JPH05261982A - Printing device - Google Patents

Abstract

PURPOSE:To use standardized DCT data as a transferring data to a printer from a personal computer or a computer and perform resolution conversion in accordance with resolution of the printer based on said data efficiently in the printer. CONSTITUTION:In a printing device for printing in accordance with printing instruction from a computer as an external device, an interface 101, a data memory means 102, a designated size memory means 103, a reverse DCT conversion means 106, and a print engine section 108 are provided for performing reverse DCT conversion of a compressed DCT data into a designated size so as to generate a data for a printer engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus for outputting character information or the like created or processed by a personal computer, a workstation or the like on paper.

[0002]

2. Description of the Related Art A printer, which is a peripheral device such as a personal computer or a workstation, receives print data from the host device and performs a process in accordance with a print engine in the printer for printing. There is a slight difference between the print result and the display result on the host device. On the host device side, the performance is becoming higher and higher, more detailed display is possible, and it is necessary for the printer to support it. As a means for achieving this, it is conceivable that the display processing in the computer and the print processing in the printer are processed by the same algorithm. To do this, the processing capacity of the computer must match the processing capacity of the computer. It cannot be processed at a reasonable speed. Therefore, in order to obtain the same print result without increasing the processing capacity of the printer, convert it to data that is as close as possible to the print state of the printer in the computer,
I will transfer it to the printer.

However, if the data to be printed is sent as pixel data in the spatial domain as it is, the resolution of the printer is high, and in the case of print processing including gradation processing, color processing, etc., the amount of information increases, Both transfer time and processing time increase.

Therefore, conventionally, the data compressed according to the interface rule of the printer or the rule of the page description language is transferred, and the printer decompresses according to each rule. FIG. 10 shows the flow. The data restoration processing unit 1002 restores the data compressed by the computer or the like to the original data by the inverse conversion of the compressed algorithm, and the resolution conversion unit 1002.
In 3, the resolution is converted according to the engine of the printer, the resolution fixing unit 1004 performs fixing in accordance with the dots in the area corresponding to the size of the printing of the printer, and the engine processing unit 1005 performs processing for printing on the engine. Then, the printer unit 1006 prints. An example of data compression at this time is shown in FIG. Here, a state of data in the case where information of a plurality of data formats is compressed and transferred to the printer and is converted and printed according to the resolution of the printer in the printer is shown. When data is arranged in different file formats A and B when printing the area shown in FIG. 11A, as another data group,
The compression as shown in (2) is performed, the plurality of data states are transferred to the printer, and the original data is restored in the printer as shown in (3). Here, the original data is 300 dpi (dots per inch), and the resolution of the printer is 600 dpi. In the restoration of the original data in (3), when the original data is data in the unit of printing pixels, restoration to 300 dpi is performed, but it is drawing data such as straight lines and curves, and further, in the printer. For those having a function of interpreting drawing data, it is also common to directly perform the final output 600 dpi conversion without performing the resolution conversion to 300 dpi in (3). In (4), the final output 600 dpi data is pasted (fixed), and print data is completed. In this way, when printing to an output device with a resolution different from the original data, data compression,
Restoration and resolution conversion processing is performed. As a compression method here, there is compression by conversion into a two-dimensional frequency domain. FIG. 12 shows a procedure of data compression by the conversion into the two-dimensional frequency domain, restoration of the compressed data, and further expansion. (1) is an N × N spatial domain original data block, (2) is the one obtained by compressing the region into the N × N two-dimensional frequency region, (3) is obtained by restoring the N × N spatial region original data, and (4) is the M × M.
The resolution is converted to. In this enlarging process, if the enlarging ratio is not an integral multiple, it is necessary to perform a complicated interpolation calculation by referring to the peripheral pixels, which takes a lot of time.

[0005]

On the other hand, Japanese Unexamined Patent Publication No. 2-76472 discloses an enlargement method using the frequency domain. FIG. 13 is a block diagram for explaining Japanese Patent Laid-Open No. 2-76472, in which conversion is performed using frequency conversion by discrete cosine transform (DCT), expansion processing is performed in the preceding stage at the time of inverse conversion, and then inverse conversion is performed and expansion processing is performed. Is a way to do.

According to Japanese Patent Laid-Open No. 2-76472, since an image can be enlarged by a simple process, it is possible to easily perform an enlargement process of an arbitrary magnification without using a high speed processor. However, this is based on the premise that the same resolution is guaranteed, and a problem arises when the resolution on the host device side and the resolution on the printer side are different. The present invention has been made in view of such problems, and an object thereof is to perform high-quality printing based on compressed data in a two-dimensional frequency domain processed at a resolution different from that of the printer. To provide a printer.

[0007]

According to the present invention, in a printing apparatus for printing according to a printing instruction from a computer or the like which is an external apparatus, an interface section, a data storage section, a designated size storage section, and an inverse DCT conversion section. , A DCT-compressed data having a print engine unit, and the inverse DCT converting means converts the DCT-compressed data to a specified size.
It is characterized by converting and generating printer engine data.

[0008]

1 is a block diagram for explaining an embodiment of the present invention, 101 is an interface section, 102 is a data storage means for storing compressed data input from the interface section, and 103 is print data from the outside. A designated size storage means for storing data defining the size, 104
Is pre-demodulation processing means, which is a pre-processing of data restoration processing, 105 is DCT block setting means, and 106 is inverse DC.
T conversion means, 107 is a print control means, and 108 is a print engine. The operation of the device configured as described above will be described according to the flow of data. When compressed data for printing, commands, etc. are transferred to the interface unit 101 from a personal computer, a workstation, etc., a data group of commands, etc. is processed by a processor process (not shown in the figure) in the printer and printed. The compressed data for use is stored in the data storage unit 102, and information regarding the print size is stored in the designated size storage unit 103. This size designation storage means is the most important part of the present invention, and here, based on the given size information or resolution information and the resolution information specific to the printer engine, processing such as enlargement or reduction of print data is performed. It is determined. In the pre-demodulation means 104, the print data compression method is not a simple DCT compression method, but a means for realizing a functional block for demodulating the pre-processing for increasing the compression efficiency. An example of this internal processing will be described later. The DCT block setting unit 105 is a functional block that sets an instruction such as a conversion processing coefficient when performing the inverse DCT conversion by the inverse DCT conversion unit 106, and based on this instruction, the conversion to the size of the final print data is reversed. It is implemented by the DCT conversion means 106. The resolution-converted data of the print data is subjected to local conversion, transfer, etc. in accordance with the engine by the print control means 107, and is sent to the print engine 108 to be subjected to the print processing.

FIG. 2 is an explanatory diagram of the embodiment, and shows a flow of conversion of a basic pixel block from original data sent from a computer or the like to data to be printed. FIG. 12 shows that the original data is a conventional method when it is required by the entire system to convert an N × N pixel block into an M × M pixel block in print data. As shown, once the compressed data is N × N
The original data (1) of N × N is 2 × N × N on the personal computer or the workstation in this embodiment.
Is converted to the two-dimensional frequency domain (2), or already handled as two-dimensional frequency domain data, and that data is transferred to the printer and first corrected in the printer in the two-dimensional frequency domain to an M × M size. (3), M ×
Pixel conversion of M data into real space is performed (4). The instruction of the conversion from N to M is determined by the information from the designated size storage means 106 of FIG. 1 as described above. In the case of N = 8, the range of this size takes an integer value for M. For example, in the case of M = 8, 9, 10, 1, 1.125, 1.25 The size of the interval can be specified.

FIG. 3 shows a situation in which, when data is compressed by a computer or the like, the compression method compresses the entire print page by one compression method.

Conventionally, as shown in FIG. 11, depending on the command system or page description language system used,
Character information, image information, etc. are processed by different compression styles, and the printer interprets each and performs conversion according to the final print size. On the other hand, in the present embodiment, the compression is performed by a single compression method, that is, compression for conversion into the two-dimensional frequency domain. If the original data (1) described in the same page description language as the conventional example is drawing data or the like that is not pixel data, the entire page is developed into pixel data (2), and the entire resolution is the same. This pixel data is compressed in the two-dimensional frequency domain (3), the compressed data is transferred to the printer, and the restored data that matches the resolution of the printer is reproduced in the printer (4).

FIG. 4 is a front demodulation means 104 of the embodiment of FIG.
And the inverse DCT conversion means 106 is a more specific embodiment. 5 to 9 are diagrams for supplementing the description of FIG. The compression method described here is based on the compression method based on the JPEG standard standardized by CCITT / ISO,
We propose resolution conversion inside the printer based on the compressed data. 401 is a Huffman coding demodulator,
402 is a Huffman table, 403 is a quantizer,
Reference numeral 404 is a quantization table, and 405 is an extended inverse DCT means. The operation of the apparatus thus configured will be described in detail based on the data flow. As the input to the Huffman coding / demodulating device 401, the compressed data 401A is input. 40
1A is the encoded data shown in FIG. It is input as JPEG standardized data based on the specifications. That is, J
The compressed image data in various data of the compressed data set of the PEG standard is input as 401A. Header information (image start data, quantization table, quantization table length, Huffman table type, Huffman table length, etc.) placed before the compressed image data is processed in the same manner as the command information described above, and the Huffman table shown in FIG. It is used for setting the 402, the quantization table 404, and the like. As the internal data, as shown in FIG. 5, compressed data as a result of DCT, quantization, run length, and zigzag scanning are sequentially input. In the Huffman coding demodulator 401, based on the Huffman table 402 described above,
Pixels in each block are demodulated for each block of 8 × 8 pixels. 401B supplies Huffman table information. At the time of this pixel reproduction, the pixel data is demodulated based on the zigzag scan order shown in FIG. That is,
At the time of run-length conversion, the encoded data are arranged in the order of FIG. 6 in order to improve the compression efficiency. The pixel data restored here is the data in the two-dimensional frequency domain in the state in which the DCT transform and the quantization transform have been applied, and this data is 403A and is the quantizer 40 of the next stage.
Move to 3. This data is the quantized DCT coefficient value shown in FIG. 7 (1). The quantizer 403 performs the conversion shown in FIG. 7 to restore the DCT coefficient value of (3). Reference numeral 403B is a line for calling the quantized inverse table based on the visual characteristics in FIG. The data 405A processed by the quantizer 403 is the expanded inverse DCT means unit 4 at the next stage.
In 05, resolution conversion and pixel restoration are performed, and the two-dimensional frequency domain data is converted into a resolution suitable for the print engine of the real space data.

Next, an extended inverse transform process which is an enlarging / reducing process at the DCT inverse transform stage will be described. Figure 8
9A and 9B are explanatory diagrams of the expansion processing in the two-dimensional frequency domain, and FIG. 9 is an explanatory diagram of the inverse DCT processing after the expansion processing. Figure 8
(1) Quantization coefficient value is 2 of 8 × 8 pixels (when N = 8)
This value is in the next frequency domain, and this conversion is restored as a result of conversion by the following equation.

[0014]

[Equation 1]

The resulting block is in the state of N = 8 in FIG. 8 (1), and in each value, the upper left value is the DC term part and the coefficient of the lowest frequency part. ,
The other part is AC, and the coefficient value becomes higher as the distance from the DC value increases. Increasing the size of the block in this frequency region means adding a high frequency region that does not exist in the past to the surroundings. To increase the block size (when M> N) shown in (2), just add 0. It will be possible. At the time of reduction, the high frequency component is reduced to change the size, that is, the portion far from the DC value is removed. The result is the extended quantized coefficient value. Next, it is an inverse DCT transform which returns to the original real time domain, and the basic formula is shown by the following formula.

[0016]

[Equation 2]

In this equation, by setting the value of N to the size obtained in the real space, the data of the target size is restored.

In the method of the present invention, when standard data for printer is adopted, what kind of value should be adopted for the resolution of the image or character information generated on the computer or the like is a problem. Is determined by conditions such as the visual limit at the time of printing, the viewpoint of the performance of the input device, the data size, etc., and the data at the determined resolution and the size information are added, so that it becomes standard data. The printer according to the present invention can be employed, and printing adapted to the capability of the printer can be obtained.

[0019]

In the past, it was not possible to eliminate the resolution dependency of the printer by using only general-purpose compressed data such as JPEG, but it is necessary to have an inverse DCT means and a designated size conversion function extended in the printer. As a result, the standardized DCT compressed data can be used as data for transfer from the personal computer or workstation to the printer, and the resolution conversion can be efficiently performed according to the resolution of the printer using the data.

Further, since the compression of the two-dimensional frequency domain using the DCT operation has a great compression effect on the gradation data, the transfer time can be reduced by using this data as the transfer data to the printer. You can

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an example.

FIG. 3 is an explanatory diagram of an example.

FIG. 4 is a partial block diagram showing an embodiment of the present invention.

FIG. 5 is a diagram illustrating FIG. 4;

FIG. 6 is a diagram illustrating FIG. 4;

FIG. 7 is a diagram illustrating FIG. 4;

FIG. 8 is a diagram illustrating FIG. 4;

FIG. 9 is a diagram illustrating FIG. 4;

FIG. 10 is a block diagram of a conventional example.

FIG. 11 is an explanatory diagram of a conventional example.

FIG. 12 is an explanatory diagram of a conventional example.

FIG. 13 is a partial block diagram of a conventional example.

[Explanation of symbols]

 Reference Signs List 101 interface unit 102 data storage unit 103 designated size storage unit 104 pre-demodulation unit 105 DCT block setting unit 106 inverse DCT conversion unit 107 printing unit 108 print engine

Claims (1)

[Claims] 1. A printing apparatus for printing according to a printing instruction from a computer or the like which is an external apparatus, comprising an interface section, a data storage section, a designated size storage section, an inverse DCT conversion section, and a print engine section, A printing apparatus, wherein the DCT-compressed data is inversely DCT-converted to a size of a designated size by the inverse DCT conversion means to generate printer engine data.