JP4366447B2 - Image processing apparatus and image processing method - Google Patents

Description

  The present invention relates to an image processing apparatus and an image processing method, and more particularly to an image processing apparatus and an image processing method for performing pseudo-halftone processing by performing error diffusion processing on multi-value image density data.

  Conventionally, an error diffusion method is known as pseudo gradation processing for expressing a multi-valued image in binary (Non-Patent Document 1). In this method, if the pixel of interest is P, its density is v, and the surrounding pixels P0, P1, P2, and P3 of the pixel of interest P are v0, v1, v2, v3, and the threshold for binarization is T. The binarization error E at the target pixel P is distributed to the peripheral pixels P0, P1, P2, and P3 by weight coefficients W0, W1, W2, and W3 that are empirically obtained, and the average density is macroscopically equal to the density of the original image. It is a method to do.

For example, if the output binary data is o
If v ≥ T, then o = 1, E = v-Vmax; . . . (1)
If v <T, o = 0, E = v-Vmin;
(However, Vmax: Maximum concentration, Vmin: Minimum concentration)
v0 = v0 + E × W0; . . . (2)
v1 = v1 + E × W1; . . . (3)
v2 = v2 + E × W2; . . . (4)
v3 = v3 + E × W3; . . . (5)
(Examples of weighting factors: W0 = 7/16, W1 = 1/16, W2 = 5/16, W3 = 3/16)
It can be expressed as.

  Conventionally, when a multi-value image is output using, for example, a color ink jet printer, cyan (C), magenta (M), yellow (Y), and black (K) inks, error diffusion is performed independently for each color. Since pseudo gradation processing is performed using a method or the like, when one color is viewed, even if the visual characteristics are excellent, good visual characteristics cannot always be obtained when two or more colors overlap.

  In order to improve this problem, in Patent Document 1 and Patent Document 2 and the like, by using an error diffusion method by combining two or more colors, a pseudo-intermediate that provides good visual characteristics even when two or more colors overlap. A tone processing method is disclosed.

  Further, Patent Document 3 discloses a method of performing similar improvements by correcting the output value based on the sum of input values after performing pseudo-middle gradation processing on two or more colors independently.

  In particular, it is effective to form an image so that the dots of the cyan component (C) and the magenta component (M) do not overlap each other in order to reduce the graininess in the middle density region of the color image. The following methods are used.

  FIG. 10 is a diagram showing image formation control according to a conventional ink jet system.

  Here, the image data will be described on the assumption that the density component (YMCK) of each pixel is expressed by multi-value data having 8 bits (gradation value of 0 to 255).

If the C component and M component density Ct and Mt of the target pixel of the multi-valued color image are respectively C and M, respectively,
Ct = C + Cerr
Mt = M + Merr
It is expressed. Here, Cerr and Merr are values obtained by error diffusion with respect to the pixel of interest for each of the C component and the M component.

As shown in FIG. 10, regarding the C and M image formation, four types of image formation control are performed according to the density of the C component and the M component of the target pixel.
1. If the sum of (Ct + Mt) is equal to or less than the threshold (Threshold 1), that is, belongs to the region (1) in FIG.
2. The sum of (Ct + Mt) exceeds the threshold (Threshold 1), the sum of (Ct + Mt) is less than another threshold (Threshold 2), and Ct> Mt, that is, the region (FIG. If it belongs to 2), dot recording is performed only with C ink.
3. The sum of (Ct + Mt) exceeds the threshold (Threshold 1), the sum of (Ct + Mt) is less than another threshold (Threshold 2), and Ct ≦ Mt, that is, the region (FIG. If it belongs to 3), dot recording is performed only with M ink.
4). If the sum of (Ct + Mt) is equal to or greater than another threshold (Threshold 2), that is, belongs to the region (4) in FIG. 10, dot recording is performed using C ink and M ink.

  Here, Threshold 1 <Threshold 2.

JP-A-8-279920 Japanese Patent Laid-Open No. 11-10918 Japanese Patent Laid-Open No. 9-139841

An Adaptive Algorithm for Spatial Gray Scale "in society for Information Display 1975 Symposium Digest of Technical Papers, 1975, 36

  However, as in the conventional example described above, when an image is formed by completely arranging C component dots and M component dots, in the case of an original image with 50% each of the C component and the M component, for example, FIG. As shown in FIG. 11A, ideally, all pixels are filled with dots of C ink or dots of M ink. In this state, as shown in FIG. 11B, when the dot position by the C ink and the dot position by the M ink are relatively shifted for some reason, the dot by the C ink and the dot by the M ink in most of the image. Pixels that overlap with each other (this is a pixel that looks bluish) and white pixels in which no dots are formed are dominant.

  Therefore, for example, when recording is performed using a recording head having a configuration in which nozzles for ejecting C ink and nozzles for ejecting M ink are arranged in the carriage scanning direction of an ink jet printer, fluctuations in the carriage scanning speed, etc. Thus, according to the position in the scanning direction, the formed image periodically varies as shown in FIG. 11A or 11B, and the region corresponding to the human eye due to the variation in the existence probability of white pixels. It appears that the concentration of fluctuates periodically. In other words, it appears as a poor quality image to the human eye.

  On the other hand, when an image is formed by disposing C ink dots and M ink dots completely independently, in the case of an original image in which the C component and the M component are 50% each as described above, for example, FIG. As shown in (a), pixels that are ideally recorded nothing, pixels that are recorded with only C ink, pixels that are recorded with only M ink, and pixels that are recorded with both C ink and M ink are evenly distributed. It is formed with an existence probability of about 25%.

  In the case where such C ink dots and M ink dots are arranged independently, for example, as shown in FIG. However, there is a possibility that the pixels to be recorded by both the C ink and the M ink are recorded only by either the C ink or the M ink. The change in density as a whole is small compared to the case where the dots made of C ink and the dots made of M ink are arranged completely exclusively.

  Therefore, although the arrangement of the C ink dots and the M ink dots exclusively has the effect of reducing the graininess of the highlight portion, conversely with the accuracy of image formation, There is a problem that the uniformity of the image tends to be impaired in the intermediate density to the high density region. On the other hand, focusing only on the highlight portion, since the dots are originally arranged sufficiently apart from each other, the image quality degradation due to the shift of the dot position is very small, and the effect of performing the exclusive arrangement is larger.

  The present invention has been made in view of the above conventional example, and an object thereof is to provide an image processing apparatus and an image processing method capable of forming a high-quality image by performing optimal pixel arrangement according to image density.

  In order to achieve the above object, an image processing apparatus of the present invention has the following configuration.

That is, for the image data indicated by the plurality of color component data for one pixel, an image processing apparatus that performs quantization processing using the error diffusion processing method, the plurality of color component data and the noticed pixel of interest and a multi-level error data corresponding to the respective error diffused plurality of color component data for the pixel, and generation means for generating a plurality of diffused error correction color component data for the pixel of interest, the plurality of diffusion errors The first diffusion error correction based on the combination of the first diffusion error correction color component data and the second diffusion error correction color component data included in the correction color component data and (N−1) threshold values. and a quantizing means for quantizing the color component data a second diffusion error correction color component data into N values, wherein N is a positive integer of 3 or more, it said quantization means, said first Diffusion error correction color Both the value of the component data and the value of the second diffusion error correction color component data are smaller than the minimum threshold value among the (N−1) threshold values, and the first diffusion error correction color component data When the sum of the value and the value of the second diffusion error correction color component data is equal to or smaller than a predetermined value, the dot corresponding to the first diffusion error correction color component data is also displayed in the second diffusion error correction color component The first diffusion error correction color component data and the second diffusion error correction color component data are quantized so that dots corresponding to the data are not formed, and the value of the first diffusion error correction color component data and the value Both of the value of the second diffusion error correction color component data are smaller than the minimum threshold value among the (N−1) threshold values, and the value of the first diffusion error correction color component data and the second value are the same. The sum of the value of the diffusion error correction color component data is the predetermined value. If larger, the first diffusion error correction color so that the dot corresponding to the first diffusion error correction color component data and the dot corresponding to the second diffusion error correction color component data are exclusive. Based on the magnitude relationship between the value of the component data and the second diffusion error correction color component data, the first diffusion error correction color component data and the second diffusion error correction color component data are quantized, and the first diffusion error correction color component data is quantized. If any one of the diffusion error correction color component data value and the second diffusion error correction color component data value is equal to or greater than the minimum threshold value among the (N-1) threshold values, the first diffusion is performed. Quantization is performed according to a result of comparing each of the value of the error correction color component data and the value of the second diffusion error correction color component data independently with the (N−1) threshold values. To do.

In the above case, the plurality of color component data includes yellow density data, magenta density data, cyan density data, and black density data, and the first diffusion error correction color component data corresponds to cyan. The second diffusion error correction color component data corresponds to magenta . Furthermore, it is desirable to have an image forming means for forming an image using an ink jet method based on the quantization result.

According to another aspect of the present invention, for the image data indicated by the plurality of color component data for one pixel, an image processing method for performing quantization processing using the error diffusion processing method, the target pixel of the plurality of and a multi-level error data corresponding to each of the plurality of color component data error diffusion with respect to the color component data and the target pixel, a generation step of generating a plurality of diffused error correction color component data for the pixel of interest , Based on a combination of first diffusion error correction color component data and second diffusion error correction color component data included in the plurality of diffusion error correction color component data, and (N−1) threshold values, and a quantization step of quantizing the first diffusion error correction color component data and said second diffusion error correction color component data into N values, wherein N is a positive integer of 3 or more, the quantization The process is the first Both the diffusion error correction color component data value and the second diffusion error correction color component data value are smaller than the minimum threshold value among the (N-1) threshold values, and the first diffusion error When the sum of the value of the correction color component data and the value of the second diffusion error correction color component data is equal to or less than a predetermined value, the dot corresponding to the first diffusion error correction color component data is also the second color. The first diffusion error correction color component data and the second diffusion error correction color component data are quantized so that dots corresponding to the diffusion error correction color component data are not formed, and the first diffusion error correction color component is obtained. Both the value of the data and the value of the second diffusion error correction color component data are smaller than the minimum threshold value among the (N-1) threshold values, and the value of the first diffusion error correction color component data And the value of the second diffusion error correction color component data When the sum is greater than the predetermined value, the first diffusion error correction color component data and the dot corresponding to the second diffusion error correction color component data are exclusive of the first diffusion error correction color component data. Based on the magnitude relationship between the value of one diffusion error correction color component data and the second diffusion error correction color component data, the first diffusion error correction color component data and the second diffusion error correction color component data are When quantization is performed and one of the value of the first diffusion error correction color component data and the value of the second diffusion error correction color component data is greater than or equal to the minimum threshold value among the (N−1) threshold values Quantization according to the result of comparing the value of the first diffusion error correction color component data and the value of the second diffusion error correction color component data independently with the (N−1) threshold values and an image processing method and performing

  According to still another invention, a computer-readable storage medium storing a program for executing the above image processing method is provided.

  As described above, according to the present invention, the graininess of the medium density portion is reduced from the highlight of the image, and the uniformity of the image is maintained from the intermediate density to the high density region, thereby forming a high quality image. There is an effect that can be.

It is a block diagram showing a schematic structure of an information processing system concerning a common embodiment of the present invention. 2 is a block diagram showing an outline of hardware configurations of a host device 51 and an image output device 52 that constitute an information processing system. FIG. 1 is an external perspective view showing an outline of a configuration of an inkjet printer IJRA that is a representative embodiment of an image output device 52. FIG. It is a block diagram which shows the structure of the software used with an information processing system. It is a flowchart which shows an image processing outline. It is a flowchart shown about the image formation control according to 1st Embodiment. It is a figure which shows the threshold condition used in 1st Embodiment. It is a flowchart shown about the image formation control according to 2nd Embodiment. It is a figure which shows the threshold value conditions used in 2nd Embodiment. It is a figure which shows the image formation control according to the conventional inkjet system. It is a figure which shows a mode that C component and M component are arrange | positioned exclusively, and image formation is performed. It is a figure which shows a mode that C component and M component are arrange | positioned independently, and image formation is performed.

11 Application software 21 Drawing processing interface 22 Spooler 31-1, 31-2, ..., 31-n Device-specific drawing function 33 Color characteristic conversion 34 Halftone processing (halftoning)
35 Print Command Generation 51 Host Device 52 Image Output Device 53 Bidirectional Interface 54 Driver Software 1000 Processing Unit 1001 MPU
1002 Bus 1003 DRAM
1004 Bridge 1005 Graphic adapter 1006 HDD controller 1007 Keyboard controller 1008 Communication I / F
2001 Display device 2002 HDD device 2003 Keyboard 3001 MCU
3003 Control circuit section 3004 ROM
3005 DRAM
3006 Communication I / F
3007 Head driver 3008 CR motor driver 3009 LF motor driver 3010 Recording head 3011 Carrier (CR) motor 3012 Conveyance motor

  Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

[Common embodiment]
First, an overall overview of an information processing system, a hardware configuration overview, a software configuration overview, and an image processing overview that are commonly used in the following embodiments will be described.

  FIG. 1 is a block diagram showing a schematic configuration of an information processing system according to a common embodiment of the present invention.

  As shown in FIG. 1, the information processing system includes a host device 51 configured by a personal computer or the like and an image output device 52 configured by a printer or the like, and a bidirectional interface 53 is provided therebetween. Connected through. The driver software 54 to which the present invention is applied is loaded in the memory of the host device 51.

1. Hardware Configuration of Host Device 51 and Image Output Device 52 Next, the hardware configuration of the host device 51 and the image output device 52 will be described.

  FIG. 2 is a block diagram showing an outline of the hardware configuration of the host device 51 and the image output device 52 constituting the information processing system.

  As shown in FIG. 2, the host device 51 constitutes the entire host device including the processing unit 1000 and peripheral devices. The image output device 52 includes a recording head 3010, a drive unit such as a carrier (CR) motor 3011 that drives a carrier that transports the recording head 3010, a transport motor 3012 that transports paper, and a control circuit unit 3003. ing.

  The processing unit 1000 of the host device 51 includes an MPU 1001 that controls the entire host device according to a control program, a bus 1002 that connects system components to each other, a DRAM 1003 that temporarily stores programs executed by the MPU 1001, data, and the like, a system bus and a memory bus A graphic adapter 1005 having a control function for displaying graphic information on a bridge 1004 for connecting the MPU 1001, for example, a display device 2001 such as a CRT.

  Further, the processing unit 1000 is a parallel interface communication I that manages communication between the HDD controller 1006 that controls the interface with the HDD device 2002, the keyboard controller 1007 that controls the interface with the keyboard 2003, and the image output device 52 in accordance with the IEEE1284 standard. / F1008.

  Furthermore, a display device 2001 (CRT in this example) that displays graphic information and the like to the operator is connected to the processing unit 1000 via a graphic adapter 1005. Furthermore, a hard disk drive (HDD) device 2002 and a keyboard 2003, which are large-capacity storage devices storing programs and data, are respectively connected via a controller.

  On the other hand, the control circuit unit 3003 of the image output device 52 connects the MCU 3001 that has the control program execution function and the peripheral device control function, and controls the overall control of the image output device main body 52, and each component in the control circuit unit. The system includes a gate array (GA) in which a system bus 3002, supply of recording data to the recording head 3010, memory address decoding, a control pulse generation mechanism for a carrier motor, and the like are housed as control circuits.

  The control circuit unit 3003 includes a ROM 3004 that stores a control program executed by the MCU 3001 and host print information, a DRAM 3005 that stores various data (image recording information, recording data supplied to the head, and the like), and a host device in accordance with the IEEE1284 standard. 51, a communication I / F 3006 that is a parallel interface that controls communication with the head 51, and a head driver 3007 that converts the head recording signal output from the gate array 3003 into an electric signal for driving the recording head 3010.

  Further, the control circuit unit 3003 converts the carrier motor control pulse output from the gate array 3003 into an electric signal for actually driving the carrier (CR) motor 3011, and the carrier motor control pulse output from the MCU 3001. Is converted to an electric signal for actually driving the transport motor.

  Next, a specific configuration of the image output device 52 will be described.

  FIG. 3 is an external perspective view showing an outline of the configuration of an ink jet printer IJRA which is a typical embodiment of the image output device 52.

  In FIG. 3, the carriage HC engaged with the spiral groove 5004 of the lead screw 5005 that rotates via the driving force transmission gears 5009 to 5011 in conjunction with the forward / reverse rotation of the drive motor 5013 has a pin (not shown). It is supported by the guide rail 5003 and reciprocates in the directions of arrows a and b. On the carriage HC, an integrated ink jet cartridge IJC incorporating a recording head IJH and an ink tank IT is mounted. Reference numeral 5002 denotes a paper pressing plate that presses the recording paper P against the platen 5000 in the moving direction of the carriage HC. Reference numerals 5007 and 5008 denote photo-couplers which are home position detectors for confirming the presence of the carriage lever 5006 in this region and switching the rotation direction of the motor 5013. Reference numeral 5016 denotes a member that supports a cap member 5022 that caps the front surface of the recording head IJH. Reference numeral 5015 denotes a suction unit that sucks the inside of the cap, and performs suction recovery of the recording head through the cap opening 5023. Reference numeral 5017 denotes a cleaning blade, and reference numeral 5019 denotes a member that enables the blade to move in the front-rear direction, and these are supported by a main body support plate 5018. Needless to say, the blade is not in this form, and a known cleaning blade can be applied to this example. Reference numeral 5021 denotes a lever for starting suction for suction recovery, which moves in accordance with the movement of the cam 5020 engaged with the carriage, and the driving force from the driving motor is controlled by a known transmission mechanism such as clutch switching. Is done.

  These capping, cleaning, and suction recovery are configured so that desired processing can be performed at their corresponding positions by the action of the lead screw 5005 when the carriage comes to the home position side region. As long as the above operation is performed, any of these can be applied to this example.

  As described above, the ink tank IT and the recording head IJH may be integrally formed to constitute a replaceable ink cartridge IJC. However, the ink tank IT and the recording head IJH can be separated from each other. Then, only the ink tank IT may be exchanged when the ink runs out.

  Further, the control circuit unit referred to in FIG. 2 is built in the ink jet printer IJRA.

  The recording head IJH records a color image using at least four inks of yellow (Y), magenta (M), cyan (C), and black (K) based on multi-value density data of each component of YMCK. Can do.

2. Outline of Software Configuration and Outline of Image Processing FIG. 4 is a block diagram showing the structure of software used in the information processing system described above.

  As can be seen from FIG. 4, in order to output recording data to the image output device 52, in the host device 52, the application software, operating system and driver software having a hierarchical structure cooperate with each other to perform image processing. Do.

  In this embodiment, the parts that depend on each of the image output apparatuses are handled by the apparatus-specific drawing functions 31-1, 31-2, ..., 31-n, and are program components that depend on the individual implementation of the image processing apparatus. Are separated from a program that can perform processing in common, and the fundamental processing portion of the driver software has a structure independent of individual image output apparatuses.

  The line-divided image converted into the quantized amount is subjected to image processing such as color characteristic conversion 33 and halftone processing (halftoning) 34, and after data compression / command is added in print command generation 35. The created data is transferred to the image output device 52 through the spooler 22 prepared in the OS (operating system).

  As shown in FIG. 4, application software 11 is provided in the application software layer, and a drawing processing interface 21 that receives a drawing command from the application software 11 and generated image data are provided in the OS (operating system) layer. A spooler 22 is provided that passes to an image output device 52 such as an ink jet printer.

  The driver software hierarchy receives device-specific rendering functions 31-1, 31-2,..., 31-n in which representation formats unique to the image output device are stored, and line-divided image information from the OS. A color characteristic conversion unit 33 that performs conversion from a color system inside the driver to a device-specific color system, a halftoning unit that performs conversion into a quantization amount that represents the state of each pixel of the device, and halftoning There is provided a print command generation unit 35 for adding the command to the image output device 52 to output the applied image data to the spooler 22.

  Next, the case where the application software outputs an image to the image output device 52 will be described in detail with reference to the flowchart of FIG.

  When the application software 11 outputs an image to the image output device 52, first, the application software 11 issues a drawing command such as a character, a line segment, a figure, and a bitmap through the drawing processing interface 21 of the OS (step S1). .

  When drawing commands constituting the screen / paper surface are completed (step S2), the OS calls each of the drawing commands while calling the device-specific drawing functions 31-1, 31-2, ..., 31-n in the driver software. Is converted to a device-specific representation format (each drawing unit is divided into lines) (step S3), and then the screen / paper is line-divided into image information and passed to the driver software (step S4).

  Inside the driver software, the color characteristic conversion unit 33 corrects the color characteristics of the device, converts the color system in the driver software from the color system specific to the device (step S5), and further, the halftoning unit 34 Conversion (halftoning) into a quantization amount representing the state of each pixel of the device is performed (step S6). The conversion to the quantization amount here corresponds to the form of data processed by the image output device 52. For example, when recording by the image output device is performed based on binary data, binarization is performed. When recording by the image output device is performed based on multi-value data (for recording with dark and light inks and recording with large and small inks), it is multi-valued.

  Details of the halftoning will be described in each embodiment described later.

  The print command generation module 35 receives the image data that has been quantized (binarized, multivalued) (step S7). The print command generation module 35 processes the quantized image information according to the characteristics of the image output apparatus by different methods. Further, data compression and command header addition are performed with this module (step S8).

  Thereafter, the print command generation module 35 delivers the generated data to the spooler 22 provided in the OS (step S9), and outputs the data to the image output device 52 (step S10).

  In this embodiment, the above control method can be realized by storing and operating the program according to the flowchart of FIG. 5 in the storage device in the host device 51.

  As described above, the basic processing part of the driver software is structured independently of the individual image output device, so that the data processing between the driver software and the image output device can be flexibly assigned without damaging the configuration of the driver software. It becomes possible to make changes, which is advantageous in terms of software maintenance and management.

  Next, several embodiments using the system according to the common embodiment described above will be described. In the following embodiments, details of error diffusion processing executed by the halftoning unit 34 will be described.

  The error diffusion processing described below is density data in which each pixel is composed of a yellow (Y) component, a magenta (M) component, a cyan (C) component, and a black (K) component, and each component has 8 bits ( It is assumed that multivalued image data composed of (256 gradation expression) is used.

[First embodiment]
Here, unlike the conventional example, an error diffusion process capable of adjusting the pixel arrangement of each density component according to the density value will be described. The target of error diffusion processing according to this embodiment is multi-value image data of C component and M component.

  In this embodiment, the case where the multi-value density data is binarized by error diffusion processing is handled.

  FIG. 6 is a flowchart showing image formation control according to this embodiment.

  The features of this embodiment will be described below with reference to this flowchart.

  First, in step S10, the density values Ct and Mt of the C component and M component of the target pixel are obtained as in the conventional example. In step S20, it is checked whether the sum of the obtained density value Mt of the M component and the density value Ct of the C component is greater than the density value 127 used as the threshold value. If Ct + Mt> 127, the process proceeds to step S30, and the magnitude relationship between the density value Mt of the M component and the density value Ct of the C component is further examined.

  Here, if Ct> Mt, the process proceeds to step S40, and the recording is set to be performed with C ink. Further, in step S50, the process checks whether the density value Mt of the M component is greater than the threshold value 127. Here, if Mt> 127, the process proceeds to step S70, and the recording is set to be performed with M ink. Thereafter, the process ends. On the other hand, if Mt ≦ 127, step S70 is skipped and the process ends as it is.

  If it is determined in step S30 that Ct ≦ Mt, the process proceeds to step S80, and the recording is set to be performed with M ink. Further, in step S 90, the process checks whether the C component density value Ct is greater than the threshold value 127. Here, if Ct> 127, the process proceeds to step S100 to set to perform recording with C ink. Thereafter, the process ends. On the other hand, if Ct ≦ 127, step S100 is skipped and the process ends as it is.

  In step S20, if Ct + Mt ≦ 127, the process ends.

  FIG. 7 illustrates threshold conditions regarding the C component and the M component of the processing shown in FIG.

  In summary, the following dot arrangement is made according to the density value Mt of the M component and the density value Ct of the C component.

(1) Ct + Mt ≦ 127
(C component and M component both in the low concentration region → corresponds to the region (a) in FIG. 7)
Do not record dots in C ink or M ink.

(2) Ct + Mt> 127 and Ct> Mt and Mt> 127
(Both C and M components correspond to medium to high concentration region → region (d) in FIG. 7)
Dots are recorded with both C ink and M ink (superposition recording).

(3) Ct + Mt> 127 and Ct> Mt and Mt ≦ 127
(Only the C component corresponds to the middle to high concentration region → the region (b) in FIG. 7)
Dots are recorded using only C ink (exclusive recording).

(4) Ct + Mt> 127 and Ct ≦ Mt and Ct> 127
(Both C and M components correspond to medium to high concentration region → region (d) in FIG. 7)
Dots are recorded with both C ink and M ink (superposition recording).

(5) Ct + Mt> 127 and Ct ≦ Mt and Ct ≦ 127
(Only the M component corresponds to the middle to high concentration region → the region (c) in FIG. 7)
Dots are recorded only with M ink (exclusive recording).

  Therefore, according to the embodiment described above, when only one density component is sufficiently high in density, a recording pixel is formed regardless of the other color components for that color component. Since the recording independence of the C component and the M component is increased during recording, it is possible to maintain image uniformity at medium density or higher.

[Second Embodiment]
In the first embodiment, the case where the multi-value density data is binarized by the error diffusion process is dealt with. In this embodiment, the case where the multi-value density data is binarized by the error diffusion process is dealt with.

  FIG. 8 is a flowchart showing image formation control according to this embodiment.

  The features of this embodiment will be described below with reference to this flowchart.

  First, in step S110, the density values Ct and Mt of the C component and M component of the target pixel are obtained as in the conventional example. In step S120, the calculated sum of the density value Mt of the M component and the density value Ct of the C component is compared with a threshold value (Threshold). If Ct + Mt> Threshold, the process proceeds to step S130. If Ct + Mt ≦ Threshold, the process proceeds to step S160.

  In step S130, the magnitude relationship between the density value Mt of the M component and the density value Ct of the C component is examined. If Ct> Mt, the process advances to step S140 to determine an output value obtained by error diffusion processing of the C component and the M component.

  That is, referring to a common multi-value conversion table for the C component and M component shown in Table 1, first, as the C component output value (Cout), 1 and f (Ct) (the value of the density value Ct Select the larger one of the values in the multi-value table). For example, if f (Ct) is “0”, Cout = 1, Cout = 1 if f (Ct) is “1”, and Cout = 2 if f (Ct) is “2”.

  Also, as the output value (Mout) of the M component, the value corresponding to the density value Mt is referred to the multi-value conversion table of Table 1, and Mout = g (Mt) (multi-value conversion using the value of the density value Mt as a function) Table).

  If Ct ≦ Mt, the process proceeds to step S150, and the output by the error diffusion process of the C component and the M component is performed by referring to the common multi-value table for the C component and the M component shown in Table 1. Determine the value.

  That is, as the C component output value (Cout), the value corresponding to the density value Ct is determined by referring to the multi-value conversion table of Table 1 as Cout = f (Ct), and the M component output value (Mout) ), The larger of the values of 1 and g (Mt) (multi-value conversion table using the density value Mt as a function) is selected.

  Further, in step S160, referring to the multi-value conversion table common to the C component and M component shown in Table 1, the value corresponding to the density value Ct is set as the output value (Cout) of the C component in Table 1. With reference to the multi-value conversion table, the value corresponding to the density value Mt is referred to as the output value (Mout) of the M component as Cout = f (Ct), and Mout = g It is determined as (Mt).

  After step S140, S150, or S160, the process ends.

  In this embodiment, “85” is used as the threshold (Threshold).

  FIG. 9 illustrates threshold conditions relating to the C component and M component of the processing shown in FIG.

  In this embodiment, the multi-value tables f (Ct) and g (Mt) are shared for the sake of simplification. However, it is not always necessary to use the same table, and separate tables may be used. Needless to say.

  Further, Table 1 is a table having density values of only 0 to 255, but the actual density values Ct and Mt include the accumulation of errors, depending on conditions such as multi-value conversion means and error diffusion error distribution methods. Although different, there are cases where the density fluctuation range is about −128 to +383 at the maximum, so it goes without saying that the present invention is not limited to the values shown in Table 1. In this embodiment, although not described for simplification of description, the table portion where Ct (Mt) not shown is actually “0” or less is the same as the value of the multivalued table of Ct (Mt) = 0. It is preferable to set the same value as the multi-value table value of Ct (Mt) = 255 for the table portion where Ct (Mt) is “255” or more.

  In this embodiment, only ternary processing is dealt with. However, an ink jet printer which is an image output device uses inks having different densities of the same color system as drop modulation (for example, light cyan ink, dark cyan ink, light magenta ink, dark ink) If it is possible to cope with quaternarization or quinarying by using magenta ink), a threshold value table for performing multivalued error diffusion processing such as quaternarization and quinarization may be created. It goes without saying that it is good.

  Therefore, according to the embodiment described above, even when multi-value image data is converted to n-values, processing is performed using a predetermined multi-value conversion table. Therefore, even if the threshold condition is complicated, the processing is not complicated. Since it can be easily performed and the processing is simple, complicated threshold condition processing can be performed at high speed.

  In the above embodiments, the liquid droplets ejected from the recording head have been described as ink, and the liquid stored in the ink tank has been described as ink. However, the container is limited to ink. It is not something. For example, a treatment liquid discharged to the recording medium may be accommodated in the ink tank in order to improve the fixability and water resistance of the recorded image or to improve the image quality.

  The above embodiment includes means (for example, an electrothermal converter, a laser beam, etc.) that generates thermal energy as energy used for performing ink discharge, particularly in the ink jet recording system, and the ink is generated by the thermal energy. By using a system that causes a change in the state of recording, it is possible to achieve higher recording density and higher definition.

  As its typical configuration and principle, for example, those performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 are preferable. This method can be applied to both the so-called on-demand type and continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to the sheet or liquid path holding the liquid (ink). By applying at least one drive signal corresponding to the recorded information and applying a rapid temperature rise exceeding nucleate boiling to the electrothermal transducer, the thermal energy is generated in the electrothermal transducer, and the recording head This is effective because film boiling occurs on the heat acting surface of the liquid, and as a result, bubbles in the liquid (ink) corresponding to the drive signal on a one-to-one basis can be formed. By the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection opening to form at least one droplet. When the drive signal is pulse-shaped, the bubble growth and contraction is performed immediately and appropriately, and thus it is possible to achieve the discharge of liquid (ink) with particularly excellent responsiveness.

  As this pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by employing the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate of the heat acting surface.

  As the configuration of the recording head, in addition to the combination configuration (straight liquid flow path or right-angle liquid flow path) of the discharge port, the liquid path, and the electrothermal transducer as disclosed in each of the above-mentioned specifications, the heat acting surface The configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose a configuration in which is disposed in a bending region, are also included in the present invention. In addition, Japanese Patent Application Laid-Open No. 59-123670, which discloses a configuration in which a common slot is used as a discharge portion of an electrothermal transducer, or an opening that absorbs a pressure wave of thermal energy is discharged to a plurality of electrothermal transducers. A configuration based on Japanese Patent Laid-Open No. 59-138461 disclosing a configuration corresponding to each part may be adopted.

  Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length is satisfied by a combination of a plurality of recording heads as disclosed in the above specification. Either a configuration or a configuration as a single recording head formed integrally may be used.

  In addition to the cartridge-type recording head in which the ink tank is integrally provided in the recording head itself described in the above embodiment, it can be electrically connected to the apparatus body by being attached to the apparatus body. A replaceable chip type recording head that can supply ink from the apparatus main body may be used.

  In addition, it is preferable to add recovery means, preliminary means, and the like for the recording head to the configuration of the recording apparatus described above because the recording operation can be further stabilized. Specific examples thereof include a capping unit for the recording head, a cleaning unit, a pressurizing or sucking unit, an electrothermal converter, a heating element different from this, or a preheating unit using a combination thereof. In addition, it is effective to provide a preliminary ejection mode for performing ejection different from recording in order to perform stable recording.

  Further, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but the recording head may be integrated or may be a combination of a plurality of colors. An apparatus having at least one of full colors can also be provided.

  In the embodiment described above, the description is made on the assumption that the ink is a liquid, but it may be an ink that is solidified at room temperature or lower, or an ink that is softened or liquefied at room temperature, Alternatively, the ink jet method generally controls the temperature of the ink so that the viscosity of the ink is within a stable discharge range by adjusting the temperature within a range of 30 ° C. or higher and 70 ° C. or lower. It is sufficient if the ink sometimes forms a liquid.

  In addition, it is solidified in a stand-by state in order to actively prevent temperature rise by heat energy as energy for changing the state of ink from the solid state to the liquid state, or to prevent ink evaporation. Ink that is liquefied by heating may be used. In any case, by applying heat energy according to the application of thermal energy according to the recording signal, the ink is liquefied and liquid ink is ejected, or when it reaches the recording medium, it already starts to solidify. The present invention can also be applied to the case where ink having a property of being liquefied for the first time is used. In such a case, the ink is held as a liquid or solid in a porous sheet recess or through-hole as described in JP-A-54-56847 or JP-A-60-71260, It is good also as a form which opposes with respect to an electrothermal converter. In the present invention, the most effective one for each of the above-described inks is to execute the above-described film boiling method.

  In addition, as a form of the recording apparatus according to the present invention, a copying apparatus combined with a reader or the like, and a transmission / reception function are provided as an image output terminal of an information processing apparatus such as a computer or the like. It may take the form of a facsimile machine.

  Note that the present invention can be applied to a system (for example, a copier, a facsimile machine, etc.) consisting of a single device even when applied to a system composed of a plurality of devices (for example, a host computer, interface device, reader, printer, etc.). You may apply.

  Another object of the present invention is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU or CPU) of the system or apparatus. Needless to say, this can also be achieved by the MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

Claims (5)

For the image data indicated by the plurality of color component data for one pixel, an image processing apparatus that performs quantization processing using the error diffusion processing method,
And a multi-level error data corresponding to the respective error diffused plurality of color component data to the plurality of color component data and the target pixel of the target pixel, a plurality of diffused error correction color component data for the pixel of interest Generating means for generating
Based on the combination of the first diffusion error correction color component data and the second diffusion error correction color component data included in the plurality of diffusion error correction color component data and (N−1) threshold values, the first and a quantizing means for quantizing the first diffused error correction color component data and said second diffusion error correction color component data into N values,
N is a positive integer of 3 or more,
The quantization means includes
Both the value of the first diffusion error correction color component data and the value of the second diffusion error correction color component data are smaller than the minimum threshold value among the (N-1) threshold values, and the first When the sum of the value of the diffusion error correction color component data and the value of the second diffusion error correction color component data is equal to or less than a predetermined value, the dot corresponding to the first diffusion error correction color component data is also The first diffusion error correction color component data and the second diffusion error correction color component data are quantized so that dots corresponding to the second diffusion error correction color component data are not formed,
Both the value of the first diffusion error correction color component data and the value of the second diffusion error correction color component data are smaller than the minimum threshold value among the (N-1) threshold values, and the first If the sum of the value of the diffusion error correction color component data and the value of the second diffusion error correction color component data is greater than the predetermined value, the dot corresponding to the first diffusion error correction color component data The magnitude relationship between the value of the first diffusion error correction color component data and the second diffusion error correction color component data is set so that dots corresponding to the second diffusion error correction color component data are exclusive. And quantizing the first diffusion error correction color component data and the second diffusion error correction color component data,
If any of the value of the first diffusion error correction color component data and the value of the second diffusion error correction color component data is greater than or equal to the minimum threshold value among the (N−1) threshold values, the first Quantization is performed according to a result of comparing each of the value of one diffusion error correction color component data and the value of the second diffusion error correction color component data independently with the (N−1) threshold values. An image processing apparatus. The plurality of color component data includes yellow density data, magenta density data, cyan density data, and black density data,
The image processing apparatus according to claim 1, wherein the first diffusion error correction color component data corresponds to cyan, and the second diffusion error correction color component data corresponds to magenta . The image processing apparatus according to claim 1, further comprising an image forming unit that forms an image using an inkjet method based on the quantization result. For the image data indicated by the plurality of color component data for one pixel, an image processing method for performing quantization processing using the error diffusion processing method,
And a multi-level error data corresponding to the respective error diffused plurality of color component data to the plurality of color component data and the target pixel of the target pixel, a plurality of diffused error correction color component data for the pixel of interest A generating step for generating
Based on the combination of the first diffusion error correction color component data and the second diffusion error correction color component data included in the plurality of diffusion error correction color component data and (N−1) threshold values, the first and a quantization step of quantizing first diffusion error correction color component data and said second diffusion error correction color component data into N values,
N is a positive integer of 3 or more,
The quantization step includes
Both the value of the first diffusion error correction color component data and the value of the second diffusion error correction color component data are smaller than the minimum threshold value among the (N-1) threshold values, and the first When the sum of the value of the diffusion error correction color component data and the value of the second diffusion error correction color component data is equal to or less than a predetermined value, the dot corresponding to the first diffusion error correction color component data is also The first diffusion error correction color component data and the second diffusion error correction color component data are quantized so that dots corresponding to the second diffusion error correction color component data are not formed,
Both the value of the first diffusion error correction color component data and the value of the second diffusion error correction color component data are smaller than the minimum threshold value among the (N-1) threshold values, and the first If the sum of the value of the diffusion error correction color component data and the value of the second diffusion error correction color component data is greater than the predetermined value, the dot corresponding to the first diffusion error correction color component data The magnitude relationship between the value of the first diffusion error correction color component data and the second diffusion error correction color component data is set so that dots corresponding to the second diffusion error correction color component data are exclusive. And quantizing the first diffusion error correction color component data and the second diffusion error correction color component data,
If any of the value of the first diffusion error correction color component data and the value of the second diffusion error correction color component data is greater than or equal to the minimum threshold value among the (N−1) threshold values, the first Quantization is performed according to a result of comparing each of the value of one diffusion error correction color component data and the value of the second diffusion error correction color component data independently with the (N−1) threshold values. An image processing method characterized by the above.   A computer-readable storage medium storing a program for executing the image processing method according to claim 4.

Images