specifying the apparatus to an input image signal so that the pattern is hardly discernible to human eyes. , the image signal obtained by said adding means,-out based on the environmental change data in the device,該装
A constant level of the pattern is output regardless of environmental changes
A tone conversion processing means (703) for performing a tone conversion process so as to obtain power . Also, preferably,
A recording unit (212) for recording an image based on the image signal obtained by the gradation conversion unit; Further, in order to solve the above-described problems and achieve the object, an image processing method according to the present invention identifies a pattern representing information for identifying a device with respect to an input image signal to human eyes. An adding step of adding the image data to the image signal obtained by the adding step, based on environmental fluctuation data in the apparatus.
At a certain level regardless of environmental fluctuations in the device.
And a gradation conversion process for performing a gradation conversion process so that a turn output is obtained . Preferably, the image processing apparatus further includes a recording step of recording an image based on the image signal obtained in the gradation conversion step.

[0013]

According to this structure, the adding means adds a pattern representing information for specifying the apparatus to the human eye so that it is hard to identify, and the gradation conversion processing means adds the pattern to the image signal obtained by the adding means. in contrast,-out <br/> group Dzu to environmental change data in the device, before the constant level irrespective of the environmental changes in the system
A gradation conversion process is performed so that the pattern output is obtained .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the following embodiments, an example of a copying machine will be described as an application example of the present invention. However, the present invention is not limited to this, and it is needless to say that the present invention can be applied to various other apparatuses. Each device to which the present invention can be applied is:
To prevent counterfeiting, specific documents such as banknotes and securities are symmetric.

<First Embodiment> [Overview of Apparatus] FIG. 2 is a side sectional view showing the internal structure of a color copying machine according to a first embodiment of the present invention. In FIG. 2, reference numeral 201 denotes an image scanner unit, which is 400 dpi.
This is a part that reads an original at a resolution of (dot / inch) and performs digital signal processing. Reference numeral 202 denotes a printer unit which prints out an image corresponding to a document image read by the image scanner unit 201 on a sheet of paper at a resolution of 400 dpi in full color.

In the image scanner unit 201, 20
Reference numeral 0 denotes a mirror surface pressure plate, and a platen glass (hereinafter, “platen”)
The original 204 on the original 203 is irradiated by a lamp 205, guided to mirrors 206, 207, and 208, forms an image on a three-line sensor (hereinafter referred to as a “CCD”) 210 by a lens 209, and outputs full-color information red ( R), green (G), and blue (B) components are sent to the signal processing unit 211. The speed of the lamp 205 and the mirror 206 is v, and the speed of the mirrors 207 and 208 is は.
At v, the front surface of the document is scanned (sub-scanning) by mechanically moving the line sensor in a direction perpendicular to the electrical scanning (main scanning) direction.

The signal processing section 211 electrically processes the read image signal, decomposes the image signal into magenta (M), cyan (C), yellow (Y), and black (Bk) components. Send to 202. In addition, M, C,
One component of Y and Bk is sent to the printer unit 202, and one printout is completed by a total of four document scans.

The M, C, Y, and Bk image signals sent from the image scanner unit 201 are sent to the printer video processing unit 212. Printer video processing unit 212
Corresponds to the semiconductor laser 213 according to the transmitted image signal.
Is modulated. The laser light is applied to a polygon mirror 214,
It scans the photosensitive drum 217 via the f-θ lens 215 and the mirror 216.

Reference numeral 218 denotes a rotary developing unit, which includes a magenta developing unit 219, a cyan developing unit 220, and a yellow developing unit 22.
1. The black developing unit 222 includes four developing units that alternately come into contact with the photosensitive drum 217 and develop the electrostatic development formed on the photosensitive drum with toner. Reference numeral 223 denotes a transfer drum which wraps a sheet supplied from a sheet cassette 224 or 225 around the peripheral surface and transfers an image developed on the photosensitive drum to the sheet.

After the four colors of M, C, Y, and Bk are sequentially transferred in this manner, the sheet passes through the fixing unit 226, and is discharged after the toner is fixed on the sheet. [Image Scanner] FIG. 1 is a block diagram showing a circuit configuration of an image scanner unit 201 according to the first embodiment. In the figure, reference numeral 210 denotes a CCD line sensor having R, G, and B spectral sensitivity characteristics, and 101 denotes an A / D &
S / H circuit 102, shading correction circuit 103
A bridge correction circuit; 104, an input masking circuit;
5 is a LOG conversion circuit, 106 is a masking / UCR (under color removal) circuit, 107 is a gamma correction circuit, 108 is an MTF correction circuit, 109 is a pattern addition circuit, and 110 is a modulation circuit.

In the above configuration, the CCD line sensor 2
The image signal input from the A / D & S / H circuit 1
After being subjected to A / D conversion and S / H at 01, they are output as 8-bit outputs 0 to 255, respectively. further,
The shading correction circuit 102 performs shading correction and black correction. The connection correction circuit 103 performs connection correction. That is, the bridge correction circuit 103
Since the CCD line sensor 210 is arranged at a fixed distance, the R signal and the G signal are delayed and their spatial displacement is corrected. In the input masking circuit 104, the correction to the NTSC signal is performed, and the LOG conversion circuit 1
At 05, the conversion from the luminance signal to the density signal is performed.
In the masking / UCR circuit 106, the magenta (M), cyan (C), yellow (Y), and black (Bk) signals for output are read out of the three input signals (R, G, B). Each bit is output with a predetermined bit length (for example, 8 bits) in a frame sequence. γ correction circuit 107
M or RAM and its peripheral circuits. MTF
In the correction circuit 108, edge enhancement or smoothing is performed. The pattern adding circuit 109 performs a process of adding a pattern that cannot be identified by human eyes to the copied image. The modulation circuit 110 is a circuit for encryption, and includes, for example, a ROM, a RAM, and peripheral circuits. For example, when the video length is 8 bits, the contents of these ROMs and RAMs are obtained by a one-to-one correspondence function created by a well-known random number generation formula in an input range of 0 to 255 and an output range of 0 to 255. Can be

[Printer Video Processing Unit] FIG. 7 is a block diagram showing the configuration of the printer video processing unit 212 according to the first embodiment. In the figure, reference numeral 701 denotes a frequency conversion circuit, which converts the frequency of a video sent from the reader unit 201 into an image clock of a printer. Frequency conversion circuit 7
01 is a FIFO. Reference numeral 702 denotes a demodulation circuit for encryption, for example, ROM or RAM.
And its peripheral circuits. ROM and R
The contents of the AM memory are inverse functions of the functions handled by the modulation circuit 110 described above. The output of the demodulation circuit 702 is a video image at the time of printout. A gamma correction circuit 703 of the printer unit includes a RAM and a peripheral unit for selecting one of a video and a CPU (not shown) for access. The gamma correction circuit 703 can obtain a constant output irrespective of environmental fluctuations by rewriting the table based on environmental fluctuation data with a CPU (not shown) taking into account the density change of the printer. In this way, it is not always discernible to the human eye, but if a certain method is used, it is possible to obtain an output with a dot pattern that can be read reliably. A D / A converter 704 converts a video into an analog signal. Reference numeral 705 denotes a PWM (pulse width modulation) modulation circuit which performs PWM modulation on an analog signal and sends the analog signal to a laser driver 706. Reference numeral 706 denotes a laser driver, which outputs M, C, and C signals transmitted from the PWM modulator 704.
The semiconductor laser 213 is driven according to the Y and K video signals.

[Pattern Adding Circuit] FIG. 3 is a block diagram showing the structure of the pattern adding circuit 109 according to the first embodiment. In the figure, reference numeral 301 denotes a sub-scanning counter;
2 is a main scanning counter, 303 is a look-up table RAM (hereinafter referred to as “LUT”), and 304 is AND
Gate, 305 is a flip-flop, 306 is an inverter, 307 is an AND gate, 308 is a register, 309
Is an AND gate, and 310 is an adder.

Here, the sub-scanning counter 301 repeatedly counts the main scanning synchronizing signal HSYNC and the main scanning counter 302 counts the pixel synchronizing signal CLK with a 7-bit width, ie, 128 cycles. Further, the LUT 303 is a random access memory (hereinafter, referred to as “RAM”) holding a pattern to be added. The LUT 303 stores the lower 5 bits of the count value of each of the sub-scan counter 301 and the main scan counter 302 from the lower 5 bits. Each of the removed 4 bits is input. The output of the LUT 303 refers to only one bit, and this one bit is supplied to the main scanning counter 301 and the sub-scanning counter 302 by the AND gate 304.
AND with the upper two bits of

The result is synchronized by the flip-flop 305 with the CLK signal, and after ANDed with both the 2-bit CNO signal “0” and the CNO signal “1” by the AND gate 307, AND gate 3
09. CNO “0” and CNO “1” are set by a CPU (not shown), and M → 0, 0, C
→ 0,1, Y → 1,0, K → 1,1 are set respectively. In this case, a valid signal is generated only when CNO = 2, that is, when printing is currently performed in yellow.

Here, the level (modulation amount) of the pattern to be added is stored in a register 308 set in advance by a CPU (not shown).
It is valid only when CNO = 2 (when the surface is yellow) and is added to the image data V by the adder 310. 31
1 is an AND gate, 312 is a register set by a CPU (not shown), and becomes 0 at reset.
Therefore, if the pattern addition circuit is not accessed by the CPU, the input video is modulated and output fixed at 0.

The additional pattern is added only with yellow toner so that it is difficult for the human eye to identify it. However, the additional pattern has weak discriminating ability with respect to a pattern in which human eyes are drawn with yellow toner. It is a thing that utilizes that. FIG. 4 is a diagram illustrating an additional pattern according to the first embodiment. L
The UT 303 holds a dot pattern as shown in FIG. 4, that is, an additional pattern. One cell in FIG. 4 corresponds to one bit held in the LUT 303, where white represents 0 and black represents 1. The left and right directions correspond to the lower 4 bits of the address, and the upper and lower directions correspond to the upper 4 bits of the address. 256 bits constitute an additional pattern. A line in which the upper bits of the address on the left side of FIG. In addition, the six lines of the upper 4 bits of the address 2, 3 and 8, 9, 9, E, and F, which are shaded on the left side of FIG. 4, are lines on which dots are placed, and are used every two lines. As shown on the right side of FIG. 4, each of these two lines represents 16 types of information by hitting one or two 2 × 2 bit dots at predetermined locations. That is, each two lines represent 4-bit information. Since these two lines are three below the mark,
It can represent two bits of information. For example, "BBB" or "12"
When two lines of dot arrangement are continuous like "3",
This is to prevent dots from being connected vertically or diagonally to make the additional pattern conspicuous.

The LUT 303 shown in FIG.
(Not shown) so that the information for specifying the source of the copy document, such as information for specifying the copying machine, is converted into data of the additional pattern. It is. Further, since the data excluding the least significant bit of the main scanning counter 302 and the sub-scanning counter 301 in FIG.
One bit on the UT 303 corresponds to 2 × 2 pixels on a copy. This is because, in the printer unit 202 of the present embodiment, for example, a well-known 200-line process is performed in an image area, and therefore, it may be difficult to read by adding a pattern in units of one pixel.

[Copy Result] FIG. 5 is a diagram showing an example of a copy result according to the first embodiment, and FIG. 6 is a diagram for explaining the effect of the first embodiment. First, in FIG.
Is an added pattern, and the content held in the LUT 303 is added as an image. In the example shown in FIG. 5, a pattern meaning “3FC” is added in a pattern of 32 pixels × 32 pixels so that it is difficult for the human eyes to recognize, and is repeated for every 128 pixels of main scanning and 128 lines of sub-scanning. . Therefore, by setting this as a machine-specific serial number or a pattern that encodes the serial number,
By judging the copy, the copied device can be limited.

Further, in the present embodiment, the pitch at which a pattern is added is set every 128 pixels (or lines) in the main scanning. In the present embodiment, the pitch is 400 dpi (dot / inc.).
Since the resolution is h), a pattern is added about every 8 mm. This is an interval at which the additional pattern is reliably placed on a watermark or a surrounding margin of a bill which is easy to read.

In the method using the additional pattern described above, as shown in FIG. 6B, the method of modulating the image signal using the numerical values or the like as it is, as shown in FIG. With a method using a pattern as shown in FIG. 6A, it is possible to reduce the number of pixels to be modulated and make the additional pattern less noticeable. In this way, modulation is performed by recording a specific additional pattern on a copy with a mark indicating a position reference and a pattern of one or more dots in order to limit devices and the like in the copy. Since the number of pixels to be added is reduced and the additional pattern is made less noticeable, it is possible to reduce image quality deterioration. Further, since the conversion of the additional pattern into a pattern of dot arrangement is a kind of encryption, it also has an effect that this pattern is hardly operated intentionally by a third party.

Here, another point is that the modulation circuit 110 and the demodulation circuit 702 which constitute the encryption circuit.
After the pattern adding circuit. As a result, it is possible to add a pattern independent of encryption. That is, since the modulation circuit is provided after the pattern addition circuit, the pixels of the pattern addition section are prevented from being messed up, and since the modulation circuit and the demodulation circuit are provided after the pattern addition circuit, the function of the encryption is sufficiently satisfied. be able to.

As described above, according to the first embodiment, the following effects can be obtained. That is, (1) The specific pattern added to limit the apparatus and the like in a copy is represented by dispersed dots, thereby making the pattern less noticeable and reducing image quality deterioration. Also, since converting the additional information into a pattern of dot arrangement is a type of encryption, it also has the advantage that it is difficult to operate intentionally. (2) A pattern can be added which is not affected by the environment. (3) Since the printer unit has the gradation processing, it is possible to add a pattern independent of the environment without performing complicated operations such as communication between the reader and the printer. <Second Embodiment> Next, a second embodiment in which the gamma correction circuit is improved will be described.

FIG. 8 is a block diagram showing the configuration of the gamma correction circuit according to the second embodiment, and FIG. 9 is a diagram for explaining the characteristics of the gamma correction circuit. In the second embodiment, as shown in FIG. 8, the gamma correction circuit 703 is realized by hardware.
8, the gamma correction circuit 703 includes a selector 802,
815, a register 803 set by a CPU (not shown)
808, 816, 817, multiplier 801 and adder 81
2, comparators 818, 819, PAL 820, inverter 809, AND gates 810, 813, NAND
A gate 811 and an OR gate 814 are provided.

The gamma correction circuit 703 can be selected by three linear equations according to the input video signal.
The registers 803 to 805 are used to set the inclination to 0 to 8 times 1
/ 32 steps, and register 806
808 is a y-intercept and can be set from -100H to + FFH. Reference numeral 813 denotes a 0 limiter and 814 denotes an FF limiter. Registers 816 and 817, comparators 818 and 819, and PAL 820 determine which area the input data belongs to. In such a hardware configuration, in order to obtain the characteristics shown in FIG.
1 ← 0AH, reg82 ← 80H, reg83 ← 1A
H, reg84 ← 20H, reg85 ← 180H, re
g86 ← 40H, reg87 ← 60H, reg88H ←
This can be realized by setting A0H. <Third Embodiment> Next, a third embodiment in which the gamma correction circuit is improved will be described.

FIG. 10 is a block diagram showing the configuration of the gamma correction circuit according to the third embodiment. In the figure, 1001
Indicates a ROM for γ correction. In this embodiment, RA
M, an example is shown in which not only hardware but also a ROM 1001 realizes a γ correction circuit. In this case, it can be realized by previously obtaining a density correction table according to each environmental condition, having a plurality of tables, and switching these depending on the environmental state. This is shown in FIG. 10 in which the upper three bits are switched by a CPU (not shown) depending on the environment.

In each of the embodiments described above, a laser beam printer has been described as an example. However, the present invention is not limited to this, and can be applied to an ink jet printer and a thermal transfer printer. In particular, a so-called bubble jet type printer using a head that discharges liquid droplets using film boiling due to thermal energy may be used.

Further, in each of the above-described embodiments, the color to be added is yellow, but the present invention is not limited to this. For example, an inconspicuous color such as yellow-green or gray or light purple or light green is used. A color with high brightness may be used. Also,
In each of the above-described embodiments, the original image is input by the image scanner. However, the present invention is not limited to this. Still video cameras, those input by a video camera, and those created by computer graphics It may be.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus.

[0040]

As described above, according to the present invention,
To the input image signal, a pattern representing information for specifying the device is added to the human eye so that it is hard to identify, and the image signal to which the pattern is added is added to the environmental fluctuation data in the device. -out group Dzu, regardless of environmental changes in the system
The gradation conversion process is performed so that the pattern output at a certain level can be obtained . This makes it possible to add a pattern representing information for specifying an apparatus to an image signal without being easily recognized by human eyes, without being affected by the environmental state of the apparatus. As a result, it is difficult to identify all output images when they are seen with the naked eye, and it is possible to reliably identify a copy of a specific document such as a target securities by any method, thereby preventing abuse.

[Brief description of the drawings]

FIG. 1 is an image scanner unit 201 according to a first embodiment.
FIG. 3 is a block diagram showing a circuit configuration of FIG.

FIG. 2 is a side sectional view showing the internal configuration of the color copying machine according to the first embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a pattern adding circuit 109 according to the first embodiment.

FIG. 4 is a diagram illustrating an additional pattern according to the first embodiment.

FIG. 5 is a diagram illustrating an example of a copy result according to the first embodiment.

FIG. 6 is a diagram illustrating the effect of the first embodiment.

FIG. 7 shows a printer video processing unit 21 according to the first embodiment.
2 is a block diagram illustrating a circuit configuration of FIG.

FIG. 8 is a block diagram showing a configuration of a gamma correction circuit according to a second embodiment.

FIG. 9 is a diagram illustrating characteristics of the γ correction circuit according to the second embodiment.

FIG. 10 is a block diagram showing a configuration of a gamma correction circuit according to a third embodiment.

[Explanation of symbols]

 Reference Signs List 101 A / D & S / H circuit 102 Shading correction circuit 103 Bridge correction circuit 104 Input masking circuit 105 LOG conversion circuit 106 Masking / UCR circuit 107 γ correction circuit 108 MTF correction circuit 109 Pattern addition circuit 110 Modulation circuit 200 Mirror surface plate 201 Image scanner 202 Printer 203 Platen 204 Document 205 Lamp 206, 207, 208 Mirror 209 Lens 210 CCD 211 Signal processing unit 212 Laser driver 213 Semiconductor laser 214 Polygon mirror 215 f-θ lens 216 Mirror 217 Photosensitive drum 218 Rotary developing unit 219 Magenta developing unit 220 Cyan Developing unit 221 Yellow developing unit 222 Black developing unit 223 Transfer drum 224, 225 Paper cassette 226 Fixing unit To

Continuation of the front page (56) References JP-A 1-316783 (JP, A) JP-A 4-227365 (JP, A) JP-A 2-297496 (JP, A) JP-A 3-230975 (JP) JP-A-59-171252 (JP, A) JP-A-2-294882 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1/38-1/393 G06T 1/00 500

Claims (4)

(57) [Claims] An adding unit (109) for adding a pattern representing information for specifying a device to the input image signal so as to be difficult for a human eye to identify; and an image signal obtained by the adding unit. in contrast,-out based on the environmental change data in the device, the environmental change in the device
Irrespective of the level of the pattern output
And a gradation conversion processing means (703) for performing a gradation conversion process. 2. The image processing apparatus according to claim 1, further comprising recording means for recording an image based on an image signal obtained by said gradation conversion means. 3. An adding step of adding a pattern representing information for specifying a device to an input image signal so that the pattern is hardly discernible to human eyes. -out based on environmental change data in the device, the environmental change in the device
Irrespective of the level of the pattern output
And a gradation conversion processing step of performing a gradation conversion processing. 4. The image processing method according to claim 3, further comprising a recording step of recording an image based on an image signal obtained in said gradation conversion step.