JPH0946524A - Image processing unit and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the gradation correction processing by controlling the gradation correction processing to regulate a total amount of a recording medium in response to a set resolution so as to form an output image in response to the set high resolution in an excellent way. SOLUTION: An output gradation correction characteristic revision means 19 does not apply any revision to a gradation correction table storing output correction curves corresponding to low resolution recording when a revamping degree setting means 18 designates the low resolution recording, and sets a gradation correction table having a characteristic reducing an output correction cure both for input and output at the same rate to an output gradation correction means 20 when the revamping degree setting means 18 designates a high resolution recording. Thus, a color correction section 2 conducts under color reduction/black level correction processing by selecting a minimum CMY to be K in this way, a color correction section 1 obtains the value K based on the product of the CMY before obtaining a CMYK signal and conducts correction in advance based on the value K. Thus, a gray balance of a CMYK signal outputted from a color correction section 2 is improved.

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 method for performing color processing.

[0002]

2. Description of the Related Art Conventionally, as this type of apparatus, a host apparatus that transfers print data to a printing apparatus, and print data by receiving print data from the host apparatus and adhering a plurality of colors of ink to a printing surface according to the data There is a system including a color ink jet recording apparatus for performing.

In these systems, the image data is handled by the RGB three primary colors in order to interactively process with the display device in the host device, while the recording device uses CMYK4 for printing with the inks of four colors of CMYK. It is generally handled by color.

In such a system, from the RGB value depending on the display device to the C value depending on the recording device.
Correction / conversion processing to MYK values must be performed.
At this time, the above conversion process may be performed on all pixels after creating one page of data to be printed by the recording device, but recently, to increase the processing speed, one page of data is processed. When creating a, you can perform the above conversion in advance on objects placed on the page, such as graphics such as lines and circles, images such as characters and scanning images, and place this on the page. Some have been adopted.

However, in a system adopting such a method, since it is originally assumed that the object is used in a display device, it is possible to arrange the above object on the page in three colors of RGB. However, it is often impossible to arrange the four colors of CMYK used in the recording apparatus.

In such a system, the correction / conversion processing from RGB to CMYK first depends on the display device which is the color attribute of each object.
The GB value is corrected to the recording device-dependent RGB value, the object is arranged on the page using this value, and after creating one page of data, all pixels are converted from the recording device-dependent RGB value. The procedure of setting the CMYK values depending on the recording device is adopted. Here, the process performed on each object will be referred to as a color correction process, and the process for all pixels for one page will be referred to as a color conversion process.

The data thus corrected / converted from RGB to CMYK is finally subjected to the output gradation correction processing for linearly correcting the characteristics of the data input value and the output density of the recording apparatus. Be seen.

[0008]

However, there are some recent recording apparatuses that make the resolution of the recording apparatus variable by setting means for setting the resolution. In such a recording apparatus, when a high resolution is set, there is a problem that the amount of recording material per unit area exceeds a predetermined amount and the quality of an output image is deteriorated.

The present invention has been made in view of the above points, and it is an object of the present invention to control gradation correction processing so that an output image is formed favorably in accordance with a set high resolution.

[0010]

In order to achieve the above object, the present invention provides an image for outputting image data to an image forming apparatus capable of forming an image on a recording medium using a recording material at a plurality of resolutions. The processing device is a setting device for setting a resolution, a gradation correction processing device for performing a gradation correction process, and the gradation correction processing device for restricting the total amount of the recording material according to the set resolution. And a control unit for controlling the gradation correction process of.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments will be described below with reference to the drawings.

(Embodiment) FIG. 1 shows an example of the configuration of an image processing system according to the present embodiment, which includes a host 100 and a monitor 2.
00 and printer 300. Further, FIG. 5 is a flowchart showing the flow of the entire processing.

The image generator 110 generates object image data representing an image using an application running on the host. As shown in FIG. 4, the generated object image data is composed of a drawing command and a color designation command represented by 8 bits of R ₀ G ₀ B ₀ indicating the color of each object.

The object image data includes, for example, an image (natural image), a text, and a figure.

Object image data indicating an image is composed of a drawing command indicating that an image exists and R ₀ G ₀ B ₀ corresponding to each pixel of the image.

The object image data indicating text is a drawing command indicating that it is text, a character code indicating the text, and R indicating the color of the character.
₀ G ₀ B ₀ .

The object image data indicating a figure is composed of a drawing command indicating the type of the figure (eg circle, line, etc.) and R ₀ G ₀ B ₀ indicating the color of the figure.

Further, in the color designation command, R ₀ G ₀ B
_{The 0} data is created by the application while being confirmed on the monitor 200, and thus has characteristics depending on the monitor.

The color correction unit 1 (120) depends on the monitor characteristics set for each object R ₀ G ₀
The color correction described below is performed on the B ₀ data, and the printer 3
The color correction is performed on the R ₄ G ₄ B ₄ data depending on the printer characteristic of 00 (S10).

The rendering driver 130 analyzes the object image data composed of a drawing command and an R ₄ G ₄ B ₄ color designation command for each object using the command analysis unit 100 and develops it on the rendering memory 170. Raster R ₄ G ₄ B ₄ image data is generated (S20).

An object based on the R ₄ G ₄ B ₄ data depending on the printer characteristics color-corrected by the color correction unit 1 is
Each is arranged at a predetermined position on the page. When the raster data for one page is created by arranging all the objects on the page, the color correction unit 2 then performs color correction for all the pixels for one page for each pixel.

The color correction unit 2 (140) is a raster R ₄ G
₄ B performs color correction 2 for each pixel with respect to _fourth image data to color correction in a raster C ₆ M ₆ Y ₆ K ₆ image data (S30).

The binarization processing unit 150 uses a raster C ₆ M ₆
Binarization processing such as dither processing and error diffusion processing is performed on the Y ₆ K ₆ image data, and the binarized data is output to the printer 300 (S40).

The above-mentioned processing units are controlled by the CPU 230 via the CPU bus 260. The CPU 230 executes RA based on the program stored in the ROM 240.
Each processing unit is controlled using M250 as a work memory.

Further, each monitor 20 is connected to the CPU bus 260.
A monitor I / F 210 connected to 0 is connected.

The printer 300 forms an image based on the CMYK 1-bit data output from the binarization processing unit 150.

Further, the printer 300 forms an image by using a head of a type that causes film boiling due to thermal energy and ejects droplets.

(Color Correction Unit 1) FIG. 2 shows the color correction unit 1 (12
It is a figure which shows an example of a structure of 0). As described above, the color correction unit 1 uses R ₀ G ₀ B ₀ depending on the monitor characteristic set for each object and R ₄ depending on the printer characteristic.
Color correct to G ₄ B ₄ .

The color correction section 1 (120) is a color correction means 2
1, a first equalizing signal detecting means 2, a second equalizing signal detecting means 6, an unequal signal producing means 7, an equalizing signal producing means 8, a first selecting means 9, and a second selecting means 10. Further, the color correction means 21 is composed of a luminance / density conversion means 1, a black generation means 3, a masking means 4, and a density / luminance conversion means 5.

First, each 8-bit input signal R ₀ G ₀ B ₀ in the specific object color designation command is the luminance of one of the elements constituting the first uniform signal detecting means 2 and the color correcting means 21. It is input to the density converting means 1.

The first equalizing signal detecting means 2 receives the input signal R
It is detected whether ₀ G ₀ B ₀ is equal, that is, R ₀ = G ₀ = B ₀ , and if it is equal, true is output, and false is output, and the output is output to the second selection means 10. Is entered.

In the brightness density converting means 1, the input signal is X ₀ (X = R, G, B) and the output signal is Z ₀ (Y = C,
M, Y), the brightness density conversion process is performed based on the following formula.

Z ₀ = A × 1 / log (X ₀ ) ... (A is a constant)

By this brightness density conversion processing, R ₀ G
_The distortion is corrected based on the monitor characteristics of ₀ B ₀ .

Outputs C ₀ , M from the brightness density converting means 1
₀ and Y ₀ are input to the first black generation means 3 and achromatic color components K ₀ and K ₀ ² are generated and input to the masking means 4.

Further, the output C from the brightness density converting means 1
₀ , M ₀ and Y ₀ are input to the masking means 4 together with the outputs K ₀ and K ₀ ² from the black generating means 3.

FIG. 7 is a block diagram showing the configuration of the first black generating means 3.

In the figure, reference numerals 25, 27 and 29 denote multipliers which multiply two inputs (each 8-bit) and output the result (16-bit). Also, 2
Reference numerals 6, 28, and 24 are shift registers, which convert 8-bit data by shifting the output from the multiplier to the 8-bit right. Through these processes, K ₀ and K ₀ ² based on the following formula are obtained.

K ₀ = (C ₀ × M ₀ × Y ₀ ) / (256 × 256) K ₀ ² = (K ₀ × K ₀ ) × 256

As described above, K ₀ and K ₀ ² are C ₁ , M
_It is calculated by the product of ₁ and Y ₁ .

In this way, K is an achromatic component due to the product.
By generating ₀ and K ₀ ² , good gray balance can be maintained.

Further, the output C from the brightness density converting means 1
₀ , M ₀ , and Y ₀ are input to the masking unit 4 together with the outputs K ₀ and K ₀ ² from the black generation unit 3, and color correction is performed by matrix calculation based on the output characteristics of the printer, and color correction is performed. C ₁ , M ₁ and Y ₁ are output.

Here, the relationship between C ₀ , M ₀ , Y ₀ , K ₀ , K ₀ ² and C ₁ , M ₁ , Y ₁ is defined by the following equation.

C ₁ = a ₀₀ × C ₀ + a ₀₁ × M ₀ + a ₀₂ × Y ₀ + a ₀₃ × K ₀ + a ₀₄ × K ₀ ² M ₁ = a ₁₀ × C ₀ + a ₁₁ × M ₀ + a ₁₂ × Y ₀ + A ₁₃ × K ₀ + a ₁₄ × K ₀ ² Y ₁ = a ₂₀ × C ₀ + a ₂₁ × M ₀ + a ₂₂ × Y ₀ + a ₂₃ × K ₀ + a ₂₄ × K ₀ ² (aij: 0 <= i <= 2, 0 <= j <= 4 is a constant) As can be seen from this expression, color-converted C ₁ , M ₁ , Y
₁ is a color-corrected values in the form including the K ₀ and K ₀ ^2, moreover K ₀ and K ₀ ² is a value determined by the product of _{C 0, M 0, Y 0} .

Further, the masked data C ₁ ,
The M ₁ and Y ₁ are input to the density / luminance conversion means 5, converted into the luminance signals R ₁ , G ₁ and B ₁ again and output.

The luminance signals R ₁ , G ₁ and B ₁ are input to the second equal signal detecting means 6, the non-uniform signal producing means 7 and the equal signal producing means 8. The second equalization signal detecting means 6 is
The luminance signals R ₁ , G ₁ , B ₁ are equal, that is, R ₁ = G ₁
= B ₁ is detected, and if equal, tr
ue Otherwise, false is output, and the output is input to the first selecting means 9. The first selection means 9 is
When the output of the second uniform signal detecting means 6 is true, the input signals R ₀ , G ₀ , B ₀ to the color correcting means are not uniform signals, but are processed by the color correcting means 21 to become uniform signals. Since there is a possibility that it has happened, the signals R ₂ , G ₂ , B ₂ created by the unequal signal creation means 7 are selected and output. On the other hand, the output of the second equalization signal detecting means 6 is f
If it is “alse”, the normal signals R ₁ , G ₁ , and B ₁ processed by the color correction means 21 are selected and output.

Further, the output of the first selecting means 9 is inputted to the second selecting means, and the first equal signal detecting means 2
If the output is false, the same output is selected and output. On the other hand, the output of the equal signal detecting means 2 is true.
In this case, since the achromatic color data has been input to the color correction means 21, the output from the uniform signal generation means 8 is selected and output.

Here, the unequal signal generating means 7 uses R ₁ ,
The G ₁ and B ₁ signals are input and the R ₂ , G ₂ and B ₂ signals are output. At this time, R ₁ , G ₁ , B ₁ signals and R ₂ , G ₂ ,
There is the following relationship with the B ₂ signal.

R ₂ = R ₁ G ₂ = G ₁ B ₂ = B ₁ -1

Further, the equalizing signal producing means 8 uses R ₁ , G
Inputs ₁ and B ₁ signals and outputs R ₃ , G ₃ and B ₃ signals. At this time, R ₁ , G ₁ and B ₁ signals and R ₃ , G ₃ and B signals
There are the following relationships with the _three signals.

R ₂ = G ₂ = B ₂ = (R ₁ + G ₁ + B ₁ ) / 3

According to the processing of the non-uniform signal generating means 7 and the uniform signal generating means 8, the non-uniform signal and the uniform signal can be generated while maintaining the color correction result of the color correcting means 21 as much as possible.

With the above configuration, the R ₀ G ₀ B ₀ object image data depending on the monitor characteristic is color-corrected to the R ₄ G ₄ B ₄ raster image data depending on the printer characteristic.

Further, only when the R ₀ G ₀ B ₀ object image data is uniform (that is, achromatic color), R ₄ G ₄
Color correction is performed so that the B ₄ raster image data is even.

(Color Correction Unit 2) FIG. 3 shows the color correction unit 2 (14
It is a figure which shows an example of a structure of 0).

The color correction section 2 is composed of a color conversion means 22, a third uniform signal detection means 12, a black replacement means 16, a third selection means 17, and an output gradation correction means 20,
Further, the color conversion means 22 comprises a luminance density conversion means 11, a black generation means 13, and an undercolor removal / black correction means 15.

First, the created data of each pixel of one page is 8-bit R ₄ , G ₄ and B ₄ ,
It is input to the third uniform signal detecting means 12 and the luminance density converting means 11 which is one of the elements constituting the color converting means 22.

The third equalizing signal detecting means 12 detects whether the input signals R ₄ , G ₄ and B ₄ are equal, that is, R ₄ = G ₄ = B ₄ , and if so, true If not, false is output and the output is input to the third selecting means 17.

On the other hand, in the brightness density converting means 11, the signal converted into the brightness signal by the density / brightness converting means 5 is converted again into the density signal.

Outputs C ₂ and M from the brightness density conversion means 11
₂ and Y ₂ are input to the black generating means 13 and the achromatic component K ₂
Is generated based on the following formula.

K ₂ = min (C, M, Y) where min (C, M, Y) represents a function for selecting the minimum value of C, M, Y.

As described above, by generating K ₂ with the minimum values of C, M, and Y, it is possible to maintain good color balance.

The achromatic color component K ₂ generated by the black generating means 13 and the C ₂ M generated by the luminance density converting means 11
₂ Y ₂ is input to the undercolor removal / black correction means 15.

Here, the under color removal / black correction means 15 performs the under color removal and black correction processing by referring to the lookup table set by the under color removal / black correction table setting means 14, and C ₃ , M ₃ , Y ₃ , K
Generates ₃ . C ₂ , M ₂ , Y ₂ , K ₂ and C ₃ , M ₃ ,
The relationship between Y ₃ and K ₃ is as follows.

C ₃ = C ₂ -Table _UCRC (K ₂ ) M ₃ = M ₂ -Table _UCRM (K ₂ ) Y ₃ = Y ₂ -Table _UCRY (K ₂ ) K ₃ = Table _BGR (K ₂ )

Here, Table _UCRC and Tabl
e _UCRM and Table _UCRY respectively _refer to the under color removal table set by the under color removal / black correction table setting means 14, and Table _BGR refers to the black correction table set by the setting means.

FIG. 6 shows the curves set in the black correction and undercolor removal table. First, the black correction curve is 0 up to 1/3 of the maximum input value (255), and is 1/3.
When it exceeds, the curve rises smoothly due to a quadratic curve. As a result, K is not entered in the low-density portion, and the reproducibility of the color in the low-density portion such as the skin color is improved.

Further, the black correction curve takes the maximum output value (255) at the maximum input value, while the undercolor removal curve also takes the maximum output value at the maximum input value. Therefore, C ₂ = M ₂ = Y ₂ = 255
In this case, K ₂ = 255, and K1 color is recorded. As a result, the K1
No other color is mixed in the 00% portion.

The curves indicated by C, M and Y in the figure are
It is a curve in which the input value-undercolor removal value is plotted. Even if the black correction curve is added to the curve tripled (C, M, Y, 3 colors), the output = input * 2 line It is configured not to exceed. As a result, for each input value, the total value of the C, M, Y, and K outputs is less than or equal to twice the input value. Therefore, for any input value, the maximum value of the ink ejection amount in the printing apparatus, 200 if
It does not exceed%.

The color-converted C ₃ , M ₃ , Y ₃ and K ₃ are input to the black replacing means 16 and the third selecting means 17.

The black replacing means 16 is composed of C ₃ , M ₃ and Y.
Input ₃ and K ₃ signals and replace with only one black color C
_It outputs ₄ , M ₄ , Y ₄ , and K ₄ signals. At this time, C ₃ ,
The following relationships exist between the M ₃ , Y ₃ , K ₃ signals and the C ₄ , M ₄ , Y ₄ , K ₄ signals.

C ₄ = M ₄ = Y ₄ = 0 K ₄ = K ₃ + α × C ₃ + β × M ₄ + γ × Y ₄ (α,
β and γ are constants)

The third selecting means 17 determines the undercolor removal / black correcting means 15 according to the detection result of the third equalization signal detecting means 12.
And one of the outputs from the black replacement means 16 is selected and output. That is, the third equal signal detecting means 12
If the output is true, an achromatic color has been input, so the input from the black replacement means 16 is selected and false
In this case, the input from the normal undercolor removal / black correction means 15 is selected and output as C ₅ M ₅ Y ₅ K ₅ .

Therefore, color correction can be performed so that C ₅ M ₅ Y ₅ K ₅ is uniform only when the R ₄ G ₄ B ₄ raster image data is uniform.

C ₅ , M ₅ , Y from the third selecting means 17
_{The 5} , ₅ outputs are input to the output tone correction means 20, are subjected to tone correction processing, and are output as C ₆ , M ₆ , Y ₆ , K ₆ .

Reference numeral 18 denotes a resolution setting means, which sets the value according to the resolution to be recorded in the recording apparatus.

Reference numeral 27 is a gradation correction table that stores gradation correction characteristics used when low-resolution recording is performed by the recording device, and is read out by the output gradation correction characteristic changing means 19 and changed. , To the output gradation correction means 20.

Reference numeral 19 is an output gradation correction characteristic changing means,
The gradation correction table 27 is read out, and the gradation correction table 27 is changed according to the resolution set by the resolution setting means of 18, and is passed to the output gradation correction means 20.

FIGS. 10 and 11 are diagrams schematically showing how the output gradation correction characteristic changing means changes the gradation correction characteristic of the recording apparatus. FIG. 10 shows that the low resolution is the resolution. The output characteristic curve and the output characteristic correction curve when set by the setting means 18 are shown, and FIG. 11 shows the output characteristic curve and the output characteristic correction curve when the high resolution is set by the resolution setting means 18.

First, the recording method in the case of forming an image at a low resolution and the case of forming an image at a high resolution by the printer 300 will be described with reference to FIGS. 12 and 13.

In the printer 300 of this embodiment, recording is performed while moving the recording head in which a plurality of nozzles are arranged in the sub-scanning direction in the main scanning direction, and when one line of recording is completed, the recording medium is moved in the sub-scanning direction. The serial recording method is used in which the recording head is moved to the recording start position, the next line is recorded again, and one page is recorded by the same procedure.

In such a recording apparatus, in order to form an image at high resolution, the recording head is moved in the main scanning direction at a half of the normal pitch without changing the dot diameter of the recording head. Moreover, the resolution in the main scanning direction can be doubled.

The vertical × horizontal resolution is 360 dpi (dot).
In a recording device of per inch) × 360 dpi, recording is performed as shown in FIG. On the other hand, when the recording head is moved in the main operation direction (horizontal direction in this case) at half the normal pitch, recording should be performed as shown in FIG. However, since the size of the ink droplets ejected from the recording head is designed to be appropriate at the original resolution, the recording is performed as it is, so twice the amount of ink is deposited on the recording medium. Ink may overflow depending on the media.

Therefore, when an image is formed with high resolution,
C with 0-255 level to regulate ink volume
Each signal of ₅ M ₅ Y ₅ K ₅ is compressed to 0 to 216 levels.

Hereinafter, the output gradation correction means 20 will be described with reference to FIG.
The configuration of will be described.

Fourth selection section 30 and output gradation correction section 32
Are controlled in conjunction with a control signal from the gradation correction table.

The fourth selecting section 30 is the resolution setting means 18
When the high resolution recording is set by, the control signal from the gradation correction table changing means 19 causes C ₅ M ₅ Y ₅ K
₅ is output to the gradation compression unit 31. Gradation compression section _{31, C 5 M 5 Y 5 K} 5 with 0 to 255 levels as shown in FIG. 9 in order to regulate the amount of ink in response to high-resolution recording
Each component signal in FIG. 9A is set to 0 depending on the input level.
To 216 levels (FIG. 9B) and output to the output gradation correction unit 32.

By thus compressing in accordance with the input level, gradation can be maintained as much as possible.

On the other hand, when low resolution recording is set by the resolution setting means 18, the fourth selecting section 30 sets C ₅ M ₅ Y ₅
K ₅ is output to the output gradation correction unit 32.

The output gradation correction unit 32 is the resolution setting means 1
Based on the resolution recording set in 8, the output gradation correction processing shown below is performed with reference to the above gradation correction table changed by the gradation correction table changing means 19.

C ₆ = Table γ _C (C ₅ orC ₅ ′) M ₆ = Table γ _M (M ₅ orM ₅ ′) Y ₆ = Table γ _Y (Y ₅ orY ₅ ′) K ₆ = Table γ _K (K ₅ orK ₅ ′) ) Here, Table γ _C , Table γ _M , Table γ
_Y and Table γ _K indicate that the gradation correction table corresponding to each color is referred to.

When the low resolution recording is designated, the output gradation correction unit 32 outputs the output value (in this embodiment, in the present embodiment) for the entire range of input values (0 to 255), as can be seen from FIG. The output correction curve is set so that the density value mapped from 0 to 255) is linear.
That is, the output correction curve is set based on the distortion of the output characteristics of the printer 300.

On the other hand, as can be seen from FIG. 11, when the high resolution is designated, the output correction curve is set so that the output value becomes linear with respect to a part (0 to 216) of the entire range of the input value. Is set. This is because even if you change the resolution
If the recording media are the same, the output characteristics do not change,
This reflects the phenomenon that the input range is simply narrowed, that is, the input amount increases for higher input resolutions of 217 or more, and the density reaches a ceiling. . Therefore, the shape of the output characteristic curve in FIG. 11 is the same as that of the output characteristic curve in FIG. 10, since the maximum ink amount per unit area does not change.

That is, in the case of high resolution recording, the range for each pixel is regulated to 216, but since the image recording density is high, the maximum ink amount per unit area on the recording medium is
It does not change for low resolution recording.

In high resolution recording, maximum density can be maintained. Rather, high-resolution recording has a higher recording density, so that the overall contrast is emphasized.

On the other hand, in the low resolution recording, since the levels 0 to 255 are used as shown in FIG. 10, the halftone area can be reproduced well.

As described above, the gradation correction processing can be performed based on the set resolution recording.

The output gradation correction characteristic changing means 19 makes a change to the gradation correction table holding the output correction curve corresponding to the low resolution recording when the low resolution recording is designated by the modification degree setting means 18. When the high resolution recording is designated, the output gradation correction means 20 is set with a gradation correction table having a characteristic that the same output correction curve is reduced at the same ratio for both input and output.

Therefore, even in a system in which the characteristics of the output gradation correction change according to the set resolution, it is possible to construct a system in which it is not necessary to wait for a plurality of output gradation correction data to be held. Become.

As described above, according to the present embodiment, before the CMYK signal is obtained by performing the undercolor removal / black correction process with the minimum value of CMY in the color correction unit 2 as K, the CMY Since K is obtained from the product and the value is corrected in advance, the gray balance of the CMYK signal output from the color correction unit 2 becomes good.

Further, according to the structure of the present embodiment, even in the structure in which the color correction unit 1 and the color correction unit 2 are color-processed separately, only when the input signal is an achromatic color, the printer is black. It can be recorded in one color.

Further, according to the under color removal / black correction means 15, K is not added in the low density portion and the tint is reproduced well, and in the high density portion, K is also reproduced, so that it is high. It is possible to record the concentration.

Further, when C, M, and Y all have the maximum density, it is possible to record with K1 color.

Recording can be performed without exceeding the maximum ink ejection amount in the recording apparatus for any input signal.

Further, as in the present embodiment, the color correction unit 1 is provided in front of the rendering driver that analyzes and develops the object image data, the luminance density conversion unit 1 corrects the distortion based on the monitor characteristic, and the masking unit. Since the color signal is corrected in 4 according to the printer characteristics, the processed image signal can be processed efficiently and at high speed as compared with the color correction for each pixel.

(Modification) FIG. 14 is a block diagram for explaining a modification of the above embodiment.

The same parts as those in the above-mentioned embodiment are designated by the same reference numerals and their explanations are omitted.

In the present modification, the interpolation processing means 25 and the look-up table 26 are used in place of the color correction means 21 composed of the brightness / density conversion means 1, the black generation means 3, the masking means 4, and the density / brightness conversion means 5. The color correction means composed of is used. In the case of the modified example, the luminance / density conversion processing, the black generation processing, the masking processing and the density / luminance,
The color correction process is performed by an interpolation calculation that refers to the lookup table 26 that has the values that have been subjected to the conversion process in advance on the grid points. With such a configuration, it is possible to reduce a plurality of color correction processes to one interpolation process.

In the embodiment described here, each signal is an 8-bit digital signal.
Data composed of 16 bits, ..., N bits and the like may be used.

The recording device is not limited to the color ink jet recording device as long as it uses black as an achromatic color, and may be a thermal transfer recording device, an electrophotographic recording device, or the like.

Further, in the above-described embodiment, the black correction means sets the threshold value at which the output is 0 to 1/3 of the maximum input value, but it is not limited to this value. Moreover, although the total value of the C, M, Y, and K outputs at each input value is not more than twice the input value, this is not limited to this value either.

[0112]

According to the present invention, the gradation correction processing can be controlled so that an output image is formed favorably in accordance with the set high resolution.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a configuration of an image processing apparatus.

FIG. 2 is a diagram showing an example of a configuration of a color correction unit 1.

FIG. 3 is a diagram showing an example of a configuration of a color correction unit 2.

FIG. 4 is a diagram showing an example of the configuration of object image data.

FIG. 5 is a diagram showing an example of the overall flow of processing.

FIG. 6 is a diagram showing an example of a black correction / undercolor removal curve.

FIG. 7 is a diagram showing an example of a configuration of a black generation unit 3.

FIG. 8 is a diagram showing an example of a configuration of an output gradation correction unit 20.

FIG. 9 is a diagram showing an example of processing of a gradation compression unit 31.

FIG. 10 is a diagram showing an example of output gradation correction processing.

FIG. 11 is a diagram showing an example of output gradation correction processing.

FIG. 12 is a diagram showing an example of high resolution recording.

FIG. 13 is a diagram showing an example of low resolution recording.

FIG. 14 is a diagram showing an example of a configuration of a color correction unit 1 in a modified example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location H04N 1/60 H04N 1/40 D 1/46 1/46 Z (72) Inventor Yoko Hirosugi Tokyo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masahiro Hase 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kazuyoshi Sumai Ota, Tokyo 3-30-2 Shimomaruko-ku, Canon Inc. (72) Inventor Toyohiro Moro 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (4)

[Claims] 1. An image processing apparatus for outputting image data to an image forming apparatus capable of forming an image on a recording medium using a recording material at a plurality of resolutions, comprising setting means for setting resolution and gradation. A gradation correction processing unit that performs a correction process; and a control unit that controls the gradation correction process of the gradation correction processing unit so as to regulate the total amount of the recording material according to the set resolution. Image processing device. 2. The setting unit can set a high resolution or a low resolution, and the control unit generates a gradation correction process for the high resolution based on the gradation correction process for the low resolution to generate the gradation. The correction processing means sets the correction processing means.
The image processing apparatus according to any one of the preceding claims. 3. The image processing apparatus according to claim 3, wherein the characteristics of the gradation correction processing relating to the low resolution and the characteristics of the gradation correction processing relating to the high resolution have a similar relationship. 4. An image processing method for outputting image data to an image forming apparatus capable of forming an image at a plurality of resolutions, comprising a setting step of setting the resolution, and gradation compression according to the set resolutions. An image characterized by including a gradation correction processing step of performing a gradation correction processing and a control step of controlling the gradation correction processing of the gradation correction processing step according to the set resolution. Processing method.