JP2002247374A - Noise diffusing printing system, noise diffusing printer with noise diffusing function and noise diffusing printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noise diffusing printing system, a noise diffusing printer with a noise diffusing function and a noise diffusing printing method which can diffuse a scanning noise due to mechanical errors of a printer in printing an image and/or a block noise appearing in compression/decompression. SOLUTION: The printing system 1 composed of a computer 11 and a printer 12 diffuses a scanning noise, etc., resulting from mechanical errors of the printer during printing of images. The computer 11 comprises an AC component changing means 112 for changing the values of specified diagonal elements in AC component of DCT-processed compressed image data JD, an inverse DCT means 113 for inverse-DCT-processing the image data having the changed AC components to obtain reproduced image data RD, and a printing data generating means 114 for generating printing data PD from the reproduced image data RD.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DCT (Disc
The present invention relates to a noise diffusion printing technique for a print image of compressed image data that has been subjected to a “rete cosine transform” process, and diffuses a scanning noise caused by a mechanical error of the printer and / or a block noise generated at the time of compression / decompression generated at the time of printing an image. The present invention relates to a printing system that diffuses noise, a printer with a noise diffusion function, and a noise diffusion printing method.

[0002]

2. Description of the Related Art In recent years, the resolution of a color printer has been increased, and an image or the like taken by a digital camera can be printed at a quality comparable to that of a film photograph.

A printer has a print engine as
There are ink jet type and sublimation type.

A user can download image data from a site on a network, a CDROM, or the like to a computer main body, display an image on a display using an appropriate graphics application, and print the image.

FIG. 8 is a diagram schematically showing a printing system 8 including a computer 81 and a printer 82 connected thereto. JPEG (Joint Photo) stored in the compressed image data storage area 8111 of the storage device 811
The OG (Joint Expert Group) image data JD (DCT compression format) is converted into reproduction image data by the inverse DCT means 812 and stored in the reproduction image data storage area 8112. The image relating to the reproduced image data RD can be converted into image display data by the image display circuit 813 and displayed on the display 814. On the other hand, the reproduced image data storage area 81
The image stored in the print data generating unit 8
The data is converted into print data PD by 15. The print data PD is transferred to the print buffer 821 of the printer 82, output to the print engine unit 822, and printed on the printing paper 100.

On the other hand, with the spread of digital cameras, printers having a slot into which a memory card can be inserted, and high-resolution printers having an interface for connection with the digital camera have also become commercially available.

FIG. 9 is a schematic view showing an example of a conventional printer 9 having a memory card slot. An image captured by the digital camera is stored in the memory card 200 in a JPEG format. The JPEG image data JD stored in the memory card 200 is loaded into the storage device 92 via the memory card drive 91.

When printing an image, the JPEG image data JD stored in the storage device 92 is expanded by an inverse DCT processing device 93 and converted into reproduced image data RD. Further, the print data generating means 94 generates print data PD from the reproduced image data RD and stores the print data PD in the print buffer 95. Print buffer 9
The print data PD stored in the printer 5 is output to the print engine unit 96, and printing on the printing paper 100 is performed.

[0009]

However, when the print data PD is printed by the printer 82 of FIG. 8 or the printer 9 of FIG.
No. 6, a scanning noise due to a mechanical error of the printer and / or a block noise generated at the time of compression / decompression may occur.

For example, in an ink jet printer, a printing paper is sent in a sub-scanning direction at a predetermined pitch.
A carriage provided with a print head reciprocates in the main scanning direction to perform printing. For this reason, scanning noise due to the mechanical error of the printer, that is, mechanical error of the printing paper transport mechanism or mechanical error of the reciprocating mechanism of the carriage may appear as noise in the printed image.

In addition, since the DCT conversion is performed in units of 8 × 8 pixel blocks, block noise may occur during compression / decompression.

An object of the present invention relates to a noise diffusion printing technique for a print image of a DCT-processed compressed image data, and relates to a scanning noise caused by a mechanical error of a printer generated at the time of printing an image and / or a compression noise generated at the time of compression / decompression. It is an object of the present invention to provide a noise diffusion printing system capable of diffusing block noise, a printer with a noise diffusion function, and a noise diffusion printing method.

[0013]

SUMMARY OF THE INVENTION A noise diffusion printing system according to the present invention comprises a computer and a printer connected to the computer, and includes scanning noise and / or scanning noise caused by a mechanical error of the printer when printing an image. Alternatively, the computer diffuses block noise generated at the time of compression / decompression, and the computer includes an AC component change unit, an inverse DCT unit, and a print data generation unit.

The AC component changing means, the inverse DCT means, and the print data generating means are, specifically, a CPU of a computer and software (specifically, a printer driver or a printer driver) attached to the computer. Software).

Here, the AC component changing means changes the value of the predetermined diagonal element of the AC component for the N × N pixel block of the compressed image data, and the inverse DCT means changes the AC component. Converts image data such as JPEG images to inverse DC
T processing is performed to obtain reproduced image data, and the print data generating unit generates print data from the reproduced image data.

The change of the value of the predetermined diagonal element of the AC component by the AC component changing means can be performed for (1) decoded image data or (2) inverse quantized image data.

When the AC component changing means processes the decoded image data of (1) or the dequantized image data of (2), the AC component changing means changes the value of the coefficient of a predetermined diagonal element of the AC component of the coefficient matrix together. change. Which diagonal element of the AC component of the inversely quantized DCT coefficient matrix (inversely quantized image data) should be changed and how much can be determined by printing an image of an appropriate compressed image data such as a test pattern or the like. It can be determined appropriately.

A change can be made to only one of the diagonal elements, or a change can be made to a plurality of elements. It is also possible to determine which frequency component is to be changed (that is, which diagonal element of the coefficient matrix is to be changed) according to the enlargement ratio (input resolution) of the image data. For example, it is preferable to emphasize frequency components corresponding to 0.5 cycles to 2 cycles / mm during printing. Table 1 shows the relationship between the input resolution, the AC components of the matrix to be processed (diagonal rows), and the printing frequency (spatial frequency cycle / mm on the printed image).

[0019]

[Table 1]

In Table 1, assuming that the input resolution is a combination of 72 dpi and matrix elements (7, 7) as in the embodiment described later, in both the main scanning direction and the sub-scanning direction, 1.
2 cycles / mm is emphasized and noise is diffused.

An AC component change user interface for changing the value of a predetermined diagonal element of the AC component is provided by:
It can be provided in the computer or the printer.

The printer with a noise diffusion function according to the present invention comprises:
An image is printed by diffusing scanning noise caused by a mechanical error of the printer and / or block noise generated at the time of compression / decompression.
T means and print data generating means are provided.

The AC component changing means, the inverse DCT means, and the print data generating means can be specifically realized by software installed in the CPU of the printer and the ROM in the printer. Further, all or a part of each of these units may be realized by a dedicated processor.

Here, the functions and operations of the AC component changing means, the inverse DCT means and the print data generating means are the same as those of the above-described noise diffusion printing system. Further, it is also possible that the AC component changing means can change the value of the predetermined diagonal element of the AC component for (1) coded data or (2) dequantized image data. The same as in.

Further, in the printer with the noise diffusion function of the present invention, an AC component change user interface for changing the value of the predetermined diagonal element of the AC component can be provided. Further, an input interface for changing the value of the AC component from an external device can be provided.

The noise diffusion printing method according to the present invention takes in compressed image data subjected to DCT processing and performs printing. An AC component change processing step for changing only the AC component of the compressed image data is provided. , An inverse DCT processing step of performing inverse DCT processing on the image data whose AC component has been changed to obtain reproduced image data, and a print data generating step of generating print data from the reproduced image data. It is characterized by.

The AC component change processing step can be performed on (1) coded data or (2) on dequantized image data.

The noise diffusion printing method of the present invention diffuses scanning noise caused by a mechanical error of a printer and / or block noise generated at the time of compression / decompression at the time of printing an image. The method includes an inverse DCT processing step and a print data generation step. The noise diffusion printing method can be executed in a computer or in a printer.

In the AC component change processing step, the JPEG
For the compressed image data such as image data, the value of the predetermined diagonal element of the AC component is changed, and in the inverse DCT processing step, the image data for which the AC component has been changed is inverted D
In the print data generating step, print data is generated from the reproduced image data by performing CT processing to obtain reproduced image data.

The AC component change processing step can be performed on (1) coded data or (2) on dequantized image data.

An example of the processing of the present invention (FIG. 1A) performed on the JPEG image data JD is described by using a conventional processing (FIG. 1).
This will be described in comparison with (A)).

In the conventional processing shown in FIG.
The G image data JD (encoded data) is converted into decoded image data A '(frequency space notation), and is converted into inverse quantized image data C' (frequency space notation) using a quantization table B '. Further, the inversely quantized image data C 'is subjected to an inverse quantization process, and the reproduced image data E'
(Real space notation) is generated. Thereafter, the reproduced image data E 'is converted into print data and passed to print processing.

On the other hand, in the processing example of the present invention shown in FIG. 1A, first, as in FIG.
The (encoded data) is converted into decoded image data A (frequency space notation), and is converted into inverse quantized image data C (frequency space notation) using a quantization table B. In the present invention, noise diffusion processing is performed on the dequantized image data C, and noise diffusion processed image data D (frequency space notation) is generated. In FIG. 1B, the lower right diagonal element (7, 7) (the element of the maximum row and the maximum column) of the 8 × 8 pixel block is changed. Thereafter, the noise diffusion processed image data D
Are subjected to an inverse quantization process, and reproduced image data E (real space notation) is generated. Thereafter, the reproduced image data E is converted into print data and passed to print processing.

In the example shown here, by adding noise to the diagonal element of the AC component of the dequantized image data (compression), the scanning noise and / or
Alternatively, block noise generated at the time of compression / decompression is diffused.

[0035]

FIG. 2 is an explanatory diagram showing one embodiment of a noise diffusion printing system according to the present invention.

In FIG. 2, the noise diffusion printing system 1
Comprises a computer 11 and a printer 2. The computer 11 has a storage device 1 having a compressed image data storage area 1111 and a reproduced image data storage area 1112.
11, an inverse DCT processing device 112 including an AC component changing unit 1121 and an inverse DCT unit 1122, a print data generating unit 113, an AC component adjusting unit 114, an image display circuit 115, and a display 116. Have been.

The printer 12 includes a print buffer 121 and a print engine unit 122.

In FIG. 2, since the computer 11 is functionally represented, the CPU and the ROM are not shown, but the AC component changing means 1121 and the inverse DCT means 11 are not shown.
22, the functions of the print data generation unit 113 and the like can be achieved by the central processing unit and the processing program stored in the ROM.

As will be described later, the AC component changing means 1121 changes the AC component of the inversely quantized image data of the pixel block of the JPEG image data JD (by changing the value of the diagonal element of the AC component). Can be changed). In the present embodiment, the AC component of the dequantized image data is changed, but the AC component of the encoded data is changed.
The component can be changed, and the AC component of the decoded image data (an inverse-quantized image data matrix before the inverse quantization is performed) can be changed.

The inverse DCT means 1122 converts the inverse quantized image data in which the AC component has been changed,
CT can be performed to reproduce an 8 × 8 pixel block (that is, to generate reproduced image data RD).

The print data generating means 113 can convert the reproduced image data RD into print data PD.

The AC component adjusting means 114 is provided with the AC component
This is for appropriately selecting the diagonal element of the component and setting the change value. The selection and change are not shown, but are performed through a user interface displayed on the display 116.
This can be performed by a printer user as appropriate.

FIG. 4 is an explanatory view showing an embodiment of a printer with a noise diffusion function according to the present invention.

In FIG. 4, a printer 2 includes a memory card drive 21, an I / O port (serial port) 2
2, a storage device 23, an inverse DCT processing device 24, a print data generation unit 25, a print buffer 26, a print engine unit 27, and an AC component adjustment unit (user interface) 28. In FIG. 4, user interfaces such as operation buttons and switches, and a display and a lamp for displaying operation status are not shown because they are not essential for understanding the present embodiment.

The memory card drive 21 can be loaded with a memory card 200 for a digital camera. In the present embodiment, the memory card 200 has a JPE
It is assumed that G image data JD is recorded.

The user can load predetermined JPEG image data JD from the images stored in the memory card 200 into the storage device 23 via a user interface (not shown).

The serial port 22 is connected to a port of an external device such as a computer. This serial port 2
2, the JPEG image data can be loaded from an external device into the storage device 23, and is also used as an input interface for changing the value of an AC component described later from the external device.

The inverse DCT processor 24 expands the JPEG image data JD to obtain reproduced image data RD, and includes an AC component changing unit 241 and an inverse DCT unit 24.
2

In FIG. 4, since the printer 2 is functionally represented, the CPU and the program storage ROM are not shown, but the function of the inverse DCT processor 24 is
This can be achieved by the PU and the processing program stored in the ROM. Of course, a dedicated processing circuit equipped with a DSP (digital signal processor) can be used instead of the central processing unit.

The AC component changing means 241 is, like the noise diffusion printing system of FIG. 2, an AC component of the inversely quantized image data for the pixel block of the JPEG image data JD.
Although the value of the predetermined diagonal element of the component is changed, a change may be made to the predetermined diagonal element of the AC component of the encoded data or the AC component of the dequantized image data.

As will be described later, the inverse DCT means 242
Inverse DC is applied to the inverse quantized image data in which the C component is changed.
T to reproduce an 8 × 8 pixel block (ie,
(Reproduction image data RD).

The print buffer 26 stores the print data PD generated by the print data generating means 25. The print data PD is sequentially output to the print engine unit 27, and the print engine unit 27 can print an image related to the print data PD on the printing paper 100.

The AC component adjusting means 28 is provided in the printer so that the user can set (change) the value of the AC component. In FIG. 4, the AC component adjusting means 28 is indicated by a dial, but is not limited to this. The value of the diagonal element of the AC component can be changed from an external device such as a computer connected via the serial port 22. The changed value is stored in a non-illustrated nonvolatile register or the like. Of course, the value of the predetermined diagonal element of the AC component can be changed by the printer manufacturer at the time of manufacturing or shipping of the printer, so that the user is not allowed to set (change) the value.

An image (original image) photographed by a digital camera is usually converted into a JPEG format by a processing device in the digital camera. As shown in FIG. 6, the conversion of the original image into the JPEG image is performed on a pixel block of interest (8 × 8 pixel block) 310 of the original image.

First, regarding the pixel block 310 of interest,
DCT processing is performed, and DCT coefficients (frequency space data)
320 is required.

Next, the DCT coefficient 320 is converted into a quantized DCT coefficient 340 using the quantization table 330.

In a photographic image, the change in pixel value between localized pixels is small. Therefore, in a JPEG image, the high-frequency component of the quantized DCT coefficient 340 is often “0”.

Further, the quantized DCT coefficient 340 is encoded, and encoded data 350 is generated. Then, the encoded data (JPEG image data JD) 350 is obtained from the encoded data of the 8 × 8 pixel block constituting the image.
Is created.

First, in order to facilitate understanding of this embodiment, the inverse DCT conversion processing in the conventional printing system 8 shown in FIG. 8 or the conventional printer 8 shown in FIG. 9 will be described with reference to FIG. explain. In FIG. 7A, an inverse DCT process is performed on the decoded image data (frequency space display) to obtain 8 ×
An 8-pixel block (reproduction image data RD) is generated.
In the printing system 8, this reproduced image data RD
Are generated by the inverse DCT unit 812, converted into print data PD by the print data generation unit 815, and stored in the print buffer 8 of the printer 82.
21. Further, in the printer 9, the reproduced image data RD is transmitted to the inverse DCT unit 9 as shown in FIG.
3 for generating print data.
Is converted to print data PD and sent to the print buffer 95.

Hereinafter, the inverse DCT conversion processing in the noise diffusion printing system 1 of the invention shown in FIG. 2 and the printer 2 of the invention shown in FIG. 4 will be described with reference to FIG.

In FIG. 7 (B), before the decoded data (frequency space representation) is subjected to the inverse DCT processing, a noise diffusion processing is performed to generate noise diffusion processed image data ND. Here, “10” is given to the element of the maximum row and the maximum column of the 8 × 8 matrix. This 8 × 8 pixel block (reproduced image data RD) is generated. The inverse DCT process is performed on the noise diffusion processed image data to generate reproduced image data RD. In the noise diffusion printing system 1,
As shown in FIG. 2, the noise diffusion processed image data ND is generated by the AC component changing unit 1121, and the reproduced image data RD is generated by the inverse DCT unit 1122. The reproduced image data RD is output to the print data generation unit 113.
Is converted into print data PD and sent to the print buffer 121 of the printer 12. In the printer 2, as shown in FIG. 4, the noise diffusion processed image data ND is generated by the AC component changing unit 241 and the reproduced image data RD is generated by the inverse DCT unit 242. The reproduced image data RD is converted into print data PD by the print data generation unit 25, and
To the print buffer 26.

Hereinafter, the flow of processing of the noise diffusion printing system 1 of FIG. 2 will be described with reference to FIG.

First, JP data is sent from the compressed image data storage area 1111 of the storage device 111 to the AC component changing unit 1121.
When the EG image data JD is captured (S110), A
The J component image data J
D 8 × 8 pixel block (target pixel block 31 in FIG. 6)
For each of the data according to (0), the value of the predetermined diagonal element of the AC component is changed for (1) coded data or (2) dequantized image data, and noise diffusion processed image data ND is generated. (AC component change processing step S120).

Next, the inverse quantized image data in which the value of the AC component has been changed is
The image data is converted into 8-pixel blocks and restored to the reproduced image data RD (inverse DCT processing step S130).

Then, the print data PD is generated from the 8 × 8 pixel block by the print data generator 113 (print data generation step S140).

The print data PD is sent to the print buffer 121 of the printer 12, and is sent to the print engine unit 122 as needed (printing step S150).

Next, the processing flow of the printer 2 in FIG. 4 will be described with reference to FIG.

First, when the JPEG image data JD is fetched from the storage device 23 into the inverse DCT processing device 24 (S
210), by the DC component changing means 241, for each data of the 8 × 8 pixel block (target pixel block 310) of the JPEG image data JD, (1) encoded data, or (2) inverse quantized image data , A
The value of the predetermined diagonal element of the C component is changed, and noise diffusion processed image data ND is generated (AC component change processing step S220).

Next, the inversely quantized image data in which the value of the AC component is changed is converted into 8 × 8
The image data is converted into a pixel block and restored to the reproduced image data RD (inverse DCT processing step S230).

Then, the print data generation means 25 generates print data PD from the 8 × 8 pixel block (print data generation step S240).

The print data PD is stored in the print buffer 26, and is sent to the print engine 27 as appropriate (printing step S250).

[0072]

According to the present invention, scanning noise and / or scanning noise caused by a mechanical error of a printer which occurs when printing an image.
Alternatively, block noise generated during compression / decompression can be diffused. In particular, in the present invention, processing is performed on image data in a compressed state, so that printing throughput does not decrease.

[Brief description of the drawings]

FIG. 1A is a diagram showing an example of a conventional process performed on JPEG image data, and FIG. 1B is a diagram showing an example of a process of the present invention.

FIG. 2 is an explanatory diagram showing one embodiment of the noise diffusion printing system of the present invention.

FIG. 3 is an explanatory diagram showing a processing flow of the printer in FIG. 2;

FIG. 4 is an explanatory diagram showing one embodiment of a printer with a noise diffusion function of the present invention.

FIG. 5 is an explanatory diagram showing a flow of processing of the printer in FIG. 4;

FIG. 6 is an explanatory diagram showing conversion of an original image into a JPEG image.

7A is an explanatory diagram of the inverse DCT transform processing in the conventional printing system shown in FIG. 8 or the conventional printer shown in FIG. 9, and FIG. 7B is a diagram showing the noise diffusion of the present invention shown in FIG. FIG. 5 is an explanatory diagram of an inverse DCT conversion process in the printing system and the printer of the present invention illustrated in FIG. 4.

FIG. 8 is a diagram illustrating an example of a conventional printing system including a computer and a printer.

FIG. 9 is a diagram illustrating an example of a conventional printer having a memory card slot.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 noise diffusion printing system 2 printer 11 computer 12 printer 21 memory card drive 22 serial port 23 storage device 24 inverse DCT processing device 25 print data generation unit 26 print buffer 27 print engine unit 28 AC component adjustment unit 100 printing paper 111 storage device 112 Inverse DCT processing device 113 Printing data generating means 114 AC component adjusting means 115 Image display circuit 116 Display 121 Print buffer 122 Print engine unit 200 Memory card 241 AC component changing means 242 Inverse DCT means 310 Pixel block of interest 320 DCT coefficient 330 Quantum Conversion table 340 Quantized DCT coefficient 350 Encoded data 1111 Compressed image data storage area 1112 Reconstructed image data storage area 112 AC component changing unit 1122 inverse DCT unit JD JPEG image data ND noise spreading processing image data PD print data RD reproduced image data

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C087 AB05 BA03 BD24 BD40 5C059 KK03 MA00 MA23 MC00 MC34 SS26 SS28 5C077 LL02 MP10 PP48 PP68 PQ08 RR21 SS05 TT02 5C078 AA04 BA21 CA22 DA00 DA02 EA08 5J064 AA01 BC16BB13

Claims (12)

[Claims] 1. A printing system comprising a computer and a printer connected to the computer, wherein the printing system diffuses scanning noise caused by a mechanical error of the printer and / or block noise caused by compression / decompression when printing an image. The computer comprises: an AC component changing unit configured to change a value of a predetermined diagonal element of an AC component with respect to the compressed image data on which the DCT process has been performed; , Inverse DCT
A noise diffusion printing system, comprising: inverse DCT means for processing to obtain reproduced image data; and print data generating means for generating print data from the reproduced image data. 2. The method according to claim 1, wherein the change of the value of the predetermined diagonal element of the AC component by the AC component changing means is performed for (1) decoded image data or (2) dequantized image data. The noise diffusion printing system according to claim 1, wherein: 3. The noise diffusion printing system according to claim 1, wherein the compressed image data subjected to the DCT processing is JPEG image data. 4. The computer or the printer according to claim 1, wherein the computer or the printer includes an AC component change user interface for changing a value of a diagonal element of the AC component. Noise diffusion printing system. 5. A printer with a noise diffusion function for printing an image by diffusing scanning noise caused by a mechanical error of the printer and / or block noise generated during compression / decompression, wherein a DCT process is performed. AC component changing means for changing the value of a predetermined diagonal element of the AC component for the compressed image data; and inverse DCT for the image data for which the AC component has been changed.
A printer with a noise diffusion function, comprising: inverse DCT means for processing to obtain reproduced image data; and print data generating means for generating print data from the reproduced image data. 6. The method according to claim 6, wherein the change of the value of the predetermined diagonal element of the AC component by the AC component changing means is performed for (1) decoded image data or (2) inverse quantized image data. A printer with a noise diffusion function according to claim 5. 7. The printer with a noise diffusion function according to claim 5, wherein the compressed image data subjected to the DCT processing is a JPEG image. 8. An A signal for changing a value of the AC component.
8. The printer according to claim 5, further comprising a C component change user interface. 9. The printer with a noise diffusion function according to claim 5, further comprising an input interface for changing the value of the AC component from an external device. 10. A printing method for diffusing scanning noise caused by a mechanical error of the printer and / or block noise generated at the time of compression / decompression, which is generated at the time of printing an image. , An AC component change processing step of changing a value of a predetermined diagonal element of an AC component, and an inverse DCT
A noise diffusion printing method comprising: an inverse DCT processing step of performing processing to obtain reproduced image data; and a print data generating step of generating print data from the reproduced image data. 11. The noise diffusion printing method according to claim 10, wherein the AC component change processing step is performed for (1) decoded image data or (2) dequantized image data. . 12. The method according to claim 1, wherein the compressed image data subjected to the DCT processing is a JPEG image.
12. The noise diffusion printing method according to 0 or 11.