JPH01184137A - Color image forming apparatus - Google Patents

Abstract

PURPOSE:To form a color image with reduced memory capacity, by repeating image development forming one output color component image and image formation with respect to a plurality of output components corresponding to the value of image data. CONSTITUTION:A CPU bus 24 connects a CPU 5, a ROM 6, a RAM 7, a DMAC 8, a control I/O port 9, a font ROM 31, a PDL data memory 3 and a full page image memory 4 and can perform data transmission between them and the control by the CPU 5. The CPU 5 analyzes PDL data to develop an indicated image on a full page image memory with respect to one output color component. The CPU 5 repeats a process, which develops an image with respect to one output color component and forms an output color component image on the basis of the developed output color component image data, with respect to the output color components of yellow, magenta, cyan and black to form a full color image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to a color image forming apparatus, particularly a color image forming apparatus that receives at least one of coded character information, coded graphic information, and bit image information from a host device. - relates to an apparatus for forming color images.

[Conventional technology]

Conventionally, PDL (Page Des
As a device that forms an image using (cription language) data as input data,
Color graphic displays were the main focus. P.D.
L is a language for describing the output data of the page layout software, and as shown in Figure 5(a), the page layout software handles image description using character codes, 1 image description using graphic codes, and image description using bit data. Describe the desired image by combining them. P
Graphic displays that use DL data as input data are usually red (R) and green (G).

It has three blue (B) bitmap memories, and the PD
Image description using character codes on each bitmap memory according to the color information of the L data.

The image data specified by the graphic code and the bit data are developed and displayed. Furthermore, since the color images used in Calculation Machines are often separated into three color components, R, G, and H, PDL containing color information is generally divided into three color components, R, G, and B. Color information is handled using color components.

[Problem that the invention is trying to solve] However,
General color printers use subtractive color mixture primary color components, such as cyan, to mix color materials.

Images are formed in magenta and yellow, and red, green, and blue, which are additive color primary color components used in color graphic displays (for example, CRTs), cannot be used and must be converted.

Furthermore, if the above-mentioned image forming method for a display is applied to a high-resolution, multi-gradation color printer, the amount of memory will be large for the following two reasons.

1) It would have been better if the display had 3 sets of RGB bitmap memory, but in order to obtain high-quality images such as beautiful black characters on a color printer, a black component is required in addition to the cyan, magenta, and yellow components. However, in order to obtain an image with even higher gradation, each component must be
It must have 8 bits of data, which increases the amount of memory required per pixel.

2) The resolution of a high-resolution printer is 400 dpi (d
otpar 1nch), and the number of pixels making up the image is larger than that of a graphic display of about 70 dpi.

For this reason, for example, the resolution is 400 dpi and the color material is yellow.

In a color printer with 8 bits of data for each component of the four colors magenta, cyan, and black, it takes approximately 64 MByt to configure a bitmap memory for A4 size.
e memory is required. The need for such a large amount of memory has been one problem in developing color image forming apparatuses (for example, color printers) that use PDL data as input data.

In view of these problems, it is an object of the present invention to enable an image forming apparatus to be configured with less memory.

[Means for solving problems]

In order to achieve the above object, the color image forming apparatus of the present invention comprises: an input means for inputting at least one of coded character information, coded graphic information, and bit image information; an image storage means; and the input means. Image developing means for developing input information into the image storage means for one output component; and image forming means for forming one output color component image according to the value of image data in the storage means. The method is characterized in that a color image is formed by repeating the image development and the image formation for a plurality of output color components.

[Effect]

In the above configuration, image development by the image development means and image formation by the image forming means are repeated, and a plurality of output color components of a color image are sequentially formed.

〔Example〕

According to the embodiment of the present invention described below, the bitmap memory is provided for one page, and each time an image is formed for each color component,
A color image forming device that reduces the required bitmap memory capacity by repeating the development of a portion of DL data related to that color component into a bitmap memory, and the formation of an image for that color component using data in the bitmap memory. will be disclosed.

Hereinafter, the above-described embodiments will be described in detail with reference to the accompanying drawings.

Embodiment 1 FIG. 1 is a block diagram of a color printer according to this embodiment. 23 is a general-purpose digital interface such as a GPIB interface or a Centro/Custom interface;
is their interface circuit. 24 is a CPU including an address bus and a data bus (Central
Processing Unit) bus, CPU5
．． ROM (Read Only Memory)
6゜RAM (Ra m d o m A c c
e ss M e m o r y ) 7 .

DMAC (Direct Memory Access)
ss Controller) 8° Control I10 port 9. Font ROM31. PDL data memory 3.
A full page image memory 4 is connected to enable data transfer and control by the CPU 5. ROM6
is a ROM for holding a program for the CPU 5, and a RAM 7 is a working RAM for the CPU 5. C
The PU 5 communicates with an external host device via the external interface circuit 2 and exchanges various commands, statuses, and image data. PDL of commands
Upon receiving the data transfer command, the CPU 5 sends DM
After operating AL8, the PDL data transferred via the external interface circuit 2 is transferred to the PDL data memory 3.
transfer). DMA transfer is a data transfer method used in general microcomputer systems.

When the transfer of all PDL data is completed, the CPU 5
First, the full page image memory 4 is cleared. Clearing the memory here means writing into the memory a value that will not form an image during image formation, which will be described later.

In this embodiment, the value O is written by the CPU 5, but it can also be written by hardware using a simple circuit consisting of a clock generator and a counter.

The CPU then reads the PDL data stored in the PDL data memory.
The data is interpreted and the indicated image is developed into a full page image memory for one output color component. This expansion method will be detailed later.

The full page memory 4 has a capacity for a small amount (both one color) of the color image of one document sheet, and is used for data write and read access via the CPU bus, and for read access using addresses generated by the address generator 12. It is possible to access both I10 and I10 for control.
Switching is performed by a control signal 25 from port 9. The image development described above is performed on the access side via the CPU bus. When the development of one output color component into the full page image memory is completed, the CPU 5 switches access to the full page memory to the address generation section side. The color component image data read out from the full page image memory according to the address generated by the address generator is input to the laser driver 10, and the color component image data is inputted to the laser driver 10.
Image formation is performed by driving the .

The CPU 5 repeats the process of developing an image for one output color component and forming an output color component image using the developed output color component image data for each output color component of yellow, magenta, cyan, and black. Performs full color image formation.

In addition to communicating with external devices, the CPU 5 controls each control element of the color printer 1 via the control I10 port. Reference numeral 15 is a potential sensor for detecting the electric charge charged on the photoreceptor 16, and 14 is a potential measurement unit that converts the output from the potential sensor 15 into a digital signal and inputs the digital signal to the control I10 port 9.

The potential data input to the control I10 port 9 is CP
It is read by U5 and used for control. The drive motor 20 is used to drive each drive element of the color printer, such as the transfer drum.

On the other hand, the signal 30 from the image leading edge detection sensor 18 is input to the control I10 port 9, read by the CPU'5, and given to the address generator 12 as a vertical synchronizing signal (
ITOP) used to create 29.

Also, the signal 2 from the ED (beam detector) detector 13
8 is given to the address generator 12 as a horizontal synchronizing signal (H8YNC).

Further, the outputs of the humidity sensor 21 and temperature sensor 22 for correcting the development characteristics are inputted to the control section I10 port 9 via the A/D changing section 19.

FIG. 2 is a block diagram of the color printer of this embodiment. 4
Yellow, magenta, and cyan are developed in the full page image memory 4 each time the image is formed.

Each output color component image of black is subjected to PWM processing etc. by a laser driver 10, and finally drives a laser 11.

The laser beam modulated in accordance with the image data is scanned at high speed by a polygon mirror 99 that rotates at high speed.
The light is reflected onto the surface of the photosensitive drum 91 to expose dots corresponding to the image. One horizontal scan of the laser beam corresponds to one horizontal scan of the image, and in this example, the width is 1/16 mm. On the other hand, since the photosensitive drum 91 rotates at a constant speed in the direction of the arrow, the above-described laser beam scans in the main scanning direction, and the constant rotation of the photosensitive drum 91 in the sub-scanning direction sequentially creates a planar image with -exposure, light be done. Prior to exposure, the photosensitive drum 91 is uniformly charged by a charger 97, and a latent image is formed by exposing the charged photosensitive member to light.

A latent image based on a predetermined color signal is visualized by developing units 92 to 95 corresponding to a predetermined color.

For example, considering the first image formation in which a yellow component signal is output from the full page image memory 4, a dot image of the yellow component of the document is first exposed onto the photosensitive drum 91 and developed by the yellow developer 92. .

Next, this yellow image is transferred to the photosensitive drum 91 and transfer drum 11 onto the paper wound on the transfer drum 96.
' A yellow toner image is transferred and formed by a transfer charger 98 at the contact point with the drum 96 . During the second, third, and fourth image formations in the same process, magenta, cyan, and black are By repeatedly transferring and forming toner images and superimposing each image on a sheet of paper, a color image using four color toners is formed.

FIG. 3 is a diagram for explaining a method of implementing the address generation section 12 of FIG. 1 in this embodiment.

Reference numeral 200 denotes an image clock generating device that generates an image transport lock. The counter 202 receives a horizontal synchronization signal (H8YN
C) It is cleared at 28 and generates the horizontal address 205 by counting the transport lock 203.

On the other hand, the counter 201 receives the vertical synchronization signal (ITOP) 2
9, and a vertical address 204 is generated by counting the horizontal synchronizing signal (H3YNC). This horizontal address is the lower address.

The address 26 of the full page image memory is configured using the vertical address as the upper address. When using a full-page image memory with such an address configuration, the image must be expanded according to this address assignment even when the image is expanded into the full-page image memory by the CPU prior to this. For example, if the horizontal method address is
The image data of a point whose vertical address is Y has an upper address of Y and a lower address of X in the full page image memory.
must be written to the address.

Figure 4(a) shows the vertical synchronization signal (ITOP) 29 degrees input to the address generation section when image formation is performed four times, the horizontal synchronization signal (H8YNC) 28, and the full page generated by the address generation section. Upper address 2 of image memory 4
04 and the contents of the full page image memory read out as the image forming signal (VOUT) 27 accordingly. As shown, each vertical sync signal is followed by yellow (Y) component data.

Magenta (M) component data, cyan (C) component data.

Black (Bk) component data is read out and sent to the laser driver 10. The high-order addresses in the diagram are written so that they change continuously for ease of viewing, but in reality they are H8
Since it is the output value of a counter that inputs the YNC signal,
It has a staircase shape that is synchronized with H8YNC.

FIG. 4(b) is a timing chart of each signal in the section of FIG. 4(a). This timing chart is for the period from one horizontal synchronization signal (H8YNC) 28 to the next horizontal synchronization signal, and represents the timing of each signal in one horizontal period. Upper address 20
4 is counted up by 1 for each H8YNC.

The lower address 205 becomes 0 at H8YNC, and is counted up by 1 at the image transport lock 203. The data at the address specified by the lower address 205 and upper address 204 in the full page image memory 4 is read out and becomes the image forming signal V. Since it becomes U127, the fourth (b)
) In the figure, Y1 to Y8 are the data of the upper address n+1° and lower address θ to 7, respectively, and Y1' to
Y8' are upper addresses n+2, respectively. The data is the address data of lower addresses 0 to 7.

That is, y, /~Y8' is 1 for Y1~Y8
The image data will be at a position vertically shifted by .

Figures 5(a) to 5(e) are PDL (Page
FIG.

As shown in Figure 5(a), PDL is a system for describing one or more images by combining image description using character code, image description using graphic code, and image description using bit data. It is a general term for languages. Imaichi, - Po5tScr is included in PI) L, who is considered to be a strong candidate.
ipt (Adobe Systems), DDL
(Imagen.

Hewlett Packard), Interpr.
There is ess (XEROX).

In the explanation of this example, a simple PDL shown in FIGS. 5(b) to 5(d) will be used.

FIG. 5(b) is an example of image description using character codes. First, in n5b-1, an instruction is given to write subsequent characters in a color in which the brightness data of red (R), green (G), and blue (B) are all 0, that is, black. Next, in tt 51)-2,
Assign the character string "IC" to the variable String, and in A5b-3, change it from the origin (top left corner) to the maximum horizontal coordinate (hereinafter referred to as XMAX) and below XO9 to the maximum vertical coordinate (hereinafter referred to as XMAX). (called YMAX) xo,
In other words, from the upper left corner, width XMAX
Xo, 3. String from character spacing XMAXX0.11m
It is giving instructions to print the contents of.

FIG. 5(c) is an example of image description using graphic codes. First, for j25cm1, the subsequent figure descriptions are marked in red (R),
The brightness data of green (G) and blue (B) are each 1.0.
0.0.0. , the instruction is given in the color O, that is, red. Next, at f5cm2, the horizontal coordinates are XMAXXo
,0. The vertical coordinate is YMAXXO, and the horizontal coordinate is XMAX X 1.0. Vertical coordinate is YMA
It gives instructions to draw a straight line to the point XXO, 4.

FIG. 5(d) is an example of image description using bit data.

First, in A5d-1, the subsequent bit data is red (
R), green (G), and blue (B) brightness data are each 1
．． 0. 1.0. The instruction is to use a color of 0.5, that is, pale yellow.

Next, in j25d-2 to j25d-6, the variables bit, d
Assign 25 bit data to ata and write I! 5d-7
Now, change it to horizontal coordinates XMAXX0.1. It is instructed to expand as bit data with a horizontal size of 5 and a vertical size of 5, with the point of vertical coordinate YMAXXO, 5 as a reference.

In FIG. 5(e), XMAX is 10. This is an example in which the image descriptions shown in FIGS. 5(b) to 5(c) are developed for an image forming apparatus with YMAX of 10.

First, according to the description using the character code shown in Figure 5(b), the characters "IC" are created in black at the top, and the 5th (c)
) A red line is created in the center by the description using the graphic code shown in the figure, and a pale yellow diamond is created at the bottom by the description using the bit data shown in FIG. 5(d).

(Control by CPU) FIGS. 6(a) and 6(b) are flowcharts for explaining control by the CPU 5. First step 5PI
The OI checks whether a command has been sent from an external host device, and if so, branches and processes each command in step 5P102. If it is a status request command, the status is returned to the host device in step 5P103 and the process returns to step 5PIO1.

For PDL data transfer command, step 5P105
- In step 5P114, PDL data is received, image formation is performed based on it, and the process returns to step 5P101. For other commands, processing is performed in accordance with each command in step 5P104, and the process returns to step 5PIOI. For PDL data transfer command, first step 5
The PIOEi receives PDL data from an external host device and stores it in the PDL data memory.

This transfer can also be performed by the CPU 5, but as described above, in this embodiment, it is performed by DMA transfer using the DMAC.

Next, in step 5P106, the PDL data in the PDL data memory is interpreted, and the image specified by it is developed on the full page image memory 4 for the yellow component.

Next, in step 5P107, image formation is performed using this developed yellow component image. Below is step 5
In steps 108 to 5P113, image development and image formation for this color component are repeated for the remaining magenta, cyan, and black components to form a full-color image. Finally, in step 5P114, the toner on the paper is fixed and the paper is discharged outside the machine.

6(a) according to the flowchart in FIG. 6(b).
Step 5P106 in the figure will be explained in detail.

In step 5P201, the full page image memory is cleared so that no image is formed except for the portion where the image is developed later. In step 5P202, a variable εcalor representing the color for text is set.

Initialize the variable gcalor, which represents the color for graphics, and the variable bcolor, which represents the color for bit data.

These are expressed by three sets of brightness data: red (R), green (G), and blue (B).

Next, in steps 5P203 to 5P216, one line of P
The DL data is developed and the process is repeated for all lines of PDL data in the PDL data memory.

Step 5P217 checks whether all lines of PDL data have been expanded.

First, in step 5P203, one line is read from the PDL data memory, and then in step 5P204, the process branches depending on the type of the read PDL data.

When setting the text color (I!5b-1 in the example in Figure 5),
In step 5P205, ccolor is reset.

When setting the figure color (475cm1 in the example in Figure 5),
In step 5P206, gcolor is reset. When setting the color for bit data (l15d-1 in the example of FIG. 5), bcolor is reset in step 5P207.

When a character string is assigned (I!5b-2 in the example shown in FIG. 5), variables and their contents are associated with each other using the table set on the work R'AM7 in step 5P208. When bit data is assigned (I!5d-2 to I!5d-6 in the example of FIG. 5), variables and their contents are similarly related in step 5P209.

When developing characters (A5b-3 in the example in Figure 5), first, in step 5P210, the yellow component value D is changed from ccolor.
Calculate Y. Red (R) makes up ccolor.

Green (G) and blue (B) data are DR9Do and DB, respectively.
Then, logarithmic transformation is first performed as shown below to obtain density data of complementary colors cyan (C), magenta (M), and yellow (Y) "C+" M + D'Y.

D' n=LG(DR) O<DR<1 0≦
p10≦ID',=LG(D,) O<DG<1
0<D'M<ID' Y=LG(DB) 0<
DB<1 0<D'Y<1 (*However, LG is an appropriate function for density data after logarithmic transformation.) Next, calculate the amount of smear from these and use it as the amount of black toner. At the same time, an under color removal (UCR) operation is performed to reduce the amount of each toner added according to the amount of black toner added. MIN
Let (a, b, c) be a function to find the minimum value among a, b, c, then D' K= MIN (D' C, D' ,, D
'y) D'Y: D'Y-(alXD'g-bl)
D' M= D' M (a2XD' K b2
)D'c=D' c (a3XD' K b3)
D' Y + D' $1 + D' C+ DK, where DK = (a4XD' K - b4), is obtained. Furthermore, since the yellow, magenta, and cyan components are not formed using ideal coloring materials, masking calculations are performed to perform color correction.

Medicine''= D't' X (aY+) 10D;'X
(bMθ+Da' x (cc,)n=”=D;
'X (aY2) Ten Melon' X (bMJ + D
a′X (CC2)Da” =Dy′X (aYs)
+DL'X (bMs) +D'c'X (-cC
s) Finally, since these values are floating point, they are normalized to the value O~255 which is actually placed in the full page image memory 4.

DY=0, (when CyX" is less than 0)
(Cy is a constant) 255 (When CYXD', `` is 255 or more) CYXD-'' (When CYXD; '' is other than 255) The same applies to Do, DM, and DK.

In step 5P210, the yellow component value DY is calculated in this way, but when developing other color component images, the value of that color component is calculated.

Next, in step 5P211, the font pattern corresponding to the character code is read from the font ROM 31, and expanded on the full page image memory 4 in step 5P212. At this time, DY is used as data to be written. At this time, it will be enlarged to the specified size.

Although reduction is performed, it is easy to perform this using software, so it will not be explained.

Next, when developing a figure (475 cm2 in the example of FIG. 5), first calculate the yellow component value DY from gcolor in step 5P213 in the same manner as step 5P210,
In step 5P214, a figure is written on the full page image memory 4 using this value DY. the indicated shape,
For example, algorithms for drawing lines, circles, and ellipses using software are generally known, so they will not be explained here.

Next, bit image expansion (I!5d-
7), first step 5P215 and step 5P2
Similarly to 10, yellow component value DY is obtained from bcolor.
is calculated, and bit data is written into the full page image memory 4 using this value DY in step 5P216.

When developing the image in steps 5P212, 5P214, and 5P216, as described above, address calculation is performed using the horizontal coordinate value as the lower address and the vertical coordinate value as the upper address.

In this manner, the yellow component image of the input PDL data can be developed on the full page image memory 4 by the control flow shown in FIG. 6(b). Step 5 in Figure 6(a)
The magenta component, cyan component, and black component of P108, 5PIIO, and 5P112 are developed in the same way.

[Other Embodiments] In the embodiments described above, all image development was performed by software, but some parts such as font development may be replaced by hardware.

Further, in the above embodiment, the image forming means was realized by an electrophotographic color printer, but if it is a surface-sequential color printer in which each color is formed on each surface, thermal transfer method, silver halide method, electrostatic method, etc. A method such as the above may also be used. Alternatively, it may be a line-sequential color printer, for example.

Furthermore, in the above embodiments, a general-purpose interface such as GPIB is used as an input means, but this may also be a CPU bus such as a VME bus, or an offline medium such as a magnetic tape or a magnetic disk (or even an offline medium such as an Ethernet). LAN is also fine.

Further, in the above embodiment, the full page memory shown in FIG. 1, which has the same resolution as the image forming apparatus, was used as the image storage means, but a frame memory smaller than this was used.
Enlargement processing may be performed during image formation.

Further, an image development means for developing the information input by the input means into the image storage information for one output color component is shown in FIG. 6(b) 5P212.5P214.5P216
The CPU 5 executes 5PI0 to repeat image development and image formation for multiple output color components.
This is done by executing steps 6 to 5P114.

As explained above, according to this embodiment, only the bitmap memory necessary for developing one color component is provided, and each time an image is formed for each color component, ■ the bitmap memory for the part of the PDL data related to that color component is stored. ■ By repeating the formation of the color component image using data in the bitmap memory, P
It is possible to configure a full-color printer that uses DL data as input data.

〔Effect of the invention〕

As explained above, according to the present invention, color image formation can be performed with a small memory capacity.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a color printer embodying the present invention, Fig. 2 is a block diagram of a color printer embodying the present invention, Fig. 3 is a block diagram of an address generation section, Fig. 4(a),
FIG. 4(b) is a timing chart diagram of image signals and control signals, FIG. 5(a), FIG. 5(b), FIG. 5(c), and FIG. 5(d).
)figure. Figure 5(e) is a diagram for explaining PDL, and Figure 6(a) is a diagram for explaining PDL.
) and FIG. 6(b) are control flowcharts. 2, 3. 5. 8. 24・・・・・・・・・・・・
...Input means 4 for each image information...
・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・Image record■闥i 3, 5. 31. 7 ・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・Image expansion hand i

Claims (2)

[Claims] (1) An input means for inputting at least one of coded character information, coded graphic information, and bit image information; an image storage means; information input by the input means is input into the image for one output component; an image developing means for developing an image in a storage means; an image forming means for forming one output color component image according to the value of image data in the storage means; A color image forming apparatus characterized in that a color image is formed by repeating the process for output color components. (2) The image development means each color component (each input color component) of the input character information, graphic information, and bit image information.
For each piece of information whose configuration is different from the configuration of the output color component for which image formation is performed, image development is performed along with a conversion process from each of the input color components to the output color component. The device according to item 1.