JPH10126610A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow an image processor to conduct high image quantity smooth magnification processing with higher precision and capable of multi-value output in the case of using a multi-value output device. SOLUTION: A smoothing magnification matching section 4 scans sequentially a received binary image and discriminates whether or not a specific area around a noted picture element is in matching with any of a plurality of jaggy patterns stored in advance in a pattern ROM 5. When the specific area is in matching with a detected pattern, the matching section 4 provides outputs of a jaggy correction high resolution multi-value pixel pattern corresponding to the detected pattern and a triangle wave selection signal S. A SEL 8 selects any triangle wave among outputs from triangle wave generators 6a-6c that generate triangle wave signals A, B, C. A comparator 9 provide a laser control signal at a high level when analog data converted by a D/A converter 7 are higher than the selected triangle wave signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of increasing the resolution of low-resolution binary image data represented by a facsimile and using an output device such as a digital copying machine or a laser printer.
The present invention relates to an image processing device that outputs with high image quality.

[0002]

2. Description of the Related Art In recent years, there have been proposed various image processing apparatuses for improving the image quality by increasing the resolution of a low-resolution binary image such as a facsimile, and outputting the image from a digital copying machine, a laser printer or the like. One of these techniques is a smoothing enlargement technique. Smoothing enlargement is a technology that smoothly converts (enlarges) the resolution of images composed of straight lines and curves such as characters and line drawings without jaggies, and has conventionally received facsimile images and increased the resolution. It has been often used for output.

A facsimile is often transmitted and received at one of the following three resolutions. That is, assuming that the main scanning direction × the sub-scanning direction, 8 × 3.85 dots / mm 8 × 7.7 dots / mm 16 × 15.4 dots / mm

Images received at these three resolutions are:
For example, in the case of outputting with a high-resolution device such as a 400 dpi (dot / inch) printer, it is necessary to enlarge the pixel density as much as it becomes smaller. When enlarging an image,
Resolution conversion (enlargement) may be performed at an accurate magnification, but resolution conversion of a received image using the following magnification is generally performed because conversion at an approximate magnification does not substantially affect the resolution. . , A resolution of 2 in the main scanning direction
If the resolution is 2 times, 4 times in the sub-scanning direction, the resolution is 2 times in the main scanning direction, the resolution is 2 times in the sub-scanning direction, and the resolution is 1 time in the main scanning direction and 1 time in the sub-scanning direction. Equivalent to not expanding).

[0005] In the prior art, enlargement processing was initially performed using a simple interpolation method. However, the simple interpolation method has a disadvantage that jaggies occur in a character portion and a line drawing portion. Smoothing enlargement processing performs smooth enlargement processing while correcting this jaggy. FIG. 10 is a conceptual diagram for explaining smoothing enlargement by a conventional image processing apparatus. 10A is an image before enlargement, FIG. 10B is an image simply enlarged by 2 times in the main scanning direction and 4 times in the sub-scanning direction, and FIG. An image is shown when the image is enlarged twice in the scanning direction and four times in the sub-scanning direction. That is,
As shown in FIG. 10C, the image shown in FIG. 10A is enlarged while smoothly correcting a step (jaggy) as shown in FIG. 10C.

The conventional smoothing expansion method will be briefly described. Here, FIG. 11 shows that 8 × 3.85 dots / m
FIG. 3 is a conceptual diagram for explaining a case where an m image is converted into 400 dpi, that is, a case where the image is doubled in the main scanning direction and quadrupled in the sub-scanning direction. In other words, each pixel of the input image having a resolution of 8 × 3.85 dots / mm is 2 × 4
Is converted to 8 pixels. Specifically, jaggies in the input (received) image are detected, and if detected,
A jaggy-corrected 2 × 4 pixel is output, and if no jaggy is detected (if it is not a jaggy location),
2x without jaggy correction equivalent to simple enlargement processing
Outputs 4 pixels.

First, input binary pixels are sequentially scanned,
A specific area (13 × 7 pixels in this case) centering on the target pixel is set, and it is detected whether or not the set area matches a jagged pattern stored in advance. A jaggy pattern having a long cycle, a short cycle, and a plurality of jaggy patterns are prepared. The example shown in FIG. 11 is an example of detecting a jaggy pattern having a cycle in which one black pixel shifts in the sub-scanning direction after seven black pixels continue in the main scanning direction. If the detected pattern is coincident with the detected pattern, the enlarged jaggy correction 2 × 4 pixels corresponding to the detected pattern are output. On the other hand, if they do not match, 2 × 4 pixels equivalent to simple enlargement are output.

The above-mentioned method of preparing a jaggy detection pattern and a jaggy correction output pixel pattern in advance and performing smoothing enlargement is described in, for example, "" Higher Image Quality by Smoothing Facsimile Received Image ", 1991, Image Proceedings of IEICE Annual Conference 18, pp. 69-72]. Further, instead of using the above-described detection pattern, a technique of performing a logical operation using pixels around the processing pixel to detect jaggies is also disclosed in Japanese Patent Application Laid-Open No. 2-9268.

[0009]

However, the above-mentioned conventional image processing apparatus is premised on binary output. Also, regarding the output device, print reproducibility is not very good, and if we look at it in more detail,
There is a problem that the jaggy correction is not completely performed and a wavy jaggy is generated. This is because the output device is a binary output.

On the other hand, in a high-performance multi-value and high-resolution output device represented by a recent digital copying machine, print reproducibility is improved and high-definition output is possible. For example, as shown in FIG. 12, multi-value digital image data is converted into an analog signal using a D / A converter 1, and the converted analog signal is compared with a reference triangular wave signal from a triangular wave generator 2 by a comparator 3. In addition, a halftone image can be satisfactorily output using a pulse width modulation (PWM) method for controlling a laser beam.

FIG. 13 shows the above-described D when the xerography (electrophotography) technique of the image writing method in which the laser is turned on during the period in which the toner adheres to the paper is used.
FIG. 3 is a conceptual diagram schematically showing waveforms at respective points of an output of a / A converter 1, an output of a triangular wave generator 2, and an output of a comparator 3. The comparator 3 compares the analogized image signal with the reference triangular wave, and turns on the laser beam only in a portion where the level of the image signal is higher than the triangular wave.

The digital copying machine is provided with an external interface in addition to a copying function, and is provided with functions of a printer and a facsimile. In a conventional laser printer or the like, a binary image is simply output. Therefore, the halftone section transmits the printer data after performing pseudo halftone processing by an error diffusion method, a dither method, or the like. In a multifunction machine to which a copying machine is applied, it is possible to directly handle multi-valued data. However, conventional digital copiers cannot cope with various jaggies of an input image, and depending on the occurrence of jaggies, there is a problem that jaggies are not completely corrected and wavy jaggies occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an image processing apparatus capable of performing high-quality smoothing enlargement processing capable of outputting higher definition and multi-values.

[0014]

In order to solve the above-mentioned problems, according to the present invention, an edge shape pattern storage means for storing a plurality of edge shape patterns for a pixel of interest and an edge shape pattern storage means for storing a plurality of edge shape patterns. Multi-valued pixel pattern storage means for storing a high-resolution multi-valued pixel pattern for performing a smoothing process by multi-valued pixel output corresponding to the edge shape pattern
An edge shape pattern determining unit for determining an edge shape pattern for the pixel of interest from a plurality of edge shape patterns stored in the edge shape pattern storage unit; and an edge determined by the edge shape pattern determining unit. And a multi-valued pixel pattern selecting means for selecting a specific multi-valued pixel pattern from the high-resolution multi-valued pixel patterns stored in the multi-valued pixel pattern storing means based on the shape pattern. I do.

According to the present invention, the edge shape pattern determining means determines the edge shape pattern for the pixel of interest from the plurality of edge shape patterns stored in the edge shape pattern storage means for the input binary image. . The multi-valued pixel pattern selecting means is configured to select a specific multi-valued pixel pattern from the high-resolution multi-valued pixel patterns stored in the multi-valued pixel pattern storing means based on the edge shape pattern determined by the edge shape pattern determining means. Select Therefore, if a multi-valued pixel pattern that minimizes jaggies is set in accordance with the edge shape of the pixel of interest, smooth reproduction without print cracks at the edges, especially when outputting characters and line drawings, is possible. Become. Also,
Smooth reproduction of the above-described multi-valued image can be performed. Also,
By performing smoothing using multi-value data, it is possible to perform pixel printing in more detail.

[0016]

Embodiments of the present invention will now be described with reference to the drawings.

A. Configuration of Embodiment A-1. First, data used in the image processing apparatus according to the present embodiment will be described. Basically, black and white binary data such as a facsimile is targeted. For example, "red (R), green (G), blue (B)", "yellow (Y), magenta (M), cyan" (C), “lightness (L ^* ), hue (H ^* ), saturation (C ^* )”, and “L ^* a ^* b ^* ”. In the case of color image data, one pixel data is generally represented by a plurality of components. In this case, if the image data of each component is binary data, the following embodiment can be applied to each component as it is.

A-2. Configuration of Image Processing Apparatus FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus according to an embodiment of the present invention. In the figure, a smoothing expansion matching section 4 is input using a plurality of jaggy detection patterns stored in advance in a jaggy detection pattern and a jaggy corrected high-resolution multi-valued pixel pattern ROM 5 (hereinafter simply referred to as a pattern ROM 5). A matching process is performed on the binary image. If the result of the matching process matches, a corresponding jaggy-corrected high-resolution multi-valued pixel pattern is output.
A process equivalent to that in which a normal high resolution process is performed is performed, and a preset multi-value data signal is output, and a triangular wave selection signal S is output. The jaggy corrected high resolution multi-valued pixel pattern is a signal including a multi-valued data signal and a triangular wave selection signal S (described later).

The triangular wave generators 6a, 6b and 6c respectively generate triangular waves having different phases or periods, and
8 The D / A converter 7 converts the multivalued data signal output from the smoothing expansion matching section 4 from digital data to analog data, and supplies it to one input terminal of the comparator 9. The SEL 8 selects one of the triangular waves generated by any of the triangular wave generators 6 a, 6 b, 6 c according to the triangular wave selection signal S from the smoothing expansion matching unit 4 described above, and supplies the selected input to the other input terminal of the comparator 9. Supply. Comparator 9
The analog data from the D / A converter 7 is compared with the triangular wave signal from the SEL 8, and a laser drive signal that is turned on when the analog data becomes larger than the triangular wave signal is output. In the triangular wave generators 6a to 6c,
The triangular waves generated in each case are set so that the multi-valued pixel pattern to be output (printed) is drawn to the edge side.

B. Next, an operation of the image processing apparatus according to the present embodiment will be described. First, 2 input from an image input device (not shown)
The value image is input to the smoothing expansion matching unit 4. As described above, the smoothing expansion matching unit 4
In, jaggy detection and jaggy correction high-resolution processing for an input image are performed. For example, the resolution of the input image is doubled in the main scanning direction and quadrupled in the sub-scanning direction.

The jaggy detection is performed using pixel-by-pixel pattern matching. First, the input binary image is sequentially scanned to set a specific area (13 × 7 pixels in the present embodiment) centered on the target pixel. Next, it is determined whether or not the set area matches a plurality of jaggy patterns stored in the pattern ROM 5 in advance. A plurality of jaggy patterns having long and short periods are prepared. Here, FIG. 2 shows four black pixels in the sub-scanning direction.
It is an example of a pattern for detecting a jaggy having a cycle in which one black pixel shifts in the main scanning direction after continuous pixels. If the pattern matches the detection pattern, the jaggy correction high-resolution multi-valued pixel pattern (2
× 4 pixels) and a triangular wave selection signal (signal for 2 × 4 pixels corresponding to each pixel of the multi-valued pixel pattern) S.
On the other hand, if they do not match, a 2 × 4 pixel and a triangular wave selection signal S equivalent to those obtained by simple enlargement are output. That is, when the target pixel of the input image is a black pixel, FIG.
The multi-valued pixel pattern and the triangular wave selection signal S shown in FIG. On the other hand, if the target pixel is a white pixel,
The multi-valued pixel pattern and the triangular wave selection signal S shown in FIG.
Is output.

Next, the jaggy-corrected high-resolution multivalued pixel pattern (2 × 4 pixels) output from the smoothing expansion matching section 4 is supplied to the D / A converter 7 as a multivalued data signal. The D / A converter 7 converts the input digital multi-level data signal into analog data. The analog data is further supplied to a comparator 9. Further, the triangular wave selection signal S, which is another output from the smoothing expansion matching unit 4, is represented by S
It is supplied to EL8. The SEL 8 selects one of the output signals (triangular wave) from the triangular wave generators 6 a to 6 c based on the input triangular wave selection signal S, and supplies the selected triangular wave signal to the comparator 9.

Each triangular wave signal A, supplied to SEL8,
B and C are as shown in FIG. As shown in FIG. 4, a triangular wave signal A synchronized with a signal for each pixel and having a cycle twice as long as the pixel clock, a triangular wave signal B obtained by inverting the phase of the triangular wave signal A, and a triangular wave signal C having the same cycle as the pixel clock To the respective triangular wave generators 6a, 6b, 6
c. Subsequently, the triangular wave signal selected by SEL8 is supplied to the comparator 9, and
The data is compared with the data converted into analog data by the / A converter 7 to generate a laser control signal.

Here, the effect of selecting a triangular wave signal and generating a laser control signal will be described. Assuming that the image data and the triangular wave selection signal S shown in FIG. 5 are input, the generated laser control signal is as shown in FIG. here,
It is assumed that the laser printer according to the present embodiment is a so-called image writing type printer in which toner adheres to a place where a laser is irradiated on a photoconductor and is output as a black image on paper. FIG. 7 is a conceptual diagram showing a case where a laser control signal is generated using a triangular wave signal C having the same cycle as the pixel clock without selecting the waveform of the image data shown in FIG. When FIG. 6 is compared with FIG. 7, in FIG. 7, the laser ON signal is divided into three, that is, three multi-valued pixels continuous in the main scanning direction have a print crack. As a result, the electron latent image actually generated on the photoconductor has a gap G as shown in FIG. On the other hand, in FIG. 6, the three multi-valued pixels are smoothly connected, and no print crack occurs.
Also, as shown in FIG. 8, no division occurs in the electronic latent image generated on the photoconductor.

Thus, the three triangular wave signals A, B, C
Is switched according to the situation, and a laser control signal is generated, so that when a character or a line image is output, smooth reproduction without print cracks particularly at an edge portion can be performed. Further, smooth reproduction of the above-described multi-valued image can be performed. In addition, by performing smoothing using multi-value data in this manner, it is possible to perform pixel printing in more detail. That is, the amount of smoothing can be adjusted according to the concentration,
Compared with the conventional smoothing of only binary data, processing with a high degree of freedom and extremely high image quality can be performed. In consideration of the above effects, the multi-value data and the triangular wave selection signal S, which are the outputs of the jaggy-corrected high-resolution multi-value pixel pattern, are designed and stored in the pattern ROM 5 in advance.

In the above-described embodiment, a case has been described in which a low-resolution image used in facsimile is multivalued smoothed and enlarged. However, the image used as an input image is not limited to this, and an image of another resolution may be used. May be used. Further, the detection pattern used for jaggy detection does not have to be composed of 13 × 7 pixels as shown in FIG. 2 and may have another size. Instead of using such a pattern, a logic circuit may be used. May be configured. Further, the triangular wave signals generated by the triangular wave generators 6a to 6c shown in FIG. 1 may not be those shown in FIG. 2, and other waveforms may be used to more effectively perform pixel pulling and the like. Good.

[0027]

As described above, according to the present invention, according to the present invention, the edge shape pattern determining means converts the input binary image from the plurality of edge shape patterns stored in the edge shape pattern storage means. The edge shape pattern for the pixel of interest is determined, and the high-resolution multi-valued pixel stored in the multi-valued pixel pattern storage unit is determined by the multi-valued pixel pattern selection unit based on the edge shape pattern determined by the edge shape pattern determination unit. Since a specific multi-valued pixel pattern is selected from the patterns, if a multi-valued pixel pattern that minimizes jaggies is set according to the edge shape of the pixel of interest, characters /
When a line image is output, smooth reproduction without print cracks can be realized, particularly at the edge portion, and by performing smoothing using multi-value data, there is an advantage that pixel printing can be performed more precisely.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram illustrating an example of a jaggy detection pattern.

FIG. 3 is a conceptual diagram showing a multi-valued pixel pattern and a triangular wave selection signal S.

FIG. 4 is a conceptual diagram showing signals including triangular wave signals A, B, and C.

FIG. 5 shows processed image data and a triangular wave selection signal S;
It is a conceptual diagram which shows an example of.

FIG. 6 is a conceptual diagram showing a process of generating a laser control signal.

FIG. 7 is a conceptual diagram showing a process of generating a laser control signal using a triangular wave C.

FIG. 8 is a conceptual diagram showing pixels generated on a photoconductor by the laser control signal shown in FIG.

FIG. 9 is a conceptual diagram showing pixels generated on a photoconductor by the laser control signal shown in FIG.

FIG. 10 is a conceptual diagram illustrating a smoothing enlargement process.

FIG. 11 is a conceptual diagram for explaining a conventional binary smoothing expansion process.

FIG. 12 is a block diagram illustrating a configuration of an image processing apparatus using a pulse width modulation method.

FIG. 13 is a conceptual diagram illustrating an operation of an image processing apparatus using a pulse width modulation method.

[Explanation of symbols]

4 Smoothing expansion matching section (edge shape pattern determining means, multi-valued pixel pattern selecting means) 5 pattern ROM (edge shape pattern storing means, multi-valued pixel pattern storing means) 6a-6c triangular wave generator 7 D / A converter 8 SEL 9 comparator

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 1/409 H04N 1/40 101D

Claims (3)

[Claims] 1. An edge shape pattern storage means for storing a plurality of edge shape patterns for a target pixel, and a smoothing process by multi-valued pixel output corresponding to the edge shape pattern stored in the edge shape pattern storage means. A multi-valued pixel pattern storage means for storing a high-resolution multi-valued pixel pattern to be applied; and a plurality of edge shape patterns stored in the edge shape pattern storage means for the input binary image. An edge shape pattern determining means for determining an edge shape pattern; and a high-resolution multi-valued pixel pattern stored in the multi-valued pixel pattern storage means based on the edge shape pattern determined by the edge shape pattern determining means. Pixel value selecting means for selecting a specific multivalued pixel pattern from An image processing apparatus comprising: 2. The high-resolution multi-valued pixel pattern draws a pixel to a multi-valued data signal for obtaining a pulse width-modulated binary signal by comparing with a pattern signal of a predetermined period and an edge side. 2. An image processing apparatus according to claim 1, wherein the image processing apparatus comprises a pixel pull-in signal for the image processing. 3. The method according to claim 1, wherein the pixel pull-in signal has a pixel cycle of two.
3. A binarized signal is obtained by performing a pulse width modulation based on one of the pair of pattern signals having a double cycle and having a phase inverted with respect to each other. Image processing device.