JP2003219192A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a color image forming apparatus in which color conversion processing is relatively simple, and high quality color print is ensured with good color reproducibility without requiring a large memory capacity. <P>SOLUTION: The color image forming apparatus 101 connected with an external information processor 102 through a network 103 receives and interprets page data described by a page describing language generated at the information processor 102, develops it into image data represented by the luminance and the color difference and then outputs it while converting into data on a color space. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus, and more particularly to a color image forming apparatus for forming an image of color image data created and displayed on an information processing apparatus on a recording medium such as paper.

[0002]

2. Description of the Related Art Generally, documents and image data handled by an information processing device such as a personal computer are composed of data expressed in a color space of a display system such as red (R), green (G) and blue (B). There is. On the other hand, when printing this data, a color image forming apparatus such as a color printer expresses a color using ink or toner such as yellow (Y), magenta (M), cyan (C), and further black (Bk). Therefore, from the data expressed in the color space of the display system such as red (R), green (G), and blue (B), yellow (Y), magenta (M), cyan (C), and further Conversion to data on a color space such as black (Bk) is performed.

At this time, the color space conversion of the image data is performed by an information processing device such as a personal computer, and the color space of yellow (Y), magenta (M), cyan (C), and further black (Bk). A method in which the data described above is described using a page description language, and the data described in this page description language is printed by a color printer, and display of red (R), green (G), blue (B), etc. The data expressed in the system color space is described in the page description language as it is, and the data described in the page description language is written in yellow (Y), magenta (M), cyan (C), and further in the color printer. There is a method of printing by converting to data in a color space such as black (Bk).
In addition, image data represented in a color space of red (R), green (G), and blue (B) is converted into yellow (Y), magenta (M), cyan (C), and further black (Bk) colors. Japanese Patent Application Laid-Open No. Hei 1 (1999) -1999 for a device and a device for converting the data into space data and printing the data.
No. 234251 and Japanese Patent Application Laid-Open No. 1-234252. In the color correction method disclosed in JP-A-1-234251, the color spaces of R, G, and B are divided into a plurality of colors, and the C, M, and Y ink amounts having the best reproducibility are found for each division point. The ink amount is stored in the up table and the ink amount at the intermediate points other than the division points is obtained by linear interpolation.

By the way, ideally, from the image data represented by R, G, and B, C, M, and
Y data can be calculated, but R, G, B to C, C, M, and Y ink and toner characteristics can be calculated.
The problem that a sufficient color reproduction cannot be achieved by the linear color conversion into M and Y has been conventionally shown. In order to overcome this problem, in JP-A-1-234251, R, G, and B are disclosed.
The color space represented by is divided into multiple parts, and better color reproducibility is realized by linearly interpolating the color conversion within that space. However, this process is complicated, and if it is realized by software. May not be able to achieve comfortable performance. Further, since these characteristics depend on the model, it is very difficult to realize appropriate color conversion when performing color conversion with an information processing device such as a personal computer.
In addition, when a plurality of page data described in the page description language are developed as a plurality of image data in the memory and the images are sequentially printed a plurality of times to realize a sort print of a plurality of copies, If the data size of the image data obtained by expanding the data is large, the amount of memory required to realize the same printing process becomes too large.

[0005]

As described above, R,
In the method of color conversion from G, B to C, M, Y, by dividing a color space into a plurality of spaces and linearly interpolating the color conversion in the space,
Since the processing is complicated, there is a problem that an information processing apparatus such as a personal computer cannot perform appropriate color conversion. Further, there is a problem that the data size of the image data is large and the required memory amount becomes too large. The present invention solves this problem relatively easily, a color conversion process is relatively simple, a large memory amount is not required, and a color image forming apparatus capable of high-quality color printing with good color reproducibility is provided. The realization is an issue.

[0006]

In order to achieve the above objects, the present invention is described in a color image forming apparatus, which is connected to an external device through some interface and described in a page description language created in the external device. Page data receiving means for receiving the page data, the image data expanding means for interpreting the page data received by the page data receiving means, and expanding the image data represented by the luminance and the color difference, and the image data expanding means. Color space data conversion means for converting image data represented by brightness and color difference into data on a color space that can be expressed by output means, and image data obtained by the conversion by this color space data conversion means as an image on a recording medium. And an output means for forming the same. As a result, it is not necessary to develop page data described in the page description language into image data represented by brightness and color difference, and to perform color conversion processing into Y, M, C, and Bk by software, which speeds up processing. Is achieved, and since complex color conversion processing can be performed by the image processing circuit,
It is possible to realize high-quality color printing with good color reproduction.

According to the present invention, in a color image forming apparatus, an image data receiving means which is connected to an external device through some interface and receives image data sent from the external device, and the image data receiving means receives the image data. Image data expansion means for expanding the image data represented by the brightness and color difference into image data represented by the brightness and color difference, and the image data represented by the brightness and color difference expanded by the image data expansion means into data in a color space which can be represented by the output means. It is characterized by having a color space data converting means for converting and an output means for forming image data obtained by the conversion by the color space data converting means as an image on a recording medium. As a result, it is necessary to directly receive the image data represented in the color space of R, G, B, etc., develop the image data, and perform the color conversion processing into Y, M, C, and Bk by software. Since it is eliminated, the processing speed can be increased, and complicated color conversion processing can be performed by the image processing circuit, so that high-quality color printing with good color reproduction can be realized.

[0008]

DETAILED DESCRIPTION OF THE INVENTION A color image forming apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

First, a first embodiment of the present invention will be described. This embodiment includes the technical contents of claim 1, claim 3, claim 4, claim 5, claim 6, claim 7, claim 8, claim 9, claim 10, and claim 11. It is a waste. FIG. 1 shows a block diagram of a color printing system including an information processing apparatus such as a personal computer and a color image forming apparatus. In FIG. 1, reference numeral 101 is a color image forming apparatus, reference numeral 102 is an information processing apparatus, and reference numeral 103 is a network such as Ethernet (registered trademark) connecting both the apparatuses.

FIG. 2 shows an internal block diagram of the color image forming apparatus 101. Reference numeral 201 is a controller that controls color image development and color image formation, and reference numeral 202 is an image forming engine that prints the color image data developed by the controller 201 on a paper medium. In the present embodiment, a system for printing on a paper medium is shown as an example, but the medium to be recorded is generally metal, such as ceramics, painted,
It may be any medium as a drawing target. Code 2
Numeral 03 is a C for performing image development and color image hygiene control
PU, reference numeral 204 is a main storage device that temporarily stores the expanded image data, reference numeral 205 is a network controller for communicating with the information processing apparatus 102 via the network 103, and reference numeral 206 is appropriate for the image data to be printed. An image processing unit that performs image processing, reference numeral 207 is a secondary storage device that stores a large amount of expanded image data, reference numeral 20
Reference numeral 8 denotes a ROM that stores a program that controls image data development and color image formation.

FIG. 3 is a block diagram of the image processing unit 206.
Reference numeral 301 indicates luminance (Y), color difference (Cr, Cb) image data of yellow (Y), magenta (M), cyan (C), black (B).
r) is a color conversion unit for performing color conversion, reference numeral 302 is a density gamma correction unit for correcting density gamma characteristics, and reference numeral 303 is a pseudo gradation processing unit for performing a dither process on multi-valued image data to obtain a pseudo gradation. The dither processing performed here may be binary dither processing or multi-value dither processing. In addition to dither processing, binary error diffusion processing or multi-value error diffusion processing may be performed. In the color conversion of this example, Y, Cr,
Although the Cb image data is color converted into Y, M, C and Br image data, it may be color converted into a finer color space depending on the characteristics of the toner and ink.

FIG. 4 is a flowchart showing a color image development process in the controller 201. The color image development process will be described with reference to FIG. Step S40
If the page data described in the page description language is accepted via the network starting with 0 (S4
01), the color space to which the image forming the page data belongs is discriminated from the color space description in the page data (S40).
2) This color space is checked (S403), and if the color space is a luminance (Y) and color difference (Cr, Cb) color space, one element of page data is interpreted (S404), and the luminance color difference is calculated. An image is expanded as data (S405), and the brightness data obtained by this expansion process is dithered to obtain binary brightness data (S406).

Next, the average color difference data of 2 × 2 pixels of the color difference data obtained by the expansion processing is calculated (S407),
Further, multi-valued dither processing is applied to the average color difference data to obtain 4-bit color difference data Cr and Cb (S408), and binary luminance data and each 4-bit color difference data are written to the memory (S409). Then, it is confirmed whether or not the page data interpretation process has reached the end of the accepted page data (S410). If the end has not been reached, the next page data interpretation is continuously performed and the end is reached. For example, the engine 202 is controlled to start the printing process (S419).

If the color space is the RGB space in S403, one element of the page data is interpreted (S41
1) develop the image as RGB data (S412),
The RGB data obtained by this expansion processing is color-converted into luminance and color difference data (S413), and the luminance data is subjected to dither processing to obtain binary luminance data (S414). The average color difference data of 2 × 2 pixels of the color difference data obtained by the expansion processing is calculated (S415), the multi-value dither processing is applied to the average color difference data, and the 4-bit color difference data Cr,
Cb is obtained (S416), binary luminance data and 4
The bit color difference data is written to the memory (S417). Then, it is confirmed whether or not the page data interpretation process has reached the end of the accepted page data (S418). If the end has not been reached, the next page data interpretation is continuously performed and the end is reached. For example, the engine 202 is controlled to start the printing process (S41).
9).

In the present embodiment, the color space to which the image data forming the page data belongs is not limited to the luminance and the color difference space, but the RGB space is taken as an example. However, CIEL * a * represented by lightness and saturation. The space may be the b space, the HLS space represented by the hue (H), the lightness (L), and the saturation (S), or the hue (H), the saturation (S), and the brightness (S). It may be the HSB space represented by B).

Next, a second embodiment of the present invention will be described. In this embodiment, claim 2, claim 3, claim 4, claim 5, claim 6, claim 7, and claim 8 are provided.
It includes the technical contents of. The hardware configuration of this embodiment is the same as that of the first embodiment shown in FIG.

FIG. 5 is a flowchart showing a color image development process in the controller 201. Color image development processing will be described with reference to FIG. If the image data represented by RGB is received via the network (S501), the RGB image data is converted into luminance (Y),
Color conversion is performed on color difference (Cr, Cb) data (S502), and the obtained brightness data is subjected to dither processing to obtain binary brightness data (S503). The average color difference data of 2 × 2 pixels of the color difference data obtained by the color conversion is calculated (S50
4) Further, multi-valued dither processing is applied to the average color difference data to obtain 4-bit color difference data Cr and Cb (S50).
5) The binary luminance data and the 4-bit color difference data are written to the memory (S506). And then
It is confirmed whether the page data interpretation process has reached the end of the accepted page data (S507). If the end has not been reached, the next page data is continuously interpreted, and if the end has been reached, the engine 202 is reached. Control to start the printing process (S508).

In this embodiment, image data belonging to the RGB color space is taken as an example, but C represented by lightness and saturation is used.
The IEL * a * b space may be used, the HLS space represented by the hue (H), the lightness (L), and the saturation (S) may be used, or the hue (H) and the saturation (S) may be used. ), And an HSB space represented by brightness (B). Although not particularly mentioned in the above description, the image data may be received in a file format such as TIFF in S501.

[0019]

As described above, according to the first aspect of the present invention, the page data described in the page description language is expanded into the image data represented by the luminance and the color difference, so that YMC and Since it is not necessary to perform the color conversion processing to Bk, the processing speed can be increased,
Further, since the image processing circuit can perform complicated color conversion processing, high-quality color printing with good color reproduction can be realized.

According to the second aspect of the present invention, RGB
Directly receives image data represented in a color space such as
By expanding this into image data represented by luminance and color difference, color printing can be realized with the same hardware configuration as in claim 1.

According to the third aspect of the present invention, since the appropriate image processing is performed according to the characteristics of the output means, higher quality color image printing can be realized.

According to the fourth aspect of the present invention, by including the gamma processing in the image processing, the gamma characteristic can be corrected, and higher quality color image printing can be realized.

According to the fifth aspect of the present invention, by including the pseudo gradation processing in the image processing, it is possible to realize higher-quality color image printing with high gradation reproducibility.

According to the sixth aspect of the present invention, the gradation processing is performed on the image data based on the luminance, so that the image data can be expressed with a smaller data amount while maintaining the gradation property.

According to the seventh aspect of the present invention, the image data based on the color difference is obtained from the average color difference value of a plurality of pixels, so that the image data can be expressed with a smaller data amount while maintaining the color gradation. You will be able to.

According to the eighth aspect of the present invention, by performing gradation processing on the image data based on the color difference, it is possible to express the image data with a smaller data amount while maintaining the color gradation.

According to a ninth aspect of the present invention, R generally used in an information processing apparatus such as a personal computer,
Since page data to be printed in the G and B color spaces can be handled,
Complicated processing such as color conversion is not required, and sufficient printing performance can be realized even in an information processing device having a low processing speed.

According to the tenth aspect of the present invention, since page data to be printed in the color space handled by the color image forming apparatus can be handled, color conversion from RGB to luminance color difference data is performed on the color image forming apparatus. It is not necessary to realize high printing performance in the color image forming apparatus, and the information processing apparatus equipped with a processor having higher performance than the processor performance for performing software processing in the color image forming apparatus is a printing system in response to a printing request from the apparatus. Overall performance can be improved.

According to the eleventh aspect of the present invention, the color space to which the color information forming the page data described by the page description language belongs can be discriminated and the process can be switched for each discriminated color space. Therefore, it is possible to print a plurality of page data having different color spaces belonging to one color image forming apparatus.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a color printing system to which the present invention is applied.

FIG. 2 is a block diagram showing the configuration of a color image forming apparatus of the present invention.

FIG. 3 is a block diagram showing a configuration of an image processing unit of the present invention.

FIG. 4 is a flowchart showing a color image development process in the controller of the present invention.

FIG. 5 is a flowchart showing a color image development process in the controller of the present invention.

[Explanation of symbols]

101 color image forming apparatus 102 information processing device 103 network 201 controller 202 Image forming engine 203 CPU 204 main memory 205 network controller 206 Image processing unit 207 Secondary storage device 208 ROM 301 Color converter 302 Density gamma correction unit 303 Pseudo gradation processing unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/405 H04N 1/40 101E 1/407 1/46 Z 1/46 1/40 BF term (reference) ) 2C262 AB19 AB20 BA01 BA02 BA09 BA10 BA16 BA17 BB03 BB05 BB06 BC19 EA06 EA11 EA12 5B057 CA01 CA08 CA18 CB01 CB07 CB08 CB16 CE11 CE13 CE18 CH18 5C077 MP08 NN02 PP15 PP32 PP33 PP34 PP35 PP36 PP46 PQ08 RR06 5C079 HB01 HB03 HB04 HB06 HB07 HB11 LA12 LA31 LB02 LC01 NA03

Claims (11)

[Claims] 1. A page data receiving means connected to an external device through some interface to receive page data described in a page description language created in the external device, and page data received by the page data receiving device. And an image data expanding means for interpreting the image data and expanding it into image data represented by luminance and color difference,
Color space data conversion means for converting the image data represented by the brightness and color difference developed by the image data development means into data on a color space that can be represented by the output means, and an image obtained by the conversion by the color space data conversion means. An output device for forming data as an image on a recording medium, the color image forming apparatus. 2. An image data receiving means which is connected to an external device through some interface and receives image data sent from the external device, and image data received by the image data receiving device is represented by brightness and color difference. Image data developing means for developing the image data, color space data converting means for converting the image data represented by the brightness and color difference developed by the image data developing means into data on a color space expressible by the output means, and A color image forming apparatus comprising: an output unit that forms image data obtained by conversion by the color space data conversion unit as an image on a recording medium. 3. The color image forming apparatus according to claim 1, further comprising an image processing unit that performs appropriate image processing according to a characteristic of the output unit. 4. The color image forming apparatus according to claim 3, wherein the image processing performed by the image processing means includes a γ processing. 5. The color image forming apparatus according to claim 3, wherein the image processing performed by the image processing unit includes a pseudo gradation process. 6. The image data expansion means performs gradation processing on the image data based on the brightness and expresses pixels with a smaller number of bits than before the gradation processing. The color image forming apparatus according to any one of 1. 7. The color image forming apparatus according to claim 1, wherein the image data developing unit obtains image data based on color difference from an average color difference value in a plurality of pixels. . 8. The image data expansion means performs gradation processing on the image data based on color difference, and expresses a pixel with a smaller number of bits than before the gradation processing. 7. The color image forming apparatus according to any one of 7. 9. The page data described by the page description language received by the page data receiving means is composed of color information on a color space represented by red (R), green (G), and blue (B). The color image forming apparatus according to claim 1, or any one of claims 3 to 8. 10. The page data described in the page description language received by the page data receiving means is composed of color information on a color space represented by luminance and color difference. The color image forming apparatus according to claim 3. 11. From page data described in a page description language received by the page data receiving means,
4. A color space to which color information constituting page data belongs is discriminated, and an image development processing selection means is provided for switching the processing for developing an image according to the discriminated color space. Item 11. The color image forming apparatus according to item 10.