JP2003348353A - Method of compressing/extending gradation object - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To use a memory for line data storage for the other purpose when it is not necessary to hold and refer to data of a preceding line in the case of compressing/extending a gradation object. <P>SOLUTION: When compressing the gradation object, a direction of applying a gradation is judged and when high compressibility is achieved even without referring to pixels of the preceding line, the data of the preceding line are not held. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an object compression / decompression method.

[0002]

2. Description of the Related Art Printer controllers are roughly classified into two types. One is a printer controller that receives image data and sends it to the printer engine. In this type of printer controller, the process of expanding print data from print application software into bitmap data must be performed on the host computer side.

In another type, print data from print application software is temporarily converted into an intermediate language code called PDL on a host computer and transmitted to a printer, and the PDL is analyzed by a printer controller and bitmap data is analyzed. It is of the type that expands to. This type of printer is called a PDL printer.

FIG. 1 shows a color laser beam printer 501.
Shows a state where a host computer is connected.

[0005] Image data output from application software on the host computer 502 is also converted to PDL on the host computer. At this time, FIG.
The graphic data (object data) 801 to which the gradation is applied is composed of data 802 indicating the outline of the figure and data 803 of a gradation pattern for painting the inside of the figure. The outline data 802 and the fill data 803 Each of them is separately compressed on the host computer 502.

[0006] The compressed object data is
The data is transmitted to the video controller 200 of the color laser printer 501 through an interface cable or a network cable, and the video controller 200 expands the compressed data and performs the subsequent drawing processing.

By the way, the gradation data is shown in FIG.
When attention is paid to the line in the direction perpendicular to the gradation direction as shown in FIG. 1, similar image data repeatedly appears. For example, it is assumed that an arbitrary horizontal line of the gradation data 901 is coded at regular intervals every several pixels as shown by 902 in FIG. In this case, there is a high possibility that the current pixel block to be compressed and the pixel block data immediately before or a few blocks before the current pixel block are equal. This is because similar image patterns repeatedly appear in a direction perpendicular to the direction in which the gradation is applied.

For this reason, at the time of compression, data immediately before the pixel block of interest or several pixel blocks before is held, and when the data of this pixel block and the data of the current pixel block of interest are equal, a short code length is used. By assigning a code such that In addition, when compressing the target pixel block, a sufficiently high compression ratio can be achieved by only holding several pixel blocks immediately before the target pixel block and comparing them, and the circuit scale can be reduced.

On the other hand, if attention is paid to a line parallel to the gradation direction as shown in FIG. 10, although the correlation with the preceding and succeeding lines is strong, the data changes in the line direction, so that the pixel block of interest is compressed. At this time, it is not possible to achieve a very high compression ratio only by comparing with the pixel block immediately before the target pixel block.

In this case, it is possible to achieve a high compression ratio by having a memory for one line, holding the previous line data, and comparing it with the pixel block data of the previous line having a high correlation with the current pixel block of interest. I can do it.

However, conventionally, when a gradation object is compressed, the compression is performed without considering the direction of the gradation, so that it cannot be said that an optimum compression method is always selected.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of these circumstances. When compressing a gradation object, it is necessary to pay attention when compressing the gradation object in a direction perpendicular to the direction in which the gradation is applied. Focusing only on the current line with pixels, while compressing a gradation object, when the direction in which the gradation is applied matches the compression direction,
By referencing the pixels of the previous line and compressing by referring to the peripheral pixels of the previous line that are highly correlated with the pixel of interest, it is possible to always select the optimal compression method, and in the direction perpendicular to the direction in which the gradation is applied. Since there is no need to look at the correlation with the previous line when compressing the data toward the front, the memory for holding the data of the previous line can be used for other purposes.

[0013]

According to the present invention, there is provided a printing apparatus having the following configuration. That is, in the information processing apparatus, a means for compressing the gradation object with reference to only the data of the current line having the pixel of interest, a memory for storing the image information of the previous line of the pixel of interest, and the gradation object Means for compressing while referring to the peripheral pixel data of the line before the current line with pixels, and when compressing in the direction perpendicular to the gradation direction of the gradation object,
When the gradation object is compressed while referring to the data of only the current line having the pixel of interest, and is compressed in a direction parallel to the gradation direction of the gradation object, the compression of the gradation object is performed when there is the pixel of interest stored in the memory. Means for compressing while referring to the peripheral pixel data of the line before the current line, and when compressing in the direction perpendicular to the gradation direction of the gradation object, stores the image information of the previous line of the pixel of interest. And means for using the memory to be used for another purpose.

[Operation] In such a configuration, when compressing a gradation object in a direction perpendicular to the direction in which the gradation is applied, the compression is performed by paying attention only to the current line having the pixel of interest.
On the other hand, when compressing a gradient object,
When the direction in which the gradation is applied matches the compression direction, the pixel in the previous line is also referred to, and compression is performed by referring to peripheral pixels in the previous line having a high correlation with the pixel of interest, and the gradation is applied. Since it is not necessary to look at the correlation with the previous line when compressing in the direction perpendicular to the direction, the memory for retaining the data of the previous line can be used for other purposes.

[0015]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the components described in this embodiment are merely examples, and are not intended to limit the scope of the present invention.

The present invention will now be described with reference to the accompanying drawings.
A preferred embodiment when applied to a 0 dpi color laser beam printer will be described in detail.

FIG. 1 shows an outline of a color laser beam printer according to the present invention.

As shown in FIG. 1, a color laser beam printer 501 receives code data and image data written in a printer language sent from an external host computer 502 and, based on these data, one page of magenta and cyan data. , A video controller 200 for generating multi-valued image data of yellow and black (hereinafter, may be simply referred to as a “controller”), and scanning a photosensitive drum with a laser beam modulated according to the input multi-valued image data. The printer engine 100 (hereinafter, may be simply referred to as “engine”) that performs recording by a series of electrophotographic processes in which a latent image is formed, transferred onto a recording sheet, and then fixed. The printer engine 100 has a resolution of 600 dpi.

The video controller 200 and the printer engine 100 are connected by an interface signal line 300. Hereinafter, main interface signals will be described.

The / RDY signal is a signal sent from the engine to the controller, and must be in a state where the printing operation can be started or the printing operation can be continued whenever the engine receives a / PRNT signal described later. Is a signal indicating the following.

The / PRNT signal is a signal sent from the controller to the engine, and is a signal for instructing the start of the printing operation or the continuation of the printing operation.

The / TOP signal is a synchronization signal in the sub-scanning (vertical scanning) direction, and is sent from the engine to the controller.

The / LSYNC signal is used for main scanning (horizontal scanning).
A direction synchronization signal sent from the engine to the controller.

The signals / VDO7 to / VDO0 are image signals sent from the controller to the engine and indicate image density information to be printed by the engine. / VD
O7 is represented by the most significant bit and / VDO0 is represented by the least significant eight bits. In the engine, the / VDO7 to / VDO0 signals are 0
At 0H, printing is performed at the maximum density of the developing toner color, and at FFH, printing is not performed.

The / IMCHR signal is a signal indicating an image attribute, and is sent from the controller to the engine. When the main signal is “true”, it indicates that the image emphasizes the gradation, and when the main signal is “false”, it indicates that the image emphasizes the resolution. In the engine,
When this signal is "true", printing is performed with the number of lines of PWM (unit indicating the density) set to 200 lines / inch (hereinafter, "/ inch" is abbreviated), and this signal becomes "false". "
In the case of, printing is performed with the PWM line number set to 600 lines.

The VCLK signal is the image signal / VDO7- /
A transfer clock signal of VDO0 and the image attribute signal / IMCHR, which is sent from the controller to the engine. The controller synchronizes the / VDO7 to / VDO0 signals and / IMC in synchronization with the rising edge of the VCLK signal.
Send out the HR signal.

Next, a color image forming process in the color laser beam printer will be described.

FIG. 2 is a block diagram of the video controller 200. Referring to FIG. 1, reference numeral 201 denotes a host interface, which communicates with a host computer and receives code data and image data described in a printer-specific language. Reference numeral 202 denotes a CPU that controls the entire controller 200; 203, a ROM that stores a control program of the CPU 202 and font data;
A RAM serving as a work area of the PU 202. 206
A compression / expansion circuit has a function of compressing and expanding RGB 8-bit multi-valued image information. 205 is a page memory,
RG for one page of print compressed by compression / expansion circuit 206
B multi-valued image data is stored. Reference numeral 207 denotes an image processing unit.
The RGB multivalued image information expanded by the compression / expansion circuit 206 is converted into magenta (M), cyan (C), yellow (Y), black (B)
k), and further converts it to 600 dpi smoothed information, and converts the image attribute signal / IMC
It has a function of generating HR.

Reference numeral 208 denotes a printer interface, which is an interface circuit with the printer engine 100. 2
An operation panel 09 allows the operator to directly perform various settings for the printer by operating the operation panel. Data exchange between the blocks in the controller is performed via a data bus 210.

In the above configuration, the code data input from the host interface 201 is converted into 300d characters, graphics or image images by a predetermined drawing algorithm.
pi, which are expanded into 8-bit RGB multivalued image data for each color. The decompressed RGB image data is supplied to a compression / decompression circuit 20.
6. Compressed. This compression / expansion circuit can compress the input image data by, for example, a JPEG algorithm, and can output the compressed data in real time while expanding the data in real time. The compressed image data is stored in the page memory 205.

When the compressed image data for one page is prepared in the page memory as described above, the video controller 200 sets the / PRNT signal to "true" if the / RDY signal from the printer engine 100 is "true". To instruct the printer engine to start a printing operation.

Next, the operation of the printer engine 100 will be described with reference to FIGS.

Upon receiving the / PRNT signal, the printer engine 100 drives the photosensitive drum 1 by a driving unit (not shown).
06 and the transfer drum 108 are rotated in the direction of the arrow shown in the figure. Subsequently, charging of the roller charger 109 is started, and the potential on the photosensitive drum 106 is uniformly charged to a predetermined value. Next, the recording paper cassette 11 is fed by the paper feed roller 111.
The recording paper 128 is fed to the transfer drum 108 from 0.
The transfer drum 108 has a dielectric sheet stretched on a hollow support, and rotates in the direction of the arrow at the same speed as the photosensitive drum 106. When the recording paper 128 is supplied to the transfer drum 108, the recording paper 128 is held by a gripper 112 provided on a support of the transfer drum, and the recording paper 128 is transferred to the transfer drum by an attraction roller 113 and an attraction charger 114. Adsorb to 108. At the same time, by rotating the support 115 of the developing device,
Developing devices 116M, 116C, 116Y, 116B
The developing device 116 </ b> M containing magenta toner, which is the first toner, of k, is opposed to the photosensitive drum 106.
Reference numeral 116C denotes a developing device containing cyan toner,
16Y is a developing device containing yellow toner, 116B
k is a developing device containing black toner.

On the other hand, the printer engine 100 detects the leading end of the recording paper 128 attracted to the transfer drum 106 by the detector 117, generates a vertical synchronization signal / TOP at a predetermined timing, and sends it to the controller 200.

When the controller 200 receives the first / TOP signal for the print page, the page memory 205
The reading of the compressed image data stored in is started. The data to be read is compressed by the compression / expansion circuit
The image data is decompressed in real time into 24-bit image data of 8 bits for each GB and input to the image processing unit 207. In the image processing unit 207, magenta data as the first print color is generated at 300 dpi and 8 bits from the input image data of RGB each having 8 bits of 300 dpi and further 600 dpi.
i, which is converted into 8-bit smoothed data, and at the same time, an image attribute signal / IMCHR for each pixel is generated. Details of the processing in the smoothing processing unit 207 will be described later. 600dp generated above
The image data of i is sent to the printer engine as image signals / VDO7 to / VDO0 together with the image attribute signal / IMCHR in synchronization with the VCLK signal.

/ VDO7 output from the controller
The / VDO0 signal and the / IMCHR signal are input to the pulse width modulation circuit 101 as shown in FIG. 4, and become a laser drive signal VDO having a pulse width according to the level.

FIG. 5 shows an internal block diagram of the pulse width modulation circuit 101. In the figure, 129 is a line memory. The line memory 129 is configured in a toggle buffer format, so that writing and reading can be performed simultaneously by independent clocks. Reference numeral 130 denotes a clock generation circuit, which is a horizontal synchronization signal / HS.
Pattern clock signals PCLK and P synchronized with YNC
A clock signal 1/3 PCLK obtained by dividing CLK by 1/3 is generated. PCLK has a cycle corresponding to one dot printing at 600 dpi. Also, 131 is a γ conversion circuit, 13
2 is a D / A conversion circuit, 133 is a phase control circuit, 134,
135 is a triangular wave generation circuit, 136 and 137 are comparators, 138 is a selector, and 139 is a D flip-flop. Hereinafter, the operation of the pulse width modulation circuit 101 will be described.

First, / VDO7 to / VDO7 for one line in the main scanning
The VDO0 signal and the / IMCHR signal are the clock signal VC.
The data is written to the line memory 129 by the LK. When the writing of the first line is completed, the write bank of the line memory 129 is switched by the horizontal synchronization signal / HSYNC of the next line, and simultaneously with the writing of the next signal of the second line, the writing of the second line is performed. One line of data is read by the pattern clock signal PCLK. / VDO7 to / VDO read
The 0 signal and the / IMCHR signal are input to the gamma correction circuit 131. In the γ correction circuit 131, / VDO7 to / VDO0
Signal suitable for the process conditions of the printer engine according to the number of lines of PWM specified by the / IMCHR signal.
Perform the conversion. γ-converted 8-bit image signal / VD
7 to / VD0 are D / A conversion circuits 132
Is converted to an analog voltage by the analog video signal AVD.
It becomes. At this time, the D / A conversion circuit 132 outputs the image signal /
A minimum voltage is generated when the value of VD7 to / VD0 is 00H,
Generates maximum voltage at FH. The analog video signal A
VD is input to the negative inputs of comparators 136 and 137.

On the other hand, the positive inputs of the comparators 136 and 137 are connected to the output TRI1 of the triangular wave generation circuit 134, respectively.
And the output TRI2 of the triangular wave generation circuit 135 is input. The triangular wave generation circuit 134 is configured, for example, as shown in FIG. In the figure, the changeover switch 152 is supplied with the pattern clock signal PCLK by a phase control circuit
Is input. When the clock PCLK ′ is at the H level, the switch 152 is connected between the terminals “a” and “c”, and flows the current I from the current source 150 to the capacitor 153. Then capacitor 15
3 is charged, and the voltage value V increases linearly. Next, when the clock PCLK 'goes to L level, the terminals b and c of the switch 150 are connected, the current I flows to the current source 151, the electric charge accumulated in the capacitor 153 is discharged, and the voltage value V becomes linear. Decrease. As described above, the triangular wave signal T having the same cycle as PCLK
RI1 is obtained. The triangular wave generation circuit 135 is similarly configured, but since the input clock is ３PCLK ′, the cycle of the output triangular wave signal TRI2 is １ ／ PC
LK, ie, three times TRI1.

Next, the comparators 136 and 137 compare the voltage levels of the analog video signal AVD and the triangular wave signals TRI1 and TRI2 to obtain pulse width modulation signals PWM1 and PWM2, respectively. Accordingly, the number of lines of the pulse width modulation signal PWM1 is 600, and the number of lines of the pulse width modulation signal PWM2 is 200.

The pulse width modulation signals PWM1 and PWM
2 is input to the selector 138 and the image attribute signal / IMC
It is selected according to HR. When / IMCHR is “true”, that is, at L level, PWM2 excellent in gradation is selected. Also, if / IMCHR is "false", that is, H
At the level, PWM1 which is excellent in resolution is selected.

The selected signal is sent to the laser driver as a laser drive signal VDO. At the time of development, which will be described later, the density of the image is reproduced according to the pulse width of the laser drive signal VDO. Pulse width modulation circuit 10 described above
7 is a timing chart of FIG.

Next, referring to FIG.
A laser beam 127 from a laser diode 103 driven according to DO is deflected by a rotating polygon mirror 104 driven to rotate in the direction of the arrow by a motor (not shown), passes through an imaging lens 105 arranged on an optical path, and Drum 106
The upper part is scanned in the main scanning direction to form a latent image on the photosensitive drum 106. At this time, the beam detector 107 detects the scanning start point of the laser beam, and generates a / LSYNC signal, which is a horizontal synchronizing signal for determining an image writing timing of main scanning, from the detection signal.

The above-described main scanning operation is repeated to
A magenta latent image for a page is formed on the photosensitive drum 106. The pattern clock signal PCLK
Are the same in each main scan, the formed image is connected in the vertical (sub-scan) direction, and especially when the number of lines of PWM is 20
At the 0 line, it becomes a vertical streak and stands out. Therefore, this is prevented by shifting the phase of the pattern clock signal PCLK within one cycle of the clock for each main scan by the phase control circuit 133 of FIG.

Referring back to FIG. 3, the latent image formed on the photosensitive drum 106 is a developing device 11 containing the magenta toner.
Developed by 6M to form a magenta toner image. This magenta toner image is transferred by the transfer charger 119.
Recording paper 1 attracted to rotating transfer roller 108
28. At this time, the photosensitive drum 1 is not transferred.
06 is removed by the cleaning device 125. With the above operation, a magenta toner image for one page is formed on the recording paper 128.

Next, the support 115 of the developing device is rotated so that the developing device 116 C containing cyan toner as the second toner is opposed to the photosensitive drum 106. continue,
As in the case of magenta, the leading end of the recording paper 128 rotating while being attracted to the transfer roller 108 is detected by the detector 117, and a vertical synchronization signal / TOP is generated and sent to the video controller 200. In response to this, the video controller 200 reads out the compressed image data from the page memory 205, and decompresses the original RGB and 8-bit image data in real time by the compression / decompression circuit 206.
07. The image processing unit 207 generates data of cyan as a second print color and an image attribute signal / IMCHR from the input image data of RGB and 8 bits each. Hereinafter, by the same operation, the cyan toner image is transferred onto the recording paper 128 so as to overlap the magenta toner image.

Further, similarly, a yellow toner image as the third toner and a black toner image as the fourth toner are transferred onto the recording paper 128 in a superimposed manner, thereby forming a full-color toner image.

The recording paper 128 onto which all of the four color toner images have been transferred passes through a separation charger 120 and is then separated by a separation claw 121.
Is peeled off from the transfer drum 108 by the
2 to the fixing device 123. At this time, the transfer drum cleaner 126 cleans the surface of the transfer drum.

The toner image on the recording paper is melted and fixed by being heated and pressed by the fixing device 123, and becomes a final color output image. Then, the recording paper on which the recording has been completed is discharged to the paper discharge tray 124.

[First Embodiment] A preferred embodiment of the present invention in a printer having the above-described configuration will be described below.

FIG. 1 shows a color laser beam printer 501.
Shows a state where a host computer is connected.

The image data including the gradation object output from the application software on the host computer 502 is also stored on the host computer.
Converted to PDL. At this time, graphic data (object data) with gradation as shown in FIG.
Reference numeral 801 includes data 802 indicating the outer shape of the figure and data 803 of a gradation pattern that fills the inside of the figure. The outer shape data 802 and the fill data 803 are included.
Are separately compressed on the host computer 502.

If the gradation pattern data that fills the inside of the figure is gradation data in which the density changes from left to right on the paper as shown in FIG. 10, the compression target pixel (as shown in FIG. 10) The feature is that the correlation of the image is high between the front and rear lines in the moving direction of the (pixel of interest) (from left to right on the paper).

However, in this case, since the image density changes in the moving direction of the compression target pixel (pixel of interest) (from left to right on the paper), it is too high just to compare with the pixel block immediately before the pixel block of interest. Compression ratio cannot be achieved.

Therefore, when compressing the first line, the current line is held in the line memory while compressing the target pixel, and when compressing the second and subsequent lines, the appearance symbol prediction is performed by referring to the previous line pixel data around the target pixel. It is necessary to increase the compression ratio by performing the encoding process.

In this case, since it is necessary to store the pixel data in the line memory at the same time as encoding, a memory for at least one line is required. This is the same at the time of decoding, which also requires one line of memory.

In an actual image layer, the probability that a pixel (target pixel) takes 0 or 1 depends on Markov's that the finite number of pixel values before that depends on the pattern taken by the pixel preceding the target pixel. The principles of model coding are well and widely known.

FIG. 12 shows an example of a reference pixel position in Markov model coding.

On the other hand, if the data of the gradation pattern that fills the inside of the figure is gradation data in which the density changes from the top to the bottom of the paper as shown in FIG. The feature is that similar image data repeatedly appears in the moving direction of the pixel (pixel of interest) (from left to right on the paper).

In such a case, the gradation data 90
Assuming that an arbitrary horizontal line 1 is encoded by dividing it at equal intervals every several pixels as shown by 902 in FIG. 9, the current pixel block to be compressed and the immediately preceding or several blocks before the current pixel block It is highly likely that the pixel block data is equal to the pixel block data. For this reason, data before the target pixel block or several pixel blocks before is stored at the time of compression, and when the data of this pixel block and the data of the current target pixel block are equal, the code length becomes short. , A high compression ratio can be achieved.

FIG. 9 shows a case in which five pixels are divided in the line direction and codes are assigned to the five pixel blocks. In this case, for example, encoding as shown in FIG. 11 using Huffman encoding can be considered.

This compression processing is performed by software on the host computer.

In FIG. 11, 9 is set for the pixel block of interest.
This shows a case where the data becomes the same as the pixel block 1 to 3 blocks before with a probability of 0%.

In the case of gradation data in which the density changes from the top to the bottom of the paper, it is possible to achieve a sufficiently high compression ratio by paying attention only to the pixel block of the current line including the target pixel. In this case, it is not necessary to hold the data of the previous line and refer to it. In this case, the memory for holding the data of the previous line is released so that it can be used for other purposes. .

The gradation data is shown in FIG. 9 and FIG.
Although there are various angles and patterns other than those shown in FIG. 15 as shown in FIG. 15, basically, except for a gradation pattern in which the density changes from top to bottom as shown in FIG. The previous line is referred to as in the case of encoding / decoding the 10 patterns.

As described above, the host computer 5 shown in FIG.
The gradation data compressed on 02 is transmitted to the color laser printer 501 through the I / F unit. After the compression gradation data passed to the printer controller is decompressed by the gradation data decompression circuit 220 by judging the compression method, the image processing unit 207 generates bitmap data.

As described above, in the case of gradation data in which the density changes from the top to the bottom of the paper (or from the bottom to the top) at the time of expansion, as described above, the data of the previous line is not referred to. Therefore, in this case, the memory for holding the data of the previous line is released so that it can be used for other purposes.

As a use of this memory, for example, a dither memory can be considered.

FIG. 13 shows the flow of processing on the host computer side in the above operation, and FIG. 14 shows the processing on the printer controller side.

In this embodiment, the case where the gradation data is compressed by software on the host computer has been described, but the present invention is not limited to this. Dedicated hardware for compressing the gradation data may be used.

In a printer controller that receives compressed gradation data, the expansion can be performed not by dedicated hardware but by software.

(Other Embodiments) Although the embodiments of the present invention have been described in detail, the present invention may be applied to a system including a plurality of devices, or may be a device including a single device. May be applied.

According to the present invention, a software program for realizing the functions of the above-described embodiments is directly or remotely supplied to a system or apparatus, and a computer of the system or apparatus reads the supplied program code to read the supplied program code. It includes the case where it is also achieved by executing. In that case, the form need not be a program as long as it has the function of the program.

Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. That is, the claims of the present invention also include the computer program itself for realizing the functional processing of the present invention.

In this case, as long as it has the function of the program, the form of the program does not matter, such as the object code, the program executed by the interpreter, and the script data supplied to the OS.

As a recording medium for supplying the program, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, MO, CD
-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM,
DVD-R).

Other methods of supplying the program include:
It can also be supplied by connecting to a homepage on the Internet using a browser of a client computer and downloading the computer program itself of the present invention or a compressed file including an automatic installation function to a recording medium such as a hard disk from the homepage. Further, the present invention can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. In other words, a WWW server that allows a plurality of users to download a program file for implementing the functional processing of the present invention on a computer is also included in the claims of the present invention.

The program of the present invention is encrypted to
By storing the information in a storage medium such as a D-ROM and distributing it to users, and allowing users who have cleared predetermined conditions to download key information for decryption from a home page via the Internet and using the key information It is also possible to execute the encrypted program and install the program on a computer.

The functions of the above-described embodiment are implemented when the computer executes the read program, and the OS or the like running on the computer executes actual processing based on the instructions of the program. Is performed, and the functions of the above-described embodiments can also be realized by the processing.

Further, after the program read from the recording medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instructions of the program,
CPU installed in the function expansion board or function expansion unit
Perform part or all of the actual processing, and the functions of the above-described embodiments are also realized by the processing.

[0081]

As described above, according to the present invention, when a gradation object is compressed in a direction perpendicular to the direction in which the gradation is applied, only the current line having the pixel of interest is compressed. When compressing a gradation object, if the direction in which the gradation is applied matches the compression direction when compressing the gradation object, the pixel of the previous line is also referred to and the previous line having a high correlation with the pixel of interest is compressed. The memory for holding the data of the previous line because it is not necessary to look at the correlation with the previous line when compressing in the direction perpendicular to the gradation direction by referring to the peripheral pixels of Can be used for other purposes.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a color laser beam printer.

FIG. 2 is a block diagram of a video controller.

FIG. 3 is a side view of the printer engine.

FIG. 4 is a diagram illustrating a flow of an image signal of a printer engine.

FIG. 5 is a block diagram of a pulse width modulation circuit according to the first embodiment.

FIG. 6 is a configuration diagram of a triangular wave generation circuit.

FIG. 7 is a timing chart in the pulse width modulation circuit according to the first embodiment.

FIG. 8 is a diagram showing a gradation object.

FIG. 9 is a diagram showing a gradation object.

FIG. 10 is a diagram showing a gradation object.

FIG. 11 is an example of encoding to which the first embodiment is applied.

FIG. 12 is an example of encoding to which the first embodiment is applied.

FIG. 13 is a flowchart showing the operation of the first embodiment.

FIG. 14 is a flowchart showing the operation of the first embodiment.

FIG. 15 is a diagram showing a gradation object.

[Explanation of symbols]

100 printer engine, 101 pulse width modulation circuit 102 Laser Driver 103 laser diode 104 rotating polygon mirror 105 imaging lens 106 Photosensitive drum 107 Beam Detector 108 transfer drum 109 Roller charger 110 Recording paper cassette 111 Paper feed roller 112 gripper 113 Suction roller 114 Charging device for adsorption 115 Developing device support 116M, 116C, 116Y, 116Bk are developing devices 117 Detector 119 Transfer charger 120 Separator charger 121 separation claw 122 Conveying means 123 fixing device 124 output tray 125 Cleaning device 126 Transfer Drum Cleaner 127 laser beam 128 recording paper 129 line memory 130 Clock generation circuit 131 γ conversion circuit 132 D / A conversion circuit 133 phase control circuit 134 Triangular Wave Generator 135 Triangular wave generation circuit 136 Comparator 137 Comparator 138 Selector 139 D flip-flop 150 current source 151 current source 152 switch 153 Capacitor 200 video controllers, 201 Host interface 202 CPU 203 ROM 204 RAM 205 page memory 206 compression / expansion circuit 207 Image processing unit 208 Printer Interface 209 Operation panel 210 Data bus 501 color laser beam printer 502 Host computer 300 Engine I / F 801 Gradation object data 802 External data 803 gradation data 804 Registration roller 901 gradation data 902 block data 1001 gradation data 1002 Block data

Claims (2)

[Claims] 1. An information processing apparatus, comprising: means for compressing a gradation object by referring to data of only a current line having a pixel of interest; a memory for storing image information of a previous line of the pixel of interest; Means for compressing the pixel of interest in the direction perpendicular to the gradation direction of the gradation object by referring to the peripheral pixel data of the line before the current line having the pixel of interest. When compression is performed with reference to data of only a certain current line and compression is performed in a direction parallel to the gradation direction of the gradation object, peripheral pixels of a line before the current line having the target pixel stored in the memory are stored. It has a means to compress while referring to data, and And an information processing apparatus. 2. A method of compressing a gradation object in a direction perpendicular to a gradation direction of a gradation object, the method comprising: using a memory for storing image information of a previous line of a pixel of interest for another purpose. The information processing device according to claim 1.