JPH0640086A - Color image forming device - Google Patents

Abstract

PURPOSE:To reduce capacity and make quality of external input image of large size highly graded by a device comprising a means for storing each color data corresponding to arranging interval and outputting to each work unit in delay, and a means for compacting and storing a data quantity with priority of image angle or image quality when a quantity of input image data exceeds a memory capacity, which is also used as a memory means. CONSTITUTION:When a data exceeding an A4 size is to be inputted at storing in a memory and at a high gradation mode of a printer, RGB data are respectively contracted to the A4 size or less by magnification conversion circuits MAG0-MAG2, and stored in a memory MEM. Next, the RGB data RGB0-RGB3 of 4 systems read out from the memory MEM are respectively returned to the circuits MAG0-MAG3, enlarged to the former size, respectively converted into M, Y, C data by image processing sections IP2-0-IP2-3. The M, Y, C data are outputted being delayed respectively by delay memories DLY-1 DLY-3.

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 such as a digital color copying machine, a color facsimile or a color printer.

[0002]

2. Description of the Related Art In recent years, colorization of images has progressed, and the need for colorization has also increased in copying machines. Further, the request for a hard copy of a color image is not limited to a document original, but may be DTP (Desk Top Publishing) or CG.
(Computer Graphics) and other images created using a computer, images captured by video cameras, images stored in optical files, etc., and images sent via communication lines such as facsimiles. And so on.

On the other hand, from the viewpoint of space saving and efficient use of resources, OA (Office Automation) devices have been systematized and compounded. In this case, the copying machine has not only a copying function but also an appropriate function. I / F (InterFace) with external signal
), It can be used as a printer or a facsimile.

Incidentally, as a color image forming apparatus for obtaining a hard copy, a silver salt photographic system, an electrophotographic system, a fusion type thermal transfer system, a sublimation type transfer system, an ink jet system and the like have been put into practical use. It is used when a laser printer using an electrophotographic system is required to have high speed, high image quality and recordability on plain paper.

However, since it is difficult to change or stop the speed of the image forming process in the electrophotographic method, it is necessary to make the input of image data follow the speed of the output system (image forming process speed). In a system that cannot be guaranteed, the RGB frame memory 6 is normally used as shown in the conventional example of FIG. 27, external input data is temporarily stored in the frame memory 6, and then read from the memory 6 in accordance with the image forming process speed. Is being done.

When obtaining color image hardware, Y (yellow), M (magenta), C (cyan)
3 colorants or 4 colorants with K (black) added are used. FIG. 26 shows an outline of an image forming system of this type of color image forming apparatus. In this example, K, M, Y and C image forming units 24K, 24M, 24Y and 24C (only the photoconductor is shown in the drawing). Are arranged in this order, and the K, M, Y, and C toner images are transferred so as to be superimposed on the transfer paper, and a color image is formed on the recording paper. Therefore, K, M,
To superimpose the Y and C toner images on the transfer paper,
K, M, Y, C image forming units 24K, 24M, 24
It is necessary to delay each image data according to the arrangement interval of Y and 24C to shift the writing timing to each photoconductor.

Incidentally, briefly explaining a conventional example with reference to FIG. 27, in this apparatus, internal input data which is a document image is read by an image reading unit (scanner) 1 and then processed by an image processing unit IP1. On the other hand, the external input data is transmitted through the external I / F 5 to the RGB frame memories 6
Stored in. Then, each of the data is selected by the multiplexer 7, processed by the image processing unit IP2, and then stored in the delay memory 14 in accordance with the arrangement intervals of the image forming units 24K, 24M, 24Y and 24C as shown in FIG. It is delayed and output to the output system 15.

The image processing unit IP1 is a processing circuit for correcting the internal input system and processing and editing an image peculiar to the copy mode, and a scaling circuit 2 for enlarging and reducing the internal input data.
Image processing / editing circuit 3 for italicizing, hollowing, shadowing, moving (shifting), and MTF (Modulation T) of input data
It is composed of an RGB filter circuit 4 that performs spatial filter processing for correction of deterioration of ransfer function) and noise removal.

The image processing unit IP2 is a circuit mainly for adjusting the image quality of an output image (hard copy), and input data is commonly used regardless of whether it is internal or external. Specifically, the image processing unit IP2 includes an RGBγ correction circuit 8, a color correction circuit 9 for converting an RGB system into a YMCK system, and a UCR (Unde).
r Color Removal) circuit 10, YMCKγ correction circuit 11 for correcting the gradation characteristics of the output system 15, YMCK filter circuit 12 for adjusting the sharpness of the image, and output system 15 to realize a sufficient number of gradations. When it is not possible, it is composed of a gradation processing circuit 13 which performs gradation expression by an area gradation processing method such as a dither method or an error diffusion method.

[0010]

The memory capacity when a DRAM (dynamic random access memory) is used as the delay memory 14 will now be described.
The distance between each photosensitive drum is L [mm], and the output dot density is M
[Dot / mm] The number of bits per dot of one color output is N
[Bit / dot] and paper width W [mm], the total memory capacity S is S = W × M × L × M × N + W × M × 2L × M × N + W × M × 3L × M × N W × It becomes M × 6L × M × N [bit]. Therefore, for example, W = 297 mm, L = 100
mm, M = 16dot / mm, N = 8bit / dot, S = 297 × 16 × 6 × 100 × 16 × 8 = 364,953,600 [bit] = 348.0 [Mbit], and the capacity of 4Mbit 87 DRAMs are required.

When forming an external image,
As described above, the frame memory 6 is required, but the memory capacity T of the color image of A4 size (297 mm × 210 mm) is separated into R (red), G (green), and B (blue). Is input at 8 bits / dot, T = 297 × 16 × 210 × 16 × 8 × 3 = 383,201,280 [bit] = 365.4 [Mbit], and 92 4Mbit DRAMs are required.

Therefore, if the internal and external images are formed as shown in FIG. 27, a total of 179 4 Mbit DRAMs are required as the delay memory 14 and the frame memory 6, which is an expensive system. There is a problem that

In view of the above-mentioned conventional problems, the present invention provides a color image forming apparatus capable of reducing the memory capacity and forming a large size externally input image with the same size or high quality. The purpose is to provide.

[0014]

In order to achieve the above object, a first means is to arrange image forming units of a plurality of colors at a certain interval, and transfer an image of a color formed by each image forming unit. In a color image forming apparatus that forms a color image by overlapping on paper, storage means for storing and delaying data of each color according to the arrangement interval of the image forming unit, and outputting to each image forming unit, When the amount of image data input from the outside exceeds the storage capacity of the storage means,
And a compression unit for compressing the data amount and storing the compressed data amount in the storage unit by giving priority to the angle of view or the image quality.

A second means is means for performing image processing by selectively prioritizing resolution or gradation when the compression means of the first means compresses the data amount by prioritizing the angle of view. It is characterized by having.

A third means is to compress image data from the outside by the area gradation processing method when the compressing means of the first or second means compresses the data amount by prioritizing the resolution. Is compressed.

The fourth means is provided with means for performing image processing by giving priority to the resolution of the character image area when the compression means of the third means compresses the data amount by the area gradation processing method. Is characterized by.

The fifth means is that the compression means of the second means is
In the mode in which gradation is prioritized, image data from the outside is reduced, stored in the storage unit, and enlarged to the original size when output to the image forming unit.

In a sixth means, the compression means of the fifth means is
It is characterized by reducing and enlarging in the main scanning direction.

In a seventh means, in the first to sixth means, when the compression means compresses the data amount by prioritizing the angle of view, a plurality of recordings are performed when the image size exceeds the maximum size of the recording paper. It is characterized in that it is provided with a means for dividing and outputting to paper.

[0021]

In the first means, with the above configuration, the image input from the outside to the storage means for storing and delaying the data of each color according to the arrangement interval of the image forming units and outputting to each image forming unit. When the data amount exceeds the storage capacity of the storage means, the angle of view or the image quality is prioritized and the data amount is compressed and stored. Therefore, the capacity can be reduced by also using the storage means, and a large size external input image can be formed with the same size or high quality.

In the second means, the resolution or gradation is selectively prioritized when compressing the data amount by prioritizing the angle of view. Therefore, a large size external input image is selected by the user as desired image quality. Can be formed with.

In the third means, when the data amount is compressed by prioritizing the resolution, the image amount from the outside is compressed by the area gradation processing method. It can be formed with high quality.

In the fourth means, since the resolution of the character image area is prioritized when the data amount is compressed by the area gradation processing method, the resolution of the character image of the large size external input image is deteriorated. Can be prevented.

In the fifth means, image data from the outside is reduced and stored in the storage means in the mode in which the gradation is prioritized, and enlarged to the original size when output to the image forming unit. Gradation or color reproducibility can be selectively prioritized according to the size of the image.

Since the sixth means reduces and enlarges in the main scanning direction, it is possible to simplify the hardware such as the line memory when changing the magnification.

In the seventh means, when the data amount is compressed by prioritizing the angle of view, when the image size exceeds the maximum size of the recording paper, the data is divided into a plurality of recording papers and output. The input image can be formed at the same size.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an embodiment of a color image forming apparatus according to the present invention, FIG. 2 is a block diagram for explaining a signal flow in a copy mode in FIG. 1, and FIG. 3 is a printer mode in FIG. 4 is a block diagram for explaining the signal flow of FIG. 4, FIG. 4 is a block diagram showing the memory configuration in the delay memory mode of YMCK data in FIG. 1, and FIG. 5 is the memory configuration in the frame memory mode of RGB data in FIG. FIG. 6 is an explanatory diagram showing the selection operation of the multiplexer in FIG. 5, FIG. 7 is a block diagram for explaining the signal flow in the high gradation mode of the printer in FIG. 1, and FIG. 8 is a scaling circuit. FIG. 9 is a block diagram showing the same, FIG. 9 is an explanatory diagram showing pulse width modulation, FIG. 10 is an explanatory diagram showing the operation of the smoothing filter, and FIG. FIG. 12 is a block diagram showing a filter, FIG. 12 is a block diagram showing another smoothing processing circuit, FIG. 13 is a block diagram showing a memory configuration in YMCK data frame memory mode, and FIG. 14 is another YMCK data frame memory mode. 15 is a block diagram showing the memory configuration of FIG. 15, FIG. 15 is an explanatory diagram showing divided images in FIG. 14, FIG. 16 is an explanatory diagram showing a margin of a divided image in FIG. 15, and FIG. 17 is an explanation showing an example of a margin of adhesive in FIG. FIG. 18 is an explanatory diagram showing another example of the margin of the divided image in FIG.
19 is an explanatory diagram showing the binding margin of the divided images in FIG. 15, FIG. 20 is an explanatory diagram showing the numbers of the divided images in FIG. 15, FIG. 21 is an explanatory diagram showing the connection map of the divided images in FIG. 15, and FIG. 14 is an explanatory view showing the operation of the circuit of FIG. 14, FIG. 23 is a block diagram showing the main parts of a modification of the embodiment, and FIG.
25 is a block diagram showing an image processing circuit having an image area determination circuit, FIG. 25 is a block diagram showing an image processing circuit having a gradation processing circuit by an error diffusion method, and FIG. 26 is an image forming system of the output system in FIG. FIG.

In FIG. 1, internal input data, which is a document image, is read by an image reading unit (scanner) 21, and external input data such as a facsimile image is input via an external I / F 22. The data is selected by the multiplexer MUX1. The data selected by the multiplexer MUX1 is input to the input terminal A of the multiplexer MUX2, selected, and processed by the image processing unit IP1.

As shown in FIG. 27, the image processing unit IP1 includes a scaling circuit 2 for enlarging and reducing the internal input data,
A processing / editing circuit 3 for italicizing, hollowing out, shading, moving (shifting) an image, and correcting spatial deterioration of MTF of input data and spatial filtering for noise removal.
It is composed of a filter circuit 4.

The data processed by the image processing unit IP1 is input to the input terminals A of the multiplexers MUX3 and MUX4 to be selected, and the data selected by the multiplexer MUX3 is temporarily stored in the memory 23 and then read out. And multiplexers MUX1, MUX4, MU
It is input to each input terminal B of X5 and selected. The data selected by the multiplexer MUX4 is the image processing unit I.
The processed data is processed by P2, and the processed data is input to the input terminal A of the multiplexer MUX5 and selected, and the output system 24
Is output to. The data processed by the image processing unit IP2 is input to the input terminal B of the multiplexer MUX3 and selected.

As shown in FIG. 27, the image processing unit IP2 includes an RGBγ correction circuit 8, a color correction unit 9 for converting the RGB system into a YMCK system, a UCR circuit 10, and an output system 15.
YMCKγ correction circuit 11 that corrects the gradation characteristics, the YMCK filter circuit 12 that adjusts the sharpness of the image, and the dither method or the error diffusion method when the output system 24 cannot realize a sufficient number of gradations. It is composed of a gradation processing circuit 13 which performs gradation expression by such an area gradation processing method.

As an example, the memory 23 has a capacity corresponding to A4 size, and the output system 24 is shown in FIG.
As shown in, each of the K, M, Y, and C image forming units 24
K, 24M, 24Y, and 24C (only the photoconductor is shown in the figure) are arranged in this order, and the K, M, Y, and C toner images are transferred so as to be superimposed on the transfer paper, and a color image is recorded. Formed on paper.

In such a configuration, in the copy mode, as shown in FIG. 2, the data read by the image reading unit (scanner) 21 is the multiplexers MUX1 and MU.
X2 selects and is processed by the image processing unit IP1, and this processed data is selected by the multiplexer MUX4 and processed by the image processing unit IP2, and the memory 23
Is used as a delay memory for each data of YMCK for the output system 24, as shown in FIG. The data read from the memory 23 is the multiplexer MU.
It is selected by X5 and output to the output system 24.

Next, referring to FIG. 3, the printer mode,
That is, the operation of the external input data recording mode will be described. 3A shows the case where the external input data is A4 size or smaller, FIGS. 3B and 3C show the case where the external input data is A4 to A3 size, and FIG. e)
Indicates the case where the external input data exceeds A3 size.

First, when the external input data is RGB data of A4 size or less, it is input through the external I / F 22 and input to the multiplexer MUX1, as shown in FIG.
The data is selected by the MUX2 and processed by the image processing unit IP1, the processed data is selected by the multiplexer MUX3, and the memory 23 is used as an A4 size frame memory. Then, at the time of output, the RGB data is read from the memory 23 in synchronization with the pixel synchronization signal, selected by the multiplexer MUX4, processed by the image processing unit IP2, and converted into YMCK data.
This YMCK data is selected by the multiplexer MUX5 and output to the output system 24.

Next, a case where the external input data exceeds A4 size will be described with reference to FIGS. First, as shown in FIGS. 3B and 3D, there is a method of reducing the size to A4 size or less by the scaling circuit 2 of the image processing unit IP1 and storing it in the memory 23. And at the time of output,
This data is returned to the scaling circuit 2 of the image processing unit IP1 via the multiplexer MUX2, enlarged to the original size, processed by the image processing unit IP2 and converted into YMCK data, and this YMCK data is transmitted to the multiplexer MU.
It is selected by X5 and output to the output system 24. In addition,
In this case, since reduction is performed, details of the data may be lost and the resolution and sharpness may be reduced.

Here, in FIG. 3B, the external input data is A
A case is shown in which the size exceeds A4 size and is the maximum recording paper size and is equal to or smaller than A3 size, and by using at least A3 size paper, one external input image can be stored in one paper. FIG. 3D shows a case where the external input data exceeds the A3 size, and one external input image can be divided and output to be divided and recorded on a plurality of sheets.

When the memory 23 is used as a frame memory, the data once transferred to the frame memory is saved without being destroyed even after being read, so that various parameters of the image processing unit IP2 are changed. By doing so, color adjustment and color conversion can be repeated. Next, as shown in FIGS. 3C and 3E, a method in which the number of bits per dot is reduced by the gradation processing unit 13 of the image processing unit IP2, the number of bits is returned via the multiplexer MUX3, and stored in the memory 23. There is. Specifically, YMC
When converting to K data, the number of gradations per dot, that is, the amount of data can be reduced by the area gradation method.

For example, when the RGB input data are each 8 bits, the data amount per dot is 24 bits, but in order to store the A3 size data in the memory 23, when the number of dots is the same, The amount of data per dot must be reduced to 1/2, that is, 12 bits or less per dot. That is, since four colors of YMCK have 12 bits, each color can be realized with 3 bits of 1/4, that is, 8 gradations or less. In the case of image data of a larger size, it is sufficient to reduce the number of bits per dot, and if one dot corresponds to one bit per color, up to 6 times A4, that is, B2 size can be stored in the memory 23. Also, FIG.
In the example shown in (e), since the size exceeds A3 size, one external input image can be divided and output to be divided and recorded on a plurality of sheets.

In the case of using the acquaintance gradation method, gradation is expressed in units of a plurality of dots in order to secure the number of gradations of 64 to 256 necessary for reproducing a pictorial image. Therefore, although the resolution decreases when the acquaintance gradation method such as the dither method is used, the deterioration of the resolution can be suppressed by devising the gradation expression pattern. Here, in general, the resolution and the stability of gradation expression are in a trade-off relationship, and it is difficult to achieve both at the same time. However, in the case of characters and line drawings that require resolution, gradation is not so necessary. However, the resolution is not so necessary in a picture area such as a photograph that requires gradation. Therefore, as shown in FIG. 24, an image area determination circuit 2 for automatically determining an image area such as a character area and a picture area.
5, the reproduction image quality can be totally improved by adaptively selecting the gradation processing method of the gradation processing unit 13 according to the image area.

As another example of the area gray scale method, an error diffusion method is known as a method for reproducing the resolution and the gray scale in a better balance than the dither method. Since this method can reproduce a high-quality image as the number of gradations per dot increases, as shown in FIG. 25, as long as the capacity of the memory 23 permits the gradation processing unit according to the size of the input image. A multi-valued (binary) error diffusion method with a large number of 13 is selected. The multiplexer MUX shown in FIG. 25 is used for the data to bypass the gradation processing unit 13 when the copy mode or the high gradation mode is selected.

Next, referring to FIG. 4, a case where each data of YMCK is delayed by the memory 23 will be described. In addition,
In this example, the image forming units 24K, 24M of the output system 24,
K based on the arrangement order of 24Y and 24C (equal distance L)
However, the present invention is not limited to this order. First, in order to delay the M, Y, and C data with respect to the K data by the distances L, 2L, and 3L, respectively, M,
The capacities (bits) of the Y and C memories MEM0, MEM1, and MEM2 are: MEM0 = W × M × L × M × N MEM1 = W × M × 2L × M × N MEM2 = W × M × 3L × M × N.

For each of the M, Y, and C data input to each of the memories MEM0, MEM1, and MEM2, the pixel clock CLK for the number of pixels of each is generated by the address generator AG.
It is read when it is counted by 0, AG1, and AG2.
That is, the address generators AG0, AG1, and AG2 are respectively (W × M × L × M) base and (W × M × 2L × M).
It operates as a binary (W × M × 3L × M) counter. Here, the image forming units 24K, 24M, 24Y,
The 24C interval L is expected to vary depending on the device, but the capacities of the memories MEM0, MEM1, and MEM2 should be increased by an amount corresponding to this deviation, and the address generator A
By changing the set values of G0, AG1, and AG2, it is possible to correct a minute positional deviation.

Next, a case where the memory 23 stores RGB data as a frame memory will be described with reference to FIGS. 5 and 6. For example, when each color has a gradation of 8 bits per pixel, since three colors have 24 bits / pel, one word has a memory structure of 24 bits, and the memories MEM0 to MEM4 shown in FIG.
It has a capacity (1 block) corresponding to the interval L of 24M, 24Y, and 24C. However, the last memory MEM4 has a capacity of a fraction.

The address generator AG for each of the memories MEM0 to MEM4 functions as a counter that operates in synchronization with the pixel clock CLK at the time of input, and when the number of pixels for one block is counted, the carry signal C is converted into the phase signal generator PG. And the count output value is reset. The phase signal generator PG counts the carry signal C and selects the memories MEM0 to MEM4 to be input in order to indicate the positional relationship between the recording paper and the image forming unit.

Next, at the time of outputting the data, it is necessary to read the data in parallel from a maximum of four memories MEM0 to MEM4 corresponding to the image forming units 24K, 24M, 24Y and 24C. In this example, the image forming units are used. Since the interval L of 1 is one block, the read address signal can be commonly used for each of the memories MEM0 to MEM4.

Here, the output signals RGB-0 to RGB-0 shown in FIG.
RGB-3 are original data converted into K, M, Y, and C data, respectively, and the memories MEM0 to MEM4 to be referred to are changed each time the phase advances, but as shown in FIG. 6, the multiplexer MUX0 is changed. .. to MUX3 change the correspondence between the memories MEM0 to MEM4 and the output data according to the phase signal S. It should be noted that although a gap occurs in the image forming period of each color due to the interval L of the image forming units, the image data corresponding to white is output in a phase that is not involved in image formation, so that the dust data is output by the data outside the effective area. Can be prevented.

In the case of the image division shown in FIG. 3D, the memories MEM0 to MEM to be referred to according to the output page.
Although the EM4 is different, the image can be divided and output by loading the offset address of the reference start for each page into the address generator AG shown in FIG. 5 by the system controller (not shown).

Next, the operation of the printer in the high gradation mode will be described with reference to FIG. 7A shows the time of storage in the memory 23, and FIG. 7B shows the time of reading from the memory 23. In FIG. 7A, when the data exceeding A4 size is input, the RGB data is reduced to A4 size or less by the scaling circuits MAG0 to MAG2 (scaling circuit 2 shown in FIG. 27), respectively, and then, as shown in FIG. It is stored in the memory MEM described in the above.

In FIG. 7B, the RGB data RGB0 to RGB3 of the four systems read from the memory MEM are respectively returned to the scaling circuits MAG0 to MAG3 to be enlarged to the original size, and the image processing unit IP2- 0-IP2-3
(Image processing unit IP2 shown in FIG. 1) causes K,
The M, Y, and C data are converted into M, Y, and C data, and the M, Y, and C data are respectively delayed memory DLY-1 to DLY-3 (memory 2
The output is delayed by 3).

Here, if the scaling process is performed only in the main scanning direction, it is sufficient to refer to only one line of data using the line memory as shown in FIG.
There is an effect that the number of line memories may be smaller than that of the variable magnification circuit in the sub-scanning direction as shown in (b).

Further, in the output system 24, there is known a pulse width modulation system in which the exposure time of the elliptical laser beam is modulated to change the coloring area in order to express one dot in multi-value as shown in FIG. ing. FIG. 9A shows pulse width modulation for each dot, and the exposure time t of the laser beam is 1
It is possible to express from white to the maximum density by changing the time per dot from 0 to T. However, time T
Is the scanning time per dot.

Further, in the output system 24, in order to improve the stability of gradation expression, the gradation expression unit may be pulse-width modulated into a plurality of dot units continuous in the main scanning direction.
FIG. 9B shows the exposure time t of the laser beam in units of 2 dots.
Is changed within the range of time 0 to 2T. In this case, if the dot density is 400 dpi, a 200-line vertical line screen type halftone dot is formed, and banding and development unevenness due to mechanical jitter are formed. It is possible to express gradations that are unlikely to produce poor performance in image forming systems such as. However, when the gradation is expressed in units of 2 dots, the resolution in the main scanning direction becomes 1/2.

Therefore, in the case of outputting in the high gradation mode, considering that the resolution in the main scanning direction decreases,
Even if the input data is reduced in the main scanning direction, the reduction in resolution due to the reduction process does not substantially occur. However,
A point to be noted in the reduction processing is that, for example, when reducing to 1/2, the spatial frequency of the input data is 100 cycles /
If there is a high-frequency component of inches or more, folding distortion occurs according to the sampling theorem. Further, in the case of an image having a strong periodicity such as a shaded pattern, a moire pattern is generated by the reduction processing, and the image is significantly deteriorated.

Therefore, in the present embodiment, as shown in FIGS. 10 to 12, smoothing is performed in order to remove or reduce the high frequency component which causes the aliasing distortion according to the reduction ratio before the reduction. Process. FIG. 10 shows a digital filter for smoothing the main scanning direction. In the example shown in FIG. 10A, an average value with the next pixel is obtained, and in the example shown in FIG. , And the target pixel is multiplied by a coefficient “2” to smooth the pixel.

Since the smoothing filters shown in FIGS. 10A and 10B can realize multiplication and division by bit shifting by making the coefficient a power of "2",
As shown in FIGS. 11A and 11B, the flip-flops FF1 to FF3 and the adders ADD1 and ADD2 can be configured by a simple circuit. Further, as shown in FIG. 12, in the image processing unit IP1, if an RGB filter is provided on the upstream side of the scaling circuit 2 and the coefficient of the RGB filter is set so that the RGB filter performs smoothing processing at the time of reduction, It is not necessary to separately provide a smoothing circuit as shown.

Next, referring to FIG. 13, the memory 23 is set to Y
A case where the MCK data is used as a frame memory will be described. In the memory 23 in this mode, YM
Memory MEM0 to ME of the same capacity for each data of CK
M3 is assigned. In addition, each memory MEM0 to ME
The address generators AG0 to AG3 for M3 count up in synchronization with the pixel clock CLK and operate so as to be reset by a reset signal from the address generator controller AGC.

At the time of inputting image data, the address generator controller AGC inputs a data input start signal as a signal START to the clear terminal CLR, and outputs reset signals at the same timing from the output terminals S0 to S3 respectively. It is output to the clear terminals CLR of the vessels AG0 to AG3. On the other hand, at the time of output, the address generator controller AGC receives the image formation start signal as the signal START, and the image forming units 24K, 24M, 24
A signal obtained by delaying the signal START by counting the pixel clocks by the amount that compensates the interval L of Y and 24C is applied to the terminal S0.
~ Output from S3. Therefore, the address generator AG
Based on these signals, 0 to AG3 can shift the start timing of the read address by the distance L of the image forming unit.

Next, referring to FIGS. 14 to 22, A3
A case will be described in which image data that exceeds the size is divided and output on a plurality of recording sheets in the high resolution mode. In this case, as shown in FIG. 3 (e), the gradation processing unit IP2 converts the YMCK data into a reduced number of bits per dot and then stores the YMCK data in the memory 23.

When the image data is divided into 3 × 3 = 9 pieces as shown in FIG. 15, one divided area is output in one image forming process. The output of all images is completed by continuously performing the image process. The large image output by dividing the image may be joined by the user later or may be bound together, but in the present embodiment, a joint margin area as shown in FIGS. A mode for securing a binding margin area as shown in FIG. 19 is provided.

As shown in FIG. 15, a description will be given by assigning numbers from 1 to 9 to these nine divided areas. When forming a margin area indicated by diagonal lines in FIG. 16, numbers 3 and 6 to 8 are used.
In the divided image of the end portion of, it is necessary only in one end, and it is unnecessary in the divided image of number 9. Further, as shown in FIG. 17, if a glue margin is added with a marker such as a solid line and the result is outputted, the binding margin work becomes easy. Note that this glue substitute marker may be output in a single color even when it is added to a full-color or multi-valued color image, but since Y color has poor visibility, it may be output in M, C, or K. desirable.

In an image forming system, a recording prohibited area (blank area) is generally provided at the leading edge of the image in order to ensure the separability of the recording paper and the fixing roller. As shown in FIG. 18, if a margin area is provided at the tip of each divided image, it is not necessary to separately provide a blank area.

As shown in FIGS. 19 (a) to 19 (c), the binding margin can be provided either vertically or horizontally on the recording paper, but the operator can easily select it from the operation section. It is desirable to configure. In the case of division and output, the order of divided images is unknown to the user, so that numbers may be added to the paste margin area and the binding margin area of each divided image as shown in FIG. The connection map of each divided image may be separately output as shown in FIG.

Referring to FIGS. 14 and 22, the memory 23
A case where YMCK data is stored in will be described. Comparing the circuit shown in FIG. 14 with the circuit shown in FIG. 13, it can be seen that the image data to be accessed does not exist in the continuous address space on the memories MEM0 to MEM3, and for this purpose the offset address generators OAG0 to OAG3 are present. Are added to the K, M, Y, and C stages, respectively. Further, output control units OC0 to OC3 for forming a margin and a character generator CG for adding numbers of divided images are added.

This access order will be described with reference to FIG. 22. The size of the large image data in the main scanning direction is X, and the image blocks (image number 5 in the example shown in FIG. 22) divided and output are divided. When the head address is OFS, the head address of each line is shifted by X, so that the address generator controller AGC outputs the image formation start signal START to the image forming unit 24K corresponding to each color when outputting an image.
A signal whose timing is shifted by an amount to compensate for the interval L of 24M, 24Y, and 24C is output from the terminals S0 to S3.

Offset address generators OAG0-OA
G3 is the start address O of the image area applied from the system controller every time the image area to be output is updated.
FS is loaded at the time of inputting the signal START, and every time the line synchronization signal LSYNC is input, the head address of the pixel data of the new line is calculated and output via the Q terminal. The address generators AG0 to AG3 respectively load the head address data for each line from the offset address generators OAG0 to OAG3 each time the line synchronization signal LSYNC is input, and divide the pixel clock by N to obtain a clock CLK.
Count up in sync with. Then, the address data at this time is output from the Q terminal and the respective memories MEM0 to MEM0
It is applied to MEM3.

The address generators AG0 to AG3 also output the margin marker signal and the output inhibition signal (mask) signal corresponding to the non-image area to the output control units OC0 to OC3 with reference to the address data. The output control unit OC3 at the final stage operates so as to output recording dots when the marker signal is active and output non-recording dots when the mask signal is active. Also, the character generator C
The number font data from G is the address generator AG3.
Is applied to the output control unit OC3 based on the address data from, and thus the C color number is added to the divided image in this example. The numerical value and position of this number are instructed to the address generator AG3 by the system controller.

When nine divided images are output in this way,
A connection map as shown in FIG. 21 may be output, and in this case, a grid line as shown in FIG. 21 may be output as the boundary of the divided images.

In the above description, the control of the memory 23 in each mode has been described. However, as shown in FIG. 23, a plurality of memory control circuits MC1 and MC2 are provided, and control signals to the memory MEM are supplied from the memory control circuits MC1 and MC2. A plurality of memory modes can be selected by selecting with the selector SEL according to the memory mode signal MODE.

In the above embodiment, the input data is RG.
Although the case of B has been described, L * a * b *, L * u *
Display color data such as v * and YIQ can also be applied by changing the color conversion circuit. Also, the output data is not limited to the case of the four YMCK components,
The present invention can be applied to the case of three colors of YMCK, two colors, or a combination of other colors.

[0072]

As described above, according to the first aspect of the invention, the image forming units of a plurality of colors are arranged at certain intervals,
In a color image forming apparatus that forms a color image by superposing on a transfer paper the images of the colors formed by the image forming units, the data of each color is stored and delayed according to the arrangement interval of the image forming units. Storage means for outputting to each image forming unit, and when the amount of image data input from the outside exceeds the storage capacity of the storage means, the storage means for compressing the data quantity by giving priority to the angle of view or image quality Since it is provided with the compressing means for storing in, the capacity can be reduced by also using the storing means, and a large size external input image can be formed with the same size or high quality.

According to a second aspect of the invention, when the compression means according to the first aspect compresses the amount of data by giving priority to the angle of view, the image processing is performed by selectively giving priority to resolution or gradation. Since the means is provided, a large size external input image can be formed with the image quality desired by the user.

The invention according to claim 3 is the invention according to claim 1 or 2.
When the described compression means compresses the data amount by prioritizing the resolution, the image amount from the outside is compressed by the area gradation processing method. It can be formed with image quality.

According to a fourth aspect of the invention, when the compression means according to the third aspect compresses the data amount by the area gradation processing method,
Since the image processing means is provided with priority given to the resolution of the character image area, it is possible to prevent the resolution of the character image of a large size external input image from deteriorating.

According to a fifth aspect of the present invention, the compression means according to the second aspect reduces image data from the outside in a mode in which gradation is prioritized and stores the reduced image data in the storage means. Since it expands to the original size when outputting,
It is possible to selectively give priority to gradation or color reproducibility according to the size of the external input image.

According to the sixth aspect of the invention, since the compression means according to the fifth aspect reduces and enlarges in the main scanning direction, it is possible to simplify the hardware such as the line memory when changing the magnification.

The invention according to claim 7 is the invention according to any one of claims 1 to 6.
In the invention described above, when the compression unit compresses the data amount by prioritizing the angle of view, it is provided with a unit for dividing and outputting to a plurality of recording papers when the image size exceeds the maximum size of the recording papers. It is possible to form a large size external input image at the same size.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a color image forming apparatus according to the present invention.

FIG. 2 is a block diagram for explaining a signal flow in a copy mode in FIG.

FIG. 3 is a block diagram for explaining a signal flow in a printer mode in FIG.

4 is a block diagram showing a memory configuration in a delay memory mode of YMCK data in FIG. 1. FIG.

5 is a block diagram showing a memory configuration in a frame memory mode of RGB data in FIG. 1. FIG.

FIG. 6 is an explanatory diagram showing a selecting operation of the multiplexer in FIG.

FIG. 7 is a block diagram for explaining a signal flow in the high gradation mode of the printer in FIG.

FIG. 8 is a block diagram showing a scaling circuit.

FIG. 9 is an explanatory diagram showing pulse width modulation.

FIG. 10 is an explanatory diagram showing the operation of the smoothing filter.

11 is a block diagram showing a smoothing filter that performs the smoothing process in FIG.

FIG. 12 is a block diagram showing another smoothing processing circuit.

FIG. 13 is a block diagram showing a memory configuration of YMCK data in a frame memory mode.

FIG. 14 is a block diagram showing a memory configuration of another YMCK data in a frame memory mode.

FIG. 15 is an explanatory diagram showing divided images in FIG.

16 is an explanatory diagram showing a margin of the divided image in FIG.

FIG. 17 is an explanatory diagram showing an example of a margin of glue in FIG. 16.

FIG. 18 is an explanatory diagram showing another example of the margin of the divided image in FIG. 15.

19 is an explanatory diagram showing a binding margin of the divided images in FIG.

20 is an explanatory diagram showing numbers of divided images in FIG.

21 is an explanatory diagram showing a connection map of the divided images in FIG.

22 is an explanatory diagram showing the operation of the circuit of FIG. 14. FIG.

FIG. 23 is a block diagram showing a main part of a modified example of the embodiment.

FIG. 24 is a block diagram showing an image processing circuit including an image area determination circuit.

FIG. 25 is a block diagram showing an image processing circuit including a gradation processing circuit according to an error diffusion method.

FIG. 26 is an explanatory diagram showing an image forming system of the output system in FIG.

FIG. 27 is a block diagram showing an example of a conventional color image forming apparatus.

[Explanation of symbols]

 2 variable magnification circuit 13 gradation processing circuit 23 memory 24 output system 24K, 24M, 24Y, 24C image forming unit IP1, IP2 image processing circuit MUX0 to MUX5 multiplexer

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location H04N 1/23 103 C 9186-5C 1/41 Z 9070-5C

Claims (7)

[Claims] 1. A color image forming apparatus for forming a color image by arranging image forming units of a plurality of colors at certain intervals and superposing images of colors formed by the image forming units on a transfer paper, Storage means for storing and delaying data of each color according to the arrangement interval of the image forming unit and outputting to each image forming unit, and the amount of image data input from the outside exceeds the storage capacity of the storage means. A color image forming apparatus further comprising: a compression unit that compresses a data amount and stores the compressed data amount in the storage unit by prioritizing at least one of an angle of view and an image quality. 2. A means for performing image processing by selectively prioritizing resolution or gradation when the compression means compresses the data amount by prioritizing the angle of view. Item 1. The color image forming apparatus according to Item 1. 3. The compression means compresses the amount of image data from the outside by the area gradation processing method when compressing the amount of data with priority on resolution. Alternatively, the color image forming apparatus described in 2. 4. The image processing apparatus according to claim 3, further comprising means for performing image processing by giving priority to resolution of a character image area when the data amount is compressed by the area gradation processing method. Color image forming apparatus. 5. The compression unit reduces image data from the outside in a mode in which gradation is prioritized, stores the image data in the storage unit, and expands the image data to an original size when outputting to the image forming unit. The color image forming apparatus according to claim 2, wherein 6. The color image forming apparatus according to claim 5, wherein the compression unit reduces and enlarges in the main scanning direction. 7. When the compression means compresses the data amount by prioritizing the angle of view, it is provided with means for dividing and outputting to a plurality of recording papers when the image size exceeds the maximum size of the recording papers. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is a color image forming apparatus.