JP4467771B2 - Image processing apparatus and image processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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.
[0002]
[Prior art]
Conventionally, an error diffusion method is known as pseudo gradation processing for expressing a multi-valued image in binary ("An Adaptive Algorithm for Spatial Gray Scale" in society for Information Display 1975 Symposium Digest of Technical Papers, 1975, 36). . 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.
[0003]
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.
[0004]
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.
[0005]
In order to improve this problem, Japanese Patent Application Laid-Open No. 8-279920 and Japanese Patent Application Laid-Open No. 11-10918 are good even when two or more colors are overlapped by combining two or more colors and using an error diffusion method. Disclosed is a pseudo halftone processing method capable of obtaining excellent visual characteristics.
[0006]
Japanese Laid-Open Patent Publication No. 9-139841 discloses a method of performing similar improvements by correcting the output value by the sum of input values after performing pseudo-middle gradation processing for two or more colors independently. Yes.
[0007]
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.
[0008]
FIG. 12 is a diagram showing image formation control according to a conventional ink jet system.
[0009]
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).
[0010]
If the C component and M component density Ct, Mt of the target pixel of the multi-valued color image are 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.
[0011]
As shown in FIG. 12, regarding image formation of C and M, four types of image formation control are performed according to the density of the C component and M component of the target pixel.
1. When the sum of (Ct + Mt) is equal to or less than the threshold (Threshold 1), that is, belongs to the region (1) in FIG. 12, dot recording is not performed using C ink or M ink.
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 greater than or equal to another threshold (Threshold 2), that is, belongs to region (4) in FIG. 12, dot recording is performed using C ink and M ink.
[0012]
Here, Threshold 1 <Threshold 2.
[0013]
[Problems to be solved by the invention]
However, as in the above-described conventional example, the input multi-value image data is binarized for each color component, and error diffusion processing that is pseudo halftone processing is executed. On the other hand, with the recent progress in color image recording technology by the ink jet method, the use of drop modulation and similar shades of dark and light ink makes it possible for an ink jet printer to handle multi-value image data and perform color image recording. It was.
[0014]
Therefore, it is desired to apply a multi-value error diffusion process corresponding to such an ink jet printer. However, multilevel error diffusion processing complicates threshold condition processing, and if this processing is applied to an actual apparatus, there is a concern about a decrease in recording speed. Therefore, when multi-value error diffusion processing is applied to an inkjet printer capable of handling multi-value image data, it is desired to apply a processing method capable of maintaining the processing speed at a high speed.
[0015]
The present invention has been made in view of the above-described 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 at high speed while applying multilevel error diffusion processing. Yes.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, an image processing apparatus of the present invention has the following configuration.
[0017]
That is, yellow, an image processing apparatus for outputting magenta, cyan, and multi-value image data having a density component black results of the error diffusion process is subjected to error diffusion process, the concentration of the cyan density component of the pixel of interest An adding means for adding an error value diffused for each of the density value of the cyan density component and the density value of the magenta density component of the target pixel to each of the density value and the density value of the magenta density component; and an arithmetic means for said error value and the density value of the cyan density component the error value is added to calculating the sum and difference between the density values of summed the magenta density component, a first function based on the sum M value converting means for converting the sum value into M values using N, N value converting means for converting the difference values into N values using a second function based on the difference, and M value converting means Results of M-value conversion Using the results of the N-value conversion by the N-value conversion means as an argument, by referring to the two-dimensional table of results of the error diffusion process is stored, for each of the cyan density component and the magenta density component of the pixel of interest And an image processing apparatus having processing means for obtaining a result of multi-value error diffusion processing.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[0028]
[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.
[0029]
FIG. 1 is a block diagram showing a schematic configuration of an information processing system according to a common embodiment of the present invention.
[0030]
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 between them. Connected through. The driver software 54 to which the present invention is applied is loaded in the memory of the host device 51.
[0031]
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.
[0032]
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.
[0033]
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.
[0034]
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.
[0035]
Further, the processing unit 1000 is a parallel interface communication I that controls 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.
[0036]
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.
[0037]
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.
[0038]
The control circuit unit 3003 includes a ROM 3004 that stores a control program executed by the MCU 3001, host print information, etc., a DRAM 3005 that stores various data (image recording information, recording data supplied to the head, etc.), 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.
[0039]
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.
[0040]
Next, a specific configuration of the image output device 52 will be described.
[0041]
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.
[0042]
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.
[0043]
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.
[0044]
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.
[0045]
Further, the control circuit unit referred to in FIG. 2 is built in the ink jet printer IJRA.
[0046]
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.
[0047]
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.
[0048]
As can be seen from FIG. 4, in order to output the recording data to the image output device 52, the host device 52 performs image processing in cooperation with the application software, operating system and driver software having a hierarchical structure. Do.
[0049]
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.
[0050]
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).
[0051]
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.
[0052]
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.
[0053]
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.
[0054]
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 via the OS drawing processing interface 21 (step S1). .
[0055]
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).
[0056]
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 apparatus 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.
[0057]
Details of the halftoning will be described in each embodiment described later.
[0058]
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).
[0059]
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).
[0060]
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.
[0061]
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.
[0062]
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.
[0063]
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.
[0064]
In addition, the inkjet printer IJRA can cope with multi-values by using drop modulation or / and dark and light inks of the same color system (for example, light cyan ink, dark cyan ink, light magenta ink, dark magenta ink).
[0065]
[First embodiment]
Here, unlike the conventional example, a case will be described in which multi-value density data is ternarized by error diffusion processing. The target of error diffusion processing according to this embodiment is multi-value image data of C component and M component.
[0066]
FIG. 6 is a flowchart showing image formation control according to this embodiment.
[0067]
The features of this embodiment will be described below with reference to this flowchart.
[0068]
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. Next, in step S20, it is checked whether or not the sum of the obtained M component density value Mt and C component density value Ct is greater than a first threshold value (Threshold1). If Ct + Mt> Threshold1, the process proceeds to step S30, and it is further checked whether the sum of the density value Mt of the M component and the density value Ct of the C component is less than the second threshold value (Threshold2). . On the other hand, if Ct + Mt ≦ Threshold1, the process ends.
[0069]
If Ct + Mt <Threshold2 in step S30, the process proceeds to step S40 to check the magnitude relationship between the density value Mt of the M component and the density value Ct of the C component. Here, if Ct> Mt, the process proceeds to step S50, and the recording is set to be performed with C ink of a small droplet (or light C ink). On the other hand, if Ct ≦ Mt, the process proceeds to step S60, and a setting is made to perform recording with M ink (or light M ink) of a small droplet. After step S50 or S60, the process ends.
[0070]
In step S30, if Ct + Mt ≧ Threshold2, the process proceeds to step S70, and whether the sum of the M component density value Mt and the C component density value Ct is less than the third threshold value (Threshold3). Find out. If Ct + Mt <Threshold3, the process proceeds to step S80, and it is further checked whether the difference between the density value Mt of the M component and the density value Ct of the C component is greater than a predetermined offset (Offset). Here, if Ct−Mt> Offset, the process proceeds to step S90, and setting is performed so that recording is performed with C ink (or dark C ink) of a large droplet. Thereafter, the process ends. On the other hand, if Ct−Mt ≦ Offset, the process proceeds to step S100.
[0071]
In step S100, it is checked whether the difference between the density value Mt of the M component and the density value Ct of the C component is greater than a predetermined offset (Offset). If Mt−Ct ≦ Offset, the process proceeds to step S110, and recording is performed with small droplets of C ink (or light C ink) and small droplets of M ink (or light M ink). Set. Thereafter, the process ends. On the other hand, if Mt−Ct> Offset, the process proceeds to step S110, and the recording is set to perform recording with M ink (or dark M ink) of a large droplet. Thereafter, the process ends.
[0072]
If Ct + Mt ≧ Threshold3 in step S70, the process proceeds to step S130, and whether the sum of the density value Mt of the M component and the density value Ct of the C component is less than the fourth threshold value (Threshold4). Find out. If Ct + Mt <Threshold4, the process proceeds to step S140, 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 S150, and the recording is set to perform recording with C ink (or dark C ink) of a large droplet and M ink (or light M ink) of a small droplet. . Thereafter, the process ends. On the other hand, if Ct ≦ Mt, the process proceeds to step S160, and recording is performed with small C ink (or light C ink) and large M ink (or dark M ink). Set. Thereafter, the process ends.
[0073]
On the other hand, if Ct + Mt ≧ Threshold4 in step S130, the process proceeds to step S170, and recording is performed with both large C ink (or dark C ink) and large liquid M ink (or dark M ink). Set to do. Thereafter, the process ends.
[0074]
FIG. 7 illustrates threshold conditions regarding the C component and the M component of the processing shown in FIG.
[0075]
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.
[0076]
(1) Ct + Mt ≦ Threshold1
(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.
[0077]
(2) Ct + Mt> Threshold1 and Ct + Mt <Threshold2 and Ct> Mt
(C component corresponds to medium concentration region → region (b) in FIG. 7)
Dots are recorded with small droplet C ink (or light C ink) (exclusive recording).
[0078]
(3) Ct + Mt> Threshold1 and Ct + Mt <Threshold2 and Ct ≦ Mt
(M component corresponds to medium concentration region → region (c) in FIG. 7)
Dots are recorded with small droplet M ink (or light M ink) (exclusive recording).
[0079]
(4) Ct + Mt> Threshold1 and Ct + Mt ≧ Threshold2
And Ct + Mt <Threshold3 and Ct-Mt> Offset1
(C component corresponds to the high concentration region → region (d) in FIG. 7)
Dots are recorded with large droplet C ink (or dark C ink) (exclusive recording).
[0080]
(5) Ct + Mt> Threshold1 and Ct + Mt ≧ Threshold2
And Ct + Mt <Threshold3 and Ct−Mt ≦ Offset1
And Mt−Ct ≦ Offset2
(Both C and M components correspond to medium concentration region → region (e) in FIG. 7)
Dots are recorded with both small droplet C ink (or light C ink) and small droplet M ink (or light M ink) (superposition recording).
[0081]
(6) Ct + Mt> Threshold1 and Ct + Mt ≧ Threshold2
And Ct + Mt <Threshold3 and Mt−Ct ≦ Offset1
And Mt-Ct> Offset2
(M component corresponds to high concentration region → region (f) in FIG. 7)
Dots are recorded with large droplet M ink (or dark M ink) (exclusive recording).
[0082]
(7) Ct + Mt> Threshold1 and Ct + Mt ≧ Threshold2
And Ct + Mt ≧ Threshold3 and Ct + Mt <Threshold4
And Ct> Mt
(C component corresponds to high concentration region, M component corresponds to medium concentration region → region (g) in FIG. 7)
Dots are recorded with both large droplet C ink (or dark C ink) and small droplet M ink (or light M ink) (superposition recording).
[0083]
(8) Ct + Mt> Threshold1 and Ct + Mt ≧ Threshold2
And Ct + Mt ≧ Threshold3 and Ct + Mt <Threshold4
And Ct ≦ Mt
(C component corresponds to medium concentration region, M component corresponds to high concentration region → region (h) in FIG. 7)
Dots are recorded with both small droplet C ink (or light C ink) and large droplet M ink (or dark M ink) (superposition recording).
[0084]
(9) Ct + Mt ≧ Threshold4 (>Threshold3>Threshold2> Threshold1)
(Both C and M components correspond to the high concentration region → region (i) in FIG. 7)
Dots are recorded with both large droplet C ink (or dark C ink) and large droplet M ink (or dark M ink) (overlapping recording).
[0085]
Therefore, according to the above-described embodiment, the density values of the C component and the M component are changed into three values by changing the recording method using the M ink and the C ink in accordance with the density values of the C component and the M component. It is possible to perform recording with reduced graininess by disposing them in the position.
[0086]
[Second Embodiment]
In the first embodiment, the case where the multi-value density data is ternarized by error diffusion processing has been dealt with. However, in this embodiment, the multi-value density data is converted into N-value (N ≧ 4) by error diffusion processing at high speed. An example in which the conversion processing is possible will be described.
[0087]
As is apparent from the flowchart of FIG. 6 described in the first embodiment, in the case of ternarization, since each of the C component and M component can take three values, there are 3 × 3 = 9 combinations. To do this, branch processing with a total of 8 if statements (conditional statements) is required. That is, in the case of N-value conversion, N ² −1 if statements are required. Therefore, as the value of N increases, the processing time increases accordingly.
[0088]
FIG. 8 is a flowchart showing image formation control according to this embodiment.
[0089]
The features of this embodiment will be described below with reference to this flowchart.
[0090]
When the input multi-valued image data is converted to N-value (N ≧ 3) by error diffusion processing, threshold condition processing becomes very complicated. In this embodiment, the multi-value conversion is performed according to the following procedure.
[0091]
(1) A function defined as X = Ct + Mt and Y = Ct−Mt is introduced to perform multilevel error diffusion.
[0092]
(2) Refer to the two-dimensional table based on the result of the multi-value error diffusion process, and determine the dot arrangement and dot type to be recorded. The two-dimensional table may be a common table for the C component and the M component, but actually, it is preferable to prepare separate tables (C_Table, M_Table) for the C component and the M component.
[0093]
Referring back to FIG. 8, first, in step S210, the values of X and Y are determined from the density values for the C and M components of each pixel.
[0094]
Next, in step S220, the two-dimensional table arguments (X_index, Y_index) are determined based on the X value and the Y value. In this embodiment, these arguments are determined as functions of X and Y (X_index = f (X), Y_index = g (Y)).
[0095]
Finally, in step S230, the two-dimensional table is referenced using the argument determined in step S220, and output values (Cout, Mout) obtained by error diffusion processing for each of the C component and M component are determined.
[0096]
For comparison, a case will be described in which the same ternary processing as described in the first embodiment is executed according to this embodiment.
[0097]
FIG. 9 is a diagram for explaining how ternarization is performed according to the second embodiment.
[0098]
FIG. 9 shows that quaternization is performed for X = Ct (= C + Cerr) + Mt (= M + Merr), while quaternization is performed for Y = Ct (= C + Cerr) −Mt (= M + Merr). Yes.
[0099]
In FIG. 9, straight lines rising to the right represent the same X value (= Ct−Mt), and straight lines rising to the left represent the same Y value (= Ct + Mt) (Ct and Mt are −128 including error accumulation). ≦ Ct and Mt ≦ 383.
[0100]
Therefore, since Ct and Mt have the above-mentioned fluctuation ranges, X has a fluctuation range of about −256 ≦ X ≦ 766, and Y has a range of fluctuation of about −511 ≦ Y ≦ 511. In order to perform quaternarization and quinarization of X and Y having such a fluctuation range, an X function (f (X)) and a Y function (g (Y)) are introduced. Performs 4-level and 5-level processing.
[0101]
That is, the calculation of X_index = f (X) and Y_index = g (Y) is performed. This calculation can be realized by referring to the table.
[0102]
In this way, the entire range of X and Y can be divided into 4 values × 5 values = 20 partitions by two addition operations and two multi-value conversion operations (see the table).
[0103]
Here, comparing FIG. 9 with FIG. 7, in FIG. 7, each of the regions (a), (b), (c), (e), (g), (h), (i) It can be seen that the area is only a set of two sections in FIG. 9, and the overall separation method is almost the same in FIGS.
[0104]
Therefore, by referring to the common two-dimensional table as shown in FIG. 10 based on the multi-value conversion result of X and Y, it is possible to perform the recording control based on the error diffusion process by the ternarization of C and M.
[0105]
In FIG. 10, “-” indicates that dots are not recorded with C ink or M ink, “c” indicates that dots are recorded with small droplet C ink (or light C ink), and “m” indicates Recording dots with small droplet M ink (or light M ink), “C” recording dots with large droplet C ink (or dark C ink), “M” with large droplet M Recording dots with ink (or dark M ink), “cm” means recording dots with both small droplet C ink (or light C ink) and small droplet M ink (or light M ink). “Cm” is to record dots with both large droplet C ink (or dark C ink) and small droplet M ink (or light M ink), and “cM” is small droplet C ink (or Light C ink) and large droplet M ink (or dark) The recorded dots in both the ink), "CM" indicates to record dots in both large droplet C ink (or dark C ink) and large droplet M ink (or dark M ink).
[0106]
In consideration of the color characteristics of each of the C component and M component, it is actually desirable to prepare a separate two-dimensional table for each of the C component and M component as shown in FIG.
[0107]
11A shows a two-dimensional table dedicated to the C component, and FIG. 11B shows a two-dimensional table dedicated to the M component.
[0108]
In FIG. 11, “−” indicates that dots are not recorded, “c” indicates that dots are recorded with small droplet C ink (or light C ink), and “m” indicates small droplet M ink ( “C” means to record dots with large droplet C ink (or dark C ink), and “M” means large droplet M ink (or dark M ink). ) Indicates that dots are recorded.
[0109]
In the above example, an example of ternarization has been described in order to simplify the description. However, in the present embodiment, calculation of X and Y and multi-value of X and Y are also applied to N-value conversion of N ≧ 4. This is a more effective process for higher-order N because it can be realized by using the same simple processing step without conditional branching processing, that is, multi-value processing of C component and M component.
[0110]
Therefore, according to the embodiment described above, error diffusion processing can be performed at high speed without complicating the processing even for higher-order N-ary processing.
[0111]
In addition, according to the embodiment described above, the processing is centered on table reference, and it is not necessary to use a processing operation with condition determination. For example, pipeline processing used in an MPU such as a Pentium processor Further, the use of such a processor in this embodiment can be expected to further increase the speed.
[0112]
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 stored in the ink tank in order to improve the fixability and water resistance of the recorded image or to improve the image quality.
[0113]
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.
[0114]
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 giving 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.
[0115]
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.
[0116]
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.
[0117]
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.
[0118]
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.
[0119]
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.
[0120]
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.
[0121]
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.
[0122]
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 of using ink having the property of being liquefied for the first time. 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.
[0123]
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.
[0124]
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 if it is applied to a system composed of a plurality of devices (for example, a host computer, interface device, reader, printer, etc.). You may apply.
[0125]
Also, an object of the present invention is to supply a storage medium (or recording medium) that records a program code of software that realizes the functions of the above-described embodiments to a system or apparatus, and to perform computer (or CPU or CPU) of the system or apparatus. Needless to say, this can also be achieved when the MPU) reads and executes 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.
[0126]
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 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.
[0127]
【The invention's effect】
As described above, according to the present invention, there is an effect that the multi-value error diffusion processing for the cyan density component and the magenta density component can be executed at high speed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an information processing system according to a common embodiment of the present invention.
FIG. 2 is a block diagram showing an outline of the hardware configuration of a host device 51 and an image output device 52 constituting the information processing system.
FIG. 3 is an external perspective view showing an outline of the configuration of an inkjet printer IJRA that is a representative embodiment of the image output device 52. FIG.
FIG. 4 is a block diagram showing the structure of software used in the information processing system.
FIG. 5 is a flowchart showing an outline of image processing.
FIG. 6 is a flowchart illustrating image formation control according to the first embodiment.
FIG. 7 is a diagram showing threshold conditions used in the first embodiment.
FIG. 8 is a flowchart illustrating image formation control according to the second embodiment.
FIG. 9 is a diagram showing threshold conditions used in the second embodiment.
FIG. 10 is a diagram showing a CM component common two-dimensional table used in the second embodiment.
FIG. 11 is a diagram showing a two-dimensional table dedicated to each CM component used in the second embodiment.
FIG. 12 is a diagram illustrating image formation control according to a conventional ink jet method.
[Explanation of symbols]
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

Claims (7)

An image processing apparatus that performs error diffusion processing on multi-value image data having density components of yellow, magenta, cyan, and black and outputs the result of the error diffusion processing,
An error value diffused with respect to each of the density value of the cyan density component and the density value of the magenta density component of the target pixel is added to the density value of the cyan density component and the density value of the magenta density component of the target pixel, respectively. Adding means;
By the addition means, a calculating means for said error value and the density value of the cyan density component the error value is added to calculating the sum and difference between the density values of summed the magenta density component,
M value conversion means for converting the value of the sum into an M value using a first function based on the sum;
N-value conversion means for converting the value of the difference into an N-value using a second function based on the difference;
By using the result of M-value conversion by the M-value conversion means and the result of N-value conversion by the N-value conversion means as arguments and referring to a two-dimensional table in which the result of error diffusion processing is stored, An image processing apparatus comprising processing means for obtaining a result of multi-value error diffusion processing for each of a cyan density component and a magenta density component of a target pixel.   The image processing apparatus according to claim 1, wherein M and N are each a positive integer of 3 or more. The first function used in the M-value conversion means is expressed by a first table representing a relationship between the sum value and the M value,
The image processing apparatus according to claim 1, wherein the second function used in the N-value conversion unit is expressed by a second table that represents a relationship between the difference value and the N value. . The image processing apparatus according to claim 1 , wherein the two-dimensional table is a common table for the cyan and magenta density components. The image processing apparatus according to claim 1 , wherein the two-dimensional table is a separate table for the cyan and magenta density components. An image processing method for performing error diffusion processing on multi-value image data having density components of yellow, magenta, cyan, and black and outputting the result of the error diffusion processing,
An error value diffused with respect to each of the density value of the cyan density component and the density value of the magenta density component of the target pixel is added to the density value of the cyan density component and the density value of the magenta density component of the target pixel, respectively. Adding step;
In the adding step, a calculation step of the error value and the density value of the cyan density component the error value is added to calculating the sum and difference between the density values of summed the magenta density component,
An M-value conversion step of converting the value of the sum into an M-value using a first function based on the sum;
An N-value conversion step of converting the difference value into an N-value using a second function based on the difference;
By referring to the two-dimensional table in which the result of error diffusion processing is stored using the M-value conversion result in the M-value conversion step and the N-value conversion result in the N-value conversion step as arguments. An image processing method comprising a processing step of obtaining a result of multi-value error diffusion processing for each of a cyan density component and a magenta density component of a target pixel. A computer-readable storage medium storing a program for executing the image processing method according to claim 6 .

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