JPH08275010A - Method and device for image processing - Google Patents

Abstract

PURPOSE: To adjust saturation of RGB data in details and to allow the device to contribute to reduction in the amount of ink. CONSTITUTION: A mean value arithmetic section 4 calculates a mean value (Mean_RGB) of original RGB data, a data deviation arithmetic section 5 calculates each deviation (Diff_R,G,B) of the original RGB data from the mean value and an RGB correction section 6 corrects the original RGB data according to a saturation correction amount read from a saturation correction table 7. The table 7 stores a desired saturation correction amount with respect to each RGB deviation. Since the correction processing is executed by using a lookup table, the circuit configuration is made simple, and since correction data based on the deviation of the RGB data from the mean value are used, objective saturation is surely obtained without losing the image quality of the original image, detailed saturation adjustment is conducted by properly varying the contents of the lookup table and the amount of ink is reduced as the result of saturation adjustment especially in a high saturation area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and an image processing apparatus for adjusting color saturation of input color image data, that is, RGB data for output.

[0002]

2. Description of the Related Art In color print processing, normally,
Color reproduction is performed with three color materials of C (cyan), M (magenta), and Y (yellow). For example, from color signals of R (red), G (green), and B (blue) obtained by color-separating a color document, C, M,
A color signal of Y is created, and ink of each color is attached to a recording medium, for example, paper according to each color signal to reproduce a color image. Further, K (black) may be added to the three color materials of C, M, and Y to reproduce the color with the four color materials.

With respect to a color image obtained by such a color printing process, it is an important factor that the saturation is properly set. For example, it is sometimes desirable to perform saturation enhancement processing on a portion of a color document with low saturation to enhance the saturation. In addition, it is not necessary to emphasize the saturation in a high saturation area that is already sufficiently saturated, and in some cases, a process of reducing the saturation may be performed. As image processing for such saturation adjustment, conventionally, C, M, Y or their corresponding R, G,
There has been a method of adjusting each color signal of B individually without considering the correlation between the respective colors.

[0004]

However, in the above-mentioned conventional method, each color signal of C, M, Y, etc. has to be adjusted individually, so that it is very difficult to adjust each color signal, and the target saturation is reduced. I couldn't get it. Further, in this conventional method, there was no idea to finely adjust the saturation of each of the R, G, and B color signals of the color original image in accordance with the change of each color signal.

The present invention has been made in order to solve the above problems, and with a simple structure, it is possible to surely obtain a target saturation without impairing the image quality of a color original image. The purpose is to do. Another object is to enable fine color saturation adjustment according to the wishes of a viewer of a color image. Another object is to contribute to reduction of the ink amount of each color ink of C, M, Y, K as a result of the saturation adjustment.

[0006]

In order to achieve each of the above objects, an image processing method according to the present invention comprises (1) calculating an average value (Mean_RGB) of respective color signal amounts of original RGB data, and (2)
The deviation amount (Diff_R, G, B) from the average value (Mean_RGB) is calculated for each color signal of the original RGB data, and (3) the saturation correction amount (R, G, B_satu_tbl [Diff_R, G, B ]) Is stored, the saturation correction amount corresponding to the calculated deviation amount (Diff_R, G, B) is read out,
(4) The original RGB data is corrected by the read saturation correction amount.

Further, the image processing apparatus according to the present invention is
(1) Average value of each color signal amount of original RGB data (Mean_RGB)
And (2) the deviation amount (Diff_R, from the mean value (Mean_RGB) from the mean value (Mean_RGB) for each color signal of the original RGB data.
G, B) data deviation calculation unit, (3) a saturation correction table that stores the saturation correction amount (R, G, B_satu_tbl [Diff_R, G, B]) for the above deviation amount, (4) And an RGB correction unit that corrects the original RGB data according to the saturation correction amount.

Regarding the saturation correction data to be stored in the saturation correction table and the correction processing to be performed in the RGB correction section, various forms can be considered as follows.

In the first embodiment, the saturation correction table stores correction data that changes so that the deviation amount and the saturation correction amount maintain the same sign (for example, FIG. 6). At this time, the RGB correction unit adds the saturation correction amount to the original RGB data.

In the second embodiment, the saturation correction table stores correction data that changes so that the deviation amount and the saturation correction amount maintain different signs (for example, FIG. 7). At this time, the RGB correction unit adds the saturation correction amount to the original RGB data.

In the third embodiment, the saturation correction table is for correction such that the deviation amount and the saturation correction amount maintain the same sign and the saturation correction amount becomes zero when the deviation amount is maximum and minimum. Store the data (eg, FIG. 8). At this time, the RGB correction unit adds the saturation correction amount to the original RGB data.

In the fourth embodiment, the saturation correction table is such that the saturation correction amount becomes negative from the predetermined deviation amount and the saturation correction amount increases in the negative direction as the deviation amount approaches the maximum value. The correction data is stored (for example, FIG. 9).
At this time, the RGB correction unit adds the saturation correction amount to the original RGB data. Further, in this case, the following components, that is, the CMY conversion unit for converting the RGB data after the saturation correction output from the RGB correction unit into CMY data, and the CMY data output from the CMY conversion unit are An undercolor removing unit that performs an undercolor removing process is provided. In addition,
The undercolor removal processing is to obtain the K (black) signal amount based on the minimum value of the C, M, and Y signal amounts, and
It is a process including a step of subtracting the K signal amount from each of the M and Y signal amounts.

According to the fourth aspect, in the high saturation region S where the correction data increases in the negative direction, the saturation decreases in the direction in which black is mixed. Further, in the fourth embodiment, the CMY conversion unit and the undercolor removal unit are particularly configured by the synergistic action of the saturation adjustment processing of the present invention and the C, M, Y undercolor removal processing. This is because it is intended to reduce the amount of ink used, especially in a high saturation region that requires a large amount of ink.

In the fifth embodiment, the saturation correction table is such that the saturation correction amount becomes negative from the predetermined deviation amount and the saturation correction amount increases in the negative direction as the deviation amount approaches the maximum value. The correction data is stored (for example, FIG. 9).
Then, the RGB correction unit corrects the original RGB data by subtracting the saturation correction amount for each of the R, G, and B colors from the signal amount of the remaining two colors. According to the fifth aspect, with respect to the high saturation region S in which the correction data increases in the negative direction, the saturation decreases in the direction in which white is mixed. Further, it is possible to directly reduce the respective ink amounts corresponding to the two colors for which the signal amount can be reduced.

In the sixth embodiment, the saturation correction table is (1) with the requirement that a deviation amount judgment unit for judging whether the deviation amount is larger or smaller than a predetermined threshold value (for example, 120) is provided. ) When the deviation amount is smaller than the threshold value (120),
The correction data is stored such that the deviation amount and the saturation correction amount maintain the same sign and the saturation correction amount becomes zero when the deviation amount is the threshold value (120) and the minimum value (-170),
(2) For correction such that when the deviation amount is larger than the threshold value (120), the saturation correction amount becomes negative from the threshold value and the saturation correction amount increases in the negative direction as the deviation amount approaches the maximum value. Store the data (eg, FIG. 10). Then, at this time, the RGB correction unit determines that (1) the deviation amount is the threshold value (1
20), the saturation correction amount is added to the original RGB data, and (2) when the deviation amount is larger than the threshold value, R,
The saturation correction amount for each of G and B is set to the remaining 2
The original RGB data is corrected by subtracting from the color signal amount.

According to the sixth mode, the third mode (FIG. 8) and the fifth mode (FIG. 9) described above are selectively used according to the magnitude of the deviation amount to perform saturation correction and ink amount reduction. It is to realize both efficiently.

[0017]

According to the image processing method of the first aspect and the image processing apparatus of the second aspect, a simple structure in which only the correction data stored in the saturation correction table, that is, a so-called lookup table (LUT) is used. Adjust the saturation.

Further, since the correction data uses the deviation amount from the average value of the original RGB data as an address and sets the saturation correction amount corresponding to each address, the correlation of each color signal is not considered. Compared with the method of individually adjusting each color signal, the target saturation can be reliably reproduced without deteriorating the image quality of the original color image.

Further, by appropriately changing the data content in the saturation correction table, fine-tuned saturation adjustment can be performed according to the desire of the viewer of the color image. Furthermore, by adjusting the R, G, B color signal amounts in accordance with the correction data for adjusting the saturation, as a result, the ink amounts of the C, M, Y, K color inks are reduced.

[0020]

【Example】

(Embodiment 1) FIG. 1 shows the whole example of an image creating system using an image processing apparatus according to the present invention. The image creating system includes a color image data output device 1, an image processing device 2, and an image output device 3. The color image data output device 1 is composed of, for example, a host computer, a scanner, a video camera, etc.
Is output. In this embodiment, it is assumed that the gradation value of the color image data D1 is 8 bits, that is, 256 gradations of 0 to 255.

The image processing apparatus 2 performs the following respective processes on the input color original image data D1, that is, a process for adjusting the saturation, a conversion process into C, M and Y color signals, and a gradation value. Is converted into two gradations, which is a gradation value suitable for the image output device 3, and is then output as C, M, Y two gradation final color image data D2. In the present embodiment, 0 (white) is considered as the first gradation value that constitutes two gradations, and 255 (black) is considered as the second gradation value.

The image output device 3 reproduces and outputs the original image based on the color image data D2 output from the image processing device 2. The image output device 3 is constituted by, for example, a printer of a format that cannot control gradation in pixel units, and reproduces and outputs an original image so that halftone can be displayed based on the input two gradation color image data D2. In addition to the printer, the image output device 3 may use a display, a facsimile device, a digital copying machine, or the like, if necessary.

As shown in FIG. 2, the image processing apparatus 2 includes an average value calculation unit 4, a data deviation calculation unit 5, an RGB correction unit 6, a saturation correction table 7, a CMY conversion unit 8, and It has a binarization unit 9.

The average value calculator 4 receives the R, G and B signals and calculates the average value Mean_RGB = (R + G + B) / 3 of the signal amounts. The data deviation calculator 5 receives the R, G, B color signals and the mean value Mean_RGB, and deviates from the mean value for the R, G, B colors Diff_R = R-Mean_RGB Diff_G = G-Mean_RGB Diff_B = B − Calculate Mean_RGB. If you diagram these relationships in an easy-to-understand manner,
This is as shown in FIG.

The saturation correction table 7 includes a RAM, a ROM,
It can be configured in other semiconductor memories, and R,
The deviation amounts Diff_R, Diff_G, and Diff_B of G and B colors are used as addresses, and the saturation correction amount is stored as data corresponding to each of these addresses. For example, as shown in FIG. 6, saturation correction data that changes so that the deviation amount Diff_R and the saturation correction amount R_satu_tbl [Diff_R] maintain the same sign is stored. Although FIG. 6 shows the saturation correction data for R, the same saturation correction data is set for G and B as well. Further, in FIG. 6, the point where the deviation amount Diff_R has the maximum value 170 indicates a color where G = B = 0 and R = 255, that is, a high saturation region. RGB correction unit 6
Is the R, G, B color signal, and the deviation amount D of the R, G, B color
iff_R, Diff_G, Diff_B and the correction data from the saturation correction table 7 are received, and the original data of the three colors R, G, B are corrected for saturation, and Rnew = R + R_satu_tbl [Diff_R] Gnew = G + G_satu_tbl [ Diff_G] Bnew = B + B_satu_tbl [Diff_B] is output as the corrected RGB signal. If the corrected values of Rnew, Gnew, and Bnew are out of the range of 0 to 255, it is necessary to perform processing so that they fall within the range of 0 to 255. For example, when R <0, R = 0, when R> 255, R = 255, when G <0, G = 0, when G> 255, G = 255, when B <0, B = 0, when B> 255 Process as B = 255.

The CMY conversion unit 8 is a saturation-corrected R,
The three-color data of G and B are converted into the CMY color system and used in the image output device C (cyan), M (magenta), and Y.
It is output as a signal related to the three color inks of (yellow). As the simplest conversion example, a conversion such as C = 255-RM = 255-G Y = 255-B can be considered.

The binarization unit 9 converts the CMY data of 256 tones of 0 to 255 into two tones that match the operation characteristics of the image output device 3 (FIG. 1), that is, binarization processing. In the present embodiment, it is assumed that the binarization process is performed by using, for example, the error diffusion method.

The operation of the image processing apparatus having the above structure will be described below.

In FIG. 1, the color image data output device 1 outputs R, G, and B three-color data D1 of 256 gradations of 0 to 255, which is received by the image processing device 2.
The image data D1 captured by the image processing device 2 is as shown in FIG.
In, the average value calculation unit 4, the data deviation calculation unit 5, and R
The data is sent to each unit of the GB correction unit 6. In the average value calculation unit 4,
An average value Mean_RGB = (R + G + B) / 3 is calculated from each data of R, G, and B, and the average value data is sent to the data deviation calculator 5. The data deviation calculation unit 5 calculates the deviation amount Diff_R = R−Mean_RGB Diff_G = G−Mean_RGB Diff_B = B−Mean_RGB from the average value Mean_RGB for each color of R, G, and B, and sends the deviation amount to the RGB correction unit 6. .

The RGB correction unit 6 uses the deviation amounts Diff_R, Diff_G, and Diff_B of the RGB colors sent in and the correction data of FIG. 6 stored in the saturation correction table 7 to determine the color corresponding to each deviation amount. Degree correction amount R_satu_tbl [Diff_R] G_satu_tbl [Diff_G] B_satu_tbl [Diff_B] is read, and each correction amount is added to each color original data of R, G, B, and Rnew = R + R_satu_tbl [Diff_R] Gnew = _G + Gsa [Diff_G] Bnew = B + B_satu_tbl [Diff_B] is calculated, and the calculation result is sent to the CMY conversion unit 8.

Three-color data Rnew, Gnew and Bne after correction
w is C, M, Y in the CMY conversion unit 8, respectively.
Is converted to each color data. The converted C, M, and Y color signals have gradation values of 0 to 255, but these color signals are converted into two gradation values of 0 or 255 in the binarizing unit 9. In the present embodiment, since the binarization processing is performed using the error diffusion method, the binarization is performed in the following procedure, for example.

(1) In a pixel which has already undergone binarization processing, an error component obtained by weighting an error generated at the time of binarization is added to the signal amount of the pixel of interest.

(2) The signal amount of the pixel of interest after the addition processing is compared with a predetermined threshold value, and if the signal amount is larger than the threshold value, the signal amount is converted to 255 and the image output device 3 (FIG. 1). If the signal amount is smaller than the threshold value, the signal amount is converted to 0 and output to the image processing device 3.

(3) On the other hand, the error between the 2-gradation output signal and the 256-gradation input signal is calculated, the error is given a predetermined weight, and then diffused to the pixels around the pixel of interest. The diffused error component is added to the subsequent pixel of interest as the error component described in (1) above.

(4) The processes of (1) to (3) are performed on the entire area of the image data, whereby the entire image data is binarized.

The binarized C, M, Y data are sent to a printer as an image output device 3, for example, an ink jet printer, and a full color image is created on a printing material such as paper based on the data. It

In this embodiment, as the saturation correction table, the deviation amount Diff_R and the saturation correction amount R_satu_tb from the average value of the data as shown in FIG.
Since the data that l [Diff_R] changes so as to maintain the same sign is used, R, G, and
Each color data of B is corrected so that the difference from their average value is enlarged. Therefore, the obtained print image is obtained in a state where the saturation is emphasized.

As the correction data that can be stored in the saturation correction table 7, any data such as the data shown in FIG. 7 and the data shown in FIG. 8 can be used in addition to the data shown in FIG. You can The saturation correction data shown in FIG. 7 is the deviation amount Diff_R from the average value of R, G, and B data.
And the saturation correction amount R_satu_tbl [Diff_R] change so as to maintain different signs, the R, G, and B color data output from the RGB correction unit 6 has a reduced difference from the average value thereof. Is corrected so that Therefore, the finally obtained print image is obtained in a state where the saturation is reduced.

The saturation correction data shown in FIG. 8 is R
The deviation amount of each color of GB and the saturation correction amount maintain the same sign, and the saturation correction amount becomes zero when the deviation amount is maximum (170) and minimum (-170). Therefore, if the correction is performed using the correction data, the following effects can be obtained.

(1) R, G, B deviation amounts Diff_R, G,
A color such that B is close to 170, for example G = B = 0,
A color close to R = 255 already has sufficiently high saturation, so even if the saturation enhancement is not performed by making the saturation correction amount close to 0 as shown in FIG. there is no problem. Moreover, if the saturation correction amount is lowered in this way, the ink will not be wasted.

(2) For example, when B = G = 0 and only R is 0
In the case of printing a gradation pattern that continuously changes to 255, the correction amount shown in FIG.
In the vicinity of 55, R after saturation correction is 2 regardless of the value of R.
It reaches 55 and the color change disappears. On the other hand, if the correction data shown in FIG. 8 is used, it is possible to maintain a state in which the colors continuously change in such a gradation pattern.

(Embodiment 2) In a printer that prints using four colors of C, M, Y, and K, it is possible to reduce the ink amount by replacing K, M, and Y in the mixed portion of three colors. Therefore, the maximum total ink amount is obtained by printing two colors of ink, red (M + Y) and green (Y +).
C) and blue (C + Y). In an inkjet printer or the like, the amount of ink that can be ejected is limited depending on the printing paper, and it is particularly necessary to limit the amount of ink in these color regions. The embodiment described below is suitable for such an ink amount limitation.

In this embodiment, the image processing apparatus 12 having the structure shown in FIG. 3 is used as the image processing apparatus. This image processing device 12 is different from the image processing device 2 shown in FIG. 2 in that the correction data shown in FIG. 9 is stored in the saturation correction table 7, and the CMY conversion unit 8 and the binarization unit are stored. That is, the undercolor removing unit 10 is provided between the undercolor removing unit 10 and the image forming device 9. In the correction data shown in FIG. 9, the saturation correction amount is maintained at 0 in the regions other than the high saturation region S, and the R, G, B deviation amounts Dif are set in the high saturation region S.
As f_R, G, B approaches the maximum value 170, the saturation correction amount R
_satu_tbl [Diff_R] increases in the negative direction.

In this embodiment, in FIG. 3, (1) Mean_RGB = (R
+ G + B) / 3, (2) Deviation amount Diff_R = R-Mean_RGB Diff_G = G-Mean_RGB Diff_B = B-Mean_RGB from the average value of the R, G, and B signals by the data deviation calculation unit 5, and ( 3) Addition processing by the RGB correction unit 6 Rnew = R + R_satu_tbl [Diff_R] Gnew = G + G_satu_tbl [Diff_G] Bnew = B + B_satu_tbl [Diff_B] is performed as in the embodiment of FIG.

In the saturation correction data (FIG. 9) used in this embodiment, the correction amount increases in the high saturation region S in the negative direction, so that the saturation amount is high in the high saturation region S such that the deviation amount Diff_R is close to 170. The lowering process will be performed. As a result, for example, when the saturation correction amount R_satu_tbl_ [170] = -10, the original image data R = 255, G = 0, B = 0 is changed to R = 245, G = 0, B. As in = 0, the value of R becomes small, so that the brightness decreases and the saturation decreases.

Now, the above R, G, and B color signals are converted into C, M, and
Consider the case of substituting each color signal of Y. As the simplest example now, when R, G, and B are converted into their complementary colors C, M, and Y by the conversion formula of C = 255-RM = 255-G Y = 255-B, respectively, C = 0. , M = 255, Y = 255, but after correction, C = 10, M = 255, Y = 255. This is because when K ink is used, it can be replaced by C = 0, M = 245, Y = 245, K = 10 by the undercolor removal processing by the undercolor removal unit 10. By the degree correction, the total ink amount can be reduced by 10.

Incidentally, since the gamma correction, binarization and other post-processes may be included in the actual image processing, the numerical values may not necessarily be as described above, but qualitatively such a principle is adopted. This makes it possible to reduce the amount of ink.

(Embodiment 3) FIG. 4 shows another embodiment of the image processing apparatus according to the present invention. Similar to the case of the above-described second embodiment, the image processing apparatus 22 shown here limits the ink amount particularly in the high saturation region where the total ink amount is maximum when the ink is ejected onto the printing paper by the ink jet printer or the like. Is suitable when According to the method of the second embodiment, the black ink is mixed in the pure red color, and the turbidity is easily noticeable in the case of the printer. Moreover, the effect of reducing the amount of ink is not sufficient. The present embodiment shown in FIG. 4 can solve such a problem.

In this embodiment, in FIG. 4, (1) Mean_RGB = (R
+ G + B) / 3, and (2) Calculation of the deviation amount Diff_R = R−Mean_RGB Diff_G = G−Mean_RGB Diff_B = B−Mean_RGB from the average value of the R, G, and B signals by the data deviation calculator 5. The procedure is similar to that of the embodiment shown in FIG. As the saturation correction data stored in the saturation correction table 7, the correction data shown in FIG. 9 is used as in the case of the embodiment shown in FIG.

In the present embodiment, the RGB correction unit 16 performs an operation of subtracting the saturation correction amount for each of the R, G, and B colors from the signal amounts of the remaining two colors.
For example, by using the saturation correction amount R_satu_tbl [Diff_R] for R, the two colors G and B other than the R signal are expressed as Rnew = RGnew = G−R_satu_tbl [Diff_R] Bnew = B−R_satu_tbl [Diff_R]. to correct. Also, the saturation correction amount G_sat
Using u_tbl [Diff_G], two colors B and R other than the G signal
Is corrected as Rnew = R−G_satu_tbl [Diff_G] Gnew = GBBnew = B−G_satu_tbl [Diff_G]. Also, the saturation correction amount B_sat for B
Using u_tbl [Diff_B], two colors R and G other than the B signal
Is corrected as Rnew = R−B_satu_tbl [Diff_B] Gnew = G−B_satu_tbl [Diff_B] Bnew = B.

When the subtraction processing as described above is performed, for example, the color near the pure color of "red" is not added with black ink to reduce the saturation, but M (magenta) ink and Y
(Yellow) The amount of ink itself is reduced to decrease the saturation in the direction of increasing brightness. This makes it possible to reduce the amount of ink. According to this method, it is possible to obtain the effect of reducing the amount of ink used twice as compared with the embodiment of FIG. Further, since it is not necessary to add black ink, the color of the obtained image does not become turbid, so that a more natural correction result can be obtained in the case of a printer that prints with ink.

Generally, at the pure color points of R, G and B, the deviation amount D
The values of iff_R, Diff_G, and Diff_B become the maximum value of 170,
In the high saturation region of R, G, B close to the pure color point, the value of the deviation amount becomes a value close to the maximum value 170. In the high saturation area including the pure color point, the amount of ink to be used becomes a problem, but if the saturation reduction processing is performed so as to decrease the saturation in the high saturation area in the high saturation area as in the present embodiment. As a result, the amount of ink when converted into C, M, and Y can be reduced.

(Embodiment 4) FIG. 5 shows still another embodiment of the image processing apparatus according to the present invention. The image processing device 32 shown here is different from the previous embodiment shown in FIGS. 2 to 4 in (1) the deviation amount of each of the three color signals of R, G, and B is larger or smaller than a predetermined threshold value. A deviation amount determination unit 11 for determining whether the deviation amount is determined is provided. (2) The RGB correction unit 26 performs different processing depending on whether the deviation amount is larger or smaller than a predetermined threshold. (3) The saturation correction table 7 has That is, the saturation correction data shown in FIG. 10 is stored. In this embodiment, the predetermined threshold value is set to 120.

The correction data shown in FIG. 10 is (1) When the deviation amount is smaller than the threshold value 120, the deviation amount Diff_R and the saturation correction amount R_satu_tbl_ [Diff_R] change while maintaining the same sign, and the deviation amount Is the threshold value 120 and the minimum value -1
At 70, the saturation correction amount becomes zero. Also, (2)
When the deviation amount is larger than the threshold value 120, the saturation correction amount becomes negative from the threshold value 120, and the saturation correction amount increases in the negative direction as the deviation amount approaches the maximum value 170.

In this embodiment, in FIG. 5, (1) Mean_RGB = (R
+ G + B) / 3, and (2) the deviation amount Diff_R = R−Mean_RGB Diff_G = G−Mean_RGB Diff_B = B−Mean_RGB from the average value of the R, G, and B signals by the data deviation calculator 5 has already been calculated. The same operation is performed as in the above-described embodiments.

The deviation amount judgment unit 11 judges whether the deviation amounts Diff_R, Diff_G, and Diff_B of the RGB signals are larger or smaller than the threshold value 120, and the judgment result is the RGB correction unit 2.
Sent to 6. When the deviation amount Diff_R or the like is larger than the threshold value 120 (Diff_R> 120), the RGB correction unit 26
Similar to the embodiment shown in FIG. 4, an operation of subtracting the saturation correction amount for each of R, G, and B colors from the signal amounts of the remaining two colors is performed. For example, by using the saturation correction amount R_satu_tbl [Diff_R] for R, other than the R signal,
The colors G and B are corrected as follows: Rnew = RGnew = G−R_satu_tbl [Diff_R] Bnew = B−R_satu_tbl [Diff_R]. When Diff_G> 120, the saturation correction amount G_satu_tbl [Diff_G] for G is used to set the other two colors B and R other than the G signal as Rnew = R−G_satu_tbl [Diff_G] Gnew = GBnew = B−G_satu_tbl. Correct like [Diff_G]. When Diff_B> 120, the saturation correction amount B_satu_tbl [Diff_B] for B is used to set the other two colors R and G other than the B signal to Rnew = R−B_satu_tbl [Diff_B] Gnew = G−B_satu_tbl [Diff_B]. Correct like Bnew = B.

On the other hand, the RGB correction unit 26 determines the deviation amount Diff_
When R and the like are smaller than the threshold value 120 (Diff_R ≦ 120), the original data of R is added and corrected as Rnew = R + R_satu_tbl [Diff_R] as in the embodiment shown in FIG. Similarly, the RGB correction unit 26
, The deviation amount Diff_G, etc. is smaller than the threshold value 120 (Diff_G
_G ≤ 120), the original data of G is added and corrected as Gnew = G + G_satu_tbl [Diff_G]. Further, the RGB correction unit 26
, The deviation amount Diff_B, etc. is smaller than the threshold value 120 (Diff_B
_B ≤120), the original data of B is added and corrected as in Bnew = B + B_satu_tbl [Diff_B].

As described above, by switching the correction method for each signal amount of R, G, B according to the value of the deviation amount Diff_R or the like, the area where the deviation amount Diff_R or the like is smaller than 120, that is, the saturation is Saturation enhancement processing is executed in a region that is not too high, while on the other hand, in a region where the deviation amount Diff_R or the like is greater than 120, that is, because the saturation is sufficiently high, there is no problem in image quality even if it is lowered, but the dot duty The ink amount is reduced in an area where there is concern. If the saturation correction data as shown in FIG. 10 is used as in the present embodiment, both the saturation adjustment processing and the processing for dot duty limitation, that is, ink amount limitation are performed as one saturation. It can be efficiently realized by using the correction table.

Although the present invention has been described with reference to some preferred embodiments, the present invention is not limited to these embodiments, and various modifications are possible within the technical scope described in the claims. Can be modified. For example, in each of the above embodiments,
It is assumed that the CMY conversion unit 8 performs conversion such as C = 255-RM = 255-G Y = 255-B, but, of course, other conversion forms can be adopted as necessary.

Further, although the binarization processing is performed in the binarization unit 9 using the error diffusion method, other methods such as a dither processing method and a minimum mean error method may be used. Since these techniques are well known in the art, a detailed description thereof will be omitted, but a brief description is as follows.
That is, the dither processing method is a method of comparing the input image data with the dither matrix pattern and determining the binary output of one pixel based on the magnitude relationship. The minimum average error method is a method of correcting the signal amount of the target pixel with a weighted average value of the quantization error generated in the binarized pixels around the target pixel. The error diffusion method and the average error diffusion method are basically equivalent to each other, that is, equal to each other, except that when the error diffusion work is performed.

Further, in the image creating system shown in FIG.
For the sake of convenience, the image processing devices 2 to 32 are shown separately from the color image data output device 1 and the image output device 3, but in an actual system, the image processing device 2 and the like are provided integrally with the color image data output device 1. Or image output device 3
It may be integrated with. Also, if the output device itself is capable of multi-level output instead of binary,
Of course, such a binarization unit can be omitted.
Further, the saturation correction table shown in FIG. 6 to FIG.
Although they are polygonal lines, it goes without saying that they may be curves that change smoothly.

[0062]

According to the image processing method of the first aspect and the image processing apparatus of the second aspect, the original data of R, G, B is obtained based on the correction data stored in the saturation correction table. Since the correction is performed, the circuit configuration for the saturation correction process can be simplified.

The correction data in the saturation correction table stores the correlation between the deviation amount from the average value of the R, G and B color signals and the saturation correction amount corresponding to the deviation amount. Therefore, it is possible to surely obtain the target saturation without deteriorating the image quality of the original image.

Further, by appropriately changing the contents of the correction data stored in the saturation correction table, it is possible to finely adjust the saturation according to the desire of the person who views the color redevelopment. Further, as a result of the saturation adjustment particularly in the high saturation area, it is possible to contribute to the reduction of the ink amounts of the C, M, Y and K color inks.

According to the image processing apparatus of the third aspect,
Since the difference from the average value of each color signal of R, G, B is corrected so as to be enlarged, the saturation enhancement processing can be performed on the entire region of the original R, G, B signals.

According to the image processing apparatus of the fourth aspect,
Since the difference from the average value of each color signal of R, G, B is corrected so as to be reduced, the saturation can be reduced for the entire area of the original R, G, B signals.

According to the image processing apparatus of the fifth aspect, desired saturation enhancement is performed on a region having relatively low saturation that requires saturation enhancement, while it is not necessary to enhance saturation. Saturation enhancement processing can be omitted for the high saturation region. In addition, such fine adjustment can be accurately performed.

According to the image processing apparatus of the sixth aspect,
When performing the undercolor removal processing of replacing the black component of the color to be reproduced with the three color materials of C, M, and Y with the black color material, the total amount of ink used is determined as the result of the saturation adjustment in the high saturation area. It can be reduced.

According to the image processing apparatus of the seventh aspect, when the saturation is reduced, the amount of the color material itself expressing the target color is reduced instead of reducing the saturation by adding black ink. To reduce the saturation, that is, the saturation can be reduced in the direction of increasing brightness. Therefore, the effect of lowering the ink amount in the high saturation region becomes more remarkable. Further, since the black ink is not added, the color of the reproduced image does not become muddy, so that the reproduced image in a very natural state can be obtained.

According to the image processing apparatus of the eighth aspect, one saturation correction table is used for both the desired saturation adjustment processing and the dot duty restriction processing in the high saturation area, that is, the ink amount restriction processing. Can be performed simultaneously and are extremely efficient.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an image creating system using an image processing apparatus according to the present invention.

FIG. 2 is a block diagram showing a first embodiment of the image processing apparatus according to the present invention.

FIG. 3 is a block diagram showing a second embodiment of the image processing apparatus according to the present invention.

FIG. 4 is a block diagram showing a third embodiment of the image processing apparatus according to the present invention.

FIG. 5 is a block diagram showing a fourth embodiment of the image processing apparatus according to the present invention.

FIG. 6 shows an example of correction data stored in the saturation correction table shown in FIG. 2, particularly correction data in which the RGB deviation amount and the saturation correction amount change while maintaining the same sign. It is a figure.

7 is another example of the correction data stored in the saturation correction table shown in FIG. 2, in particular, the correction data in which the RGB deviation amount and the saturation correction amount change while maintaining different signs. FIG.

8 is another example of the correction data stored in the saturation correction table shown in FIG. 2, in particular, the saturation correction amount is set to 0 (zero) at the maximum value and the minimum value of the RGB deviation amount. It is a figure which shows the data for correction.

9 is a diagram showing an example of correction data stored in the saturation correction tables shown in FIGS. 3 and 4, particularly correction data in which a saturation correction amount increases in a negative direction in a high saturation region S. FIG. Is.

10 is a diagram showing an example of correction data stored in the saturation correction table shown in FIG. 5, particularly correction data in a state where the correction data of FIG. 8 and the correction data of FIG. 9 are combined. is there.

FIG. 11 is a deviation amount Diff_ relating to R, G, and B color signals.
It is a figure which shows R, G, and B typically.

[Explanation of symbols]

 2 image processing device 4 average value calculation unit 5 data deviation calculation unit 6 RGB correction unit 7 saturation correction table 8 CMY conversion unit 9 binarization unit 10 undercolor removal unit 11 deviation amount determination unit 12 image processing device 16 RGB correction unit 26 RGB corrector D1 Original color image data D2 Final color image data

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 1/46 H04N 1/46

Claims (8)

[Claims] 1. An image processing method for adjusting the saturation of original RGB data for output, wherein an average value (Mean_RGB) of each color signal amount of original RGB data is calculated, and an average value (Mean_RGB) of each color signal of original RGB data is calculated. ), The amount of deviation (Diff_R, G, B) is calculated and the saturation correction amount (R, G, B_satu_tbl [Diff_
R, G, B]) is stored, the saturation correction amount corresponding to the calculated deviation amount (Diff_R, G, B) is read out, and the read saturation correction is performed. An image processing method characterized by correcting original RGB data according to an amount. 2. An image processing apparatus for adjusting the saturation of original RGB data and outputting the same, wherein an average value calculation unit for calculating an average value (Mean_RGB) of each color signal amount of the original RGB data, and each color signal of the original RGB data. Data deviation calculation unit that calculates the deviation amount (Diff_R, G, B) from the average value (Mean_RGB), and the saturation correction amount (R, G, B_satu_tbl [Diff_
R, G, B]) storing the saturation correction table and RG for correcting the original RGB data by the above saturation correction amount
An image processing apparatus comprising: a B correction unit. 3. The image processing apparatus according to claim 2, wherein the saturation correction table stores correction data that changes so that the deviation amount and the saturation correction amount maintain the same sign, and the RGB correction unit An image processing apparatus characterized by adding a saturation correction amount to original RGB data. 4. The image processing apparatus according to claim 2, wherein the saturation correction table stores correction data that changes so that the deviation amount and the saturation correction amount maintain different signs, and the RGB correction unit An image processing apparatus characterized by adding a saturation correction amount to original RGB data. 5. The image processing device according to claim 2, wherein in the saturation correction table, the deviation amount and the saturation correction amount maintain the same sign, and the saturation correction amount is zero when the deviation amount is maximum and minimum. The image processing apparatus is characterized in that the RGB correction unit adds the saturation correction amount to the original RGB data. 6. The image processing apparatus according to claim 2, wherein the CMY conversion unit converts the RGB data after saturation correction output from the RGB correction unit into CMY data, and CMY data output from the CMY conversion unit. On the other hand, the undercolor removal processing, that is, the K (black) signal amount is obtained based on the minimum value of the C, M, and Y signal amounts, and the K signal amount is subtracted from the C, M, and Y signal amounts. The saturation correction table has a negative color removal unit for performing processing including steps. Further, the saturation correction table has a negative saturation saturation correction amount from a predetermined deviation amount and the saturation correction is performed as the deviation amount approaches the maximum value. An image processing apparatus, which stores correction data such that the amount increases in the negative direction, and the RGB correction unit adds the saturation correction amount to the original RGB data. 7. The image processing device according to claim 2, wherein in the saturation correction table, the saturation correction amount becomes negative from a predetermined deviation amount, and the saturation correction amount becomes negative as the deviation amount approaches a maximum value. The RGB correction unit stores the original RGB data by subtracting the saturation correction amount for each of R, G, and B from the signal amounts of the remaining two colors by storing the correction data that increases in the direction. An image processing device characterized by correction. 8. The image processing apparatus according to claim 2, further comprising a deviation amount determination unit that determines whether the deviation amount is larger or smaller than a predetermined threshold, and the saturation correction table further comprises:
(1) When the deviation amount is smaller than the above threshold value, the deviation amount and the saturation correction amount have the same sign, and the correction data is stored so that the saturation correction amount becomes zero when the deviation amount is at the threshold value and at the minimum. (2) When the deviation amount is larger than the above threshold value,
The RGB correction unit stores correction data such that the saturation correction amount becomes negative from the threshold value and the saturation correction amount increases in the negative direction as the deviation amount approaches the maximum value. When the amount is smaller than the threshold value, the saturation correction amount is added to the original RGB data. (2) When the deviation amount is larger than the threshold value, R, G and B are each 1
An image processing apparatus, which corrects original RGB data by subtracting a saturation correction amount for a color from a signal amount for the remaining two colors.