JP2003145744A - Image recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an effective edge-smoothing processing in an image recorder capable of recording dots having different sizes when recording an image. SOLUTION: When a pixel that requires correction of an edge section is detected by a pattern matching operation, a dot having a size at the time when the edge smoothing operation is not performed is changed to one having a smaller size or one having a larger size which is not used in a gradation operation. As a result, an edge part of an image to be recorded is smoothed without newly recording interpolating dots so that occurrence of jaggy can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus capable of recording dots of different sizes when recording an image.

[0002]

2. Description of the Related Art Generally, an image output device such as a printer, a copying machine, a facsimile machine, etc., based on input image information.
An image composed of dot patterns is recorded as an output image on a recording medium such as paper. Usually, these dots are arranged on a square grid with a certain resolution, so a state called jaggies may occur in the shaded portions of the character outlines and figures, and the image quality may deteriorate. In order to avoid this state, the resolution should be increased, but if the resolution is increased, the amount of data increases, and accordingly, the amount and time for processing increase.

Therefore, conventionally, a method called edge smoothing has been used to extract only a necessary portion, and for that portion, dots are interpolated at a resolution higher than normal resolution so as to be smoothed to improve the image quality. Has been taken.

FIG. 4 shows a schematic diagram of a conventional method for changing the dot recording position to perform edge smoothing processing.
FIG. 4-A shows an example in which the edge smoothing process is not performed, and an example in which the edge smoothing process of the present method is applied thereto is shown in FIG. 4-B. In this method, when a pixel which becomes an edge is detected, the dots of the edge portion which should be originally recorded at the interval of the printing resolution d are changed in the recording position as shown in FIG. By smoothing the part, the occurrence of jaggies is suppressed and the image quality is improved. As shown in FIG. 4, FIG.
The edge of the recorded image subjected to the edge smoothing processing shown in FIG. 4B is smoother than the edge of the recorded image not subjected to the edge smoothing processing shown in FIG. 4B, and the deviation from the ideal straight line is smaller.

FIG. 5 shows an example of a conventional method of performing edge smoothing using dots of different sizes. Figure 5-
A is an example in which the edge smoothing process is not performed, and an example in which the edge smoothing process of the present method is applied thereto is shown in FIG. 5-B. This method can be used in an image recording apparatus capable of changing the size of recording dots, and when an edge portion is detected,
As shown in FIG. 5-B, at the position where dots are not originally recorded,
By recording an interpolation dot having a size smaller than the dot used in the edge portion, the edge portion of the recorded image is smoothed, jaggies are suppressed, and the image quality is improved. As shown in FIG.
The edge of the recorded image subjected to the edge smoothing processing shown in FIG. 5B is smoother than the edge of the recorded image not subjected to the edge smoothing processing shown in FIG. 5, and the deviation from the ideal straight line is smaller.

[0006]

FIG. 2 shows a schematic diagram of a serial type ink jet printer. As shown in FIG. 2, the serial type inkjet printer has a print head 0201 in which a plurality of recording elements 0301 are arranged at a print resolution interval d in a direction orthogonal to the moving direction of the print head 0201 as shown in FIG. The recording medium 0203 is moved along the guide 0202 in a direction (X direction) orthogonal to the moving direction (Y direction) of the recording medium 0203 to perform band-shaped image recording. Image recording is performed in combination.

FIG. 6 shows a schematic view of a line type ink jet printer. The line type inkjet printer has a recording head 06 in which recording elements are arranged at intervals of printing resolution in the X direction within a range that covers the entire width of image recording.
01, having a so-called line head. This recording head 0
A schematic diagram of 601 is shown in FIG. The recording head 0601 is
As shown in FIG. 7, it has one or more recording element arrays in which recording elements are arranged at intervals of print resolution d in the X direction. When recording an image, the recording head 0601 is fixed and X
In the direction, image recording is performed by ejecting ink from each recording element and moving the recording medium 0602 in the Y direction.

Regarding the conventional method of performing edge smoothing by changing the recording position as shown in FIG. 4, in the serial printer, the recording position of the dot is changed by changing the ejection timing in the X direction. There is no particular problem because it can be changed, but in the Y direction, the moving distance of the recording medium is, for example, 1 / of the printing resolution.
Since it is necessary to change the dot recording position by shifting and moving in units of 2, and the number of recording operations increases, the printing speed decreases. Further, in the line type printer, since the print head 0601 is fixed, dots cannot be recorded at a position smaller than the print resolution in the X direction.
It has the drawback that it can only be applied in the Y direction.

On the other hand, in the method of obtaining the edge smoothing effect by printing the interpolation dot of a size smaller than the normal dot size as shown in FIG. 5, it is not necessary to change the dot recording position. Because X
The edge smoothing effect can be obtained regardless of the direction, the Y direction, but the effect cannot be obtained as much as when the dot recording position is changed, and by printing the interpolation dots, the printing area is smaller than the original image. It has the drawback of spreading.

[0010]

SUMMARY OF THE INVENTION According to the present invention, in an image recording apparatus capable of recording dots of different sizes at the time of recording an image, the size of the dots which can be recorded by the image recording apparatus is the largest. Do not use dots of several sizes in order for gradation reproduction, and use dots of a size that is larger than the dot of the largest size of the recording pixels used for gradation reproduction and that is not used for gradation reproduction. The feature is that edge smoothing processing is performed using dots.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 6 shows a schematic diagram of a printing mechanism of an inkjet printer using a line head. The print head 0601 is connected to the printer controller 0803 in FIG. 8 by a cable 0603, does not move during printing, and performs image recording by moving the recording medium 0602 in the Y direction by the transport rollers 0604 and 0605. The print head 0601 is shown in FIG.
The schematic diagram at the time of seeing from the 02 side is shown. The print head of the inkjet printer of this embodiment has four recording element arrays 0701, 0702, 07 corresponding to four colors of CMYK (cyan, magenta, yellow, black).
03, 0704, and the respective printing element arrays are printing elements 0705, 0706, 0707, 0808 in the X direction.
, Are arranged at intervals of print resolution d in a range that can cover the width of image recording on the recording medium. Recording element array 0
The recording element 0705 of 701 ejects Y ink, the recording element 0706 of the recording element array 0702 ejects M ink,
The printing element 0707 of the printing element array 0703 ejects C ink, and the printing element 0708 of the printing element array 0704 ejects K ink. The arrow in FIG. 7 indicates the moving direction of the medium, and corresponds to the arrow in FIG. The order of the colors CMYK corresponding to these printing element arrays 0701, 0702, 0703, 0704 does not have to be this order.
Further, the number of colors need not be limited to four.

FIG. 8 shows a control block diagram of this embodiment.
The printer 0801 is connected to the host 0802,
Printer engine 0804 and printer controller 0803
It consists of The print data sent from the host 0802 is the control unit 080 of the printer control device 0803.
5 and is sent to the input buffer 0807. The data sent to the input buffer is sent to the storage device 0808 according to an instruction from the host and temporarily stored, and then the data is sent to the image processing unit 0806 or directly to the image processing unit 0806. The data sent to the storage device 0808 or the input buffer 0807 image processing unit is first converted to the color conversion processing unit 080 of the image processing unit 0806.
9 is processed. The color conversion processing unit 0809 determines that the data of the pixels to be sent has 256 gradations of 8 CMYK colors and 8 bi.
When the data is not t, for example, in the case of RGB (red, green, blue), 256 gradations of CMYK and 8 bi
It is converted to data of t and sent to the gradation processing unit 0810 and the ternarization determination processing unit 0811, and in the case of binary data of each color of CMYK, it is converted to 255 and 0 and the gradation processing unit 0810 and ternarization are similarly performed. It is sent to the determination processing unit 0811. Here, the data of 256 gradations and 8 bits is data of higher density as the value is larger.

The gradation processing unit 0810 performs gradation processing for converting the received pixel data into the value of the number of gradations printable by the printer by the dither method, the error diffusion method, etc. for each color.
The result is output to the selector 0814 as the gradation data of the pixel in synchronization with the result of the edge smoothing processing described later. In the present embodiment, the result after gradation processing is represented by 3 bits, and values of 0 to 6 are used for integers 0 to 7 that can be represented by 3 bits. 7 is not used.

The edge smoothing processing is performed in parallel with the gradation processing for each color as in the gradation processing, and the processing is performed by the ternarization determination processing unit 0811, the edge detection processing unit 0812, and the correction value generation processing unit 0813. Be seen.

The pixel classification data generation processing performed by the ternarization determination processing section will be described. The ternarization determination processing unit classifies the pixels for edge detection into three types based on the pixel values from the multi-valued image data, and generates classification data. The types of pixels to be classified do not have to be three.
FIG. 9 shows an algorithm of the ternarization determination processing performed by the ternarization determination processing unit 0811. In the ternarization determination process, the pixel is classified into three types of high density pixel, low density pixel, and halftone pixel according to the value of the pixel. The pixel value is the threshold B
If it is larger, it is classified as a high density pixel, and the pixel value is the threshold value W.
If it is smaller, it is classified as a low-density pixel, and if it is neither of them, it is classified as a halftone pixel. In this way, the number of patterns required for the pattern matching process can be suppressed to a small number by ternarizing the multi-gradation data into three values.

The edge detection processing performed by the edge detection processing unit 0812 will be described. The edge detection processing is performed by comparing the pattern of the classification data of a plurality of pixels with the pixel pattern for edge detection that is registered in advance. Here, the pixel pattern for edge detection will be described as a 3 × 3 square as an example. FIG. 10 shows an example of a pixel block of 3 × 3 pixels. The pixel e is a target pixel to be smoothed, and 9 pixels including the pixel e, 3 pixels in the X direction and 3 lines in the Y direction, a to i pixels, are referred to. The reference pixel block is
As shown in FIG. 11-A, it does not necessarily have to be a square, and as shown in FIG. 11-B, it does not have to be a rectangular region. 12A and 12B show examples of patterns for detecting edges. As shown in this example, the edge detection pattern does not distinguish between a halftone pixel and a low density pixel.
Further, FIG. 12C is an example of a pattern used for detecting the solid interior used in the correction value generation processing. As shown in FIG. 11C, it is not always necessary to refer to all pixels even within the reference pixel block, and there may be non-reference pixels.
When these detection patterns are used and the pattern of the ternarization determination result matches these patterns, and there is no halftone pixel among the reference pixels in the reference pixel block,
Depending on the pattern, enlargement correction pixel, reduction correction pixel,
If the pixel is a solid internal pixel and does not match any pattern, it is determined as an uncorrected pixel and the correction data is sent to the correction value generation processing unit 0813. Here, although only one step is set for each of the enlargement correction pixel and the reduction correction pixel, there may be a plurality of steps. The relationship between the edge detection pattern and the correction data can be realized by a logic circuit or a memory.

The correction value generation processing performed by the correction value generation processing unit 0813 will be described. In the case of the data of the enlargement correction pixel and the reduction correction pixel, the correction value generation process outputs the same data as the gradation value corresponding to the data, and it is the pixel adjacent to the enlargement correction pixel If the pixel is not adjacent to the correction pixel and is a solid internal pixel, the data of that pixel is converted into the data of the reduced correction pixel and is output. In order to realize this, pattern matching processing of 3 × 3 pixels is performed. FIG. 13 shows an example of a pattern to be converted into the reduction correction pixel. By using these patterns, it is possible to detect a pixel in which the enlargement correction pixel is adjacent to the X direction or the Y direction, is not adjacent to the reduction correction pixel, and is inside the solid area. If the patterns of the correction data output from the edge detection processing unit 0812 match these patterns shown in FIG. 13,
A solid internal pixel is used as a reduction correction pixel. Then, for the enlargement correction pixel and the reduction correction pixel, predetermined correction data corresponding to them are output. The value of the data output here is the same value as the value of the gradation data output from the gradation processing unit. In the present embodiment, the value 3 is assigned to the reduction correction pixel and the enlargement correction pixel is assigned. Is assigned a value of 7, which is not used in gradation processing. By doing so, the value of the gradation processing result and the corrected value can be treated in the same manner. For the solid internal pixels that are not corrected and the uncorrected pixels, 0 is output to the selector 0814 as correction data.

FIG. 14 shows an example of a series of processes of ternarization determination processing, edge detection processing, and correction value generation processing. Figure 14-
An example of image data after color conversion processing is shown in A. here,
The size is 5x5 for simplicity. First, the threshold B = 24
4, threshold value W = 10, ternarization processing is performed, and high density pixels, halftone pixels, and low density pixels are classified. The classification result is shown in FIG. 14-B. For each pixel of this classification result, FIG.
The edge detection processing is performed by checking whether or not each pattern shown in FIG.
The pixels are classified into solid internal pixels and uncorrected pixels. At this time, 5x
Outside the range of 5, processing is performed assuming that there are low density pixels.
The edge detection result is shown in FIG. 14-C. With respect to this edge detection result, by a pattern as shown in FIG.
In addition, a correction value generation process is performed by detecting a pixel that is not a solid pixel inside the reduced correction pixel and is a solid internal pixel, and the detected pixel is converted into a reduced correction pixel. The correction value generation result is shown in FIG. 14-D. Based on this result, the value 7 is output for the enlargement correction pixel, the value 3 is output for the reduction correction pixel, the solid internal pixel, and the value 0 is output for the non-correction pixel.

The selector 0814 is a gradation processing unit 0810.
Data and correction value generation processing unit 0813
The output buffer 08 receives the correction data output from the output buffer 08 as the gradation data when the value of the correction data is 0, and the correction data as the print data when the value of the correction data is other than 0.
It outputs to 15. Also, according to the instruction of the control unit,
It is also possible to directly output the gradation data regardless of the value of the correction data.

The output buffer 0815 includes a control unit 0805.
Print head 0601 of the printer engine
The print head 0601 assigns the received data to each print element for each color, and each print element determines the amount of ink to be ejected based on the value of the received data. The ink is ejected onto the medium at the timing instructed by the printer engine for each recording element array corresponding to the above, and image recording is performed.

FIG. 15 shows an example of printed dot sizes corresponding to print data values. If the print data value is 0, no dots are printed.

FIGS. 16A and 16B are schematic diagrams of the original image and multi-valued data after color conversion.
C and FIG. 16-D are schematic diagrams of the gradation data and the correction data after the gradation processing, and FIG. 16-E is a schematic diagram of the print data combined by the selector. FIG. 17-A shows an image of the printed image on the medium when the edge smoothing corresponding to FIG. 16-C is not performed, and FIG. 17-B is the case where the edge smoothing corresponding to FIG. 16-E is performed. 3 shows an image of a printed image on the media of FIG. Dotted lines are virtual grid lines with a spacing of printing resolution d, and thick lines are ideal straight lines corresponding to the original image. As shown in FIG. 17-B, by performing the edge smoothing process,
Edges can be smoothed as compared with those without processing as shown in FIG. 17-A, which can improve image quality. Further, by printing the dots that have been subjected to the reduction correction for the adjacent pixels of the dots that have been subjected to the enlargement correction, it is possible to minimize unnecessary ink ejection to the medium.

[0023]

According to the present invention, it is possible to perform edge smoothing processing having the same sufficient effect regardless of the X direction and the Y direction in both a serial printer and a line printer. In an ink jet printer, it is possible to suppress unnecessary ink ejection and minimize the influence on the medium. Further, since the interpolation dots are not recorded, it is possible to minimize the spread of the print area with respect to the original image.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an edge smoothing method of the present invention.

FIG. 2 is a schematic diagram showing a printing mechanism of a serial type inkjet printer.

FIG. 3 is a diagram showing an example of nozzle arrangement of a recording head of a serial type inkjet printer.

FIG. 4 is a schematic diagram showing a conventional edge smoothing method.

FIG. 5 is a schematic diagram showing a conventional edge smoothing method.

FIG. 6 is a schematic diagram showing a printing mechanism of a line-type inkjet printer.

FIG. 7 is a diagram showing an example of nozzle arrangement of a recording head of a line type inkjet printer.

FIG. 8 is a control block diagram showing an embodiment of the present invention.

FIG. 9 is a flowchart showing an algorithm for classifying multivalued image data in the embodiment of the present invention.

FIG. 10 is a diagram illustrating a range of pixels to be referred to when performing pattern matching processing in the embodiment of the present invention.

FIG. 11 is a diagram illustrating a range of pixels to be referred to when performing pattern matching processing.

FIG. 12 is a diagram showing an example of a pattern for detecting edges and solid internal pixels in the embodiment of the present invention.

FIG. 13 is a diagram showing an example of a pattern for detecting solid internal pixels adjacent to enlargement correction pixels in the embodiment of the present invention.

FIG. 14 is a schematic diagram showing a series of processes of edge smoothing processing in the embodiment of the present invention.

FIG. 15 is a diagram showing the relationship between the size of a dot printed by a printing element and data in an example of the present invention.

FIG. 16 is a schematic diagram showing a process of generating data of recording pixels in the embodiment of the invention.

FIG. 17 is a diagram illustrating an effect of edge smoothing in the example of the present invention.

[Explanation of symbols]

0201: recording head, 0202: guide, 0203:
Recording medium, 0301: recording element, 0601: recording head, 0602: recording medium, 0603: cable, 060
4: Conveyor roller, 0605: Conveyor roller, 070
1: printing element array, 0702: printing element array, 0703: printing element array, 0704: printing element array, 0705: printing element, 0706: printing element, 0707: printing element, 070
8: recording element, 0801: printer, 0802: host, 0803: printer control device, 0804: printer engine, 0805: control unit, 0806: image processing unit,
0807: input buffer, 0808: storage device,
0809: color conversion processing unit, 0810: gradation processing unit, 08
11: ternarization determination processing unit, 0812: edge detection processing unit, 0813: correction value generation processing unit, 0814: selector, 0815: output buffer.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Keiji Kunimi             Hitachiko, 1060 Takeda, Hitachinaka City, Ibaraki Prefecture             Machine Co., Ltd. F-term (reference) 2C056 EA04 EC79 ED01                 2C262 AA02 AB13 BB10 BB38 DA03                 5C074 AA05 BB16 DD05 DD14 FF08                       HH02                 5C077 LL05 MP08 NN05 PP05 PP43                       PP55 PP68 PQ08 PQ20 RR06                       SS02 TT05

Claims (4)

[Claims] 1. An image recording apparatus capable of recording dots of different sizes when performing image recording, among the sizes of dots which can be recorded by the image recording apparatus, some of the dots having a larger size in order. Is not used in gradation reproduction, and edge smoothing processing is performed using dots that are larger than the largest size dot of the recording pixels used for gradation reproduction and that are not used in gradation reproduction. Image recording device to perform. 2. The pixel classification data for edge detection is generated from the multi-valued image data based on the pixel value, and the edge detection is performed by pattern matching processing using the pixel classification data to determine the size of the recording dot. The image recording apparatus according to claim 1, wherein a pixel to be corrected is detected. 3. The image according to claim 2, wherein when generating classification data of pixels for edge detection based on pixel values from multi-valued image data, classification data is generated by classifying into three types of pixels. Recording device. 4. The size of a recording dot around an edge pixel is corrected by pattern matching by using information of a pixel for correcting the size of a recording pixel.
The image recording apparatus described.