JPH05286170A - Image formation apparatus - Google Patents

Abstract

PURPOSE:To make high-speed printing possible by storing monochrome images for a plurality of pages in an image data memory means. CONSTITUTION:Printing command from a host computer is inputted into an image spread part 9 through a communication interface 8, and discrimination is made by a monochrome mode judgement means 9a to determine whether the command is for monochrome mode or not. According to the result of the discrimination, switching can be made between a monochrome image spread means and a full-color image spread means. In the monochrome mode, pages on and after the second can be spread while printing on the first page is in operation, and thereby recording images can be formed at high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a color image printing mode and a monochrome image printing mode.

[0002]

2. Description of the Related Art In recent years, printers capable of outputting both black and white recorded images and color recorded images have been widely used as output terminals of computers. Black and white images are called black and white mode, and color images are called color mode.
Examples of printers capable of both such modes include a laser beam printer (hereinafter, LBP) that combines an electrophotographic process and a laser exposure technique, and a color inkjet printer. Hereinafter, a printer capable of a monochrome mode and a color mode will be referred to as a dual-mode printer, and the present invention can be applied to the dual-mode printer.
For convenience of explanation, the following description will be made by taking the case of LBP as an example.

The images handled by the LBP include an image that does not require gradation (for example, a character image) and an image that requires gradation (for example, a portrait photo). Furthermore, a gradation image and a non-gradation image are displayed on one screen. Images may be mixed. The above gradation image is also referred to as a halftone image. In order to reproduce a non-gradation image and a halftone image, both mode printers perform image formation with a set of black dots (dots) for a black-and-white image and a set of color dots for a color image. In that case, the dot density is, for example, 300 dots per inch (this is 30 dots).
0DPI). At 300 DPI, the total number of dots in one screen is about 1 MB in an A4 size screen. As shown in FIG. 3, the LBP 1 includes an image processing unit 5
And a printer engine 7. The image processing unit 5 performs the processing described later on the printer code signal 3 sent from the host computer 2 to obtain an image recording signal 4
And send it to the printer engine 7. Printer engine 7
Produces a dot image by laser light based on the image recording signal 4 and outputs it as a recorded image 6. The image processing unit 5 has the configuration shown in FIG. 6, and the communication interface 8 communicates with the host computer 2 and receives the printer code signal 3. The image development unit 9 interprets the printer code signal 3 to determine whether it is a monochrome image or a color image, whether it is a gradation image or a non-gradation image, and performs signal processing adapted to each of the above to perform the next processing. Image data is stored in the image data memory 10 and the image discrimination memory 11. The signal processing in the image developing unit 9 described above is called image developing processing. The image data memory 10 and the image discrimination memory 11 are collectively referred to as an image memory. Next image expansion unit 1
In step 2, the image data stored in the image memory is converted into a density signal suitable for the resolution and the number of gradations of the printer engine 7, and a process for improving the image quality of non-gradated characters and line drawings is performed. Further, the gradation processing unit 13 performs processing such as image density adjustment, gamma correction, screen angle and the like, as well as processing for improving gradation stabilization of the printer engine 7. The signal from the gradation processing unit 13 is output as the image recording signal 4 from the last engine interface 14 and sent to the printer engine 7.

In the printer engine 7, a black and white image is formed with black toner (hereinafter referred to as BK) as described above, but normally a yellow (Y), magenta (M) and cyan (C) are formed for forming a color image. It is performed with four colors obtained by adding the BK (black) toner to the three color toners. For this reason, the image data memory 10 and the image discrimination memory 11 of FIG. 6 must record four types of image data of BK, Y, M, and C in the case of a color image, and therefore each has four 1 MB recording blocks. is necessary. In the case of a black-and-white image, one 1 MB recording block for recording the BK image data is theoretically sufficient, but an actual black-and-white LBP has a memory for a plurality of pages. Therefore, in the case of a black-and-white image, the image development processing of the second page can be performed in advance before the printing of the first page is completed. As a result, the printing of the second page can be started at the same time when the printing of the first page is finished, and thus the printing speed of the black and white dedicated LBP can be improved.

[0005]

As described above, in reproducing a color image, the above-mentioned four color toners are added. For example, red (R) is reproduced by adding Y and M, green (G) is reproduced by adding Y and C, and blue (B) is reproduced by adding M and C. For other colors, Y, M, C
Reproduce with the addition of 3 colors. Further, in order to improve the color reproducibility, four colors are added because BK is added in addition to the above three colors of Y, M, and C. Therefore, in the conventional color image LBP, the printing operation starts after the image data subjected to the image expansion processing is stored in each of the four recording blocks of the image memory until the printing of the color image of one page is completed. I had to wait for the page image expansion process. For this reason, the conventional color LBP has a disadvantage that the printing speed is slower than the printing speed of the black and white LBP having a plurality of pages of memory. In order to solve this drawback, a color LBP devised so that high speed printing can be performed only in black and white printing has been devised. In this case, high speed printing is possible when continuously printing only black and white pages. However, even in this case, when the monochrome printing is performed subsequent to the color printing, the image development processing of the monochrome printing is started after the completion of the color printing, and therefore the printing speed is slowed by the image development processing for one page. It was inevitable.

The present invention is intended to solve the above-mentioned drawbacks of the conventional color LBP, and an object thereof is to provide a color LBP capable of high-speed printing even when monochrome printing is performed subsequently to color printing.

[0007]

In order to achieve the above object, an image forming apparatus of the present invention includes an image processing unit for processing a printer code signal from a host computer and outputting an image recording signal, and the above image recording unit. The image processing unit is provided with an image developing unit, an image discriminating memory and an image data memory, and the image processing unit is provided with a monochrome / color discriminating unit, a monochrome developing unit and a color. A development unit is provided, and the monochrome / color discrimination unit discriminates the image signal included in the printer code signal into a monochrome image signal or a color image signal. In the case of a monochrome image signal, the monochrome development unit binary-codes the monochrome image signal. Image data is recorded in the image discrimination memory and the image data memory. Section determines a non-gradation color image and a gradation color image, and in the case of a non-gradation color image, binarizes the same as the black and white image, and stores the image data in the image discrimination memory and the image data memory. In the case of recording a gradation color image, the image data is binarized by the dither method and the image data is recorded in the image discrimination memory and the image data memory.

[0008]

According to the present invention, when the first and second pages are black and white images by providing a black and white / color discrimination section, a black and white development section and a color development section in the image development section as in the above-mentioned construction. It is possible to start the image development processing of the second page immediately while the first page is being printed. When the first page is a color image and the second page is a monochrome image, printing of at least one color of the first page is completed. Then, the image development process for the second page can be started, and the printing speed can be increased.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, but the overall structure of the image forming apparatus (LBP as an example) described in FIG. 3 is the same as the conventional example. The printer engine 7 used in this embodiment is of a color electrophotographic type by laser exposure.
It shall have a recording density of 00 DPI. Regarding the configuration of the image processing unit 5, the same parts as those of the conventional example are shown by the same numbers, and the description thereof is omitted. Figure 2
Shows a block diagram which constitutes the image processing unit 5 of an embodiment of the present invention, but also shows a block diagram of the internal configuration of the image developing section 9. Further, FIG. 1 shows a flow chart of the image signal processing performed in the image developing section 9.

The contents of the image expanding process in the image expanding unit 9 of FIG. 2 according to the present invention will be described below, and then the flowchart of FIG. 1 will be described.

The types of images handled by the color LBP as an example of the image forming apparatus of the present invention are roughly classified into (A) monochrome images and (B) color images. Further, (A) a monochrome image is only a non-gradation monochrome image, but (B) a color image has (B-1) a non-gradation color image and (B-2) a halftone color image (gradation color image). There is.

In addition, the image data memory 10 built in the image developing unit 9 has one each corresponding to four colors of BK, Y, M and C.
It has a storage area of a page (1 MB). At the same time, the image discrimination memory 11 also has a storage area for each one page (1 MB) corresponding to four colors of BK, Y, M, and C.

When the image signal is the (A) non-gradation black-and-white image, all of the BK, Y, M, and C image memories are used as storage areas for black-and-white image data. Therefore, the storage area for black and white images is 1 page x 4 = 4 pages (4 MB).
Storage areas can be used. Then, a flag indicating that the monochrome image data has been developed on the corresponding page is set. FIG. 4A shows a state in which image data obtained by subjecting a non-gradation monochrome image to image development processing is written in the image data memory 10. As shown in the figure, the image is divided into pixels corresponding to the dot density, and 1 is written in the case of black and 0 is written in the case of white at the address on the memory corresponding to the address of each pixel. At the same time, 0, which means a binary image, is written in the image discrimination memory 11 shown in FIG. 4B at an address corresponding to the address of the image data memory 10.

Even when the image signal is a (B-1) non-gradation color image, the image data memory 10 and the image discrimination memory 1
The state of storing the image data in FIG.
This is the same as (a) and FIG. 4 (b). However, in this case, the flag of the corresponding page is not set to indicate that the page is a color image instead of a monochrome image.

When the image signal is a (B-2) halftone color image (gradation color image), 2 pixels × 2 pixels = 4 pixels are referred to as one processing unit (an image unit) as shown in FIG. Treat as). Generally, a method of binarizing a halftone image by a dither method is adopted for reproducing a halftone image. However, in one embodiment of the present invention, binarization by the dither method is performed for each image unit described above. Is going. FIG. 5A shows, as an example, a state in which image data resulting from image expansion processing by the 16-valued multi-value dither method is written in the image data memory 10. Figure 5 (a)
In the upper row, the density level of the result of the 16-value dithering of the image unit is 5. Since 5 is expressed in binary notation as 0101, 0101 is written in the corresponding pixel unit. Similarly, the lower part of FIG. 5A shows the case where the density level as a result of 16-value dithering of the image unit is 4, and 4 is expressed in a binary system and 0100 is written in the corresponding pixel unit. As described above, in the case of the non-gradation black-and-white image and the non-gradation color image, 0 is written in the image discrimination memory, but in the case of the halftone, the image discrimination memory 11 is shown in FIG. As described above, 1 indicating the halftone is written for each pixel.

The signal processing described above, that is, the image signal sent by the printer code signal is classified into non-gradation and gradation, and binarization suitable for each is performed, and the obtained image data is converted into The signal processing for writing to the address on the memory corresponding to the pixel is called image development processing. In the image developing unit 9, first, the image signal sent by the printer code signal is classified into the above-mentioned (A), (B-1), (B-2) in the monochrome / color discrimination unit 9a of FIG. Then, in the case of the black-and-white image of (A), the above-described image expansion processing is performed by the black-and-white expansion unit 9b of FIG. 2, and in the case of the color image of (B), the above-mentioned (B-1) and (B-2). In any of the above cases, the image development described above is performed by the color development unit 9c in FIG.

Next, the procedure for performing the above-mentioned image expansion processing will be described with reference to the flowchart of FIG.

First, in step (a), the printer code signal 3 from the host computer 2 is received, and in step (b) it is determined whether or not the printer code signal 3 is a page end code. If the printer code signal 3 is not the page end code, the process proceeds to step (c), and it is determined whether the printer code signal 3 is a code relating to image development. If the printer code signal 3 is a code that is not related to image development, the process proceeds to step (l) to perform the same predetermined processing as a conventional printer.

If the printer code signal 3 is a code related to image development, the process proceeds to step (d), and it is determined whether the monochrome mode is selected. Step (d) above
Is performed by the monochrome / color discrimination unit 9a in FIG. If the result of the determination in step (d) above is No, it means that the mode is (B) color image, so in the next step (h) it is either (B-1) non-gradation color image or (B-2) halftone. It is determined whether the image is a color image (gradation color image).

If the result of the determination at step (h) is (B-1), the process proceeds to step (d), where image development processing is performed for a non-gradation color image. If the determination result of step (h) is (B-2), the process proceeds to step (n),
Image development processing for a halftone color image (gradation color image) is performed. These steps (ri) and steps (nu)
The image development processing of is performed by the color development unit 9c in FIG.

The determination result in step (d) is Yes.
If so, the mode is black and white, so go to step (e). As described above, when the previous page is in the monochrome mode, only one of the four blocks (1 MB each) of the image memory is used. The remaining three blocks are free. Therefore, it is possible to immediately write the developed image data in the vacant block. However, when the previous page is in the color mode, there are cases where all four blocks of the image memory are filled with image data of four colors. In this case, even if the image expansion processing is performed, there is no place to store the resulting image data, so the image expansion processing of the next page cannot be performed. As described above, depending on whether the previous page is the monochrome mode or the color mode, the image can be immediately developed or not. Therefore, in step (e), it is determined whether the previous page was the monochrome mode, and the previous page is the monochrome mode. If so, the process proceeds to step (g) and immediately the image development process is performed on the next page as a black and white non-gradation image. The image development processing of the non-gradation monochrome image is performed by the monochrome development unit 9b in FIG.

When the previous page is not in the monochrome mode in step (e), that is, in the color mode, the four blocks of the image memory are filled with the image data of four colors as described above, but even if only one of them is used. When printing is completed, the block of the image memory for that color becomes empty. Therefore, it becomes possible to write the image data that has undergone the image expansion processing of the next page into the vacant block. Therefore, if step (e) is No, step (f) is Y,
It is determined whether or not at least one color of M, C, and BK has been printed. If the result is Yes, in step (g) the image development processing of the black and white binary image of the next page is immediately performed, and the result is vacant. Write to memory. If No,
Wait until printing of at least one color is completed, and if step (f) becomes Yes, proceed to step (g).

As described above, in the image forming apparatus according to the embodiment of the present invention, the image processing unit has a monochrome / color discrimination section, a monochrome / color mode discrimination means for the previous page, and the completion of printing of at least one color in the color mode. Is provided to determine whether the mode is monochrome mode or color mode, and if the previous page is in monochrome mode, the image development process is immediately performed, and at least one color is printed even if the previous page is in color mode. If so, the image development process can be started immediately before the printing of the previous page is completely completed by performing the image development process immediately, and the overall printing speed in the monochrome mode of the image forming apparatus can be increased. it can.

In the above description, the case where the laser beam printer is used as the printer engine has been described, but the image processing unit 5 described above is used.
The above operation can be applied to, for example, an inkjet printer other than the laser beam printer. Further, a detailed description of the multi-valued dither method used in the image forming apparatus of the embodiment of the present invention, and the image expansion unit 1 of the image processing unit 5 will be described.
2. Regarding the gradation processing unit 13, since it is lightly related to the gist of the present invention, only a brief description will be given.

[0025]

As is apparent from the above embodiments, according to the present invention, the image processing unit is provided with a black / white / color discrimination unit,
Since the black-and-white mode determining means on the previous page and the means for determining the completion of printing of at least one color in the color mode are provided, the printing speed in the monochrome mode of the color image forming apparatus can be increased.

[Brief description of drawings]

FIG. 1 is a flowchart of an image expansion unit of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a block diagram of an image processing unit of the image forming apparatus according to the exemplary embodiment of the present invention.

FIG. 3 is a block diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram when a non-gradation image is stored in an image data memory and an image discrimination memory in the image processing unit of the image forming apparatus according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram when a gradation image is stored in an image data memory and an image discrimination memory in the image processing unit of the image forming apparatus according to the embodiment of the present invention.

FIG. 6 is a block diagram of an image processing unit of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 image forming apparatus 2 host computer 3 printer code signal 4 image recording signal 5 image processing unit 6 recorded image 7 printer engine 9 image development section 9a black and white / color discrimination section 9b black and white development section 9c color development section 10 image data memory 11 image discrimination memory

Claims (2)

[Claims] 1. An image processing unit that outputs an image recording signal by processing a printer code signal from a host computer, and a printer engine that outputs a recording image based on the image recording signal. An image development unit, an image discrimination memory, and an image data memory are provided, and the image processing unit is provided with a monochrome / color discrimination unit, a monochrome development unit, and a color development unit, and the printer code signal is included in the monochrome / color discrimination unit. The image signal is discriminated into a monochrome image signal and a color image signal, and in the case of the monochrome image signal, the monochrome image signal is binarized in the monochrome development section, and the image data is recorded in the image discrimination memory and the image data memory to obtain a color image. In the case of a signal, the non-gradation color image is discriminated in the color development unit from the non-gradation color image In the case of an image, the same binarization as that of the monochrome image is performed and the image data is recorded in the image discrimination memory and the image data memory. In the case of a gradation color image, the image is discriminated by the dither method. And an image forming apparatus adapted to record image data in an image data memory. 2. The black-and-white developing section is provided with a step of discriminating the image of the previous page into a monochrome image and a color image, and a step of discriminating the completion of printing of at least one color when the previous page is a color image, If the previous page is a black-and-white image, the image signal in the printer code signal is immediately binarized, and the binarized image data is recorded in the image memory together with the data for discriminating between gradation and non-gradation. If the color image is a color image, immediately after the printing of at least one color is completed, the image signal in the printer code signal is discriminated as gradation or non-gradation and then 2
The image forming apparatus according to claim 1, wherein the image data is binarized, and the data for discriminating the gradation / non-gradation and the binarized image data are recorded in an image memory.