JP5697425B2 - Image processing apparatus and image processing method - Google Patents

Description

  The present invention relates to processing for obtaining color material data of a colored color material and a colorless color material for image data.

  As ink for an ink jet recording apparatus, dye ink using a dye as a color material and pigment ink using a pigment as a color material are used.

  When an image is formed on a recording medium using pigment ink, a phenomenon occurs in which regularly reflected light, which is light reflected on the formed image, is colored. For example, when an image formed by the recording device is placed under a light source such as a spotlight, the spotlight itself emits white light, but the light is a light reflected on the recording medium. The reflected light is colored.

  The specularly reflected light tends to be colored magenta particularly in an area where cyan ink is frequently used in a color image, and yellow as a whole in a monochrome image. Further, depending on the area of the image, the regular reflection light tends to change to a rainbow color according to the change in the ink amount. The coloring of the regular reflected light deteriorates the image quality because the regular reflected light is different from the color of the diffused light.

  Here, an evaluation method (Patent Document 1) with specular reflection light color will be described with reference to FIG. The measurement sample 101 is irradiated from a predetermined angle by the light source 102, and regular reflection light from the measurement sample 101 is detected by the light receiver 103. The light receiver 103 detects tristimulus values XxYxZx in the CIE XYZ color system. From the difference between the detected XxYxZx and the tristimulus value XsYsZs of a sample in which bronze is not generated (for example, a black polished glass plate having a small refractive index wavelength dispersion), a * b in the CIE L * a * b * color system * Is calculated. The saturation C * represented by a * b * indicates the degree of coloring of the regular reflection light. The smaller the C * is, the less the color of the specular reflected light is, and in the case of a sample without the color of the specular reflected light, the value of C * is 0 (that is, the origin is located on the a * b * plane).

  As described above, bronze and thin film interference are known as a cause of the specularly reflected light being colored.

  Bronze is a phenomenon that occurs because reflection at the interface of the formed image has wavelength dependence. Bronze is known to have a unique color depending on the ink. For example, specularly reflected light is colored magenta in an image area formed with cyan ink. Bronze greatly contributes to the wavelength dependence of reflection at the interface between the air layer and the ink layer. Therefore, by re-ejecting yellow ink after image formation, a method of reducing bronzing by covering an image area formed with a relatively large wavelength-dependent cyan ink or the like with a relatively small wavelength-dependent yellow ink Is known (Patent Document 2). Further, it is described that the discharge amount of yellow is relatively reduced at a hue angle of 180 ° to 360 ° (region from cyan to magenta hue) in the L * a * b * space.

JP 2006-177797 A JP 2004-181688 A

  However, in the method of Patent Document 2, when an overcoat is formed by covering an image with yellow ink in a cyan-> blue-> magenta region in the L * a * b * space where cyan and magenta inks are often used, the color gamut is It will decrease. In particular, since yellow is complementary to blue, the color gamut is significantly reduced. On the other hand, if the discharge amount of yellow ink is reduced, the reduction of the color gamut can be suppressed, but the bronze becomes conspicuous.

  Therefore, a method of using a colorless color material, which is an ink containing no color material, as a recording agent for overcoating an image can be considered. The colorless color material has a very small stimulus value representing bronze. In addition, since the transparent colorless color material does not affect the color development, it is expected to more effectively reduce the coloring of the regular reflection light without reducing the color gamut.

  However, when an image is overcoated with a colorless color material, thin film interference occurs due to the optical path difference of the light reflected from the upper and lower layers of the colorless color material layer. ), The color of the specularly reflected light changes. FIG. 2 plots the coloring of specularly reflected light on the a * b * plane according to the method of Patent Document 1 when the amount of colorless color material is changed and overcoated on a cyan ink solid background. The numbers on the graph in FIG. 2 indicate the amount of colorless color material. From FIG. 2, it can be seen that the coloration of the specularly reflected light on the cyan solid surface is in the magenta hue due to the influence of bronze, and that the coloration rotates clockwise as the amount of colorless color material increases. That is, even if the colored color material is overcoated with the colorless color material, the coloring of the regular reflection light is not necessarily reduced, and changes according to the amount of the colorless color material.

  Furthermore, it has been found through experiments that the change in color varies depending on the type of colored material used as a base. For example, the coloring that occurs when a predetermined amount of clear ink is overcoated on a cyan ink solid background is different from the coloring that occurs when the same amount of clear ink is overcoated on a magenta ink solid background. In other words, even when the overcoat is uniformly overcoated with a predetermined amount of colorless color material, the coloring of the regular reflection light is not sufficiently reduced.

  Therefore, an object of the present invention is to reduce coloring of specularly reflected light that is observed globally.

In order to solve the above-described problems, an image processing apparatus according to the present invention generates color material data for forming an image by recording and scanning the same area on a recording medium a plurality of times with the same color material. A conversion means for converting image data corresponding to the target pixel in the same region into color material data corresponding to the color material amount of the color material; and a recording ratio of each of the recording scans in the target pixel. The first recording ratio generates color material data corresponding to the color material amount of the colorless color material in the target pixel, and determines the recording ratio of each of the recording scans in the peripheral pixels of the target pixel. Generating means for generating color material data corresponding to the amount of the color material of the colorless color material in the peripheral pixels at a second recording ratio different from the recording ratio.

  According to the present invention, it is possible to reduce coloring of specularly reflected light observed globally.

It is a figure for demonstrating the evaluation method with a regular reflection color. It is a figure for demonstrating the example which changed the colorless color material amount on the cyan solid ground, and evaluated regular reflection light coloration. It is a schematic diagram for demonstrating the principle of this embodiment. It is a figure which shows the structure of the image processing apparatus of this embodiment. It is a figure which shows the structure of the computer system of this embodiment. It is a block diagram which shows the functional block of the image processing apparatus of this embodiment. It is a figure which shows an example of the mask process in this embodiment. It is a figure which shows an example of the mask process in this embodiment. It is a figure which shows typically the ink amount in each recording scan in this embodiment. It is a schematic diagram which shows the example of the relationship between the position control of the colorless ink layer in the colored ink layer in this embodiment, and a mask pattern.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same components are described with the same reference numerals.

  In this embodiment, in order to show an example in which the present invention is applied to an ink jet printer, an example of clear ink is shown as a colorless color material. However, the present invention is not limited to these examples, and clear toner is applied to an electrophotographic printer. May be.

  In the present embodiment, ink that is a recording material is represented by katakana notation such as cyan, magenta, yellow, black, clear (colorless or almost colorless), red, green, and blue. In addition, the color or its data, or the hue is represented by alphabetic characters such as C, M, Y, K, CL, R, G, and B. That is, C represents cyan or its color material data, or hue. Similarly, M represents magenta, Y represents yellow, K represents black, R represents red, G represents green, and B represents blue. CL represents colorless (transparent) or its color material data.

  Also, the specularly reflected light is colored means that the reflected light when the illumination light is reflected in the image formed on the recording medium shows a different color from the illumination light. The coloring of light is simply expressed as “colored” or “color”. A value indicating coloring, such as an a * b * value in the CIE-L * a * b * color system, is expressed as colored information.

  An “area” is a minimum unit in which dot on / off is defined. In this connection, “image data” in the following color matching, color separation, and γ correction represents a set of pixel data to be processed, and each pixel data has, for example, an 8-bit multi-value gradation value. Show.

  In addition, “pixel data” referred to as halftoning represents pixel data itself that is a processing target. By halftoning, pixel data having a gradation value of a plurality of bits (for example, 8 bits) is converted into pixel data (index data) having a gradation value of, for example, 4 bits. In the following description, unless otherwise specified, the smallest structural unit that can change the amount of clear ink applied is referred to as a pixel.

  First, the principle of this embodiment will be described. By generating different coloring for each pixel, the observed coloring can be reduced. For example, it is assumed that a color generated when an arbitrary pixel is overcoated with a predetermined amount of a colorless color material is red. Then, it is assumed that the coloring that occurs when another predetermined amount of a colorless color material is overcoated on the adjacent pixel is green, and that the coloring of the adjacent pixel is also blue. In such a case, as shown in the schematic diagram of FIG. 3, the color of the specularly reflected light is white by the three principles of light (additive color mixture). That is, since the color of the local specularly reflected light (for example, a combination of red, green, and blue) is viewed globally, the specularly reflected light appears to have no color to the observer.

  Here, the reason why the coloring of the specular reflected light is expressed globally and locally is because the coloring of the specular reflected light depends on the scale of observation. Colored changes that are finer than the resolution of the human eye are perceived as averaged. That is, the general coloring of regular reflection light is a color averaged within a range in which a person can resolve the coloring of regular reflection light. Further, the coloration of the local regular reflection light is a range in which a person cannot resolve the coloration of the regular reflection light, for example, a color averaged in the order of several tens of micrometers.

  The present inventor has experimentally found that when colored ink is layered on a recording medium, the coloring changes depending on the position of the colorless ink layer in a layer formed by the colored ink (hereinafter, ink layer). . For example, when a colorless ink layer is placed (overlaid) on the upper layer of a cyan ink layer in a solid cyan ink layer, a colorless ink layer is sandwiched between an intermediate layer, and a colorless ink layer is laid on a lower layer, Different. That is, the general coloring differs depending on the order of the color material layers recorded locally in a predetermined area on the recording medium.

  Therefore, the observed coloring can be reduced by generating different coloring in a predetermined area in the image, for example, each pixel depending on the order in which the coloring materials are recorded. For example, it is assumed that when a predetermined amount of a colorless color material is placed on an arbitrary pixel, the coloring generated in the pixel is red. Then, it is assumed that the coloring generated when a predetermined amount of colorless color material is sandwiched between the middle layers of the colored color material between adjacent pixels is green. Further, it is assumed that the color is blue when a predetermined amount of a colorless color material is laid on an adjacent pixel below the colored color material. In such a case, the specular reflection color of the pixel of interest and its surrounding pixels generally becomes white by three generally known light principles (additive color mixture). That is, when the color (red, green, blue) of the local specular reflection light is viewed globally, it becomes white, so that it appears to the observer that there is no specular reflection color.

  The configuration of the image processing apparatus of this embodiment is shown in FIG. In FIG. 4, 401 is a printer, 402 is a computer system having both a printer controller and a client computer, and 403 is a connector cable represented by a network cable, a SCSI cable, and the like.

<Computer system>
FIG. 5 is a block diagram showing the configuration of the computer system 402 of FIG. In the figure, an interface (I / F) 501 connects a mouse and keyboard 511 and a computer system 402 for a user to input various manual instructions. The CPU 502 controls the operation of each block inside the computer system 402 and executes a program stored in the ROM 503 or RAM 504. The ROM 503 stores in advance a program necessary for image processing and the like represented by a flowchart described later. The RAM 504 temporarily stores, as a work memory, a program for performing various processes by the CPU 502, image data to be processed, various processing results by the CPU 502, and the like. The display control unit 505 controls the display 512 that displays an image to be processed and a message to the operator. An interface (I / F) 506 connects the computer system 402 and the color printer 401. The CD drive 507 reads or writes data stored in a CD (CD-R / CD-RW / DVD / DVD-R / DVD-RW) which is one of external storage media. The FD drive 508 reads or writes from an FD that is one of external storage media. When a program for image processing, printer information, or the like is stored on a CD, FD, DVD, or the like, these programs are installed on the HD 509 and transferred to the RAM 504 as necessary. A hard disk (HD) 509 stores, as one of external storage media, programs and image data transferred to the RAM 504 and the like, and stores image data after various processes. An interface (I / F) 510 transmits various data held in various places of the computer system 402 to an external device and receives various data from the external device, such as an external input 513 such as a modem or a network card. And the computer system 402 are connected.

  FIG. 6 is a block diagram showing functional blocks of the image processing apparatus shown in FIG. The printer 401 performs printing with pigment ink, and a recording head that discharges ink is used. As shown in FIGS. 4 and 6, the image processing apparatus includes a printer 401 that uses pigment ink and a computer system 402 as a host apparatus or an image processing apparatus.

<Host>
Hereinafter, the configuration of the host device in FIG. 6 will be described. There are applications and color conversion (color matching) as programs operating on the host device. The application 601 executes processing for creating image data to be printed by the printer 401. Note that this image data or image data that is the basis of the creation can be taken into the computer system 402 via various media. For example, JPEG format image data captured by a digital camera can be captured from an external input 513 such as a flash memory via the I / F 510. Further, for example, image data stored in the HD 509 or image data stored in the CD-ROM of the CD drive 507 can be captured. Further, data on the web can be taken in via the external input 513 from the Internet. These captured data are displayed on the display 512, and are edited and processed via the application 601, for example, image data R, G, and B of the sRGB standard are created. Then, this image data is transferred to the color matching 602 in response to a printing instruction.

(Color matching process)
The color matching 602 holds a three-dimensional LUT that defines a correspondence relationship for mapping the color gamut reproduced by the image data R, G, and B of the sRGB standard into the color gamut reproduced by the printer. Interpolation is used in combination with this three-dimensional LUT, and data conversion is performed to convert 8-bit image data R, G, B into image signals R, G, B in the printer color gamut. The color matching process is not limited to the three-dimensional LUT, and may be performed using a determinant.

  Note that the processing of the application 601 and the color matching 602 described above is performed by the CPU 502 in accordance with a program that realizes these functions.

<Printer>
Hereinafter, the printer 401 will be described. In this embodiment, the processing after the color separation unit 603 is performed inside the printer 401. In the printer 401, a color separation unit 603, a γ correction unit 604, a halftoning unit 605, a dot arrangement patterning unit 606, a colored ink scanning recording amount control unit 607, a colorless ink scanning recording amount control unit 608, a random number generation unit 609, and The head drive circuit 610 operates under the control of a CPU (not shown) that constitutes the control unit of the printer 401 using a dedicated hardware circuit. The present embodiment is not limited to the above-described configuration, and the processing from the color separation unit 603 to the image forming unit 610 may be performed by the printer 401 or may be performed by the printer driver of the computer system 402, for example.

(Color separation processing)
The color separation processing 603 is based on the image signals R, G, and B of the target pixel on which the above color gamut mapping is performed, and corresponds to a combination of ink amounts (color material amounts) for reproducing the color represented by this data, for example, CMYK To color separation data of colored ink and colorless ink (CL). In the present embodiment, this process is performed using a well-known method, similar to the color matching process, using a three-dimensional LUT together with an interpolation operation. Note that the color separation data of colorless ink is also described in the three-dimensional LUT.

  The color separation data (ink amount) of the colorless ink may be a fixed amount. In this case, the predetermined amount may be stored in another storage medium instead of the LUT.

(Γ correction processing)
The γ correction unit 604 performs known gradation value conversion for each color material signal data of the color separation data obtained by the color separation unit 603. Specifically, by using a one-dimensional LUT corresponding to the gradation characteristics of each color ink of the printer 401 used in this embodiment, the color separation data is converted so as to be linearly associated with the gradation characteristics of the printer 401. To do. Note that the color separation data of the colorless ink is colorless, so the gradation value conversion process does not have to be performed.

(Halftoning)
The halftoning unit 605 performs quantization that converts, for example, 8-bit color separation data C, M, Y, K, and CL into 4-bit data, for example. The quantization performed in this embodiment converts 8-bit data into 4-bit data using a known error diffusion method. Further, in the present embodiment, the description will be continued assuming that the colored ink is four colors of C, M, Y, and K, but the present invention is not limited to this. That is, a six-color configuration of C, M, Y, and K and light C (Lc) and light M (Lm) may be used, or ink such as R, G, and B, and light K or the like may be included. The quantized 4-bit data is data serving as an index for indicating an arrangement pattern in the dot arrangement patterning unit 606.

(Dot arrangement patterning process)
The dot arrangement patterning unit 606 plays a role of reducing the multi-value level of 0 to 8 (4 bits) to a binary level that determines the presence or absence of dots. That is, for each pixel corresponding to an actual print image, dot placement is performed according to a dot placement pattern corresponding to 4-bit index data (tone value information) that is print image data. Thus, by assigning a dot arrangement pattern corresponding to the gradation value of each pixel to each pixel represented by 4-bit data, dot on / off is defined in each of a plurality of areas in the pixel, Discharge data “1” or “0” is arranged for each area in one pixel.

(Ink scanning recording amount control)
In the present embodiment, control of the scanning recording amounts of colored ink and colorless ink is performed as separate processing. By performing separate processing, the number of recording scans of colored ink and colorless ink can be made different, and the number of recording scans can be individually selected.

  The colored ink scanning recording amount control unit 607 performs mask processing using a mask pattern stored in a storage unit (not shown) of 1-bit ejection data of colored ink obtained by the above-described dot arrangement patterning process. In other words, the ejection data for each scan for completing the printing of the scanning area of the predetermined width by the recording head by a plurality of scans is generated by the mask processing corresponding to each scanning. Details of the mask processing will be described later.

  The colorless ink scanning recording amount control unit 608 stores a plurality of mask patterns of colorless ink (CL), and switches the mask pattern for each region in accordance with the output of the random number generation unit 609, whereby the colorless ink layer in the colored ink layer is switched. The position of the ink layer is changed.

(Random number generation processing)
The random number generator 609 calculates a uniform random number within a range of 0 to 1.0 by dividing a natural random number calculated by the CPU or the like (for example, an output value of the RAND () function in C language) by the maximum value. calculate. Next, for example, when 5 mask patterns are stored, indices 0 to 4 indicating the mask patterns are calculated as follows by multiplying the uniform random number by the number of patterns 5.
Mask Pattern Index = (int) (RAND () /RAND_MAX*5.0) (Processing 1)
if (Mask Pattern Index == 5) Mask Pattern Index = 4 (Process 2)
Here, Mask Pattern Index: colorless ink mask pattern index, RAND (): natural random number, RAND_MAX: maximum random number.

  Note that the random number calculated here is not limited to a uniform random number, and a normal random number centered on the central value of the mask pattern index (the central value is 2 if the number of patterns is 5) is used. Also good.

  Further, the output value may be generated using a mask process that performs a specific frequency modulation such as a commonly known Bayer type mask, white noise mask, blue noise mask, or green noise mask.

(Head drive circuit)
The head drive circuit 610 drives the print head 611 using the discharge data Y, M, C, K, CL for each print scan sent at an appropriate timing, and discharges each ink.

  In the above description, an example of switching a plurality of mask patterns prepared by the colorless ink scanning recording amount control unit 608 has been described. However, the colored ink scanning recording amount control unit 607 also performs colorless ink scanning according to the output of the random number generation unit 609. Similar to the recording amount control unit 608, a plurality of prepared mask patterns may be switched. By preparing a plurality of colored ink mask patterns, the randomness of the positions of the colored ink layer and the colorless ink layer can be further improved. On the other hand, a plurality of mask patterns to be prepared are the same for colored ink and colorless ink, and different random numbers are output from the random number generator 609 so that different mask patterns can be selected for each. Good.

(Mask processing)
Hereinafter, the mask processing of the colored ink scanning recording amount control unit 607 and the colorless ink scanning recording amount control unit 608 will be described. In addition, since both processes perform the same mask process with respect to a colored ink and a colorless ink, it demonstrates as a mask process below.

  FIG. 7 schematically shows a recording head and a recording pattern in order to explain a multi-pass recording method using ink. In order to simplify the explanation, it is assumed that the recording head 1301 has 25 nozzles. The nozzles are divided into first to fifth nozzle groups, and each nozzle group includes five nozzles. In each of the scans 1303 to 1307, the area where each nozzle performs recording is indicated by black by the mask pattern 1302.

  The recording patterns recorded by each nozzle group are complementary to each other, and when these are superimposed, recording of a region corresponding to a 5 × 5 area is completed. Each of the patterns 1303 to 1307 shows a state in which an image is completed by overlapping recording scans, and the ink amount of each recording pattern is equal. That is, the ink amount (recording ratio) recorded by each recording scan is the same. When each recording scan is completed, the recording medium is conveyed by the width of the nozzle group in the direction of the arrow in the figure. Therefore, the same area of the recording medium (area corresponding to the width of each nozzle group) is configured such that an image is completed only by a total of five recording scans.

  As described above, in the ink recording in this embodiment, the same area of the recording medium is formed by ejecting ink from a plurality of nozzle groups in a plurality of recording scans.

  The example of the recording pattern shown in FIG. 8 is an example using a mask pattern different from the mask pattern 1302. The recording head 1401 has the same configuration as the recording head 1301. The mask pattern 1402 is different in printing ratio from the printing pattern in each printing scan. Each of the patterns 1403 to 1407 shows a state in which an image is completed by overlapping the recording scans by the mask pattern 1402, and the same area (area corresponding to the width of each nozzle group) of the recording medium is 5 times in total. It is completed by recording scan. However, unlike the patterns 1303 to 1307, the recording pattern and the recording ratio are low, and the recording ratio by the initial and final recording scans in all the recording scans is low, and the recording ratio by the intermediate recording scan is high.

  By using the mask pattern as described above, the same area on the recording medium is formed by a plurality of nozzle groups by a plurality of scans, and the amount of ink ejected from the first nozzle group to the fifth nozzle group is controlled. Is possible.

  FIG. 9 schematically shows the ink amount in each printing scan when printing is performed using the mask patterns of FIGS. FIG. 9A schematically shows an ink amount 1501 by a mask pattern in which the printing ratio is not changed by each printing scan, that is, by a mask pattern as shown in FIG. FIG. 9B shows a mask pattern whose printing ratio changes according to the number of printing scans, that is, the ink amount 1502 by the mask pattern 1402 shown in FIG.

  FIG. 10 is a schematic diagram showing an example of the relationship between the position control of the colorless ink layer in the colored ink layer on the recording medium and the mask pattern. FIG. 10 is a graph showing the relationship between the amount of ink recorded in each recording scan on the vertical axis and the number of recording scans on the horizontal axis. Further, in this case, when a mask pattern for colorless ink having a different ink amount shape is combined with a mask pattern for colored ink having an ink amount 1601 in which the shape drawn by the ink amount is a flat shape, it is formed on the recording medium. An example of the ink layer to be performed is shown.

  Here, the mask pattern for colorless ink indicates three types of ink amount change 1602, monotonically increasing ink amount change 1602, parabolic ink amount change 1603, and monotonically decreasing ink amount change 1604 from the shape of the ink amount in the graph described above. . Since the ink layers for the three types have different ink ratios in each printing scan, the positions where the colored ink and the colorless ink are present change in layers as indicated by the ink layers 1605 to 1607. For example, in the ink amount 1601 and the monotonically increasing ink amount 1602, the recording ratio of the colored ink is relatively higher than that of the colorless ink as the number of scans increases. For this reason, a larger amount of the colored ink is ejected onto the recording medium before the colorless ink, and the ink layer of the colored ink is positioned closer to the recording medium. On the other hand, as the number of scans approaches the end (as the number of scans increases), the amount of colorless ink increases as compared to colored ink, so the ink layer of colorless ink is located closer to the surface of the ink layer. become.

  Accordingly, by holding a plurality of mask patterns as shown in FIGS. 7 and 8 in advance and switching (combining) the mask patterns of the colored ink and the colorless ink, the colorless ink layer in the colored ink layer is used. It is possible to control the position. If the positions of the ink layers of the respective color materials are different as described above, the coloration of the reflection that occurs at the interface between the air layer and the ink layer and the regular reflection due to the reflection that occurs inside the ink layer changes.

  Therefore, the colorless ink scanning / recording amount control unit 608 changes the mask pattern of the colorless ink for each pixel based on the random number generated by the random number generation unit 609, thereby changing various (random) pixels of interest and surrounding pixels. Glossy coloring is generated. As described above, since the group with various gloss colors appears white as described above, the overall gloss color is reduced.

  Note that the combination of the color material and the mask pattern for each color material is not limited to the above example as long as the ink layer position can be changed. For example, the color ink scanning recording amount control unit 607 may hold a plurality of mask patterns of colored ink and change them according to random numbers as described above.

  As described above, according to this embodiment, it is possible to reduce the regular reflection color by randomly changing the position of the clear ink layer present in the colored ink layer.

  The colored ink scanning recording amount control unit 607 and the colorless ink scanning recording amount control unit 608 according to the first exemplary embodiment switch the plurality of mask patterns stored in advance according to the output of the random number generation unit 609, but are not limited thereto. It is not a thing. That is, the mask pattern may be generated according to the output of the random number generator.

  Hereinafter, the mask processing by the colored ink scanning recording amount control unit 607 and the colorless ink scanning recording amount control unit 608 in this embodiment will be described with respect to an example in which the number of printing scans is eight. In addition, it demonstrates concisely centering on a different point from Example 1. FIG. Further, the colored ink scanning recording amount control unit 607 and the colorless ink scanning recording amount control unit 608 perform similar mask processing.

First, as in the first embodiment, the random number generator 609 generates uniform random numbers by the following process 3.
Rand (n) = RAND () / RAND_MAX (n = 1-8) (Process 3)
Here, Rand (n) is a uniform random number, RAND () is a natural random number, and RAND_MAX is the maximum random number.

  Next, the colored ink scanning / recording amount control unit 607 and the colorless ink scanning / recording amount control unit 608 obtain eight random numbers that are outputs of the process 3. Then, the recording ratio of colored ink or colorless ink in an arbitrary image area for each recording scan is determined as follows.

  Here, Ink_mount_ratio (n): a printing ratio in the nth printing scan.

  Next, a recording pattern (not shown) is generated according to the recording ratio, and ejection data Y, M, C, K, CL according to the generated recording pattern is output to the head driving circuit 610.

  The random number calculated above is not limited to a uniform random number, and a normal random number centered on the central value of the index of the recording pattern may be used. Furthermore, an output value obtained by performing specific frequency modulation such as a generally known Bayer type, white noise mask, blue noise mask, green noise mask, or the like may be generated.

  As described above, according to the second embodiment, it is not necessary to hold a plurality of mask patterns in advance as in the first embodiment, so that it is possible to obtain further effects such as memory area reduction.

  The present invention also provides a storage medium storing a program code of software for realizing the functions of the above-described embodiments (for example, the processing shown by the flowchart in which the processing of each unit described above is associated with each step). It can also be realized by supplying to. In this case, the functions of the above-described embodiments are realized by the computer (or CPU or MPU) of the system or apparatus reading and executing the program code stored in the storage medium so that the computer can read the program code.

Claims (9)

An image processing apparatus for generating color material data for forming an image by recording and scanning the same area on a recording medium a plurality of times with the same color material,
Conversion means for converting image data corresponding to the pixel of interest in the same region into color material data corresponding to the color material amount of the color material;
Color material data corresponding to the color material amount of the colorless color material in the pixel of interest is generated by a first recording ratio that determines the recording ratio of each of the recording scans in the pixel of interest, and the pixel in the peripheral pixels of the pixel of interest Generating means for generating color material data corresponding to the amount of the color material of the colorless color material in the peripheral pixels by a second recording ratio different from the first recording ratio, wherein the recording ratio of each recording scan is determined; An image processing apparatus comprising: Random number generating means for generating random numbers;
Holding means for holding a plurality of mask patterns having different printing ratios in each of the printing scans;
2. The image according to claim 1, wherein the generation unit selects at least two mask patterns from the plurality of mask patterns according to the random number, and generates the color material data based on the selected mask patterns. Processing equipment.   The image processing apparatus according to claim 2, wherein the plurality of mask patterns include a mask pattern in which a printing ratio monotonously increases and a mask pattern in which the printing ratio monotonously decreases according to the number of times of the printing scan. Random number generating means for generating random numbers;
The generation unit generates a plurality of mask patterns having different recording ratios in each of the recording scans according to the random number, and generates color material data corresponding to the color material amount of the color material by using the generated mask pattern. The image processing apparatus according to claim 1, wherein:   4. The recording ratio of each of the recording scans in the target pixel of the color material data corresponding to the color material amount of the colored color material is the same. 5. Image processing device.   The first recording ratio is the same recording ratio in each of the recording scans, and the second recording ratio is a different recording ratio in each of the recording scans. An image processing apparatus according to claim 1.   The image processing apparatus according to claim 1, further comprising an image forming unit that forms an image using the color material data. An image processing method for generating color material data for forming an image by recording and scanning the same region on a recording medium a plurality of times with the same color material,
A conversion step of converting image data corresponding to the target pixel in the same region into color material data corresponding to the color material amount of the color material;
Color material data corresponding to the color material amount of the colorless color material in the pixel of interest is generated by a first recording ratio that determines the recording ratio of each of the recording scans in the pixel of interest, and the pixel in the peripheral pixels of the pixel of interest Generating a color material corresponding to a color material amount of a colorless color material in the peripheral pixels by a second recording ratio different from the first recording ratio, in which a recording ratio of each recording scan is determined; An image processing method comprising:   A program that causes a computer to function as each unit of the image processing apparatus according to any one of claims 1 to 7.

Images