JPH08242360A - Image processing method and apparatus - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide an image processing method and device capable of converting a low-resolution input image into a high-quality, high-resolution output image. A switch 18 is controlled by a switch 14 so as to cut off the binarized information from the edge creating unit 13 when the average value of the surrounding pixels is close, and the edge information is not used in an image portion where an edge does not originally appear. Linear interpolation processing unit 1
Only output information from 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses input image information to
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image output device such as a printer that performs enlargement / magnification and output, and an image processing method and device that performs resolution conversion from low resolution information to high resolution information through communication between models having different resolutions.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed as a method for converting the resolution of input low resolution information into high resolution information. The proposed conventional method uses a target image type (for example, a multi-valued image having gradation information for each pixel,
The conversion method differs depending on the binary image binarized by the pseudo halftone, the binary image binarized by the fixed threshold value, the character image, etc.).

The image targeted by the present invention is a multivalued image such as a natural image having gradation information for each pixel. The conventional interpolation method is the closest to the interpolation point as shown in FIG. Depending on the closest interpolation method of arranging the same pixel value as the pixel or the distance of four points surrounding the interpolation points as shown in FIG. 8 (pixel values of four points are A, B, C and D), A co-linear interpolation method for determining the pixel value E by calculation is generally used.

E = (1-i) (1-j) A + i.multidot. (1-j) B +
j · (1−i) C + ijD (However, when the inter-pixel distance is 1, it is assumed that there is a distance i from A in the horizontal direction and j in the vertical direction. (i ≦ 1, j ≦
1))

[0005]

However, the above-mentioned conventional example has the following drawbacks. That is, FIG.
Although the method has the advantage that the configuration is simple, when the target image is used as a natural image or the like, the pixel value is determined for each block to be enlarged, so that the block is visually conspicuous and the image quality is improved. Has the disadvantage of being poor.

The method shown in FIG. 8 is a method which is generally well used for enlarging a natural image. With this method, the image quality is averaged and smoothed, but the edge part and the part where a sharp image quality is required have a blurred image quality. Furthermore, images scanned from maps,
In the case of a natural image including characters and the like, important information may not be transmitted to the recipient due to blurring due to interpolation.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an image processing method and apparatus capable of converting a low-resolution input image into a high-quality, high-resolution output image. .

[0008]

In order to achieve the above object, the image processing method of the present invention has the following steps. That is, it is an image processing method for converting the resolution of input image information from low resolution information to high resolution information, and is used when binarizing (N × M) pixels on high resolution corresponding to a target pixel on low resolution. A generation step of generating a binarization threshold value from a peripheral pixel of the pixel of interest; a binarization step of binarizing the (N × M) pixel by the binarization threshold value generated in the generation step; and the generation step. And a control step of controlling whether or not to output the binarization result in the binarization step in accordance with the comparison result between the binarization threshold value generated in step 1 and the average value of the peripheral pixels.

In order to achieve the above object, the image processing apparatus according to the present invention has the following configuration. That is, an image processing device for converting the resolution of input image information from low resolution information to high resolution information, which is used when binarizing (N × M) pixels on high resolution corresponding to a target pixel on low resolution. Generating means for generating a binarization threshold from peripheral pixels of the pixel of interest;
According to the binarization threshold generated by the generation means, the (N ×
M) Binarization means for binarizing the pixel, and the binarization result by the binarization means according to the comparison result of the binarization threshold value generated by the generation means and the average value of the peripheral pixels. Control means for controlling whether or not to output.

[0010]

In such a configuration, when the (N × M) pixels on the high resolution corresponding to the target pixel on the low resolution are binarized,
The binarization threshold value is generated from the peripheral pixels of the target pixel, the (N × M) pixels are binarized by the generated binarization threshold value, and the binarization threshold value is compared with the average value of the peripheral pixels. 2 above
It operates so as to control whether to output the binarization result in the digitization means.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described in detail below with reference to the drawings. The image processing apparatus of the present invention is effectively provided mainly in an image output apparatus such as a printer, but it may be built in as an application software in an image processing apparatus other than the image output apparatus or a host computer. .

FIG. 1 is a schematic block diagram showing the arrangement of an image processing apparatus according to this embodiment. In the figure, reference numeral 11 denotes a linear interpolation processing unit, which generates linear interpolation information of vertical N times and horizontal M times for low resolution information (for example, by linear interpolation processing by co-primary interpolation). An edge generator 13 generates edge information in order to eliminate blur due to image interpolation that occurs when the target pixel is linearly interpolated N × M times. The edge generator 13 will be described in more detail. A distribution ratio determination unit 12 determines an output balance between the generation information by the linear interpolation processing unit 11 and the edge information by the edge generation unit 13. In the present embodiment, the image information obtained by the linear interpolation processing unit 11 and the edge information obtained by the edge generation unit 13 are set to 15 and 1 according to the ratio determined by the distribution ratio determination unit 12.
It is distributed by 6 multipliers and 17 adders. Reference numeral 14 denotes a switcher, which compares reference pixels around the pixel of interest with a threshold value at the time of edge generation, disconnects 18 switches at the time of image processing without a flat image or a sharp edge close to it, and does not transmit edge information to the output. Give effect.

In the conventional method, the image information obtained by the linear interpolation processing unit 11 and the edge information obtained by the edge generation unit 13 are added to the multipliers 15 and 16 by the distribution ratio determination unit 12 under a certain ratio under any conditions. It was distributed by vessel 17. On the other hand, the present embodiment is characterized in that the output transmission of the edge information is forcibly cut off by the switch 14 and the switch 18 described above.

FIG. 2 is a block diagram of the edge generator 1 in this embodiment.
3 is a block diagram showing the configuration of FIG. In the figure, reference numeral 100 designates an input terminal to which low resolution image information as shown in FIG. This low resolution information is sent to the linear interpolation processing unit 101, and the pixels between the original samplings are filled by the linear interpolation (co-linear interpolation) processing, and the vertical N times horizontal and horizontal horizontal as shown in FIG. 4B. Interpolation information of M times is created. still,
The linear interpolation has been described in the conventional example shown in FIG. And a maximum / minimum value detection unit 102,
The pixel of interest of the low resolution image by the threshold value determining unit 103 and the binarizing unit 106 (in charge of the pixel E of FIG. 4A)
Edge information is generated for each block of interpolation information of N pixels × horizontal pixel centered at (corresponding to one pixel of low resolution, within a thick line in FIG. 4B).

Specifically, first, the maximum / minimum value detecting unit 1
02, the maximum value (MAX) within the window (in the dotted line in (a) shown in FIG. 4) of the pixels in the vicinity of the target pixel E of the low-resolution image.
Information / Minimum value (MIN) information is detected. MA detected
The X information / MIN information is sent to the threshold value determination unit 103,
The threshold value referred to when binarizing the block of the interpolation information centered on the pixel of interest E is determined. Further, this threshold value is output from the output terminal 104 and transferred to the switch 14 which is a characteristic part of this embodiment. In this embodiment, the threshold value (hereinafter referred to as “TH”) is determined by the following equation.

TH = (MAX + MIN) / 2 Next, the quantized representative value (MAX value.MIN) for each pixel position.
(Value) is sent to the binarization unit 106, and the linear interpolation processing unit 10
The interpolation information of the block centered on the target pixel E generated in 1 is binarized. Here, the binarization threshold value is compared with the interpolation pixel, and the binarization is performed by replacing the threshold value with the MAX value / MIN value.

FIG. 5 shows a threshold value T for determining how to output linear interpolation and edge information in the present embodiment.
It is a figure which shows the relationship of H and average value AV. Further, in the example shown in FIG. 5, for simplification of description, it is shown in a one-dimensional direction. In the figure, “◯” marks indicate sampling points on the low resolution, and “×” marks indicate pixels at interpolation points that interpolate between them. The circle marked in the center is the pixel of interest. In the figure, (a) shows the situation when there is a difference between TH and AV, and (b) shows the situation when there is a close difference between TH and AV. Here, assuming that the difference between TH and AV is X1 and X2, respectively, as is clear from the figure, the difference X2 is small in the flat image (b) including the peripheral pixels.

That is, in this embodiment, the edge information is transmitted to the output according to the distribution ratio determining unit 12 when there is a certain width such as the difference X1 and the result of the edge generating unit 13 is transmitted when the width is narrow like the difference X2. It is cut off by the switch 18 and controlled so as not to be transmitted to the output (see FIG. 1). The operation of the switch 14 at this time will be described with reference to FIG. FIG.
FIG. 3 is a block diagram showing the configuration of the switch 14 in the present embodiment. In the figure, 1001 is an input terminal for inputting low-resolution peripheral pixels, and 1002 is an output terminal 1 of the edge generation unit 13.
04 is an input terminal for inputting threshold data. 100
Reference numeral 3 is an average value calculation unit, which inputs reference pixel data from the input terminal 1001 and calculates an average value including the target pixel by internal calculation. A comparator 1004 compares the calculated average value with the threshold value input from the input terminal 1002. The difference X shown in FIG.
It has a threshold value for judging the difference result corresponding to 1, X2. If the image tends to be flatter as the value is expanded, the switch 1 is used so that the linear interpolation result is output as it is.
A signal for controlling 8 is output from the output terminal of 1005.
As a result, it is possible to prevent image deterioration in which noise in block units suddenly appears in the image flat portion.

[0019]

Other Embodiments Another embodiment of the present invention will be described below with reference to the drawings. FIG. 6 is a schematic block diagram showing the arrangement of an image processing apparatus according to another embodiment. In this embodiment, the distribution ratio determined by the distribution ratio determination unit 12 shown in FIG. 1 is a fixed value. In FIG. 6, a linear interpolation processing unit 11, an edge generation unit 13, a multiplier 1
5, 16 and the adder 17 have no difference from the control operation shown in the above-mentioned embodiment, and the description thereof will be omitted.

The fixed distribution ratio section 120, which is a feature of another embodiment, has a certain arbitrary value (single or plural) and multiplies by a constant ratio regardless of the characteristics of the input low resolution image. Multipliers 15 and 16 perform multiplication, and an adder 17 outputs a high-resolution image. The set value of the fixed allocation ratio unit 120 is experimentally determined. The other embodiment is not intended for an image having flat and sharp edges such as animation, but is effective as a light edge correction for a natural image in which gradation is important.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0022]

As described above, according to the present invention,
In the method of inferring and creating edge information from the input low resolution information, the problem that the gradation of the output image is lost and there is a tendency to become painterly is that the output of edge information is interrupted when a pixel signal changes slightly, This can be solved by making the information and edge information a fixed allocation ratio and eliminating excessive edge enhancement. Further, the fixed distribution ratio allows the distribution ratio calculated by the conventional calculation to be fixed, so that the processing speed can be shortened.

Although there is no restriction on the content of the input image, especially while valuing the gradation for the natural image,
In addition, it becomes possible to output a high-resolution image of high quality which has never been obtained by enabling appropriate contour correction.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing the configuration of an image processing apparatus in this embodiment.

FIG. 2 is a block diagram showing a configuration of an edge generation unit 13 in this embodiment.

FIG. 3 is a block diagram showing a configuration of a switching device 14 in this embodiment.

FIG. 4 is an explanatory diagram of an original image and a linear interpolation image.

FIG. 5 is a threshold value TH and an average value AV that determine how linear interpolation and edge information are reflected in the output in the present embodiment.
It is a figure which shows the relationship of.

FIG. 6 is a schematic block diagram showing the configuration of an image processing apparatus according to another embodiment.

FIG. 7 is a diagram showing a nearest neighbor interpolation method in a conventional example.

FIG. 8 is a diagram showing a bilinear interpolation method in a conventional example.

[Explanation of symbols]

 Reference Signs List 11 linear interpolation processing unit 12 distribution ratio determination unit 13 edge generation unit 14 switcher 15 multiplier 16 multiplier 17 adder 100 input terminal 101 linear interpolation processing unit 102 maximum and minimum value detection unit 103 threshold value determination unit 104 output terminal 106 Binarization section 107 Output terminal 120 Fixed allocation ratio section 1001 Input terminal 1002 Input terminal 1003 Average value calculation section 1004 Comparator 1005 Output terminal

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Norio Shimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kunio Imai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (5)

[Claims] 1. An image processing method for converting the resolution of input image information from low resolution information to high resolution information, which is (N × M) in high resolution corresponding to a target pixel in low resolution.
The generation step of generating a binarization threshold value for binarizing a pixel from the peripheral pixels of the pixel of interest, and the binarization threshold value generated in the generation step (N ×
M) A binarization step of binarizing the pixel, and a binarization result of the binarization step according to a comparison result of the binarization threshold value generated in the generation step and an average value of the peripheral pixels. And a control step for controlling whether or not to output the image processing method. 2. The image processing method according to claim 1, wherein the control step controls not to output the binarization result when the comparison result between the binarization threshold value and the average value is small. . 3. An image processing apparatus for converting the resolution of input image information from low resolution information to high resolution information, wherein (N × M) high resolution corresponding to a target pixel of low resolution.
The binarization threshold for binarizing the pixel is generated from the peripheral pixels of the pixel of interest, and the binarization threshold generated by the generator is used to generate the binarization threshold value (N ×
M) Binarization means for binarizing the pixel, and the binarization result by the binarization means according to the comparison result of the binarization threshold value generated by the generation means and the average value of the peripheral pixels. An image processing apparatus comprising: a control unit that controls whether or not to output. 4. The image processing apparatus according to claim 3, wherein the control unit controls not to output the binarization result when the comparison result between the binarization threshold value and the average value is small. . 5. An image processing apparatus having an interpolation processing means for converting the resolution of input image information from low resolution information to high resolution information, the high resolution (N × M) corresponding to a target pixel of low resolution.
A binarization unit that binarizes the pixel, an interpolation result by the interpolation processing unit, and a fixed distribution ratio output unit that sets an output distribution ratio of the binarized result by the binarization unit to a fixed value. An image processing device characterized by the above.