JPH07244729A - Image reduction system - Google Patents

Abstract

PURPOSE:To obtain the system which reduces an image fast on a general computer by providing a means which takes plural pixels together at a time and an after-reduction pixel determining means which determines plural pixels after reduction corresponding to the taken-out pixels. CONSTITUTION:An after-reduction pixel column can be taken out of a reduced pixel table 305 by specifying a pixel selection bit column and a before-reduction image bit column taken out of a before-reduction image line as a column and a row number. Consequently, plural pixels can be reduced together at a time according to the width (n) of the pixel selection bit column and before-reduction image bit column to reduce the image fast. Therefore, when the width of the before-reduction image bit column is 8 bits, eight pixels can be reduced together at a time. In this processing, about 20 pieces of reduced images consisting of 1000 per second pixels longitudinally and laterally can be generated on the general computer from a binary image whose pixels each consist of one bit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reducing and displaying an image, and more particularly to a method for reducing the image at high speed.

[0002]

2. Description of the Related Art The present invention aims at continuously changing the reduction ratio of an image and changing the size of the image in real time. For that purpose, it is necessary to reduce the size of about 10 images per second at least.

The conventional technique for reducing an image by software is Nobuyuki Yagi et al. "Practical image method learned in C language".
(May 30, 1992). A method of providing hardware for speeding up this is described in Japanese Patent Laid-Open No. 63-62076.
In addition, there is a method of holding images of a plurality of magnifications in advance, such as Japanese Patent Laid-Open No. 4-337877.

(1) Image Reduction FIG. 1 shows an image before reduction and an image after reduction. The image before reduction is referred to as an image before reduction, and the image after reduction is simply referred to as an image after reduction. The image is composed of a plurality of pixels aligned in the vertical and horizontal directions.
The number of pixels in the horizontal direction of the image is called the width of the image, and the number of pixels in the vertical direction is called the height of the image. For example, the image before reduction in FIG. 1 has a width of 16 and a height of 16, and the image after reduction has a width of 8 and a height of 8.

(2) Image in memory Since the image is processed on the computer, the image is held in the memory. FIG. 2 shows an image in the memory.
In the example of FIG. 2, each pixel has a value of 0 or 1. Such a case is called a binary image. For example, when the image is black, the pixel value is 1, and when the image is white, the pixel value is 0.

(3) Conventional Method FIG. 3 shows an outline of a conventional image reduction method. In the conventional method, each pixel of the image before reduction is copied pixel by pixel into the image after reduction. That is, the pixels of the image before reduction that should correspond to the image pixels after reduction are obtained, and the pixels of the image before reduction corresponding to all the pixels of the image after reduction are copied to the image after reduction. For example, when the reduction ratio is 1/2 in FIG. 3, the pixels set as the pixels of line number 2 and pixel number 4 after reduction are
It is the pixel of line number 4 and pixel number 8 of the image before reduction. In this way, the position of the pixel before and after the reduction is obtained from the reduction ratio and the pixel is copied to realize the reduction of the image.

FIG. 4 shows an image reduction method. The image is reduced by selecting some of the pixels in the image before reduction and copying it to the image after reduction.
For example, when reducing an image to a reduction ratio of 1/2,
Values A, C, E, G, I, K, M, O of the pixels of line numbers 0, 0, 2, 4, 8, 10, 12, 14 of even-numbered pixels Only the reduced image is copied to the pixel of line number 0 of the image. At this time, the pixel values of the image before reduction have odd pixel numbers, B, D, F,
H, J, L, N and P are not copied to the image after reduction. That is, it is a method of creating a post-reduction image by thinning out pixels of the pre-reduction image.

[0008]

However, the above-described method of performing image reduction processing on a pixel-by-pixel basis has a problem that the reduction processing is slow. That is, in order to obtain a row of reduced pixels, only the values of the pixels to be copied are reflected in the reduced pixels according to the pixel selection pattern, and the pixels that are not to be copied are thinned out to obtain the pixels to be copied. The process of assembling only ones is required. The pixel value is 1
In the case of expressing in bits, it is necessary to have a function of performing a process of combining only selected bits at high speed.

However, in the conventional general-purpose computer, the AN
Although it is equipped with bit-wise processing such as D, OR, etc. and bit-wise and word-wise bit shift instructions, as shown in FIG. 6, it has the function of performing the processing of combining only selected bits at high speed. Not prepared.

An object of the present invention is to provide a method for reducing an image at high speed on a general-purpose computer without using special hardware for image reduction.

[0011]

In the present invention, high-speed image reduction is realized by combining the following two means. (1) Batch processing of a plurality of pixels In the conventional method, the image is reduced in units of individual pixels, so that high-speed image reduction cannot be realized. Therefore, in the present invention, a high-speed image reduction process is realized by collectively processing a plurality of pixels as shown in FIG. In the example of FIG. 5, 8 pixels are collectively processed.

(2) Multiple Pixel Batch Processing Algorithm FIG. 7 shows a method of calculating the reduced pixels when collectively processing a plurality of pixels. In the example of FIG. 7, an image is processed in units of 8 pixels and the image is reduced to 1/2.

For 8 pixels of the pre-reduction image, 2
When the pixels are thinned out at a ratio of one to one, the pixels to be copied appear alternately with the pixels to be copied. Pixels to be copied are indicated by "○", and pixels thinned out without being copied are indicated by "x", and the pixel selection pattern indicating the pixels to be copied as shown in FIG. 7 is "○ × ○ × ○ × ○ ×". "
become.

That is, according to the present invention, the reduced pixel table shown in FIG. 7 is created and held to realize high-speed calculation of the reduced pixels in the batch processing of a plurality of pixels.
The reduced pixel table is a table for holding the pixel pattern after reduction for a plurality of pixel groups of the image before reduction. By referring to this table, the reduced pixel can be acquired at high speed.

[0015]

The operation of the above means to realize image reduction will be described below with reference to FIG. In the image reduction processing, the pixel selection pattern and the reduced pixel table are set in the first step, and then the image is reduced by copying the image while referring to the reduced pixel table in the second step. To do.

(1) Setting of table The pixel selection unit creates a pixel selection pattern according to the reduction ratio of the image. In this method, the image is reduced by thinning out pixels from the pixels of the image before reduction according to the reduction ratio. The pixel selection pattern is a pattern showing pixels to be copied and pixels to be thinned out without copying. For example, in the case of the reduction rate 1/2, one pixel is selected in two, and in the reduction rate 1/3, one pixel is selected in three.

Next, the reduced pixel table creating section creates a reduced pixel table. The reduced pixel table is a table showing a correspondence relationship between a plurality of pixel groups of an image before reduction and a column of pixels after reduction. Since this correspondence differs depending on the pixel selection pattern, the reduced pixel table creation unit
While referring to the pixel selection pattern created by the pixel selection unit, the column of pixels after reduction corresponding to the value of the pre-reduction image multiple pixel group is calculated and set in the reduced pixel table.

(2) Image Copying Process Next, the image reduction processing unit creates the post-reduction image from the pre-reduction image with reference to the reduction pixel table created by the reduction pixel table creation unit. The image reduction processing unit extracts a pre-reduction image multiple pixel group, which is a set of a plurality of pixels from the pre-reduction image, and refers to the reduction pixel table to determine the post-reduction image corresponding to the pixel value of the pre-reduction image multiple pixel group. Take a row of pixels. Further, the extracted reduced pixel row is set to the reduced image. The above operation is executed for all the pixels of the image before reduction to create the image after reduction.

[0019]

【Example】

1. Embodiment 1 An embodiment of the present invention will be described in detail below with reference to FIGS. 9 to 25. In this embodiment, it is assumed that the pixels in the image are composed of 1 bit. When one pixel is composed of 2 bits or more, it is possible to reduce the image by applying the method shown in this embodiment to each bit of each pixel.

1.1 Overall System Configuration and Control Flow The overall system configuration of an embodiment of the present invention and the operation of the overall control unit that controls the entire system will be described with reference to FIGS. 9 and 10. This system is composed of a peripheral device such as an image scanner (102) and a computer (101) for controlling these and processing data. The image scanner (102) inputs an image under the control of a computer. The disk device (103) stores the image data read by the image scanner (102) and a program for controlling the whole. The display (104) displays characters, numerical values, or images under the control of the computer. The keyboard (105) is used by the system user to input commands and parameters to the computer. The computer (101) holds the CPU (111) that executes the program stored in the memory and processes the data and the program, or the image input from the image scanner or the image displayed on the display (104). Memory (110) and an image scanner controller (10) for controlling the image scanner.
6), a disk controller (107) for controlling the disk device (103), and a keyboard (10
Keyboard controller (10)
9).

In the memory, as a program, an overall control unit (112) for controlling the entire system and an image reducing unit (113) for reducing an image are held.
Similarly, an image scanner (102) is also installed in the memory.
The more read-in image (114) before reduction and the reduced image (115) for display on the display (104) are held.

The overall control flow of FIG. 9 will be described with reference to FIG. First, an image is read by the image scanner (102), and this image is read by the disk device (10
It is stored in 3) (step 201). When the image is read into the scanner, the size of the image to be read and the image reading density are designated by the keyboard (105). Furthermore, as in (step 202),
The reduction ratio is read from the keyboard (105). next,
The image stored in the disk device (103) is input to the image reduction unit, and the reduced image (115) is created on the memory (110) (step 203). further,
The reduced image (115) created by the image reducing unit (113) is input to the display controller (108) and displayed on the display (104).

1.2 Image Reducing Unit 1.2.1 Configuration of Image Reducing Unit and Its Control The software configuration of the image reducing unit and its operation will be described with reference to FIGS. 11 and 12. Image reduction unit (11
3) is an image reduction control unit (301) that controls the entire image reduction unit, a line conversion unit (308) that creates a line conversion table (304), and a reduced pixel table creation that creates a reduced pixel table (305). Division (30
2), a pixel selection unit (303) that creates a pixel selection table (306), and a line conversion table (30
4), a reduced pixel table (305) and an image reduction processing unit (307) that reduces the pre-reduction image (114) and creates a post-reduction image (115) using the pixel selection table (306).

The image reduction unit (113) is controlled by the image reduction control unit (301). The image reduction control unit (301) first instructs the reduced pixel table creation unit (302) to create a reduced pixel table (305) as in the flowchart of FIG. 4 (step 401).
Next, the line conversion unit (308) is instructed to create the line conversion table (304) (step 402). Further, a pixel selection table (30
Instruct to create 6). Then, the image reduction processing unit (307) is instructed to reduce the pre-reduction image (114) to create a post-reduction image (115).

1.2.2 Outline of Image Reduction Process Here, an outline of the image reduction process in this embodiment will be described with reference to FIG. In the embodiment, according to the line conversion table (304), only the line of the line number designated by the line conversion table is extracted from the pre-reduction image (114) according to the line conversion table (304). The line conversion table is a table that holds the line numbers of the pixels of the pre-reduction image that correspond to the line numbers of the pixels of the reduced image. The contents of the line conversion table and the method for creating the line conversion table will be described in detail in Section 1.2.3.

In this embodiment, one pixel corresponds to one bit. In other words, it is a black and white binary image in which the brightness of one pixel is represented by 0 and 1. Therefore, in processing an image, an array of pixels corresponds to a string of bits. In the present embodiment, the extracted lines of the pre-reduction image are collectively reduced in units of a plurality of bits. The number of bits to be collectively processed is 8 bits, for example. An image bit string (50
3). In parallel with this, the pixel selection table (30
Similarly, the pixel selection bit string of a plurality of bits is taken out from 6).

In the present embodiment, as an example, the width of the bit to be reduced is set to 8 and the reduction is collectively performed in units of 8 bits. However, the bit width of the reduction is 8
You are not limited to bits. However, since the required size of the reduced pixel table also changes depending on the bit width to be reduced, the bit width to be collectively processed, that is, the number of pixels is selected in consideration of this.

The size of the reduced pixel table, that is, the number of elements in the table is 2 8 when the bit width is 8, the height,
It requires 256 horizontal elements, that is, 4096 elements. Further, when the number of bits is 9, the number of elements is 16384; when the number of bits is 10, the number of elements is 65536; when the number of bits is 11, the number of elements is 262144 and the number of bits is 12
In this case, the number of elements is 1048576. That is, the number of table elements required for each increase in the number of bits to be processed is quadrupled. Even if the number of bits to be collectively processed is increased by one, the effect of speeding up the image reduction processing is only 12.5% increase based on the case of 8 bits. In other words, even if the number of bits to be batch processed is too large, the size of the required table only increases, and the performance cannot be significantly improved. From this point of view, there is an appropriate value for the number of bits to be collectively processed, and in this embodiment, it is 8
I have chosen. The structure and setting method of the reduced pixel table will be described in detail in Sections 1.2.5 and 1.2.6.

The reduced pixel table (305) includes a pre-reduction image bit string (502) and a pixel selection bit string (50).
3) is a two-dimensional array having row and column numbers, and bit data and bits to be added to the image line (504) after reduction by designating the image bit sequence before reduction (502) and the pixel selection bit sequence. The width can be taken out. For the pixel selection bit string and its setting method,
Details are given in Section 1.2.4. The reduced pixel row (505) thus obtained from the reduced pixel table (305)
Is added to the image line (504) after reduction.
When the width of the image line after reduction reaches the width of the image after reduction, a new image before reduction is taken out,
The above process is repeated. In this way, the reduced image (115) is created.

The outline of the image reduction processing has been described above, but will be described in more detail in section 1.2.3 and subsequent sections. 1.2.3 Line Conversion Table and Creation Method Thereof The structure of the line conversion table (304) and the creation method thereof will be described with reference to FIGS. 14 and 15. As shown in FIG. 14, the line number of the image before reduction corresponding to the line number of the image after reduction is stored in each element of the line conversion table (304). That is, the line conversion table (304) holds the correspondence between the lines of the image before reduction and the lines after reduction. For example, the after-reduction image line number 2 corresponds to the before-reduction image line number 5.

A method of setting this correspondence will be described below. A method of creating the line conversion table (304) by the line conversion unit (308) will be described with reference to FIG. (Step 7
In step 01), a variable i indicating the line number of the reduced image is initialized to 0. i is the line number of the reduced image, and is also the element number of the line conversion table.
Then, while the element number i of the line conversion table (304) is less than or equal to the number of lines of the reduced image (step 70
3) The subsequent processing is repeated (step 702). In step 703, the line number of the pre-reduction image corresponding to the line number of the reduced image is calculated and set in the i-th element of the line conversion table.

The line number of the pre-reduction image corresponding to the line number of the post-reduction image is calculated by the equation 1.

Line number of image before reduction = line number of image after reduction / reduction ratio (Equation 1) Further, 1 is added to i (step 704). The line conversion table is set as described above.

1.2.4 Pixel selection table and setting method thereof Pixel selection table (306) according to FIG. 16 and FIG.
The structure of and the setting method will be described. Also, the pixel numbers shown in FIG. 16 are used to specify the pixels in the horizontal direction in the image. The pixel selection table (303) sets the pixel selection table. The present invention realizes image reduction by thinning out pixels, and the pixel selection table (306) specifies pixels to be thinned out from the image before reduction. When the bit of the pixel selection table (306) is "0", the pixel of the corresponding pixel number is thinned out. On the contrary, when the bit of the pixel selection table (306) is "1", the pixel of the image before reduction corresponding to the pixel number remains in the image after reduction without being thinned out. In this embodiment, image reduction processing is performed in 8-bit units. That is, the image is processed in bytes. Therefore, the relationship between the pixel number and the position of the byte and the position of the bit is expressed by Equations 2 and 3.

Byte Position = Pixel Number / 8 (Equation 2) Bit Position = Pixel Number mod 8 (Equation 3) Next, a method of setting the pixel selection table (306) will be described with reference to FIG. First, the pixel selection table (306)
Is cleared to "0" (step 901). Next, the pixel number j is initialized to 0 (step 902). further,
While the pixel number j is smaller than the image width after reduction (the number of pixels) (step 904), the subsequent processing is repeated (step 903). The image width after reduction is calculated by Equation 4.

Image width after reduction = Image width before reduction × Reduction ratio (Equation 4) In step 904, the pixel number of the image before reduction (114) corresponding to the pixel number j of the image after reduction (115) is calculated. The pixel number of the pre-reduction image is calculated by Equation 5.

Pixel number of image before reduction = pixel number of image after reduction / reduction ratio (Equation 5) “1” is set to the bit of the pixel selection table corresponding to the pixel number calculated in (step 904) (step 905) ). Furthermore, 1 is added to the pixel number j (step 9
06) (step 903) according to the conditions (step 9
04) and subsequent processes are repeated.

1.2.5 Structure of Reduced Pixel Table The structure of the reduced pixel table (305) will be described with reference to FIGS. The reduced pixel table includes an image bit string (a bit pattern extracted from the image line of the pre-reduction image in 8-bit units) and a pixel selection bit string (a bit pattern extracted from the pixel selection table in 8-bit units), respectively. Is a two-dimensional array table. As shown in FIG. 19, the reduced pixel column (505) and the effective pixel number (1101) are set in the elements of this table.

The reduced pixel column is a column of pixels showing a reduced image obtained by thinning out pixels from the bit sequence of the image before reduction. Further, the number of effective pixels of the reduced pixels is referred to as the number of effective pixels. For example, when the number of bits of the image bit string before reduction is 8 and the number of pixels is reduced to 1/2, the number of pixels after reduction is 4. At this time, the number of effective pixels is four. FIG. 20 shows an example of the elements of the reduced pixel table. FIG. 20 shows a case where the reduced pixel row is “10010000 (binary number)” and the number of effective pixels is “4”. Next, the reduced pixel row will be described with reference to FIG. 1.
As described in Section 2.4, each bit of the pixel selection bit string indicates whether or not each pixel of the pre-reduction image is thinned out. In the calculation of the reduced pixel string, when the bit of the pixel selection bit string is 1, the pixel of the image before reduction is stored, so that each bit of the image byte value becomes the calculation result of the reduced pixel string as it is. Further, when the bit of the pixel selection bit string is "0", the pixels of the image before reduction are thinned out, so that the pixel becomes an invalid bit that does not affect the image after reduction. As a result, the reduced pixel row has a value shifted to the left from the calculation result of the reduced pixel row, excluding invalid bits. For example, in the case of the example in FIG. 21, it is “1001xxxx (binary number)”. However, x is an invalid bit, and 0 or 1
But it doesn't matter. The number of effective pixels, that is, the “effective pixel number” is the number of bits that are “1” in the bits of the pixel selection bit string. For example, in the example of FIG. 21, the number of effective pixels is “4”.

1.2.6 Setting of Reduced Pixel Table Next, a method of setting the reduced pixel table will be described with reference to FIG. First, the pixel selection bit string is initialized to 0 (step 1401). Next, while the pixel selection bit string is smaller than 256 (step 1403), the processing after that is repeated (step 1402). Here, the upper limit of the pixel selection bit string is (256-1) because in this embodiment, the unit of pixels for which the reduction processing is collectively performed is eight. For example, when the pixel unit of the reduction processing is 10, the upper limit of the selected pixel is (1024-1). Generally, when the unit of pixels for performing the reduction processing is n pixels, the upper limit of the selected pixels is (2 to the nth power −1). Further, the image bit string is initialized to 0 (step 1403). Next, while the image bit string is smaller than 256 (step 14
05) The subsequent processing is repeated. Similarly to the upper limit of the pixel selection bit string, the upper limit of the image bit string is determined by the number n of pixels for which the reduction processing is collectively performed (2 to the nth power −1). In (step 1405), the (image bit string, pixel selection bit string) element of the reduced pixel table is calculated, and the calculation result is set. In step 1406, 1 is added to the image bit string. In addition, (step 140
In 7), 1 is added to the pixel selection bit string. Thus, all the elements of the reduced pixel table are set.

Next, FIG. 23 shows the "calculation method of the elements of the reduced pixel table" performed in (step 1405) of FIG. First, variables K, L, and tmp are initialized (step 1501). Here, the variable K is a variable indicating the pixel number of the pixel selection bit string. The variable L is a variable indicating the pixel number of the image bit string before reduction. The variable tmp is a variable for holding the value of the reduced pixel row during the calculation. K is n
While it is smaller than (the number of pixels to be processed collectively), (step 15
03) and subsequent processes are repeated (step 1502).
In (step 1503), it is determined whether the Kth bit of the pixel selection bit string is "1", and if so, the process proceeds to (step 1504). In (step 1504),
It is determined whether the Kth bit of the image bit string is "1" (step 1504), and if so, L of tmp.
The 1st bit is set to "1" (step 1505). Also, (step 1506) and (step (150
In 7), 1 is added to L and K, respectively. (Step 1503) After the subsequent processing is completed, the remaining tmp and L as a result are set in each element of the reduced pixel table as the reduced pixel column and the effective pixel number, respectively (step 150).
8).

1.2.7 Operation of Image Reduction Processing Unit The operation of the image reduction processing unit will be described with reference to FIGS. 24 and 25. First, the outline of the operation of the image reduction processing unit will be described with reference to FIG. FIG. 24 shows an example of repetitive image reduction processing. This process is shown in FIG.
Follow the flow chart for all images,
Reduces the entire image. FIG. 24 exemplifies that the reduction process is performed on the second byte of a certain row in the image, that is, the image at byte position 1. In this example, (step 1708) and (step 17
09). First, the pixel selection table (30
6) the pixel selection bit string (503) at byte position 1 and the image bit string (50 at byte position 1 of the image before reduction)
2) Take out. In this example, the pixel selection bit string is “01
“010110 (binary number)” (86 in decimal number), and the image bit string is “11000010 (binary number)” (10
It has a value of 194) in the base number. Therefore, the element in (194 rows, 86 columns) of the pixel reduction table (305) is extracted. That is, the elements corresponding to the image bit string “194” and the pixel selection bit string “86” are extracted. As shown in FIG. 24, the extracted element values are “1001xxxx” for the reduced pixel row and “4” for the number of effective pixels. Therefore, 4 bits of the reduced pixel row obtained from the pixel reduction table are added to the rear part of the image line after reduction (before adding reduced pixels). By repeating the above operation,
It is possible to create a reduced image in which pixels are thinned according to the reduction ratio from the image before reduction.

FIG. 25 shows a flowchart in which the above-described operation is configured to operate for all pixels. First,
In step 1701, the reduced line number is set to 0. Next, while the reduced line number is smaller than the number of lines after reduction (step 1703), the processes after that are repeated (step 1702). The number of lines after reduction is calculated by Equation 6.

Number of lines after reduction = Number of lines before reduction × Reduction ratio (Equation 6) Next, the line number of the image to be reduced is extracted from the line conversion table (304) (step 170).
3). The number of selected pixels is initialized to 0 (step 17)
04). The first 8 bits of the reduction target image line are taken out as an image bit string (step 1705).
The first 8 bits of the pixel selection table are taken out as a pixel selection bit string (step 1706). Further, while the number of selected pixels is smaller than the image width after reduction (step 17
08) and subsequent processes are repeated (step 1707). The image width after reduction is calculated by the equation 7.

Image width after reduction = Image width before reduction × Reduction ratio (Equation 7) In step 1708, pixel reduction table (305)
Referring to, the image bit string (502), the reduced pixel string corresponding to the pixel selection bit string (503), and the effective pixel number (1101) are extracted. Next, a reduced pixel bit string is added to the reduced image line (step 1709).
Further, the effective pixel number is added to the selected pixel number (step 1710). Image line to be reduced Next 8 bits are taken out as an image bit string (step 171)
1).

Further, the next 8 bits of the pixel selection table are taken out as a pixel selection bit string (step 171).
2). (Step 1708) After performing the subsequent processing,
In step 1713, the reduced line number is incremented by 1 (step 1713). With the above processing, it is possible to perform high-speed reduction processing of an image having an arbitrary reduction ratio.

2. Example 2 Hereinafter, Example 2 will be described in detail with reference to FIGS. 26 to 30. In this embodiment, it is assumed that the pixels in the image are composed of a plurality of bits. In the present embodiment, for example, even if one pixel is represented by a 24-bit pixel value of 8-bit RGB each, it can be easily handled.

2.1 Overall System Configuration and Control Flow In this embodiment, the configuration of the image reducing unit and its processing method are different from those in the first embodiment, but the overall system configuration and control flow are the same as those in the first embodiment. The description is omitted because they are the same and overlap.

2.2. Image Reducing Unit 2.2.1 Configuration of Image Reducing Unit and Its Control The configuration and operation of the image reducing unit in this embodiment will be described with reference to FIGS. 26 and 27.

The image reduction unit (113) controls the entire image reduction unit (1801).
And a line conversion unit (308) that creates a line conversion table (304), a pixel conversion unit (1803) that creates a pixel conversion table (1804), a line conversion table (304), and a pixel conversion table (1804). Image before reduction (114) and after reduction image (1
15), which is composed of an image reduction processing unit (1805).

The image reduction processing unit (1805) is controlled by the image reduction control unit (1801). The image reduction control unit (301) first instructs the line conversion unit (308) to create a line conversion table (304) as in the flowchart of FIG. 19 (step 190).
1). Furthermore, the pixel conversion unit (1803) is instructed to create a pixel conversion table (1804) (step 190).
2). The difference between the pixel selection table (306) of the first embodiment and the pixel conversion table of the present embodiment is that the pixel selection table is
While the presence or absence of copying each pixel of the image before reduction to the image after reduction is shown, the pixel conversion table (1804) holds the pixel number of the image before reduction corresponding to the pixel number of the image after reduction. In point. The image reduction processing unit (1805) is instructed to reduce the image before reduction (114), and the image after reduction (115) is created.

2.2.2 Outline of Image Reduction Process Here, the outline of the image reduction process using the line conversion table and the pixel conversion table and these will be described with reference to FIG. According to the present invention, only the pixels having the line number and the pixel number designated by the inner line conversion table (304) of the image before reduction and the pixel conversion table (1804) are taken out, and the pixels taken out here are subjected to the reduced image. Assigned as a pixel of. The image is reduced by performing this processing for all the line numbers and pixel numbers of the reduced image. For example, in FIG.
Then, for the pixel with line number 2 and pixel number 4 after reduction,
The pixels of the pre-reduction image of line number 5 and pixel number 9 are assigned.

2.2.3 Line conversion table and method of creating the same The structure of the line conversion table and the method of creating the same are the same as those in the first embodiment, and the description thereof is omitted.

2.2.4 Pixel conversion table setting method A pixel conversion table setting method will be described with reference to FIG.
As shown in FIG. 28, the pixel conversion table (1804)
Holds the pixel number of the pixel of the image before reduction corresponding to the pixel number of the pixel of the image after reduction. This setting is performed by the pixel conversion unit (1803). The pixel converter is shown in Figure 2.
As in 1, first, the variable j corresponding to the pixel number is initialized to 0 (step 2101). Next, while the pixel number is smaller than the number of pixels after reduction (step 2103), the processing after that is repeated (step 2102). (Step 210
In 3), the pixel number of the image before reduction corresponding to the pixel number of the image after reduction is set in the j-th element of the pixel conversion table. Further, the pixel number is incremented by 1 in (step 2104). In this way, the pixel numbers of the image before reduction corresponding to all the pixel numbers of the image after reduction are set. Here, the pixel number of the pre-reduction image set in the element of the pixel conversion table is expressed as in Expression 8.

Pixel number of image before reduction = pixel number of image after reduction / reduction ratio (Equation 8) 2.2.5 Operation of image reduction processing unit The operation of the image reduction processing unit (1805) will be described with reference to FIG. First, the reduced line number is initialized to 0 (step 2201). Next, while the reduced line number is smaller than the number of lines after reduction (step 2203), the subsequent processing is performed (step 2202). (Step 220
In 3), the line number of the pre-reduction image is extracted from the line conversion table (step 2204). Next, the reduced pixel number is initialized to 0 (step 2204). Then, while the reduced pixel number is smaller than the image width after reduction (step 2206), the subsequent processing is performed (step 22).
05). At (step 2206), the pixel number of the pre-reduction image is extracted from the pixel conversion table. Next, the pixels corresponding to the line number and the pixel number extracted from the line conversion table and the pixel conversion table are extracted from the image before reduction and assigned to the pixels of the image after reduction (step 2207). Further, the reduced pixel number is incremented by 1 (step 2208). If the reduced pixel number is the same as the image width after reduction, or becomes larger, the reduced line number is 1
Increase (step 2209). When the processing after (step 2203) is performed for all the lines, the image reduction processing ends.

[0056]

According to the present invention, image reduction processing is performed by thinning out pixels. (1) Effect of Embodiment 1 The line conversion table (304) holds the correspondence between the lines of the image before and after reduction, and is compared with the case where the correspondence between the lines before and after reduction is calculated in pixel units. The effect of shortening the line conversion processing time is obtained. Further, the pixel selection table (306) holds the pixel number selected after reduction, and it is possible to reduce the determination process of whether or not the pixel of the image before reduction is applied to the image after reduction (115). In the reduced pixel table (305), the pixel selection bit string (503) extracted from the pixel selection table (306) and the pre-reduction image bit string (502) extracted from the pre-reduction image line (501) are arranged in columns and rows. It is possible to take out the reduced pixel row (505) by designating it as the number of. As a result, the pixel selection bit string (503) and the pre-reduction image bit string (50
The reduction processing of a plurality of pixels can be collectively performed according to the width n of the bit string of 2), and high-speed reduction processing of an image becomes possible. For example, the pre-reduction image bit string (50
If the width of 2) is set to 8 bits, the reduction processing of 8 pixels can be collectively performed. By the above processing, for example, in a binary image of 1 bit per pixel, a reduced image of 1000 pixels in each of the vertical and horizontal directions is converted into 1 using a general-purpose computer of 50 MIPS.
It is possible to create about 20 sheets per second.

(2) Effect of Embodiment 2 1 pixel 8 bits 256 by the image reduction method by pixel replacement by table reference to the line conversion table (304) and pixel conversion table (1804)
For color images, a general-purpose computer of about 50 MIPS is used, and a reduced image of 1000 pixels vertically and horizontally is applied at about 5 times per second.
It is possible to create one.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of an image.

FIG. 2 is a diagram showing an image on a memory.

FIG. 3 is a diagram showing a conventional method.

FIG. 4 is a diagram showing a method of reducing an image by thinning out pixels.

FIG. 5 is a diagram showing a method of batch processing of a plurality of pixel groups.

FIG. 6 is a diagram showing an algorithm for batch processing of a plurality of pixels.

FIG. 7 is an explanatory diagram of a reduced pixel table.

FIG. 8 is a diagram showing an operation of an image reduction method.

FIG. 9 is a diagram showing the overall configuration of an embodiment of the present invention.

FIG. 10 is a flowchart showing the overall control of the embodiment.

FIG. 11 is a configuration diagram (Example 1) of an image reducing unit.

FIG. 12 is a flowchart (first embodiment) of an image reduction control unit.

FIG. 13 is a diagram showing an outline of image reduction processing.

FIG. 14 is an explanatory diagram of a line conversion table.

FIG. 15 is a flowchart of a line conversion unit.

FIG. 16 is a diagram showing a structure of a pixel selection table.

FIG. 17 is a flowchart of a pixel selection unit.

FIG. 18 is a diagram showing a structure of a reduced pixel table.

FIG. 19 is a diagram showing a structure of elements of a reduced pixel table.

FIG. 20 is a diagram showing an example of elements of a reduced pixel table.

FIG. 21 is an explanatory diagram of a reduced pixel row.

FIG. 22 is a flowchart of a reduced pixel table creation unit.

FIG. 23 is a flowchart of element calculation of a reduced pixel table.

FIG. 24 is an operation explanatory diagram of the image reduction processing unit.

FIG. 25 is a flowchart (Example 1) of an image reduction processing unit.

FIG. 26 shows a configuration of an image reducing unit (Example 2).

FIG. 27 is a flowchart (second embodiment) of the image reduction control unit.

FIG. 28 is an explanatory diagram of a line conversion table and a pixel conversion table.

FIG. 29 is a flowchart of a pixel conversion unit.

FIG. 30 is a flowchart (second embodiment) of the image reduction processing unit.

[Explanation of symbols]

101: computer, 102: image scanner, 103:
Disk device, 104: display, 105: keyboard, 106: image scanner controller, 10
7: disk controller, 108: display controller, 109: keyboard controller, 110:
Memory, 111: CPU, 112: Overall control unit, 11
3: Image reduction unit, 114: Image before reduction, 11
5: Image after reduction, 301: Image reduction control unit (Example 1), 302: Reduced pixel table creation unit, 303:
Pixel selection unit, 304: Line conversion table, 305: Reduced pixel table, 306: Pixel selection table, 307:
Image reduction processing unit (Embodiment 1), 308: Line conversion unit, 501: Image line before reduction, 502: Image bit string before reduction, 503: Pixel selection bit string, 504:
Image line after reduction, 505: Reduced pixel column, 110
1: Effective pixel number, 1801: Image reduction control unit (Example 2), 1803: Pixel conversion unit, 1804: Pixel conversion table, 1805: Image reduction processing unit (Example 2).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location G09G 5/36 H 9471-5G H04N 1/393 (72) Inventor Kenji Kagaya Sachi-ku, Kawasaki City, Kanagawa Prefecture 12 890 Kashimada, Information Systems Division, Hitachi, Ltd.

Claims (8)

[Claims] 1. A device for holding an image in a memory and reducing the size of a plurality of pixels from an image before reduction, and a means for determining a plurality of pixels after reduction corresponding to the plurality of pixels. An image reduction method characterized by having a pixel determination means. 2. The image reduction system according to claim 1, wherein the post-reduction pixel determination means is applied to the whole pre-reduction image and the whole reduced image is output. . 3. The image reduction method according to claim 2, wherein a pixel reduction table for determining a plurality of pixels after reduction corresponding to a plurality of pixels extracted from an image before reduction is held, and the pixel reduction table is referred to. An image reduction method characterized by having means for determining a plurality of pixels after reduction with respect to a plurality of pixels of an image before reduction. 4. The image reduction system according to claim 2, wherein the number of a plurality of pixels extracted from the image before reduction is eight. 5. The image reduction system according to claim 2, wherein the number of a plurality of pixels extracted from the image before reduction is 4 to 12. 6. The pixel selection table according to claim 3,
An image reduction method having a size of 6 rows and 256 columns. 7. The pixel selection table according to claim 4, which holds a pixel selection table indicating how to select pixels in the row direction of the pre-reduction image, and when the image is subjected to reduction processing in units of 8 pixels, 8 pixels are selected from the pixel selection table. An image reduction method characterized in that a selection pattern for pixels is taken out, and an image is reduced by taking out pixels after reduction in the reduction pixel table corresponding to the pixel selection pattern. 8. An apparatus for retaining and reducing an image in a memory retains a "line number of an image before reduction" corresponding to a "line number (indicating a position of a pixel in a row direction) of a reduced image". It has a line conversion table and a pixel conversion table that holds the pair relationship between "the pixel number of the image after reduction (indicating the pixel position in the column direction of each row)" and "the pixel number of the image before reduction", and reduces the image. At this time, the pixel position of the image before reduction corresponding to the pixel position of the image after reduction is obtained by referring to the line conversion table and the pixel conversion table, and the pixel of the image before reduction is assigned to the pixel of the image after reduction. Image reduction method characterized by.