JPH04222067A - Method and device for processing image - Google Patents

Abstract

PURPOSE:To execute rapid, high quality and inexpensive image processing for image expanding processing. CONSTITUTION:In order to expand an inputted image of 2X2 picture elements into 3X3 picture elements, data X11, X12, X21, X22 for the 2X2 picture elements in the original image are directly used for four picture elements Y11, Y12, Y31, Y33 on the corners of the 3X3 picture elements, four picture elements Y12, Y21, Y23, Y32 excluding the center picture element Y22 out of residual five picture elements are obtained from a memory table previously formed by calculation by referring to the data of 12 picture elements in total combining the 2X2 original picture elements X11, X12, X21, X22 and eight picture elements X01, X02, X10, X13, X20, X23, X31, X32 vertically and horizontally adjacent to the original picture elements and the center picture element is found out from the peripheral eight picture elements Y11, Y12, Y13, Y21, Y23, Y31, Y32, Y33 based upon a logical expression.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and apparatus for performing enlargement processing by converting the pixel density of an input image.

0002

2. Description of the Related Art If a facsimile output device is used in common with a printer, it is advantageous in terms of cost and has excellent applicability. However, the resolution of fax is 8
dot/mm, and the printer resolution is generally 3
00 dpi, so in order to print an image received by facsimile on a printer at its original size, the original image must be enlarged 1.5 times. For this purpose, it is necessary to perform a process of enlarging and converting the original image from 2×2 pixels vertically and horizontally to 3×3 pixels vertically and horizontally.

By the way, as a method of enlarging 2×2 pixels to 3×3 pixels, conventionally used is a method of repeating the second pixel and the second line (FIG. 10). This method is simple and can be processed quickly, but the disadvantage is that the effect of increasing resolution is small. There is also a method of weighting based on the distance to the reference pixel, but this method has the disadvantage that the calculation is complicated and the processing takes time.

0004

[Problems to be Solved by the Invention] As mentioned above, when enlarging an input image using the conventional method, the processing speed is faster if a simple method is chosen, but the image quality is not improved; The disadvantage is that it takes a long time to process.

[0005] The present invention provides 8 dots/mm at 300 dpi.
An object of the present invention is to provide an image processing method and device that can perform high-speed processing for enlargement processing that converts pixel density, such as when converting to This is the purpose.

[0006]

[Means for Solving the Problems] The image processing method according to the present invention solves the above-mentioned problems and achieves the purpose with regard to the process of enlarging and converting an input image from 2x2 pixels to 3x3 pixels. The 4 pixels at the corners of the 3x3 pixel after conversion use the 2x2 pixel data of the original image as is, and the remaining 5 pixels, excluding the center pixel, are the same as the original pixels of the 2x2 pixel. It is characterized in that it is obtained by referring to data for a total of 12 pixels, including 8 pixels adjacent to each other in the upper, lower, left, and right directions, and that the central pixel is obtained from the surrounding 8 pixels that have just been obtained.

The image processing device according to the present invention includes a pixel input unit that takes in necessary pixels, a memory table that stores calculation results, a memory reference unit that uses this memory table, and a center pixel of 3×3 pixels. It consists of a central pixel calculation section that calculates the center pixel, and a pixel output section that outputs the processing results.

[0008]

[Operation] In the image processing method of the present invention, in order to enlarge 2x2 pixels to 3x3 pixels, 2x2 pixels are expanded to 3x3 pixels.
It is used as is for the 4 pixels at the corner of 3 pixels, and the 4 pixels between the 4 pixels at the corner of 3 x 3 pixels are referred to as 2 x 2 pixels and the 8 pixels adjacent to them vertically and horizontally to ensure continuity of the line segment. The center pixel of the 3×3 pixels is determined from the 8 pixels surrounding the 3×3 pixels determined above.

Further, in the image processing device of the present invention, in the pixel input section, pixels of a portion of the raster image to be subjected to enlargement conversion processing are extracted in units of 2×2 pixels, and
Total of 8 pixels adjacent to the top, bottom, left and right of ×2 pixels is 1
Two pixels are taken out. The memory reference section refers to the memory table and selects 3 pixels from the 12 pixels taken out at the pixel input section.
Find the 4 pixels between the 4 corner pixels among the ×3 pixels. Furthermore, in the center pixel calculation unit, the center pixel of the 3×3 pixels is calculated from 8 pixels around the 3×3 pixels calculated above, and a total of 9 pixels are output from the pixel output unit.

0010

[Embodiment] First, an embodiment of the image processing method of the present invention will be described. Figure 1 (a) and (b) show the pixels before conversion (
A) and the converted pixel (b) are shown. X11 in Figure 1(a)
, X12, =1,2,3
), the surrounding 8 pixels (X01
,X02,X10,X20,X13,X23,X31,
A total of 12 pixels including X32) are referred to.

[0011] The four corners of 3×3 pixels after conversion are 2
Copy ×2 pixels as is. That is, the following equation is obtained.

0012

[Math. 1] Y11=X11, Y13=X12, Y31=X21, Y33=X22,
(1) Next, the middle four pixels (Y12, Y21, Y23, Y32) on each side of 3×3 pixels are shown in Figure 2(a).
, In order to ensure the continuity of the line segment as shown in (b),
If the pixels on both sides of the pixel are black, the pixel is also treated as a black pixel. Further, in order to ensure continuity of line segments even in the cases shown in FIGS. 3A and 3B, for example, when X01 and X12 are black pixels, Y12 is also set as a black pixel. This is X02
The same applies to X11. By applying the above to the other three pixels, the following equation is obtained.

[0013]

[Math. 2] Y12=(X11∩X12)∪(X01∩X1
2)∪(X02∩X11), Y21=(X11
∩X21)∪(X10∩X21)∪(X20∩X11)
, Y23=(X12∩X22)∪(X13∩X
22)∪(X23∩X12), Y32=(X2
1∩X22)∪(X31∩X22)∪(X21∩X32
), (2) Finally, the center pixel Y of 3×3 pixels
22 is also treated as a black pixel when two pixels located at point-symmetrical positions such as Y11 and Y33 and Y12 and Y32 are both black pixels for the same reason as in the above case. That is, the following equation is obtained.

[0014]

[Math. 3] Y22=(Y11∩Y33)∪(Y13∩Y3
1)∪ (Y12∩U32)∪(Y
21∩Y23) (3) Above formula (1) ~
According to equation (3), a 2×2 pixel can be enlarged and converted into a 3×3 pixel by referring to the surrounding 8 pixels.

Next, an embodiment of an image processing apparatus for carrying out the image processing method of the present invention will be described. FIG. 4 shows a block diagram of a configuration example of an image processing apparatus according to the present invention. In this figure, reference numeral 10 denotes an image input device, which is composed of an image reading section 11 and an input image storage section 12. Reference numeral 20 denotes an image processing device according to the present invention, which is composed of a pixel input section 21, a memory reference section 22, a memory table 23, a center pixel calculation section 24, and a pixel output section 25. 30 is an image output device;
It is composed of an image recording section 31 and an output image storage section 32.

The operation of the embodiment shown in FIG. 4 will be explained. First, the image reading unit 11 of the image input device 10 reads an image, binarizes the value of each pixel in the read image, and stores the value in the input image storage unit 12. next,
In the image processing device 2, first, the pixel input unit 21 extracts the pixels of the part to be enlarged and converted from the input image storage unit 12 in units of 2 x 2 pixels vertically and horizontally, and then extracts the pixels adjacent to the top, bottom, left and right of the 2 x 2 pixels, respectively. 8 pixels are extracted.

In the memory reference unit 22, the retrieved total 1
Referring to the memory table 23 from the second pixel, out of the 3 x 3 pixels in the vertical and horizontal directions after conversion, 4 pixels located between the 4 corner pixels are found. In other words, in this example, in order to perform high-speed processing, all patterns are calculated in advance and the results are stored in the memory table 23 instead of calculating using equation (2) explained above. During processing, four pixels after conversion can be obtained by simply referring to this memory table 23.

The center pixel calculation unit 24 executes the logical calculation of the above equation (3) using the four pixels obtained by the pixel input unit 21 and the four pixels obtained by the memory reference unit 22, and calculates the converted three pixels.
Obtain the center pixel of ×3 pixels. The pixel output unit 25 outputs the nine converted pixels obtained above to the output image storage unit 32. Finally, in the image output device 30, the image recording section 31 records the pixels on paper while extracting the pixels from the output image storage section 32. In FIGS. 6 and 7, AND represents an AND gate, OR represents an OR gate, and INV represents an inverter.

FIG. 5 shows a circuit example of the image processing device 20 according to the present invention. In this figure, M is a 1-word 8-bit memory having an 11-bit address, and stores two patterns according to the above equation (2) in one word. CB1 is a circuit block and has the circuit configuration shown in FIG. In other words, 11 of the 12 reference pixels are used to obtain 2 patterns of converted pixels from memory M, and in circuit block CB1, the remaining 1 reference pixel is narrowed down to 1 pattern to obtain 4 pixels. There is. CB2 is a circuit block having the circuit configuration shown in FIG. 7, and obtains the last center pixel from the four pixels obtained immediately before and the four pixels of the original image.

Next, an application example of the present invention will be shown. In the enlargement conversion process according to the present invention, by converting 2 x 2 pixels from the original image to 3 x 3 pixels at arbitrary intervals, a maximum of 1.5
It is possible to obtain any enlarged image from 1 to 1 times. First, it is clear that if all pixels are divided into 2×2 pixel blocks and all of them are converted to 3×3 pixels, the converted image will be 1.5 times larger than the original image.

On the other hand, as shown in FIGS. 8(a) and 8(b), if every other block is enlarged and converted, a 1.25 times enlarged image can be obtained. In this case, it is necessary to convert the 2 x 2 original pixels to 3 x 2 pixels vertically and horizontally, or 2 x 3 pixels horizontally and vertically, but as shown in Figure 9 (a) and (b), This can be solved later by adding a procedure to remove the intervening row.

By using such a method, it is possible to easily output, for example, a received facsimile image using printers having different pixel densities. This example will be explained below.

[0023] The pixel density of facsimile is 8 dots/mm.
For A4 size, the main scanning direction of the document is 1680 dots according to equation (4). On the other hand, if the pixel density of a printer is a typical 300 dpi, then from equation (5), 24
It is 80 dots. Therefore, if all pixels in the facsimile reception image are expanded and converted, it will be 2520 dots according to equation (6), so 40 dots in the horizontal direction.
It becomes more than that. Therefore, from equation (7), in the main scanning direction, the ratio is 1 block for every 21 blocks, and as shown in FIG.
The pattern (a) may be applied.

[0024]

[Math. 4] 8dot/mm x 210mm=
1680dot (4)

00
25]

[Math. 5] 300dip x 0.03936 x 210 = 248
0dot (5)

[0026]

[Math. 6] 1680 × 1.5 =
2520dots (6)

[0027]

[Math. 7] 1680 ÷ 40 ÷ 2 =
21 (7) By performing the same procedure in the vertical direction, an output image of an appropriate size can be obtained.

[0028] Also, in the case of facsimile, 8 x 3.85
There is a resolution of dot/mm, and in that case, it is necessary to further enlarge the image by a factor of two in the sub-scanning direction.
Electrophotography Society Journal Volume 25 No. 2 p. Possible methods include using this method after converting to 8×7.7 dots/mm using the interpolation method described in 84, etc., or performing interpolation after conversion using this method.

[0029]

Effects of the Invention The image processing method and device of the present invention solves the above problems and achieves the purpose with regard to the process of enlarging and converting an input image from 2 x 2 pixels to 3 x 3 pixels. The 4 pixels at the corners of the 3×3 pixels are 2× of the original image.
Using the data of 2 pixels as is, the 4 pixels excluding the center pixel out of the remaining 5 pixels are the data of a total of 12 pixels, including the 2 x 2 original pixel and the 8 pixels adjacent to each other on the top, bottom, left, and right. , and the center pixel is obtained from the surrounding eight pixels just obtained. Therefore, with a simple circuit configuration, an image processing device with inexpensive, high-speed, and high-quality enlargement processing can be realized. be able to.

[Brief explanation of the drawing]

FIG. 1 shows a pixel (a) before enlargement conversion and a pixel (b) after conversion for explaining the image processing method of the present invention.

FIG. 2 shows a pixel before conversion (a) and a pixel after conversion (b) showing an example in which continuity of lines in an original image is considered.

FIG. 3 shows a pixel before conversion (a) and a pixel after conversion (b) showing an example in which continuity of lines in an original image is considered.

FIG. 4 is a block diagram showing the configuration of an embodiment of the image processing device of the present invention.

FIG. 5 is a diagram showing an embodiment of a circuit of an image processing device according to the present invention.

FIG. 6 is a diagram showing an example of a circuit configuration of a circuit block in FIG. 5;

FIG. 7 is a diagram showing an example of the circuit configuration of another circuit block in FIG. 5;

FIG. 8 shows a pixel before conversion (a) and a pixel after conversion (b) showing an application example of the present invention.

FIG. 9: Pixel (a) before conversion showing another application example of the present invention.
and the pixel (b) after conversion.

FIG. 10 shows a pixel before conversion (a) and a pixel after conversion (b) for explaining an example of a conventional enlargement conversion image processing method.

[Explanation of symbols]

10 Image input device 11 Image reading section 12 Input image storage unit 20 Image processing device 21 Pixel input section 22 Memory reference section 23 Memory table 24 Center pixel calculation section 25 Pixel output section 30 Image output device 31 Image recording section 32 Output image storage unit M Memory CB1 circuit block CB2 circuit block

Claims (2)

[Claims] Claim 1: The vertical and horizontal 2 of a local area of a binary raster image.
When enlarging ×2 pixels to 3 × 3 pixels in the vertical and horizontal directions, the four pixels at the corners of the 3 × 3 pixels remain as the 2 × 2 pixel data.
The pixels between the two upper corner pixels of the 3×3 pixel are
The continuity of the line segment is determined from the upper two pixels of the four pixels of the 2×2 pixels of the original image, and the two pixels adjacent to each of the two pixels above, in total, to ensure the continuity of the line segment.
The pixels between the two pixels on the left corner of the 3x3 pixel are the two pixels on the left side of the original 2x2 pixel, the two pixels adjacent to the left side, and the 3x3 pixel.
The pixels between the 2 pixels on the right corner of the 3 pixels are the 2 pixels on the right side of the 2 x 2 pixels of the original image and the 2 pixels adjacent to the right side, respectively, 3 x 3
The pixels between the two pixels at the bottom corner of the pixel are determined from the bottom two pixels of the 2×2 pixels of the original image and the two pixels adjacent to the bottom, respectively.
An image processing method characterized in that the center pixel of the 3×3 pixels is determined from the surrounding 8 pixels determined above. 2. After reading, out of the raster image in which each pixel is binarized, the pixels of the part to be subjected to enlargement conversion processing are extracted in units of 2 × 2 pixels, and the upper and lower portions of the 2 × 2 pixels are A pixel input section that takes out 12 pixels in total (8 pixels adjacent to each side on the left and right) and a pixel input section that takes out 12 pixels in total (8 pixels adjacent to each other on the left and right), and 4 pixels between the 4 pixels at the corner of the 3 After calculating all the patterns, referring to the memory table in which the results are stored in advance and the memory table from the 12 pixels taken out by the pixel input section, 3.
A memory reference section that calculates 4 pixels between the corner 4 pixels out of 3 pixels, and 3 a center pixel calculation unit that obtains the center pixel of three pixels; and two of the pixel input units.
×2 pixels are taken as corner pixels of 3×3 pixels, and the image output unit outputs a total of 9 pixels, including 4 pixels obtained by the memory reference unit and the center pixel obtained by the center pixel calculation unit. Image processing device.