JPH099038A - Picture processor and picture processing method - Google Patents

Abstract

PURPOSE: To provide a picture processor and the method, by which the picture of high resolution can be formed at high speed without raising cost and enlarging the scale of processor constitution. CONSTITUTION: The various picture processings of black generation, color correction and a spatial filter processing, etc., are executed on the multilevel picture signal of 400DPI to a γ conversion part 13, and the signal is converted into that of the high resolution of 600DPI in a resolution conversion part 14. Then, the signal is binarized by a pseudo half-tone processing in a half-tone processing part 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and a method thereof, for example, an image processing apparatus and a method thereof for forming a high resolution image.

[0002]

2. Description of the Related Art Conventional image processing apparatuses such as copiers, printers, and facsimile machines that handle digital image signals generally read a document image at a resolution of about 400 dots / inch (DPI) to form an image. It was target. However, with the development of the image processing device,
In recent image processing apparatuses, 600 DPI, 720
It is possible to form images with high resolution such as DPI and 1200 DPI, and further higher resolution is progressing.

[0003]

However, the higher resolution of the formed image means that the amount of data to be processed increases, and therefore the processing speed in image reading and image processing is high. Both are required to be converted.

For example, the resolution of the image to be formed is 400D.
Considering the case of increasing from PI to 600 DPI,
The total data amount is 2.25 times, and therefore, in order to achieve the same processing speed, the processing speed in image reading and image processing also needs to be 2.25 times.

Also, in the case of a spatial filter which performs a two-dimensional processing, if it is constituted by a unit of 5 × 5 pixels at 400 DPI, a wide area processing of 7 × 7 pixels or more is required to obtain the same performance. Becomes Therefore, the circuit scale of the spatial filter processing unit is remarkably increased, which causes a cost increase. Similarly, a delay memory for synchronizing the processing of each pixel is required to be 2.25 times, which also inevitably increases the scale and cost of the device.

The present invention has been made to solve the above-mentioned problems, and an image processing apparatus capable of forming a high-resolution image at high speed without inviting an increase in cost and an increase in the size of the apparatus, and The purpose is to provide the method.

[0007]

As one means for achieving the above object, the image processing apparatus of the present invention has the following configuration.

That is, input means for inputting an N-valued image signal of a first resolution, image processing means for performing two-dimensional image processing on the N-valued image signal of the first resolution, and the image processing. Resolution conversion means for converting the N-valued signal thus converted into an N-valued image signal having a second resolution higher than the first resolution; and the image signal after the resolution conversion is converted into an M (M <N) -valued image signal. It is characterized in that it has an M-value converting means and an output means for outputting the M-value image signal.

For example, the image processing means is characterized in that the N-valued image signal is divided into image areas corresponding to image characteristics, and appropriate image processing is performed for each image area.

For example, the image processing includes black generation processing, color correction processing, spatial filter processing, and γ conversion processing.

For example, the input means inputs the multi-valued image signal by reading the original image at the first resolution.

For example, the input means inputs an N-valued image signal from a connected external device.

Further, the apparatus further comprises M-value input means for inputting an M-value image signal from a connected external device, and the output means outputs the M-value image signal input by the M-value input means. And

For example, the output means outputs the M-value image signal on a recording medium.

As one method for achieving the above-mentioned object, the image processing method of the present invention includes the following steps.

That is, a multi-valued image signal of a first resolution is input, two-dimensional image processing is performed on the N-valued image signal of the first resolution, and the multi-valued signal subjected to the image processing is aforesaid. Converting into a multi-valued image signal having a second resolution higher than the first resolution, converting the image signal after the resolution conversion into an M (M <N) valued image signal, and outputting the M valued image signal. Is characterized by.

[0017]

With the above configuration, N-valued image processing is performed on low-resolution image data, the processing result is converted to high-resolution, and an M (M <N) value recording signal is generated. The peculiar function and effect that N-valued image processing can be performed on a relatively small amount of data can be obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of a digital electrophotographic color printer which is an embodiment of the image forming apparatus according to the present invention.

In FIG. 1, the recording paper is held on the outer periphery of the transfer drum 120 by a paper feed roller 118 from a paper feed section 117.

The photosensitive drum 100 is uniformly charged to a predetermined polarity by the charger 112, is output from the laser unit 110, and is exposed to the laser beam light L through the reflection mirror 111, so that the latent image is latently printed on the photosensitive drum 100 for each color. An image is formed. The latent image formed on the photosensitive drum 100 is visualized by each color developing device Dy, Dm, Dc, Dk,
A color image is formed by being transferred a plurality of times onto the recording paper on the outer periphery of the transfer drum 120. After that, the recording paper is the transfer drum 1.
The color image that has been separated and transferred by the separation claw 114 from 20 is fixed by the fixing unit 115, and the discharge tray 1
It is discharged to 16. A cleaner 113 removes each color toner remaining on the surface of the photosensitive drum 100.

A control unit 119 performs various image processing on image data from a scanner unit (not shown) and controls the above-mentioned units.

An operation unit 300 such as an operation panel is used for inputting an instruction from the operator and notifying the operator of the status.

Next, the detailed structure of the above-mentioned control unit 119 will be described with reference to FIG.

First, the sensor 2 including a solid-state image pickup device such as a CCD reads an original image as an RGB signal at a resolution of 400 DPI, and a shading correction unit 3 uniformly corrects unevenness of each solid-state image pickup device, and a color space conversion unit. At 4, the color of the sensor filter is corrected. Then, the logarithmic conversion unit 8 converts the luminance RGB signal into a density CMY signal, and then the black generation unit 9 generates a black signal (K) based on the minimum value of the CMY signal. The density signals of these four colors of CMYK are color-corrected by the color correction unit 10 according to the characteristics of the color material. Then, after being scaled by the scaling unit 11 as necessary, the spatial filter unit 12 corrects the sharpness and removes moire. Then, the γ conversion unit 13 performs density correction.

On the other hand, reference numeral 6 denotes an image area separation unit, which determines an image attribute in order to perform optimum processing according to the image attribute in each processing unit described above. This image area determination is particularly effective for sharply recording a black character portion in an image with a single black color. An image editing unit 7 performs various image editing processes such as trimming, masking, moving and rotating, and gives an instruction to each processing unit. The processing by the image area separation unit 6 and the image edit processing unit 7 will be described later.

The YMCK image signal whose density has been corrected by the gamma conversion unit 13 has a resolution conversion unit 14 if necessary.
In step 2, resolution conversion is performed, and in the halftone processing unit 15, multi-pseudo halftone processing is performed, thereby binarizing. Then, the binarized image signal is input to the recording unit 16 and output to the laser unit 110 as a recording signal for each color.

In FIG. 2, each of the components described above has a CPU 1
It is totally controlled by 7. 18 is a ROM,
It holds a control program, fixed variables, and the like that are referenced by the CPU 17. 19 is a RAM, and the CPU 17
Used as a work area.

In addition, in each structure of FIG. 2, the resolution of the image data processed in the structure (400 DPI /
600 DPI) is also shown.

In this embodiment, the processing by the image area separation unit 6 and the image editing unit 7 is performed on a 400-DPI multivalued image signal. Therefore, in the image processing apparatus of this embodiment, binary recording is finally performed with a high resolution of 600 DPI, but when multi-value recording with a low resolution of 400 DPI is performed, for example, the output from the γ conversion unit 13 described above. The signal may be output as it is to the multilevel recording device.

In this embodiment, an image is formed after converting a low resolution image signal into a high resolution. Therefore, γ
The 400 DPI output signal from the conversion unit 13 is two-dimensionally converted into 600 DPI at the input to the resolution conversion unit 14, for example, 600 DPI. Then, in the halftone processing unit 15, the multi-valued image signal of 600 DPI is binarized by a pseudo halftone process such as a dither method or an error diffusion method. Note that the resolution conversion processing in the resolution conversion unit 14 may be realized by any method such as normal linear interpolation or sync interpolation as long as it is processing for two-dimensional multivalued data.

As described above, when high-resolution output is performed in this embodiment, only the resolution conversion section 14 and the halftone processing section 15 handle high-resolution data of 600 DPI. Therefore, the resolution conversion unit 14 and the halftone processing unit 15 are required to have a processing speed that is approximately 2.25 times as high as that in the case of 400 DPI image signal processing.
Therefore, according to the high resolution processing of this embodiment, the cost increase can be minimized.

That is, in the present embodiment, the so-called multi-valued image signal is subjected to two-dimensional processing on a low-resolution image,
By reducing the processing for high resolution images as much as possible,
It is characterized in that high-resolution binary recording is realized at low cost.

Further, in FIG. 2, the halftone processing section 15 is an external I / F section 1 for inputting a binary image signal from the outside.
The image signal input to the external I / F unit 1 is so-called vector information such as a document and a figure created by an external computer or the like, and is already converted into binary information of 600 DPI in a computer driver or the like. It has been converted. Similarly, the color space conversion unit 4 also includes an external I / F unit 5 and is connected to an external computer or the like.
A multi-value image signal of 00 DPI is handled. For example, the CCD 2 of the image processing apparatus reads an original image as a multi-valued image signal of 400 DPI and outputs the multi-valued image signal to the computer in the image section, or the multi-valued 400 DPI read by another scanner and held in the computer. An image signal (so-called raster image) is input.

Therefore, when a so-called raster type multi-valued image signal input from the outside is recorded / reproduced, the image signal is subjected to the final resolution (600DP) in the image processing apparatus.
By inputting with a resolution (400 DPI) lower than I), performing image processing, and finally converting into high resolution, it is possible to suppress an increase in data transfer time and processing time. The vector information can be treated as high resolution binary information. Therefore, a higher quality image can be formed at high speed.

Next, the image area separating section 6 in this embodiment will be described in detail.

In the image area separation unit 6, the color space conversion unit 4
By inputting an RGB image signal and detecting the attribute of the image, the image is separated into each image area. Here, in order to detect the image attribute, first, information such as "density level distribution", "edge amount", "edge distribution", etc. is detected from the image signal in the vicinity of the pixel of interest. And 1) the change of microscopic density level is small in continuous halftone,
Large for text / line drawings.

2) The edge amount increases in the order of continuous halftone, halftone dot, and character / line drawing.

3) The distribution of edges is discrete in halftone dots and continuous in characters / line drawings. Based on this feature, it is possible to distinguish between three types of "character / line drawing", "halftone dot", and "continuous halftone".

That is, in this embodiment, the image area is separated into three types of "character / line drawing", "halftone dot" and "continuous halftone". It should be noted that this separation may be performed based on only one of the features described in 1) to 3) above, or a combination of a plurality of features may be referred to. Moreover, you may make it refer to another feature-value. In the present embodiment, it is sufficient that each pixel can be separated into the above three types of attributes.

The image area separating section 6 also determines a black character / line drawing. For that purpose, black is determined from the color signals of RGB three colors. Then, by referring to the image area defined as the character / line drawing portion in the above-described image area separation,
The black character / line drawing part can be identified.

As described above, that is, in the image area separating unit 6, each pixel is defined as "black character / line drawing part", "color character other than black /
The image is divided into four types of image areas: line drawing area, halftone area, and continuous halftone area.

Based on the image area separation result in the image area separation unit 6, the image editing unit 7 sends an image to the black generation unit 9, the color correction unit 10, the spatial filter unit 12, and the γ conversion unit 13 at a predetermined timing. Output editing instructions. Then, each processing unit processes each pixel based on the image editing instruction. That is, the processing in the black generation unit 9, the color correction unit 10, the spatial filter unit 12, and the γ conversion unit 13 is performed according to the image area.

FIG. 3 shows the adaptive processing in the processing section for each image area. The adaptive processing in each image area will be described below with reference to FIG.

In the case of “black character / line drawing part”, the black generation part 9 emphasizes black by multiplying the black signal K by α (1 <α), and the color correction part 10 makes it close to a single black color. That is, in the normal color correction processing in the color correction unit 10, for a color close to a single black color, for example, K = 255,
A darker color is expressed by performing so-called four-color multiplication about 2.5 times (K + C + M + Y = 255 × 2.5) so that C = M = Y = 128. However, for the black character / line drawing portion, the coefficient of the matrix calculation in the color correction is switched so that the CMY recording signal is not generated as much as possible. Further, the spatial filter unit 12 selects a coefficient that enhances the spatial frequency component of 2 lines / mm to 3 lines / mm with respect to the black signal, which exhibits a so-called edge emphasis effect. Further, the γ conversion unit 13 performs density correction such that only the black signal is recorded darker and the other color signals are suppressed.

In the case of "color character / line drawing part", the black generation 9 and the color correction 10 perform normal processing. In the spatial filter unit 12, 2 lines / mm to 3 lines /
A coefficient that exhibits a so-called edge enhancement effect that enhances the spatial frequency component of mm is selected. Further, the γ-conversion unit 13 performs density correction such that only the color signals (C, M, Y) other than black are printed darker.

In the case of “halftone dot part”, the black generation part 9, the color correction part 10, and the γ conversion part 13 perform normal processing, and the spatial filter part 12 performs 4 lines / mm or more for all signals. A coefficient that exhibits a so-called wide-range cutoff effect of suppressing the spatial frequency component of is selected.

In the case of “continuous halftone part”, the black generation part 9, the color correction part 10, the spatial filter part 12, γ
Normal processing is performed in all the conversion units 13.

By the above processing, a CMYK multi-valued signal subjected to the most appropriate image processing for each image area is generated as an image signal input to the resolution conversion section 14. Therefore, it goes without saying that even if this image signal is converted to high resolution by the resolution conversion unit 14 and binarized by the halftone processing unit 15, a high-quality reproduced image with image area separation can be obtained. .

As described above, according to this embodiment, in the image processing apparatus for converting the low-resolution multi-valued image data into the high-resolution binary data and forming the image, the low-resolution multi-valued image data is processed. By performing adaptive processing for each image area characteristic and converting to high resolution after all the image processing apparatuses are completed, processing up to the resolution conversion front stage can be performed with a small amount of data. Therefore, it is possible to perform high-resolution image formation at high speed without increasing the scale of the apparatus configuration and increasing the cost.

In this embodiment, an example in which multi-valued image data of 400 DPI is processed and then binary recording is performed at 600 DPI has been described. However, the present invention performs this resolution conversion (400
DPI / 600DPI), but is not limited to, for example, 300DPI / 600DPI, 200DPI / 4
00DPI, 300DPI / 720DPI, 400DP
It is applicable to any combination of resolutions such as I / 1200 DPI. Alternatively, main scanning direction 400D
PI, 600 DPI for both main and sub scanning from 600 DPI in the sub-scanning direction
As described above, the effect is 1 / 1.5 of this embodiment if either one of them has a low resolution in the scanning direction, and therefore, the cost is 1.5 times that of the case where all the resolutions are high. There is a speed advantage.

The scaling process in the scaling unit 11 can be replaced by the resolution conversion process in the resolution conversion unit 14.

Although the present embodiment has been described with respect to an example in which binary printing is performed, it can be applied to a printer capable of printing with an M value smaller than the input N value.

Further, the printer is not limited to the electrophotographic system,
It may be a bubble jet type ink jet printer or the like.

The present invention may be applied to a system composed of a plurality of devices such as a printer engine and a printer, or to an apparatus composed of a single device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus.

[0056]

As described above, according to the present invention, multi-valued image processing is performed on low-resolution image data, the processing result is converted to high resolution, and a binary recording signal is generated. As a result, multivalued image processing can be performed on a relatively small amount of data. Therefore, it is possible to reduce the amount of memory required for multi-valued image processing and to increase the processing speed, that is, it is possible to perform high-resolution image formation at high speed with an inexpensive configuration.

[0057]

[Brief description of drawings]

FIG. 1 is a side sectional view of an image processing apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of a control unit 119 in this embodiment.

FIG. 3 is a diagram showing image processing for each image area in the present embodiment.

[Explanation of symbols]

 2 CCD 3 shading correction unit 4 color space conversion unit 1, 5 external interface 6 image area separation unit 7 image editing unit 8 logarithmic conversion unit 9 black generation unit 10 color correction unit 11 scaling unit 12 spatial filter unit 13 γ conversion unit 14 Resolution conversion unit 15 Halftone processing unit 16 Recording unit

Claims (8)

[Claims] 1. An input unit for inputting an N-valued image signal of a first resolution, an image processing unit for performing two-dimensional image processing on the N-valued image signal of the first resolution, and the image processing. Resolution conversion means for converting the N-valued signal thus converted into an N-valued image signal having a second resolution higher than the first resolution; and converting the resolution-converted image signal into an M (M <N) -valued image signal. An image processing apparatus comprising: an M-value converting unit that outputs the M-value image signal; and an output unit that outputs the M-value image signal. 2. The image processing apparatus according to claim 1, wherein the image processing unit separates the N-valued image signal into image areas according to image characteristics, and performs appropriate image processing for each image area. Processing equipment. 3. The image processing apparatus according to claim 1, wherein the image processing includes black generation processing, color correction processing, spatial filter processing, and γ conversion processing. 4. The image processing apparatus according to claim 1, wherein the input unit inputs a multi-valued image signal by reading an original image at the first resolution. 5. The image processing apparatus according to claim 1, wherein the input unit inputs an N-valued image signal from a connected external device. 6. The apparatus further comprises M-value input means for inputting an M-value image signal from a connected external device, wherein the output means is M-value input by the M-value input means.
The image processing apparatus according to claim 1, which outputs a value image signal. 7. The image processing apparatus according to claim 1, wherein the output means outputs the M-value image signal on a recording medium. 8. A multi-valued image signal having a first resolution is input, two-dimensional image processing is performed on the N-valued image signal having the first resolution, and the image-processed multi-valued signal is obtained. Converting into a multi-valued image signal having a second resolution higher than the first resolution, converting the image signal after the resolution conversion into an M (M <N) value image signal, and outputting the M value image signal An image processing method characterized by: