JP2002171407A - Image processing apparatus and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus and an image processing method that can simplify more complicated threshold condition processing and apply error spread processing to image data at a high-speed to form an image with high quality. SOLUTION: In the application of error spread processing to multi-value image data consisting of density components to provide an output of the processing result, when the error spread processing is executed for a first density component among density components, a threshold used for the error spread processing is decided on the basis of the density of a second density component, the error spread processing is applied to the first density component on the basis of the decided threshold and its execution result is outputted, and when the error spread processing is executed for the second density component, a threshold used for the error spread processing is decided on the basis of the density of the first density component, the error spread processing is applied to the second density component on the basis of the decided threshold and its execution result is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and an image processing method, and more particularly to an image processing apparatus and an image processing method for performing an error diffusion process on multi-value image density data to perform a pseudo halftone process.

[0002]

2. Description of the Related Art Conventionally, an error diffusion method is known as pseudo gradation processing for expressing a multi-valued image in binary ("An Adaptive Method").
Algorithm for Spatial Gray Scale "in society for I
nformation Display 1975 Symposium Digest of Techni
cal Papers, 1975, 36). In this method, the target pixel is P, its density is v, and the densities of peripheral pixels P0, P1, P2, and P3 of the target pixel P are v0, v1, v2, v3, and the threshold for binarization is T. , The binarization error E in the target pixel P is
This is a method in which weighting factors W0, W1, W2, and W3 empirically obtained are assigned to 1, P2, and P3, and the average density is macroscopically equal to the density of the original image.

For example, assuming that the output binary data is o, if v ≧ T, then o = 1, E = v−Vmax;. . . . (1) If v <T, then o = 0, E = v−Vmin; (where Vmax: maximum density, Vmin: minimum density) v0 = v0 + E × W0; . . . (2) v1 = v1 + E × W1; . . . (3) v2 = v2 + E × W2; . . . (4) v3 = v3 + E × W3; . . . (5) (Example of weighting factor: W0 = 7/16, W1 = 1/16, W2 = 5/16, W
3 = 3/16).

Conventionally, for example, when a multi-valued image is output using four color inks such as cyan (C), magenta (M), yellow (Y), and black (K) in a color ink jet printer or the like, each color is independent. Since the pseudo gradation processing was performed using the error diffusion method or the like, the visual characteristics were excellent when one color was viewed, but good visual characteristics were not always obtained when two or more colors overlapped. .

In order to improve this problem, Japanese Patent Application Laid-Open No. Hei 8-2
Japanese Patent Application Laid-Open No. 79920 and Japanese Patent Application Laid-Open No. H11-10918 disclose an error diffusion method in which two or more colors are combined to obtain a pseudo halftone processing method that can obtain good visual characteristics even when two or more colors overlap. It has been disclosed.

Japanese Unexamined Patent Application Publication No. Hei 9-139841 discloses a method in which two or more colors are independently subjected to pseudo middle gradation processing, and then the output value is corrected by summing the input values, thereby making a similar improvement. It has been disclosed.

[0007] In particular, to reduce the graininess in the middle density area of a color image, a cyan component (C) and a magenta component (M) are used.
It is effective to form an image so that the dots do not overlap with each other, and the following method is used for that purpose.

FIG. 14 is a diagram showing image forming control according to a conventional ink jet system.

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

The Ct and Mt densities of the C component and the M component of the pixel of interest in the multi-valued color image are Ct = C + Cerr, where C and M are the density values of the C and M components of the original image, respectively. Mt = M + Merr. Here, Cerr and Merr are error-diffused values of the C component and the M component, respectively, with respect to the target pixel.

As shown in FIG. 14, with respect to C and M image formation, according to the densities of the C component and the M component of the pixel of interest,
Four types of image formation control are performed. 1. When the sum of (Ct + Mt) is equal to or smaller than the threshold value (Threshold 1), that is, when the sum belongs to the area (1) in FIG. 14, dot recording is not performed using both the C ink and the M ink. 2. The sum of (Ct + Mt) exceeds the threshold (Threshold 1), and the sum of (Ct + Mt) is another threshold (Threshold
2) and Ct> Mt, that is, FIG.
If it belongs to the area (2), dot recording is performed using only the C ink. 3. The sum of (Ct + Mt) exceeds the threshold (Threshold 1), and the sum of (Ct + Mt) is another threshold (Threshold
2) and Ct ≦ Mt, that is, FIG.
If it belongs to the area (3), dot recording is performed using only the M ink. 4. If the sum of (Ct + Mt) is equal to or greater than another threshold (Threshold 2), that is, if it belongs to the area (4) in FIG.
Dot recording is performed using C ink and M ink.

Here, Threshold 1 <Threshold 2
It is.

[0013]

However, in the above conventional example, since the image forming method for the C component and the M component is changed based on the sum of the density values of the C component and the M component, only a simple image forming control is performed. For example, when there is a pixel in which the data of the image to be processed fluctuates before and after the threshold value is close to the pixel where the C ink and the M ink are overlapped in the narrow area. And non-pixels are mixed, and eventually the quality of the formed image is degraded.

In order to prevent such a situation, it is sufficient to perform more complicated threshold division. However, in such a case, it is necessary to make the threshold condition processing more complicated by that much. Is inevitable.

Further, in the conventional processing based on the sum of the density values of the C component and the M component, there is a problem in that the threshold processing must be simple, and it is difficult to perform a flexible processing. Was.

If exclusive error diffusion is to be performed using the sum of the three components in addition to the black (K) component, very complicated processing is required, for example, as shown in the following code.

Ct = C + Cerr Mt = M + Merr Kt = K + Kerr If (Ct + Mt + Kt> Threshold1) If (Ct + Mt + Kt <Threshold2) If (Ct> Mt &&Ct> Kt) Print C Else If (Mt> Ct &&Mt> Kt) Print M Else Print K Else If (Ct + Mt + Kt <Threshold 3) If (Ct <Mt && Ct <Kt) Print M Print K Else If (Mt <Ct && Mt <Kt) Print C Print K Else Print C Print M Else Print C Print M Print K The present invention has been made in view of the above-described conventional example, and performs more complicated threshold condition processing easily to achieve high-speed error diffusion. It is an object of the present invention to provide an image processing apparatus and an image processing method capable of performing processing and forming a high-quality image.

[0018]

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

In other words, there is provided an image processing apparatus for performing an error diffusion process on multi-valued image data composed of a plurality of density components and outputting a result of the error diffusion process, wherein the first density component of the plurality of density components is In performing the error diffusion process on the component, a first determination unit that determines a threshold value used for the error diffusion process based on the density value of the second density component, and a threshold value determined by the first determination unit. First error diffusion executing means for executing an error diffusion process on the first density component; first output means for outputting an execution result by the first error diffusion executing means; When performing the error diffusion process on the density component of the second density component, a second determination unit that determines a threshold value used for the error diffusion process based on the density value of the first density component, and a threshold value determined by the second determination unit. A second error diffusion execution means for executing the error diffusion processing on the second density component based on,
And a second output unit for outputting a result of execution by the second error diffusion execution unit.

It is preferable that the first and second determination means use a table in which a relationship between a density value and a threshold value is determined in determining the threshold value.

Each of the first and second determining means may determine a plurality of thresholds for multi-leveling as well as for binarizing. In that case, the first and second determining means respectively
It is preferable to use a plurality of tables for determining each of the plurality of thresholds.

Further, among the plurality of concentration components, the third
When performing the error diffusion process on the density components of the first and second density components,
And a third error diffusion unit that performs an error diffusion process on the third density component based on a threshold value determined by the third determination unit. An execution unit and a third output unit that outputs an execution result by the third error diffusion execution unit may be provided.

As described above, when the error diffusion processing is performed on the first, second, and third density components, the first determining means determines the density value of the second density component and the third density component. A threshold value used for error diffusion processing for the first density component is determined based on a sum of the density value of the density component and the density value of the first density component. It is preferable to determine a threshold value used for error diffusion processing for the second density component based on the sum of the density value and the density value.

The plurality of density components are a yellow component, a magenta component, a cyan component, and a black component, the first density component is a cyan component, the second density component is a magenta component, The density component of No. 3 is a black component.

The image forming apparatus may further include an image forming unit, such as an ink jet printer, for forming an image by inputting an error diffusion processing execution result output from the first, second, and third output units. desirable.

This ink jet printer is preferably provided with an ink jet recording head for discharging ink using thermal energy, and the ink jet recording head is preferably provided with an electrothermal converter for generating heat energy applied to the ink. is there.

According to still another aspect of the present invention, there is provided an image processing method for performing an error diffusion process on multi-valued image data including a plurality of density components and outputting a result of the error diffusion process. In performing the error diffusion process on the first density component, a threshold value used for the error diffusion process is determined based on the density value of the second density component, and the threshold value is determined in the first determination step. A first error diffusion execution step of executing an error diffusion process on the first density component based on the threshold value obtained, a first output step of outputting an execution result in the first error diffusion execution step, and the plurality of densities. A second determining step of determining a threshold value used for the error diffusion processing based on a density value of the first density component when performing the error diffusion processing on the second density component among the components; To A second error diffusion executing step of executing an error diffusion process on the second density component based on the determined threshold value, and a second output step of outputting an execution result in the second error diffusion executing step. And an image processing method characterized by the following.

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

With the above arrangement, according to the present invention, when performing error diffusion processing on multi-valued image data composed of a plurality of density components and outputting the result, an error is detected in the first density component among the plurality of density components. In performing the diffusion process, a threshold value used for the error diffusion process is determined based on the density value of the second density component, and the error diffusion process is performed on the first density component based on the determined threshold value. In addition to outputting the execution result, when performing the error diffusion process on the second density component among the plurality of density components, a threshold value used for the error diffusion process is determined based on the density value of the first density component. , Performs an error diffusion process on the second density component based on the determined threshold value, and outputs the execution result.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

[Common Embodiment] First, an overall outline of an information processing system, an outline of a hardware configuration, an outline of a software configuration, and an outline of image processing which are commonly used in the following several 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, this information processing system includes a host device 51 composed of a personal computer or the like.
And an image output device 52 composed of a printer or the like, and these are connected via a bidirectional interface 53. And, in the memory of the host device 51,
The driver software 54 to which the present invention is applied is loaded.

1. Next, a 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 a 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 5
Reference numeral 1 denotes the entire host device including the processing unit 1000 and peripheral devices. The image output device 52 includes a drive unit such as a printhead 3010, a carrier (CR) motor 3011 for driving a carrier for transporting the printhead 3010, a transport motor 3012 for transporting paper, and a control circuit unit 3003. ing.

The processing unit 1000 of the host device 51 is an MPU that controls the entire host device according to the control program.
1001, a bus 10 for connecting system components to each other
02, a DRAM 1003 for temporarily storing programs and data executed by the MPU 1001, a system bus and a memory bus, a bridge 1004 for connecting the MPU 1001,
For example, it includes a graphic adapter 1005 having a control function for displaying graphic information on a display device 2001 such as a CRT.

Further, the processing unit 1000 includes the HDD device 20
HDD controller 10 that controls the interface with the HDD 02
06, a keyboard controller 1007 that controls the interface with the keyboard 2003, and a communication I / F 1008 that is a parallel interface that controls communication with the image output device 52 according to the IEEE1284 standard.

Further, the processing unit 1000 includes a display device 2001 (CRT in this example) for displaying graphic information and the like to the operator via the graphic adapter 1005.
Is connected. Furthermore, a hard disk drive (H) which is a mass storage device in which programs and data are stored.
DD) The device 2002 and the keyboard 2003 are connected via a controller.

On the other hand, the control circuit 30 of the image output device 52
Reference numeral 03 denotes an MCU 3001 having both a control program execution function and a peripheral device control function, which controls overall control of the image output apparatus main body 52, a system bus 3002 for connecting each component inside the control circuit unit, and a recording data recording head 30.
A gate array (GA) having a control circuit for supplying power to the G.10, memory address decoding, a control pulse generation mechanism for the carrier motor, and the like is provided.

The control circuit 3003 is provided with the MCU 30
01 for storing a control program to be executed by the H.01, host print information, etc., and a DRAM 3 for storing various data (image recording information, recording data supplied to the head, etc.).
005, a communication I which is a parallel interface that governs communication with the host device 51 in accordance with the IEEE1284 standard.
/ F 3006, and a head driver 3007 that converts a head print signal output from the gate array 3003 into an electric signal for driving the print head 3010.

Further, the control circuit 3003 includes a CR motor driver 3008 for converting a carrier motor control pulse output from the gate array 3003 into an electric signal for actually driving a carrier (CR) motor 3011, and an MCU.
An LF motor driver 3009 for converting the transport motor control pulse output from the transport motor 3001 into an electric signal for actually driving the transport motor is provided.

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.

Referring to FIG. 3, a helical groove 500 of a lead screw 5005 which rotates through driving force transmission gears 5009 to 5011 in conjunction with forward and reverse rotation of a driving motor 5013.
The carriage HC engaged with the carriage 4 has a pin (not shown), and is supported by the guide rail 5003 to reciprocate in the directions of arrows a and b. The print head I is provided on the carriage HC.
An integrated ink jet cartridge IJC containing a JH and an ink tank IT is mounted. Reference numeral 5002 denotes a paper pressing plate, which presses the recording paper P against the platen 5000 in the moving direction of the carriage HC. 50
Reference numerals 07 and 5008 denote photocouplers, which confirm the presence of a carriage lever 5006 in this area, and
Is a home position detector for switching the rotation direction of the camera. A member 5016 supports a cap member 5022 for capping the front surface of the recording head IJH.
Reference numeral 15 denotes a suction device that suctions the inside of the cap, and performs suction recovery of the recording head through the opening 5023 in the cap. 5
Reference numeral 017 denotes a cleaning blade. Reference numeral 5019 denotes a member which allows the blade to move in the front-rear direction. These members are supported by a main body support plate 5018. It goes without saying that the blade is not limited to 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. The lever 5021 moves with the movement of the cam 5020 engaging with the carriage, and the driving force from the driving motor is controlled by a known transmission mechanism such as clutch switching. Is done.

The capping, cleaning, and suction recovery are configured so that desired processing can be performed at the corresponding position by the action of the lead screw 5005 when the carriage comes to the area on the home position side. If a desired operation is performed at the timing, any of the embodiments can be applied.

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 are separated. It may be configured so that only the ink tank IT can be replaced when the ink runs out.

The control circuit section mentioned in FIG. 2 is built in the ink jet printer IJRA.

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

2. 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, the image output device 52
In order to output recording data to the host device 5,
2, the application software having a hierarchical structure, the operating system, and the driver software 3
Perform image processing in cooperation with each other.

In this embodiment, the parts that individually depend on the image output devices are the device-specific drawing functions 31-1 and 31-31.
,..., 31-n, separates the program components that depend on the individual implementation of the image processing apparatus from the programs that can perform common processing, and separates the fundamental processing part of the driver software into individual images. The structure is independent of the output device.

The line-divided image converted to the quantization amount is subjected to image processing such as color characteristic conversion 33 and halftone processing (half-toning) 34, and print command generation 3.
In 5, the data created after adding the data compression / command is transferred to the image output device 52 through the spooler 22 prepared in the OS (operating system).

As shown in FIG. 4, the application software 1
1, a drawing processing interface 21 for receiving a drawing command from the application software 11 and a spooler 22 for passing generated image data to an image output device 52 such as an ink jet printer are provided in the OS (operating system) layer. ing.

.., 31-n in which a representation format unique to the image output device is stored, and an OS.
And a color characteristic conversion unit 33 that receives the line-divided image information from the device and converts the color system inside the driver into a device-specific color system, and converts it into a quantization amount representing the state of each pixel of the device. A half-toning unit 34 and a print command generation unit 35 that adds a command to the image output device 52 and outputs the half-toned image data to the spooler 22 are provided.

Next, the case where the application software outputs an image to the image output device 52 will be specifically described 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 graphic, and a bitmap through the drawing processing interface 21 of the OS ( Step S1).

When the drawing command composing the screen / paper is completed (step S2), the OS sets the device-specific drawing functions 31-1, 31-2,..., 31-in the driver software.
While calling n, each drawing command is converted from the internal format of the OS to a device-specific expression format (each drawing unit is divided into lines)
(Step S3), and thereafter, the image is passed to the driver software as image information obtained by dividing the screen / paper into lines (Step S4).

Inside the driver software, the color characteristics conversion unit 33 corrects the color characteristics of the device,
The color system in the driver software is converted into a color system specific to the device (step S5), and further converted by the half-toning unit 34 into a quantization amount representing the state of each pixel of the device (half-toning). (Step S6). Here, the conversion to the quantization amount 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 printing by the image output device is performed based on multi-valued data (for printing with dark and light inks and printing with large and small inks), multi-level printing is performed.

The details of the half-toning are described below.
This will be described in each embodiment described later.

The print command generation module 35
Each receives image data that has been quantized (binarized, multi-valued) (step S7). The print command generation module 35 processes the quantized image information according to different methods according to the characteristics of the image output device. Further, both this module performs data compression and command header addition (step S8).

Thereafter, the print command generation module 35 transfers the generated data to the spooler 22 provided inside the OS (step S9), and the image output device 52
Is performed (step S10).

In this embodiment, the above-described 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, since the fundamental processing portion of the driver software has a structure independent of the individual image output device, the sharing of data processing between the driver software and the image output device does not impair the configuration of the driver software. It can be changed flexibly without any problem, 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 the error diffusion processing performed by the halftoning unit 34 will be described.

In the error diffusion processing described below, each pixel is density data including a yellow (Y) component, a magenta (M) component, a cyan (C) component, and a black (K) component. It is assumed that multi-valued image data composed of 8 bits (256 gradations) is used.

[First Embodiment] Here, unlike the conventional example, an error diffusion process which can perform complicated threshold condition processing will be described. The target of the error diffusion processing according to this embodiment is the multi-valued image data of the C component and the M component.

This embodiment deals with a case where multi-level density data is binarized by error diffusion processing.

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

Hereinafter, the features of this embodiment will be described with reference to this flowchart.

First, in step S10, the density values Ct and Mt of the C component and the M component of the target pixel are obtained as in the conventional example. Next, in step S20, a threshold (Cthreshold) used for error diffusion of the C component is obtained based on the obtained density value Mt of the M component. Specifically, in this embodiment, a threshold table as shown in Tables 1 and 2 is set in the HDD 2002 or the DRAM 1003 of the host device 52, and the threshold is determined by referring to the threshold table.

In step S30, the threshold value (Cthreshold) obtained in step S20 is compared with the density value Ct of the target pixel. Here, if Ct ≧ Cthreshold, the process proceeds to step S40, and a setting is made to perform printing with C ink. Thereafter, the process proceeds to step S50. On the other hand, if Ct <Cthreshold, the process proceeds to step S
The process skips step S40 and proceeds to step S50.

In step S50, a threshold (Mthreshold) used for error diffusion of the M component is obtained based on the obtained density value Ct of the C component. Specifically, in this embodiment, a threshold table as shown in Tables 1 and 2 is stored in the HDD 2002 or the DRAM 1003 of the host device 52.
The threshold value is determined by referring to the threshold value table.

Therefore, in this embodiment, the threshold tables shown in Tables 1 and 2 are commonly used for the C component and the M component.

In step S60, the threshold (Mthreshold) obtained in step S50 is compared with the density value Mt of the target pixel. Here, if Mt ≧ Mthreshold, the process proceeds to step S70, and a setting is made to perform printing with M ink. Thereafter, the process proceeds to step S50. On the other hand, if Mt <Mthreshold, the process proceeds to step S
The process is terminated by skipping 70.

By executing the above processing,
The threshold condition processing as shown in FIG. 7A, which is the same threshold processing as that of FIG. 14 of the conventional example, is also shown in FIG. 8A, which is a more complicated threshold condition than the threshold condition shown in FIG. 7A. Such threshold condition processing also defines a threshold table having a common format,
By simply setting the values in the threshold table differently, complicated threshold setting processing can be easily performed.

Table 1 is a threshold table having threshold conditions corresponding to FIG. 7A, and Table 2 is a threshold table having threshold conditions corresponding to FIG. 8A.

[0078]

[Table 1]

[0079]

[Table 2] For example, when a threshold condition process as shown in FIG. 7A is executed according to this embodiment, first, step S20
In steps S50 to S40, a threshold condition process as shown in FIG. 7B is executed.
The threshold condition processing shown in FIG.

Similarly, when the threshold condition processing as shown in FIG. 8A is executed according to this embodiment, first, in steps S20 to S40, the threshold condition processing as shown in FIG. 8B is executed. Next, in steps S50 to S70, a threshold condition process as shown in FIG.

Therefore, according to the embodiment described above, the threshold condition processing is performed using a threshold table of a predetermined format. For example, as shown in FIG. 9, even if the threshold condition is complicated, the processing is complicated. Can be easily done without
Also, since the processing is simple, complicated threshold condition processing can be performed at high speed.

[Second Embodiment] The first embodiment deals with the case where the multi-value density data is binarized by the error diffusion process. In this embodiment, however, the multi-value density data is converted to the ternary value by the error diffusion process. Deal with the case.

FIG. 10 is a flowchart showing image forming control according to this embodiment.

Hereinafter, the features of this embodiment will be described with reference to this flowchart.

First, in step S100, the density values Ct and Mt of the C component and the M component of the target pixel are obtained as in the conventional example. Next, in step S110, based on the obtained density value Mt of the M component, the C component is used for error diffusion.
Two thresholds (Cthreshold1 and Cthreshold2) are obtained. Specifically, in this embodiment, a threshold table as shown in Tables 3 to 6 is set in the HDD 2002 or the DRAM 1003 of the host device 52, and the threshold is determined by referring to the threshold table.

In step S120, step S110
Is compared with the density value Ct of the target pixel. Here, if Ct ≧ Cthreshold1, the process proceeds to step S130, and another threshold (Cthreshold) obtained in step S110 is obtained.
2) is compared with the density value Ct of the target pixel. Where Ct
If ≧ Cthreshold2, the process proceeds to step S140, and a setting is made to perform printing by discharging large ink droplets using C ink. Thereafter, the process proceeds to step S16
Go to 0. On the other hand, if Ct <Cthreshold2, the process proceeds to step S150, and a setting is made so that printing is performed by discharging small ink droplets using C ink. Thereafter, the process proceeds to step S160.

In step S120, Ct <
If it is Cthreshold1, the processing is performed in steps S130 to S1.
The process skips 50 and proceeds to step S160.

Now, in step S160, the obtained C
Two thresholds (Mthreshold1 and Mthreshold2) used for error diffusion of the M component are obtained based on the density value Ct of the component. Specifically, in this embodiment, a threshold table as shown in Tables 3 to 6 is stored in the HDD 2002 of the host device 52.
Alternatively, the threshold is set in the DRAM 1003 and the threshold is determined by referring to the threshold table.

Therefore, in this embodiment, the threshold tables shown in Tables 3 to 6 are commonly used for the C component and the M component.

In step S170, step S160
Is compared with the density value Mt of the pixel of interest. Here, if Mt ≧ Mthreshold1, the process proceeds to step S180, and another threshold value (Mthreshold1) obtained in step S160 is obtained.
2) is compared with the density value Mt of the target pixel. Where Mt
If ≧ Mthreshold2, the process proceeds to step S190, and a setting is made to perform printing by discharging large ink droplets using M ink. Thereafter, the process ends. On the other hand, if Mt <Mthreshold2, the process proceeds to step S200, and a setting is made to perform printing by discharging small ink droplets using M ink. Thereafter, the process ends.

On the other hand, if Mt <Mthreshold1 in step S170, the process proceeds to step S1.
The processing is terminated by skipping steps 80 to S200.

By executing the above processing,
The threshold condition processing as shown in FIG.
As for the threshold condition processing as shown in (a), a complicated threshold setting process can be easily performed only by defining a threshold table having a common format and setting values in the threshold table differently.

Tables 3 and 4 are threshold tables having threshold conditions corresponding to FIG. 11A, and Tables 5 and 6 correspond to FIG.
2 is a threshold table having threshold conditions corresponding to 2 (a).

[0094]

[Table 3]

[0095]

[Table 4]

[0096]

[Table 5]

[0097]

[Table 6] For example, when a threshold condition process as shown in FIG. 11A is executed according to this embodiment, first, step S1 is executed.
In steps 10 to S150, a threshold condition process as shown in FIG. 11B is executed, and then in steps S160 to S200, a threshold condition process as shown in FIG. 11C is executed.

Similarly, when the threshold condition processing as shown in FIG. 12A is executed according to this embodiment, first,
In steps S110 to S150, a threshold condition process as shown in FIG.
In steps S200 to S200, a threshold condition process as shown in FIG. In particular, the threshold condition shown in FIG. 12 is effective for improving the uniformity of the halftone image.

Therefore, according to the embodiment described above, even when the multi-valued image data is ternarized, the threshold condition processing is performed using the threshold table of a predetermined format. It can be easily performed without performing, and since the processing is simple, complicated threshold condition processing can be performed at high speed.

In this embodiment, only the ternarization is dealt with. However, an ink jet printer as an image output device uses an ink having the same color system as that of the drop modulation but having a different density (for example,
Light cyan ink, dark cyan ink, light magenta ink,
If it is possible to cope with quaternary or quinary conversion by using dark magenta ink), a threshold table for performing multi-level error diffusion processing such as quaternary or quinary conversion is created. Needless to say, it is good.

[Third Embodiment] In the first and second embodiments, the case where the C component and the M component of the multi-value density data are handled by the error diffusion processing has been described. The K component is also handled in addition to the component.

FIG. 13 is a flowchart showing image forming control according to this embodiment.

Hereinafter, the features of this embodiment will be described with reference to this flowchart.

First, in step S210, C of the target pixel is
The density values Ct, Mt, and Kt of the component, the M component, and the K component are obtained. Next, in step S220, a threshold (Cthreshold) used for error diffusion of the C component is calculated based on the obtained density value Mt of the M component and density value Ct of the K component. Specifically, in this embodiment, a threshold table as shown in Table 7 is stored in the HDD 2002 or the DRAM of the host device 52.
1003, and the threshold is determined by referring to the threshold table.

In step S230, step S220
Is compared with the density value Ct of the pixel of interest. Here, if Ct ≧ Cthreshold, the process proceeds to step S240, and a setting is made so that printing is performed with C ink. Thereafter, the process proceeds to step S250. On the other hand, if Ct <Cthreshold, the process skips step S240 and proceeds to step S250.

Now, in step S250, the obtained C
Based on the density value Ct of the component and the density value Kt of the K component, M
A threshold (Mthreshold) used for error diffusion of the component is obtained. Specifically, in this embodiment, a threshold table as shown in Table 7 is set in the HDD 2002 or the DRAM 1003 of the host device 52, and the threshold is determined by referring to the threshold table.

In step S260, step S250
Is compared with the density value Mt of the pixel of interest. Here, if Mt ≧ Mthreshold, the process proceeds to step S270, and a setting is made to perform printing with M ink. Thereafter, the process proceeds to step S280. On the other hand, if Mt <Mthreshold, the process skips step S270 and proceeds to step S280.

Further, in step S280, based on the obtained density value Ct of the C component and the density value Mt of the M component,
A threshold (Kthreshold) used for error diffusion of the K component is obtained. Specifically, in this embodiment, a threshold table as shown in Table 7 is set in the HDD 2002 or the DRAM 1003 of the host device 52, and the threshold is determined by referring to the threshold table.

Therefore, in this embodiment, the threshold table shown in Table 7 is commonly used for the C component, the M component, and the K component.

In step S290, step S280
Is compared with the density value Kt of the pixel of interest. Here, if Kt ≧ Kthreshold, the process proceeds to step S300, and a setting is made to perform printing with K ink. Thereafter, the process ends. On the other hand, if Kt <Kthreshold, the process proceeds to step S30.
Skip 0 and end.

The core part of the above processing is represented by code as follows.

Ct = C + Cerr Mt = M + Merr Kt = K + Kerr Cthreshold = C_Threshold_Table [Mt + Kt] If (Ct> = Cthreshold) Print C Mthreshold = M_Threshold_Table [Ct + Kt] If (Mt> = Mthreshold) Print M Kthreshold = M_Threshold_Table [Ct + Mt] If (Kt> = Kthreshold) Print K The threshold condition processing can be easily executed only by defining a threshold table having a common format and setting values in the threshold table differently.

Table 7 is a threshold table commonly used for CMK components.

[0114]

[Table 7] Therefore, according to the embodiment described above, since the threshold condition processing is performed using the threshold table of a predetermined format, even in the error diffusion processing that handles three components in which the threshold condition is complicated, the processing can be easily performed without complicating the processing. Since the processing is simple, complicated threshold condition processing can be performed at high speed.

Further, by combining this embodiment with the ternary processing described in the second embodiment, the advantages of simplification of processing and speeding up of processing are further enhanced.

The present invention is not limited by the threshold table described in the above embodiment. By maintaining the format of the threshold table and making the values set in the table different, for example, processing under various threshold conditions as described below becomes possible.

(1) Sum of density values of C component and M component (C +
Instead of M), a threshold condition such as the sum of squares (C ² + M ² ) of the density values of the C component and the M component is used as shown in FIG. Table 8 is a threshold value table used at this time.

[0118]

[Table 8] Using an ink jet printer having a slightly large ink ejection amount as an image output device, dots formed by isolated C ink or M ink in an extremely low density area of an image are easily visually recognized, and the exclusive arrangement of these dots enables Conversely, when the uniformity of the image is impaired, the use of such a threshold condition makes it possible to slightly weaken the correlation between the C component and the M component, thereby maintaining the uniformity of the image. Become.

(2) As shown in FIG. 9B, a threshold condition in which noise is superimposed on a threshold value is used. Table 9 is a threshold table used at this time.

[0120]

[Table 9]

By using such a threshold condition, it is possible to reduce the possibility that dots are continuously formed by C ink or M ink.

(3) As shown in FIG. 9 (c), the tendency of error diffusion in a high density region from a highlight portion and a halftone is changed. By using such a threshold condition, it is possible to reduce image quality deterioration due to disturbance of the attachment position of the ink dot in the halftone area.

(4) As shown in FIG. 9D, the threshold boundary is made as gentle as possible. By using such a threshold condition, it is possible to reduce a sharp change between an area where the C ink and the M ink are exclusively used and an area where the C ink and the M ink are not used in the vicinity of the threshold boundary. Can be improved.

As described above, by using the threshold value table, flexibility is added to the threshold value condition processing. By using such a threshold table in combination with, for example, an actual ink ejection amount and an ink composition in an ink jet printer, it is possible to easily change the content and purpose of image forming processing.

In the above embodiment, the description is given on the assumption that the liquid droplet ejected from the recording head is ink.
Further, the liquid stored in the ink tank has been described as being ink, but the stored material is not limited to ink. For example, an ink tank may contain a processing liquid discharged to a recording medium in order to improve the fixability and water resistance of the recorded image or to improve the image quality.

The above-described embodiment is particularly provided with a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for performing ink ejection even in an ink jet recording system. By using a method in which a change in the state of the ink is caused by energy, it is possible to achieve higher density and higher definition of recording.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. 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, liquid (ink)
By applying at least one drive signal corresponding to the recorded information and providing a rapid temperature rise exceeding the nucleate boiling to an electrothermal transducer arranged corresponding to the sheet or the liquid path holding the Since thermal energy is generated in the electrothermal transducer and film boiling occurs on the heat-acting surface of the recording head, bubbles in the liquid (ink) corresponding to this drive signal on a one-to-one basis can be formed. It is valid. By discharging the liquid (ink) through the discharge opening by the growth and contraction of the bubble, at least one droplet is formed. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of the liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable.

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

As the configuration of the recording head, in addition to the combination of a discharge port, a liquid path, and an electrothermal converter (a linear liquid flow path or a right-angled liquid flow path) as disclosed in the above-mentioned respective specifications, A configuration using U.S. Pat. No. 4,558,333 or U.S. Pat. No. 4,459,600, which discloses a configuration in which a heat acting surface is arranged in a bent region, is also included in the present invention. In addition, for multiple electrothermal transducers,
JP-A-59-123670 which discloses a configuration in which a common slot is used as a discharge part of an electrothermal transducer, and JP-A-59-123670 which discloses a configuration in which an opening for absorbing a pressure wave of thermal energy corresponds to a discharge part. A configuration based on 138461 may be adopted.

Further, 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 determined by a combination of a plurality of recording heads as disclosed in the above specification. This may be either a configuration that satisfies the requirements or a configuration as a single recording head that is integrally formed.

In addition, not only the cartridge type recording head in which the ink tank is provided integrally with the recording head itself described in the above embodiment but also the apparatus main body, the electrical connection with the apparatus main body is achieved. A replaceable chip-type recording head, which enables a simple connection and supply of ink from the apparatus main body, may be used.

It is preferable to add recovery means for the print head, preliminary auxiliary means, and the like to the configuration of the printing apparatus described above, since the printing operation can be further stabilized. Specific examples thereof include capping means for the recording head, cleaning means, pressurizing or suction means, preheating means using an electrothermal transducer or another heating element or a combination thereof. It is also effective to provide a preliminary ejection mode for performing ejection that is different from printing, in order to perform stable printing.

Further, the printing mode of the printing apparatus is not limited to the printing mode of only the mainstream color such as black, but may be a printing head integrally formed or a combination of a plurality of printing heads. Alternatively, the apparatus may be provided with at least one of full colors by color mixture.

In the embodiments described above, the description is made on the assumption that the ink is a liquid. However, even if the ink solidifies at room temperature or lower, it is possible to use an ink that softens or liquefies at room temperature. Or, in the ink jet method, generally, the temperature of the ink itself is controlled within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range.
It is sufficient that the ink is in a liquid state when the use recording signal is applied.

In addition, in order to positively prevent a temperature rise due to thermal energy as energy for changing the state of the ink from the solid state to the liquid state, the temperature is positively prevented.
Alternatively, in order to prevent evaporation of the ink, ink that solidifies in a standing state and liquefies by heating may be used. In any case, the application of heat energy causes the ink to be liquefied by application of the heat energy according to the recording signal and the liquid ink to be ejected, or to start to solidify when reaching the recording medium. The present invention is also applicable to a case where an ink having a property of liquefying for the first time is used. In such a case, as described in JP-A-54-56847 or JP-A-60-71260, the ink is held in a liquid state or a solid state in the concave portion or through hole of the porous sheet. It is good also as a form which opposes an electrothermal transducer. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition to the above, the recording apparatus according to the present invention may be provided not only as an image output terminal of an information processing apparatus such as a computer but also integrally or separately, a copying apparatus combined with a reader, etc. It may take the form of a facsimile machine having functions.

Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (for example, a copier, a facsimile machine) comprising one device Etc.).

Further, an object of the present invention is to supply a storage medium (or a recording medium) in which a program code of software for realizing the functions of the above-described embodiments is recorded to a system or an apparatus, and to provide a computer (a computer) of the system or the apparatus. Or CPU and MPU) read and execute the program code stored in the storage medium,
It goes without saying that this is achieved. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.
In addition, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also based on the instructions of the program code,
The operating system (OS) running on the computer performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

Further, after the program code read from the storage medium is written into the memory provided in the function expansion card inserted into the computer or the function expansion unit connected to the computer, the program code is read based on the instruction of the program code. , The CPU provided in the function expansion card or the function expansion unit performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

[0140]

As described above, according to the present invention, error diffusion processing is performed in consideration of the values of other density components.
It is possible to form an image in consideration of overlapping with other components, and it is possible to form a high-quality image.

According to the second, fourth, twelfth, and fourteenth aspects of the present invention, the threshold value used for the error diffusion process is determined using the table. Can be subjected to the error diffusion process.

[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 illustrating an outline of a hardware configuration of a host device 51 and an image output device 52 that constitute the information processing system.

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

FIG. 4 is a block diagram showing the structure of software used in the information processing system.

FIG. 5 is a flowchart illustrating an outline of image processing.

FIG. 6 is a flowchart showing image forming control according to the first embodiment.

FIG. 7 is a diagram showing threshold conditions used in the first embodiment.

FIG. 8 is a diagram illustrating another threshold condition used in the first embodiment.

FIG. 9 is a diagram showing examples of various applicable threshold conditions.

FIG. 10 is a flowchart illustrating image forming control according to a second embodiment.

FIG. 11 is a diagram showing threshold conditions used in a second embodiment.

FIG. 12 is a diagram showing another threshold condition used in the second embodiment.

FIG. 13 is a flowchart illustrating image forming control according to a third embodiment.

FIG. 14 is a diagram illustrating image formation control according to a conventional inkjet method.

[Explanation of symbols]

Reference Signs List 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 (half toning) 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 unit 3004 ROM 3005 DRAM 3006 Communication I / F 3007 Head driver 3008 CR motor driver 3 09 LF motor driver 3010 recording head 3011 carrier (CR) motor 3012 conveying motor

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiromitsu Hirabayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2C262 AA02 AA24 AA26 AA27 AB13 BB03 BB08 BB22 BC01 DA06 5B057 AA11 CA01 CA08 CA12 CA16 CB01 CB07 CB12 CB16 CC01 CE13 CE14 CH07 CH08 5C077 LL18 LL19 MP08 NN11 PP33 PQ12 PQ23 RR04 RR08 RR15 RR16 TT05 5C079 HB03 KA12 KA15 LC09 LC11 MA04 MA11 NA05 NA11 NA27 PA03

Claims (17)

[Claims] 1. An image processing apparatus for performing an error diffusion process on multi-valued image data including a plurality of density components and outputting a result of the error diffusion process, wherein a first density of the plurality of density components is In performing the error diffusion process on the component, a first determination unit that determines a threshold value used for the error diffusion process based on the density value of the second density component, based on the threshold value determined by the first determination unit. A first step of executing an error diffusion process on the first density component;
Error diffusion performing means; first output means for outputting an execution result of the first error diffusion performing means; and error diffusion processing for performing error diffusion processing on a second density component of the plurality of density components. Second determining means for determining a threshold value used for processing based on the density value of the first density component; and performing error diffusion processing on the second density component based on the threshold value determined by the second determining means. Second
An image processing apparatus comprising: an error diffusion execution unit; and a second output unit that outputs an execution result of the second error diffusion execution unit. 2. The image processing apparatus according to claim 1, wherein said first and second determination means use a table that defines a relationship between a density value and a threshold value when determining said threshold value. 3. The image processing apparatus according to claim 1, wherein said first and second determination means each determine a plurality of thresholds. 4. The image processing apparatus according to claim 3, wherein each of the first and second determination means uses a plurality of tables for determining each of the plurality of thresholds. 5. When performing an error diffusion process on a third density component among the plurality of density components, a threshold value used for the error diffusion process is set to a density of the first density component and the density of the second density component. A third determining unit that determines based on a sum of the third density component and an error diffusion process for the third density component based on a threshold determined by the third determining unit.
2. The apparatus according to claim 1, further comprising: an error diffusion execution unit; and a third output unit that outputs an execution result of the third error diffusion execution unit.
An image processing apparatus according to claim 1. 6. When error diffusion processing is performed on the first, second, and third density components, the first determination unit determines the density value of the second density component and the third density component. A threshold value used for error diffusion processing for the first density component based on the sum of the density value of the first density component and the density value of the first density component. 6. The image processing apparatus according to claim 5, wherein a threshold value used for error diffusion processing for the second density component is determined based on a sum of the density value of the third density component and the density value of the third density component. 7. The plurality of density components are a yellow component, a magenta component, a cyan component, and a black component, the first density component is a cyan component, and the second density component is a magenta component. 2. The image processing apparatus according to claim 1, wherein the third density component is a black component. 8. The image forming apparatus according to claim 5, further comprising an image forming unit configured to input an error diffusion processing execution result output from the first, second, and third output units to form an image. Image processing device. 9. An image processing apparatus according to claim 8, wherein said image forming means is an ink jet printer. 10. The ink-jet printer according to claim 1, further comprising an ink-jet recording head for discharging ink using thermal energy, wherein the ink-jet recording head includes an electrothermal converter for generating thermal energy applied to the ink. The image processing apparatus according to claim 9, wherein: 11. An image processing method for performing an error diffusion process on multi-valued image data composed of a plurality of density components and outputting a result of the error diffusion process, wherein a first density of the plurality of density components is In performing the error diffusion processing on the component, a first determination step of determining a threshold value used for the error diffusion processing based on the density value of the second density component, and a threshold value determined in the first determination step. A first step of performing an error diffusion process on the first density component;
An error diffusion execution step, a first output step of outputting an execution result in the first error diffusion execution step, and an error diffusion process for executing an error diffusion process on a second density component of the plurality of density components. A second determining step of determining a threshold value used in the processing based on the density value of the first density component; and performing an error diffusion process on the second density component based on the threshold value determined in the second determining step. Second
An image processing method comprising: an error diffusion execution step; and a second output step of outputting an execution result in the second error diffusion execution step. 12. The image processing method according to claim 11, wherein the first and second determination steps use a table that defines a relationship between a density value and a threshold value in determining the threshold value. 13. The first and second determining steps are respectively
The image processing method according to claim 11, wherein a plurality of thresholds are determined. 14. The method according to claim 14, wherein the first and second determining steps are respectively:
14. The image processing method according to claim 13, wherein a plurality of tables are used for determining each of the plurality of thresholds. 15. When performing an error diffusion process on a third density component of the plurality of density components, a threshold used for the error diffusion process is set to a density of the first density component and a density of the second density component. A third determining step of determining based on a sum of the third density component and an error diffusion process based on the threshold value determined in the third determining step.
The image processing method according to claim 11, further comprising: an error diffusion execution step; and a third output step of outputting an execution result in the third error diffusion execution step. 16. When error diffusion processing is performed on the first, second, and third density components, the first determining step includes the step of determining the density value of the second density component and the third density component. Determining a threshold value used for error diffusion processing for the first density component based on a sum of the density values of the first density component and the density value of the first density component. 16. The image processing apparatus according to claim 15, wherein a threshold value used for an error diffusion process for the second density component is determined based on a sum of the density values of the third density component and the density values. 17. A computer-readable storage medium storing a program for executing the image processing method according to claim 11. Description: