JP2000168152A - Gradation-converting apparatus, and its conversion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gradation-converting apparatus for image data and its conversion method with which printing data supplied from a host apparatus is processed to be printed with a superior printing quality without increasing a memory capacity. SOLUTION: A printing image data-generating part 3 in a printer apparatus 2 generates video data according to printing data supplied from a host computer 1. An image memory 4 stores the data. A video data-converting/transferring part 5 reads out the video data stored in the image memory 4 and converts, for example, 2-bit data to 3-bit data conforming to the number of gradations of a printing head 7. A printer engine 6 processes to print the data to a recording paper. In this constitution, a printing process using the printing head of a larger number of gradations can be carried out with use of the image memory 4 of a smaller memory capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of converting the number of tones to image data stored in a memory of a printing apparatus and supplying the converted image data to a printing unit. The present invention relates to a conversion device and a conversion method.

[0002]

2. Description of the Related Art Today, printers (printing apparatuses) which are connected to a host device such as a personal computer and perform a printing process according to print data supplied from the host device are widely used.

For example, in the above-described printing apparatus,
The supplied print data is developed in the RAM in the apparatus.
Generally, the RAM is expensive and uses a small-capacity memory, and thus may not match the gradation of the printing unit. For example, the RAM stores 2-bit data per pixel, and the printing unit is capable of printing 3 bits or 4 bits per pixel.

In such a case, the following printing process has conventionally been performed. In the following example, 4-bit data of a 2-bit configuration is input to the memory, and 5
This is an example in which a printing unit (printer engine) capable of printing gradations is used.

FIG. 10 shows a printing example of five gradations by the printing unit, FIG. 10A shows a printing example of gradation "0", and FIG. 10B shows a printing example of 1/4 gradation. And FIG.
4D shows a print example of 4 gradations, FIG. 4D shows a print example of 3/4 gradation, and FIG. 4E shows a print example of 1 (4/4 gradation).

Therefore, when the printer engine having the above configuration is driven on the basis of 2-bit 4-tone data developed in the memory, one of the five printing examples shown in FIGS. It is necessary to correspond. For example, except for the 1/4 gradation in FIG.
A method of printing at / 4 gradation and 4/4 gradation. Alternatively, except for the 2/4 gray scale shown in FIG.
A method of printing at 4 gradations and 4/4 gradations. Or (d)
This is a method of printing at 0 gradation, 1/4 gradation, 2/4 gradation, and 4/4 gradation except for 3/4 gradation.

[0007]

The above-described conventional gradation conversion method has the following problems. (A) First, in the above case, any one of the 1/4 gray scale, 2/4 gray scale, or 3/4 gray scale is lost, and an error occurs particularly at an intermediate level, and the quality is deteriorated. Poor print results. (B) On the other hand, in order to effectively use the configuration of the printing unit (printer engine), the number of bits per pixel of the memory must be increased, which increases the memory capacity and increases the cost of the apparatus.

An object of the present invention is to solve the above-mentioned problems and to provide a gradation conversion apparatus for performing print processing with excellent print quality without increasing the memory capacity, and a conversion method therefor.

[0009]

According to the first aspect of the present invention, there is provided a pixel data extracting means for extracting first and second pixel data continuous in a main scanning direction; A conversion table for converting the second pixel data and converting the number of gradations of the first and second pixel data to a total value closest to the original total value, and using the conversion table, This can be achieved by providing a gradation conversion device having a gradation conversion unit for performing a gradation conversion process on the extracted first and second pixel data.

Here, the first and second pixel data are:
The pixel data is continuous pixel data in the main scanning direction, that is, continuous odd-numbered pixels and even-numbered pixels, or even-numbered pixels and odd-numbered pixels, and the pixel data extraction unit detects the pixel data of any one of the above continuous pixels.

The conversion table converts the first and second pixel data, and converts the number of gradations of the first and second pixel data to a total value closest to the original total value. The gradation conversion unit performs conversion processing of the number of gradations according to the conversion table.

With this configuration, it is possible to perform a conversion process corresponding to the total value of the number of gradations before conversion, and to provide a printing process with excellent print quality without causing a gradation error in the halftone. It can be performed.

According to a second aspect of the present invention, in the first aspect of the present invention, the pixel data extracting means includes, for example, a third and a fourth line of a next line located immediately below the first and the second pixel data. The conversion table is a table having conversion data in which the total value of the first to fourth pixel data is closest to the total value of the pixel data after conversion. Is a configuration in which a gradation conversion process of the first to fourth pixel data extracted by the extraction unit is performed using the conversion table.

Here, the third and fourth pixel data are:
The pixel data to be printed immediately below the first and second pixel data. According to this example, the conversion table is applied to the first to fourth pixel data, and the total value of the converted pixel data is obtained. Can be converted with the number of gradations closest to.

With this configuration, it is possible to perform print processing with excellent print quality without causing a tone error in a halftone. According to a third aspect, in the first or second aspect, for example, the pixel data extracting means, the conversion table, and the gradation converting means are provided for each color information, and the color information is yellow (Y ), Magenta (M), cyan (C), and black (B) color information.

In this embodiment, the pixel data extracting means, the conversion table, and the gradation converting means, which are the constituent elements of the first aspect of the present invention, are provided for each color information to eliminate a gradation error in a halftone for each color. Each of these colors is melted or sublimated by subtractive color mixture to realize color printing with excellent gradation.

According to a fourth aspect of the present invention, there is provided a pixel data extracting process for extracting first and second pixel data continuous in a main scanning direction, and a process for extracting the first and second pixel data. The first and second pixels extracted by the extraction process using a conversion table for converting the number of gradations of the first and second pixel data to the total value closest to the original total value. This can be achieved by providing a gradation conversion method for performing data gradation conversion processing.

In this embodiment, the tone converting apparatus according to the first aspect is realized by a method. Even with this configuration, it is possible to perform a conversion process corresponding to the total value of the number of tones before conversion. This makes it possible to perform print processing with excellent print quality without causing a tone error in the halftone.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. <First Embodiment> FIG. 1 is a system configuration diagram including a printing apparatus to which a gradation conversion method according to the first embodiment is applied. In FIG. 1, first, a host computer 1 is composed of, for example, a personal computer or the like, and outputs print data created based on an application to a printer device 2.

The printer device 2 includes a print image data generation unit 3, an image memory 4, and a video data conversion / transfer unit 5. The print image data generator 3 is a CPU (not shown)
And a ROM or the like containing a program for controlling the CPU, receives print data supplied from the host computer 1 described above, performs print data analysis processing, converts the print data into video data, and converts the print data into video data. 4 is stored.

The image memory 4 stores, for example, one page of video data and outputs it to the video data conversion / transfer section 5. The video data conversion / transfer unit 5 performs a gradation conversion process described later, and outputs video data to the printer engine 6. The printer engine 6 includes an engine unit 8 such as a print head 7, a photosensitive drum, a developing device, and a paper transport mechanism. The printer engine 6 performs printing processing on recording paper in accordance with the video data supplied from the video data conversion / transfer unit 5.

Here, the image memory 4 is located at 4 'in FIG.
As shown by, one pixel (one pixel) is composed of two bits. That is, data of four gradations is stored for one pixel (one pixel). Also, odd pixels (odd) and even pixels (even) are alternately located and have a storage capacity of video data for one page of recording paper, for example.

On the other hand, the configuration of the print head 7 is the same as that shown in FIG.
As shown in (1), video data can be input, and print processing of five gradations can be performed by the print head 7.
That is, data of five gradations (data up to eight gradations) can be stored per pixel (one pixel). Of course, in this case, odd-numbered pixels (odd) and even-numbered pixels (even) are alternately positioned, and printing can be performed on the image memory 4 at a resolution of 3/2 times. In the above configuration, the processing operation of this example will be described below.

As described above, the printer apparatus 2 converts the print data supplied from the host computer 1 into video data of one bit (one pixel) and two bits in the print image data generator 3. This video data is developed in the image memory 4.

Next, the video data conversion / transfer section 5 reads out the video data expanded in the image memory 4 for every two pixels, and sends it to the video data conversion / transfer section 5. FIG. 3 shows an example in which data of two pixels is extracted from the image memory 4. First, continuous odd-numbered pixels (odd) and even-numbered pixels (even) are extracted.
Is extracted (of FIG. 1).

FIG. 2 shows the video data conversion / transfer section 5 described above.
FIG. 4 is a diagram showing an arrangement position of a ROM table provided in FIG. 4, and FIG. 4 is an example of a data configuration of the ROM table, in which conversion data for input data is stored. For example, FIG. 4A shows 2 extracted as described above.
FIG. 3C shows the data after conversion. FIG. 4B is a gray scale display of the data of the two pixels shown in FIG.

For example, an odd pixel (od) which is two pixel data
d) and the even-numbered pixels (even) are “00” and “00”, the gray scale display in FIG. 3B is 0/3 gray scale and 0/3 gray scale, and is converted by the ROM table. The resulting data becomes 0/4 gradation and 0/4 gradation. Similarly, odd-numbered pixels (odd) and even-numbered pixels (even) which are the next two pixel data are “0”.
0 "and" 01 ", the gradation display in FIG.
There are three gradations and one third gradation, and the data converted by the ROM table is 2/4 gradation and 0/4 gradation. Further, odd-numbered pixels (odd) and even-numbered pixels (ev
When en) is “00” or “10”, the gray scale display in FIG. 3B is 0/3 gray scale, 2/3 gray scale, and the data converted by the ROM table is 3/4 gray scale. The gradation becomes 0/4 gradation.

The following is the structure of the converted data shown in FIG. 1, which is a data structure whose total value is approximated. Therefore, when the two-pixel data is “00” or “00”, the odd pixel (odd) becomes 0/4 gradation by the conversion processing of the video data conversion / transfer unit 5 and the even pixel (eve)
n) also has 0/4 gradation. Also, if the two pixel data is “0”
When "0" and "01" are set, odd pixels (odd) become 0/4 gradation and even pixels (even) become 1 by the above conversion processing.
/ 4 gradation. Also, two pixel data are “00”, “1”
When the value is "0", the odd pixel (odd) is obtained by the above conversion process.
Becomes 0/4 gradation, and even-numbered pixels (even) become 2/4 gradation.

Further, the same processing is continuously performed. For example, two pixel data are changed to "01" and "11" shown in FIG.
, The odd pixel (odd) becomes 3 by the above conversion process.
/ 4 gradation, and even-numbered pixels (even) have 2/4 gradation. In this case, in the related art, even-numbered pixels (even) have a 3/4 gradation as shown by a circle in FIG.
In this example, 2/4 gradation is used, and the number of gradations is improved.

For example, if the two-pixel data is "10" or "10" as shown in FIG. 2, the above-mentioned conversion process causes the odd-numbered pixels (odd) to have 2/4 gradation and the even-numbered pixels (eve).
n) becomes 3/4 gradation and the number of gradations is improved. In the case of "11" and "01" shown in FIG. 2, the odd pixel (odd) becomes 2/4 gradation and the even pixel (Eve
n) is 3/4 gradation, and the number of gradations is improved.

As described above, the converted data in which the intermediate gradation is improved is supplied to the printer engine 6 as described above, and the printing process is performed with the data in which the gradation is accurately improved. Therefore, according to this example, the printing process is performed using the gradation data with the improved intermediate gradation, and a printing result with excellent quality can be obtained. <Second Embodiment> Next, a second embodiment of the present invention will be described.

Unlike the above-described embodiment in which two consecutive pixel data in one line are to be converted, the present embodiment is different in that two consecutive pixel data in two continuous lines are to be converted. . In this example, the system configuration shown in FIG. 1 is used. That is, the host computer 1 is composed of, for example, a personal computer or the like, and outputs print data created based on an application to the printer device 2. The printer device 2 includes a print image data generation unit 3, an image memory 4, and video data conversion. / Transfer unit 5
The print image data generation unit 3 receives print data supplied from the host computer 1, performs print data analysis processing, converts the print data into video data, and stores the video data in the image memory 4.

The image memory 4 stores, for example, one page of video data and outputs it to the video data conversion / transfer section 5. The video data conversion / transfer unit 5 performs a gradation conversion process described later, and outputs video data to the printer engine 6.

Here, the video data conversion / transfer section 5 of the present embodiment has the configuration shown in FIG.
And a ROM table 12. Incidentally, reference numeral 4 shown in FIG. 1 denotes the above-mentioned image memory, and 6 denotes a printer engine. Each of the shift registers 10 and 11 is a register for storing one line of image data. For example, the shift register 10 stores video data of an even line (previous line), and the shift register 11 stores an odd line (current line). Is stored. The ROM table 12 reads two consecutive pixel data and performs a conversion process.

Hereinafter, the processing operation will be specifically described. As described above, the printer device 2 converts the print data supplied from the host computer 1 into video data of one bit (one pixel) and two bits in the print image data generation unit 3. This video data is developed in the image memory 4.

Next, the video data conversion / transfer section 5 reads out the video data developed in the image memory 4 for every two pixels and sends it to the video data conversion / transfer section 5. In this example, two lines of video data are output. The shift register 10 receives even-line video data, and the shift register 11 receives odd-line video data. That is, 2-bit data is input to the shift register 10 shown in FIG. 6A and the shift register 11 shown in FIG. 6B, and is alternately replaced with new line data.

The ROM table 12 extracts video data of both lines by two pixel data. FIG. 7 shows four pixel data extracted as described above. Note that a shown in the figure is the first pixel data, b is the second pixel data, c is the third pixel data, and d is the fourth pixel data.

The ROM table 12 performs a conversion process on the basis of the above four pixel data, and converts 2-bit data into three.
Convert to bit data. That is, 4 gradation data is converted to 5
Convert to gradation data.

This gradation conversion processing does not cause an error in the intermediate gradation, and the result obtained by the above-described gradation conversion processing is output to the above-described printer engine 6. Accordingly, a print image having no error in the intermediate gradation can be supplied to the printer engine 6, and an image with excellent print quality can be obtained. <Third Embodiment> Next, a third embodiment of the present invention will be described.

In this embodiment, the gradation conversion processing described in the first embodiment and the second embodiment is applied to a color printing apparatus. FIG. 8 is an overall configuration diagram of the printer device in this case. The printer used in the description of the embodiment is a so-called tandem type color printer. In FIG.
Is composed of a paper supply / transport mechanism 12, a plurality of image forming units 13, and a fixing device 14. The paper supply / transport mechanism 12 includes a paper feed cassette 15 in which paper P is loaded and stored, and a paper transport system 16. Further, the paper transport system 16 matches the toner image with a paper feed roller 17 for transporting the paper P from the paper feed cassette 15, a paper transport path 18 for transporting the paper P transported by the paper feed roller 17, and a paper position. Roll 19, drive rolls 20, 21 driven by a motor (not shown), and drive roll 2
The transport belt 22 is rotated by 0 and 21.

The rotation of the paper feed roller 17 causes the paper feed cassette 1
5 is sent to the standby roll 19 by the rotation of the paper feed roller 17, and is conveyed to the conveyor belt 2 at a timing coincident with a toner image formed on the photosensitive drum described later.
2 Move up.

While the paper P moves on the transport belt 22, each image forming unit 25,
The toner of each color is transferred by 26, 27, and 28, and color transfer is performed on the paper P. Thereafter, a heat fixing process is performed by the fixing device 14, and the sheet P is carried out of the apparatus.

The fixing device 14 is composed of a heat roll 14a and a pressure roll 14b.
While the paper P is being nipped and conveyed, for example, the color toners of a plurality of colors transferred to the paper P are melted and melted.
Printed on

On the other hand, as described above, the image forming unit 13 has four image forming units 25 of yellow (Y), magenta (M), cyan (C), and black (B).
To 28, and are arranged in this order. Yellow (Y), magenta (M), and cyan (C) are image forming units that perform color printing by subtractive color mixture, and the black (B) image forming unit is an image forming unit that is used for monochrome printing.

Each of the image forming units 25 to 28 has exactly the same configuration except for the (color of) the developer contained in the developing container, and includes a charger, a print head, and the like near the peripheral surface of the photosensitive drum.
In this configuration, a developing device and a transfer device are sequentially arranged. Where 4
The configuration will be described by taking the cyan image forming unit 27 as an example as a representative of the image forming units. Photoconductor drum 3
0, the peripheral surface is made of, for example, an organic photoconductive material,
In the vicinity of the peripheral surface of the photosensitive drum 30, a charger 31a, a print head 31b, a developing roll (developing device) 31c, and a transfer roll 31d are sequentially arranged. The photoreceptor drum 30 rotates in the direction of the arrow, and first charges the peripheral surface of the photoreceptor drum 30 uniformly by applying a charge from the charger 31a. next,
An electrostatic latent image is formed on the peripheral surface of the photosensitive drum 30 by optical writing based on print information from the print head 31b, and a toner image is formed by a developing process by the developing roll 31c. At this time, the toner image formed on the peripheral surface of the photosensitive drum 30 is based on cyan (C) toner stored in the developing container 31c. The toner image formed on the peripheral surface of the photosensitive drum 30 in this way reaches the position of the transfer roll 31d with the rotation of the photosensitive drum 30 in the direction of the arrow, and is transported on the transport belt 22 by the transfer roll 31d. Is transferred to the paper P to be printed.

The toner image transferred onto the upper surface of the sheet P is transported in the direction of the arrow along with the movement of the transport belt 22, and is sequentially transferred by another image forming unit 25 or 26 having the same configuration as described above. Color printing based on subtractive color mixing is performed with the toners of (Y) and magenta (M).

For example, if the print image is blue, the magenta (M) toner is transferred from the image forming unit 26 to the paper P based on the principle of subtractive color mixture, and then the cyan (C) color is transferred from the image forming unit 27. The toner is transferred to the paper P to realize a blue image. For example, if the print image is red, the image forming unit 25 sends a yellow (Y)
After transferring the color toner on the paper P, the image forming unit 2
From 6, the magenta (M) toner is transferred to the paper P to realize a red image.

The paper P on which the color printing has been performed as described above is guided to the paper discharge unit by the transport roll 32, and is discharged to the paper discharge unit 34 by the paper discharge roll 33. A desired color printing can be performed by the printer device having the above-described mechanism and performing the above-described processing.

On the other hand, in the present embodiment, the image memory 4 and the ROM table 9 (video data conversion / transfer section 5) are provided for each color, and specifically have the configuration shown in FIG. That is, the image memory 4 includes a plurality of memories 4Y, 4M,
C, 4B, and the video data developed in the respective memories are stored in the corresponding ROM tables 9Y, 9M, 9
C, 9B. Each ROM table 9Y, 9M,
The configuration of 9C and 9B is the same as that of the ROM table 9 described above. After the gradation conversion processing of video data is performed by each ROM table, the corresponding print head 7
Y, 7M, 7C, 7B (in FIG. 8, 31Y, 31
M, 31C, and 31B), an exposure process on the photosensitive drum 30 is performed. The transfer process after the exposure and the color printing process based on the subtractive color mixture after the transfer are as described above.

Therefore, by employing the above-described configuration, a halftone error in each color is eliminated, and color printing based on color information with excellent gradation is performed, thereby realizing color printing with extremely excellent print quality. can do.

[0051]

As described in detail above, according to the present invention, the intermediate gradation can be improved and the print quality can be improved.

Further, the printing process can be performed without increasing the capacity of the image memory, for example, by using the image memory having the current memory capacity. Further, by performing a conversion process on pixel data including a plurality of lines, an image with higher printing quality can be created.

Further, by applying the gradation conversion processing of this embodiment to the color printing processing, a color image with excellent print quality can be created.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram including a printing device using a gradation conversion device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a specific configuration of a video data conversion / transfer unit.

FIG. 3 is a diagram illustrating an example of extracting data of two pixels from an image memory.

FIG. 4 is a ROM provided in a video data conversion / transfer unit.
FIG. 4 is a diagram illustrating an example of a table.

FIG. 5 is a diagram illustrating a configuration of a video data conversion / transfer unit according to the second embodiment.

FIG. 6 is a diagram illustrating a configuration of a shift register according to a second embodiment.

FIG. 7 is a diagram illustrating an example of extracting data of four pixels in the second embodiment.

FIG. 8 is a system configuration diagram of a color printing apparatus to which a gradation conversion device according to a third embodiment is applied.

FIG. 9 is a diagram illustrating a system configuration near a ROM table when applied to a color printing apparatus.

FIG. 10 is a diagram illustrating gradation control in a conventional example.

[Explanation of symbols]

 Reference Signs List 1 host computer 2 printer device 3 print image data generation unit 4 image memory 4Y, 4M, 4C, 4B memory 5 video data conversion / transfer unit 6 print image data generation unit 7 print head 8 engine unit 9, 9Y, 9M, 9C, 9B ROM table 10, 11 shift register 12 ROM table 13 image forming unit 14 fixing device 15 paper feed cassette 16 paper transport system 17 paper feed roller 18 paper transport path 19 standby roll 20, 21 drive roll 22 transport belt 23 auxiliary roll 25 28 Image Forming Unit 30 Photosensitive Drum 31a Charger 31b Print Head 31c Developing Device 31d Transfer Roll 32 Transport Roll 33 Discharge Roll 34 Discharge Unit

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Claims (4)

[Claims] 1. A pixel data extracting means for extracting first and second pixel data continuous in a main scanning direction; and a total value closest to an original total value by converting the first and second pixel data. A conversion table for converting the number of gradations of the first and second pixel data into gradation data; and a gradation conversion of the first and second pixel data extracted by the pixel data extraction means using the conversion table. A tone conversion device, comprising: tone conversion means for performing processing. 2. The method according to claim 1, wherein the pixel data extracting means is configured to:
The third of the next line located immediately below the second pixel data,
Extraction of fourth pixel data is also performed, and the conversion table is a table in which the total value of the first to fourth pixel data has conversion data closest to the total value of the converted pixel data. 2. The gradation conversion device according to claim 1, wherein the conversion unit performs a gradation conversion process on the first to fourth pixel data extracted by the extraction unit using the conversion table. 3. The apparatus according to claim 1, further comprising a pixel data extracting unit, a conversion table, and a gradation converting unit for each color information, wherein the color information includes yellow (Y), magenta (M), cyan (C), and black (B). 3. The gradation conversion device according to claim 1, wherein: 4. A pixel data extraction process for extracting first and second pixel data continuous in the main scanning direction, and converting the first and second pixel data to obtain a total value closest to the original total value. Using a conversion table for converting the number of gradations of the first and second pixel data, and performing a gradation conversion process on the first and second pixel data extracted by the extraction process. Characteristic gradation conversion method.