JPH0983782A - Image processing method and processor therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable pixel density conversion by a projection method at low cost with a small circuit scale irrelevantly to conversion power. SOLUTION: This image processor which converts the pixel density of raster- scanned image data is provided with a 1st side length generation part 11 which generates 1st side length according to the length of a side of the image data in a horizontal scanning direction and the conversion power in the horizontal scanning direction, a 1st product sum arithmetic part 12 which calculates the sum of products of the 1st generated side length and image data, a 2nd side length generation part 13 which generates 2nd side length according to the length of the side of the image data in a vertical scanning direction and conversion power in the vertical scanning direction, and a 2nd product sum arithmetic part 14 which calculates the sum of products of the result of the product sum arithmetic and the 2nd side length.

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 converting a raster-scanned digital image to a desired pixel density.

[0002]

2. Description of the Related Art Enlarging image data by data communication between facsimile devices having different resolutions and image editing devices.
When performing reduction, pixel density conversion of an image is required. Conventionally, as the pixel density conversion method, various methods such as an SPC method (nearest neighbor method), a linear interpolation method, a distance inverse proportional method, and a projection method have been proposed (for example, IPSJ VOL.26.N.
o. 5).

Among them, the projection method is an excellent method which has advantages such as less loss of images and less moire which occurs when an image having a high spatial frequency is converted. FIG. 1 is a diagram for explaining the basic principle of the projection method. Here, the case where the conversion magnifications of both the main scanning and the sub scanning are 2/3 is shown. Also, the number of pixels of the original image is 3 × 3.

First, the converted image is projected on the original image, and the original image having a pixel surface overlapping the pixel surface of the converted pixel A, which is the target pixel, is defined as P, Q, R, and S with one pixel as a rectangular area. To do. In FIG. 1, the symbol "x" indicates the original pixel,
Converted pixels are indicated by the symbol "○". Here, in the pixel plane of the converted pixel A projected on the original image plane, the original pixel P,
The areas occupied by the pixel planes of Q, R and S are SP, SQ,
When SR, SS and the pixel values are IP, IQ, IR, IS, the average density IA of the target pixel is expressed by the following equation. Here, In is the density of the pixel n (“1” or “0” in the case of the original image).

This average density IA becomes the pixel value of the conversion pixel by the projection method. If the original image is a binary image, this IA
By binarizing, the pixel value of the converted image can be obtained. FIG.
Figure 2 shows the image enlargement / reduction processing configuration in the conventional projection method. The number of reference pixels required for the projection method calculation changes depending on the conversion magnification. Specifically, in reduction conversion, the conversion magnification is 1
When / n is set, two reference pixels (the smallest integer value exceeding n) are required. Also, in the expansion conversion, four reference pixels are always required. In Figure 2, the minimum conversion ratio is 1 /
This is a triple example. In FIG. 2, reference numeral 41 denotes a reference pixel extracting portion which extracts an original pixel having a pixel surface which appears on the conversion pixel surface. Reference numeral 42 is a conversion pixel coordinate calculation unit, which calculates the original pixel position on the projection surface.

For example, when the pixel value of the conversion pixel A shown in FIG. 1 is calculated, the relative coordinates in the conversion pixel plane of P, Q, R and S are calculated. Reference numeral 43 denotes an original image projection area calculation unit on the projection surface, which calculates SP, SQ, SR, and SS shown in FIG. 1, for example. Reference numerals 44a to 44p denote multipliers, which are reference pixel extracting units 4
The reference pixel extracted in 1 is multiplied by the result of the projection plane calculation processing unit. The contents to be multiplied are shown below using the symbols shown in the figure.

P1 = I1 × S1 P2 = I2 × S2 ... P15 = I15 × S15 P16 = I16 × S16 That is, it is composed of 15 multipliers, and the pixel value of the reference pixel and the pixel surface are the conversion pixel. Multiply the area included in the projection plane. When the input image is a binary image, that is, when In is 0 or 1, the multiplier can be realized by logical product processing.
An addition processing unit 45 adds all multiplication results. When the calculation of the projection area calculation unit is performed by normalizing the pixel area of the conversion pixel to 1, the addition result obtained here becomes the conversion pixel value as it is. 16 is a synchronization signal control unit,
For example, in the case of reduction processing, the image synchronization signal / line synchronization signal of the original image is thinned out and output.

FIG. 3 is a diagram showing a specific example of the reference pixel extracting section 41. In the figure, 51a to 51c are 1-line delay elements, each of which is composed of a line memory or the like and stores image data in 1
Delay the line. 52a to 52L are 1-pixel delay elements which delay the image data by 1 clock. With such a configuration, the 16 pixels I0 to I15 shown in FIG. 4 are extracted from the raster-scanned image data input in accordance with each synchronization signal.
Can be referred to.

[0009]

However, according to such a conventional configuration, as the conversion magnification becomes smaller, the number of pixels of the original image to be referred to increases, and the cost increases as the scale of the reference pixel extracting unit increases. The capacity of the line memory, which is the main cause of the increase, increases. Further, there is a problem that the number of multipliers increases in accordance with the conversion ratio, which makes the circuit complicated and increases the circuit scale, and there is a problem that the minimum conversion ratio is limited depending on the circuit configuration.

The present invention has been made in view of the above problems, and an object thereof is to provide an image processing method which realizes a pixel density conversion by a projection method at a low cost with a small circuit scale regardless of the conversion magnification. To provide the device.

[0011]

In order to achieve the above object, an image processing method and apparatus according to the present invention have the following arrangement. That is, an image processing method for converting pixel density of raster-scanned image data, wherein a first side length is generated based on a side length of the image data in the main scanning direction and a conversion magnification in the main scanning direction. A first side length generation step, and a first sum calculation of the generated first side length and the image data
And a second side length generation step of generating a second side length based on the side length of the image data in the sub-scanning direction and the conversion magnification in the sub-scanning direction. A second product-sum operation step of performing a product-sum operation on the result and the second side length is provided.

Further, another invention is an image processing apparatus for converting pixel density of raster-scanned image data,
First side length generation means for generating a first side length based on the side length of the image data in the main scanning direction and the conversion magnification in the main scanning direction, the generated first side length, and the image data. And a second side length for generating a second side length based on the side length of the image data in the sub-scanning direction and the conversion magnification in the sub-scanning direction. A generation means and a second product-sum operation means for performing a product-sum operation on the result of the product-sum operation and the second side length are provided. Another aspect of the present invention is an image processing apparatus for performing pixel density conversion processing on raster-scanned image data by a projection method, wherein the length of a side in the main scanning direction of an original pixel surface included in the conversion pixel surface on the projection surface. In the main scanning direction, and a first product for performing a projection method conversion process in the main scanning direction by the sum of products of the side length calculation result and the raster image data. A sum processing unit, a sub-scanning direction projection surface side length calculating means for sequentially calculating the length of the side in the sub-scanning direction of the original pixel surface included in the conversion pixel surface on the projection surface according to the line synchronization signal of the original image; A second product-sum processing unit that performs a projection method conversion process in the sub-scanning direction by a product-sum process of the long calculation result and image data, the main scanning direction projection plane side length calculation unit, and the sub-scanning direction projection plane side length calculation unit Image sync signal from the result of Gosuru and a synchronizing signal control section.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION At first, the points of the embodiment according to the present invention will be summarized, and then the detailed description will be started. An image processing apparatus for performing pixel density conversion of a raster-scanned digitizer image data according to an embodiment of the present invention by a projection method is, on a projection surface, a side in a main scanning direction of an original pixel surface included in a conversion pixel surface. A first scanning direction projection plane side length calculation unit that sequentially calculates a length according to an image clock of an original image, and a projection method conversion process in the main scanning direction by a product-sum process of the side length calculation result and raster image data. A sum-of-products processing unit, a sub-scanning direction projection surface side length calculation unit that sequentially calculates the side length in the sub-scanning direction of the original pixel surface included in the conversion pixel surface on the projection surface according to the line synchronization signal of the original image,
A second product-sum processing unit that performs a projection method conversion process in the sub-scanning direction by a product-sum process of the side length calculation result and image data, a main scanning direction projection plane side length calculation unit, and a sub-scanning direction projection plane side length calculation unit And a synchronization signal control unit that controls the image synchronization signal based on the processing result of 1.

Further, the first sum-of-products processing unit has an image data storage unit for at least one pixel, and performs the sum-of-products processing on a pixel-by-pixel basis using the side length of the converted image in the main scanning direction as the sum-of-products section. Further, the second product-sum processing unit has an image data storage unit for at least one line, and performs the product-sum processing on a line-by-line basis using the side length of the converted image in the sub-scanning direction as a product-sum section.

Next, a detailed description of this image processing apparatus will be given. <First Embodiment> Hereinafter, the principle and embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 5 is a diagram showing a basic configuration of hardware according to the embodiment of the present invention.
Referring to FIG. 5, the original image is raster-scanned image data. For example, as shown in FIG. 6, one line of image data is synchronized with page synchronization signal 22 in synchronization with line synchronization signal 21. Then, the image data for one page is input in synchronization with the image clock 23, respectively.

FIG. 6 shows an image in which one line is composed of 7 pixels in order to facilitate the reader's understanding, but it goes without saying that the present invention is not limited to this number of pixels. . In FIG. 5, reference numeral 11 denotes a main-scanning-direction projection surface side length calculation unit, which calculates the length of the main scanning direction side of the original image surface included in the pixel surface of the converted image on the projection surface.

Reference numeral 12 denotes a first sum-of-products processing unit, which has a basic structure of sum-of-products processing including a register for accumulating image data for one pixel. The processing unit uses the original image signal data and the result of the side length calculation unit 11 in the main scanning direction to perform projection method calculation processing in the main scanning direction on the raster-scanned image data. A sub-scanning direction projection surface side length calculation unit 13 calculates the length of the side in the sub-scanning direction of the original pixel surface included in the pixel surface of the converted image on the projection surface.

Reference numeral 14 denotes a second sum-of-products processing section, which is a FIFO (First In First First) for accumulating image data for one line.
Out) The basic configuration is line-by-line product-sum processing consisting of memory. The processing unit performs the projection method process in the sub-scanning direction using the main scanning direction projection method processing result obtained by the first product-sum processing unit as input data. Reference numeral 15 denotes a synchronization signal control unit, which generates an image clock of the converted image and a line synchronization signal using the synchronization signal control signal obtained by each side length calculation unit from the original image clock and the original image line synchronization signal.

By the above processing of each unit, a converted image having a desired magnification can be obtained. Next, details of each unit in the embodiment of the present invention will be described according to a specific conversion example of FIG. 7. FIG. 7 is a diagram for explaining the conversion processing in which the conversion magnification is 4/9 in both the main scanning direction and the sub-scanning direction.
The state which projected the conversion image surface on the original image surface is shown.

In the figure, "○" represents the pixel of the original image,
"●" represents the pixel of the conversion pixel. Further, the dotted line represents the pixel surface of the original image, and the solid line represents the pixel surface of the converted pixel. When the conversion ratio is 4/9, the size of the pixel surface of the converted pixel is 1
Normalized to, the side length of the pixel plane of the original image is 4/9
become. That is, the conversion magnification is equal to the side length of the pixel surface of the original image.

FIG. 8 is a side view length calculation unit 11 for the projection surface in the main scanning direction.
It is a figure which shows the specific example of. The processing unit sequentially outputs the lengths of the sides of the original image pixel surface on the projection surface in the main scanning direction in synchronization with the original image clock. Specifically, Ixn (x = 1, 2, ...) Shown in FIG. 7 is sequentially output. A pixel number counter 81 counts the original image clock. This count is cleared by the original image line sync signal.

Reference numeral 82 denotes a ROM (Read Only Memory), in which a desired side length after conversion is preprogrammed with the counter output value and the main scanning conversion magnification as an address, and the main scanning is performed in synchronization with the operation of the counter. The main side length X indicating the side length in the direction is output. In addition to the data indicating the length of the side, the output data is pre-programmed with data values corresponding to control signals for controlling the first product-sum processing and the image clock signal, which will be described later. And the product-sum processing 1 for the first product-sum processing unit is synchronized with the main side length X.
Outputs control signal.

Next, FIG. 9 is a diagram showing a configuration example of the first sum-of-products processing unit. The operation of this processing unit will be described below with reference to the timing chart shown in FIG. The original image signal (10b) is input in synchronization with the original image clock (10a). The main side length (10c), which is the calculation result obtained in the main scanning direction projection plane side length calculation unit 11, is also input to the main processing unit in synchronization with the original image clock (10a).

First, the main image length (1b) is added to the original image signal (10b).
1c) is multiplied by the multiplier (91) and the signal (M
1) is output. Reference numeral 92 is an n-bit register, which accumulates the sum of products result (signal M3) in synchronization with the original image clock. The signal M1 is added by the adder 93 to the product-sum result stored in the register 92, and a signal M3 is output.

In the flip-flop 97, the addition result (M3) is synchronized with the converted image clock and output.
The signal M3 is also input to the register 92 via the selector 94. Here, the selector 94 outputs the product-sum processing control signal (1
1d), and when the signal is "0", the output X of the selector 94 is A input, that is, the sum of products result (M3) is selectively output. On the other hand, in the case of "1", the B input, that is, the signal M2 is selectively output to the output X of the selector 94.

The main scanning direction projection plane side length calculation unit 11 calculates the sum of products 1 when the boundary of the conversion pixel surface exists in the original pixel.
"1" is output as the control signal (11d). In the example of FIG. 7, for example, x _n3 (n is arbitrary) pixels are output at the timing. The signal M2 is strobed to the register 92 at the timing. The signal M2 is different from the original image signal
This is the result obtained by multiplying the result obtained by subtracting the side length from the main scanning conversion magnification (subtractor 95) (multiplier 96). This result is, for example, the data indicated by diagonal lines in the timing chart of M2 in FIG. 10, and this corresponds to the data in the region indicated by diagonal lines in FIG.

This means that the product-sum processing is initialized with the signal M2 at this timing. At 97, the signal M3 is latched / outputted in synchronization with the converted image clock.
As described above, the original pixel area included in the pixel surface of the converted pixel is subjected to the sum-of-products process in the section, thereby realizing the process based on the projection method in the main scanning direction by the register 92 regardless of the conversion magnification. To be done.

Next, FIG. 11 is a diagram showing a specific example of the sub-scanning direction projection surface side length calculation unit 13. The processing unit sequentially outputs the length of the side of the original pixel surface on the projection surface in the sub-scanning direction in synchronization with the line synchronization signal. Specifically, Iyn = (y = 1, 2, ...) Shown in FIG. 7 is sequentially output. Referring to FIG. 11, 111 is a line counter, which counts the original image line synchronization signal. The count is cleared by the original image page sync signal.

Reference numeral 112 denotes a ROM (Read Only Memory), which is programmed in advance with a desired side length corresponding to the output value of the line counter 111 and the sub-scan conversion magnification as an address signal. When the address signal is input, the corresponding modulation in the sub-scanning direction, that is, the sub-side length Y is output. Further, not only the side length but also a control signal for controlling a second product-sum processing unit and a line synchronization signal, which will be described later, are pre-programmed in the programmed data, and at the same time the side length is output. These control signals (sum of products processing 2 control signal) are also output.

Next, FIG. 12 shows a concrete example of the configuration of the second product-sum processing section. The operation of this processing unit is shown in FIG.
It will be described according to the timing chart shown in FIG. The sum-of-products signal (13b) converted in the main scanning direction and output from the first sum-of-products processing unit is input to the second sum-of-products processing unit in synchronization with the original image line synchronization signal 13a. The sub-side length (13c) obtained by the sub-scanning projection surface side length calculation unit 13 is also input to the main processing unit in synchronization with the original image line synchronization signal.

Then, the multiplier 121 multiplies the input main product sum signal by the sub-side length and outputs the signal N1. 122
Is a FIFO capable of accumulating an image data string for one line and performs an input / output operation in synchronization with a converted image clock. Further, the FIFO initializes the internal address counter in synchronization with the original image line synchronizing signal.

The adder 123 receives the signal N1 and the FIFO 12
The sum of products accumulated in 2 is added to output the sum of products (13
g), that is, the signal N3 is output. Then, the signal N3 is input to the FIFO 122 via the selector 124.
Here, the selector 124 controls the product-sum processing 2 control signal (13
When the signal is "0", it operates in accordance with d) and selects / outputs the A input side, that is, the signal N3 (sum of products result (13g)). On the other hand, in the case of "1", the B input side, that is, the signal N2
Select / output (13f). The sum-of-products processing 2 control signal (13d) is output from the sub-scanning direction projection surface side length calculation unit 13 as "1" when the boundary of the conversion pixel surface exists in the original pixel surface. In the example of FIG. 7, for example, x _3n lines (n is arbitrary) are output at the timing. At the timing, the signal N2 is selected.

The signal N2 is obtained by multiplying the main sum-of-products signal by the calculation result (125) obtained by subtracting the side length from the sub-scan conversion magnification (12).
6) The result. At this timing, the sum of products processing is performed by the signal N2
It is equivalent to initializing with. As described above, the processing based on the projection method in the sub-scanning direction is realized by the FIFO or the like capable of accumulating one line regardless of the conversion magnification by performing the product-sum processing operation on the original pixel area included in the pixel surface of the converted pixel on a line-by-line basis. It

Next, FIG. 14 shows the synchronization signal control unit 1 of FIG.
5 is a diagram showing a specific circuit example of No. 5; FIG. Reference numerals 141 and 142 denote logical product elements, which carry out thinning processing of the synchronizing signals by logically ANDing the respective control signals with the respective original image synchronizing signals. The image clock control signal is the product-sum processing 1 as shown in FIG.
It is a signal (11h) obtained by synchronizing the control signal (11d) with the falling clock of the original image. This image clock control signal and the original image clock (10a)
Converted image clock (1
1i) is obtained.

Also in the sub-scanning direction, as shown in FIG. 13, the converted image line synchronizing signal (13h) is obtained by using the product-sum processing 2 control signal (13d). As described above, according to the present embodiment, it is possible to realize the pixel density conversion device that does not depend on the conversion magnification with a simple configuration using one FIFO. <Other Embodiments> The edge length calculators 11 and 13 have been described in the above embodiments in the case of using the ROM, but the present invention is not limited to this. It goes without saying that the function may be realized.

Further, in the above-described embodiment, the case where the processing in the sub-scanning direction is performed after the conversion processing in the main scanning direction has been described, but the present invention is not limited to this order, and the processing in the sub-scanning direction is performed. It goes without saying that it is also possible to perform the processing in the main scanning direction after performing the processing. Furthermore, in the above-described embodiment, the case where it is realized by hardware logic has been described, but the present invention is not limited to this, and it is also possible to realize it by software.

Further, according to the conventional method, the image is enlarged / scaled.
When performing the reduction conversion processing, the image memory in which the image is stored is randomly accessed. However, according to the present invention, the conversion operation is completed by accessing the image in the raster scan order. In this case, high-speed processing can be realized by effectively using the high-speed page mode and the like.

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 implemented by supplying a program to a system or an apparatus. In this case, the storage medium storing the program according to the present invention constitutes the present invention. Then, by reading the program from the storage medium to the system or device, the system or device operates in a predetermined manner.

According to each of the embodiments described above, it is possible to realize a pixel density conversion device corresponding to an arbitrary magnification with a small circuit scale or arithmetic processing.

[0040]

As described above, according to the present invention, the pixel density conversion of an image can be realized inexpensively with a small circuit scale regardless of the conversion magnification.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of a projection method.

FIG. 2 is a diagram showing a configuration example when a projection method is realized by a conventional arithmetic method.

FIG. 3 is a diagram showing a configuration of a pixel extraction unit.

FIG. 4 is a diagram illustrating positions of reference pixels.

FIG. 5 is a diagram showing a basic configuration of a pixel density conversion device according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating timing of an image signal.

FIG. 7 is a diagram for explaining a conversion process.

FIG. 8 is a diagram showing a configuration of a side length calculation unit in a main scanning direction.

FIG. 9 is a diagram showing a configuration of a first sum-of-products process.

FIG. 10 is a timing chart illustrating the operation of the first sum-of-products processing unit.

FIG. 11 is a diagram showing the configuration of a side length calculation unit in the sub-scanning direction.

FIG. 12 is a diagram showing a configuration of a second sum-of-products processing unit.

FIG. 13 is a timing chart illustrating an operation of second sum of products processing.

FIG. 14 is a diagram showing a configuration of a synchronization signal control unit.

[Explanation of symbols]

 11 Main Scanning Direction Projection Side Edge Length Calculator 12 First Product-Sum Processing Section 13 Sub-scanning Direction Projection Side Edge Length Calculating Section 14 Second Product Sum Processing Section 15 Synchronization Signal Control Section

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location G09G 5/26 G06F 15/31 S 5/36 520 15/66 355A

Claims (19)

[Claims] 1. An image processing method for converting pixel density of raster-scanned image data, wherein a first side length is determined based on a side length of the image data in the main scanning direction and a conversion magnification in the main scanning direction. A first side length generating step of generating, a first sum of products calculating step of performing a sum of products calculation of the generated first side length and the image data, and a side length of the image data in the sub-scanning direction A second side length generating step of generating a second side length based on the conversion magnification in the sub-scanning direction, and a second sum of products operation of the result of the product sum calculation and the second side length. An image processing method comprising: a product-sum operation step. 2. The length of the side of the image data in the main scanning direction is generated by counting the number of image clocks synchronized with each pixel of one line of the image data. The image processing method according to claim 1. 3. The first side length generating step uses a memory that stores a predetermined first side length corresponding to each combination of the side length of the image data in the main scanning direction and the conversion magnification in the main scanning direction. 2. The image processing method according to claim 1, wherein the length of the side of the image data in the main scanning direction and the conversion ratio in the main scanning direction are accessed as an address signal to obtain the corresponding first side length. . 4. The length of the side of the image data in the sub-scanning direction is generated by counting the number of image line synchronization signals synchronized with each image line of one page of the image data. The image processing method according to claim 1, wherein: 5. The second side length generating step uses a memory storing a predetermined first side length corresponding to each combination of the side length of the image data in the sub-scanning direction and the conversion magnification in the sub-scanning direction. 2. The image processing method according to claim 1, wherein the side length of the image data in the sub-scanning direction and the conversion ratio in the sub-scanning direction are accessed as an address signal to obtain the corresponding second side length. . 6. The first product-sum calculation step calculates the product-sum of the generated first side length and the image data by calculating a side length of the image data in the main scanning direction and the main scanning direction. 7. The end of the product-sum operation is generated in synchronization with the first product-sum operation end signal generated on the basis of the conversion magnification, and the result of the product-sum operation is output to the second product-sum operation step. 1. The image processing method described in 1. 7. The second product-sum calculation step calculates the product-sum of the result of the product-sum calculation and the second side length by calculating the side length of the image data in the sub-scanning direction and the sub-scanning direction. 2. The image data whose pixel density has been converted is obtained by terminating in synchronism with a second product-sum operation end signal generated based on the conversion ratio in the direction, and the result of the product-sum operation being image data that has undergone pixel density conversion. The image processing method described in. 8. The image processing method according to claim 1, wherein the image processing method is an image processing method for performing pixel density conversion on image data raster-scanned based on a projection method. Image processing method. 9. An image processing device for converting pixel density of raster-scanned image data, wherein a first side length is determined based on a side length of the image data in the main scanning direction and a conversion magnification in the main scanning direction. First side length generating means for generating, first sum-of-products calculating means for performing sum-of-products calculation of the generated first side length and the image data, and length of side of image data in the sub-scanning direction Second side length generation means for generating a second side length based on the conversion magnification in the sub-scanning direction, and a second side-sum calculation for performing the product-sum calculation result and the second side length. An image processing apparatus comprising: a product-sum calculation means. 10. The length of a side of the image data in the main scanning direction is generated by counting the number of image clocks synchronized with each pixel of one line of the image data. The image processing apparatus according to claim 9. 11. The first side length generation means uses a memory that stores a predetermined first side length corresponding to each combination of the side length of the image data in the main scanning direction and the conversion magnification in the main scanning direction. 10. The image processing apparatus according to claim 9, wherein the length of the side of the image data in the main scanning direction and the conversion ratio in the main scanning direction are accessed as an address signal to obtain the corresponding first side length. . 12. The length of a side of the image data in the sub-scanning direction is generated by counting the number of image line synchronization signals synchronized with each image line of one page of the image data. The image processing device according to claim 9, wherein 13. The second side length generating means uses a memory that stores a predetermined first side length corresponding to each combination of the side length of the image data in the sub-scanning direction and the conversion magnification in the sub-scanning direction. 10. The image processing apparatus according to claim 9, wherein the length of the side of the image data in the sub-scanning direction and the conversion ratio in the sub-scanning direction are accessed as an address signal to obtain the corresponding second side length. . 14. The first product-sum calculation means calculates the product-sum of the generated first side length and the image data by calculating the side length of the image data in the main scanning direction and the main scanning direction. 7. The product-sum operation is ended in synchronization with the first product-sum operation end signal generated on the basis of the conversion magnification of, and the result of the product-sum operation is output to the second product-sum operation means. 9. The image processing device according to item 9. 15. The second product-sum calculation means calculates the product-sum of the result of the product-sum calculation and the second side length by calculating the side length of the image data in the sub-scanning direction and the sub-scanning direction. 10. The image data which has been subjected to the pixel density conversion and is ended in synchronism with the second product-sum operation end signal generated based on the conversion ratio in the direction, and the result of the product-sum operation being the pixel density converted image data. The image processing device according to item 1. 16. The image processing apparatus according to claim 9, wherein the image processing apparatus is an image processing apparatus that converts pixel data of raster-scanned image data based on a projection method. Image processing device. 17. An image processing device for converting pixel density of raster-scanned image data by a projection method, wherein an original length of a side in a main scanning direction of an original pixel surface included in the converted pixel surface on a projection surface is original. Main scanning direction projection plane side length calculation means for sequentially calculating according to the image clock of an image, and first product-sum processing for performing projection method conversion processing in the main scanning direction by product-sum processing of the side length calculation result and the raster image data. Section, a sub-scanning direction projection surface side length calculating means for sequentially calculating the length of the side of the original pixel surface included in the conversion pixel surface in the sub-scanning direction on the projection surface according to the line synchronization signal of the original image, and the side length calculation. A result of the second product-sum processing unit that performs the projection method conversion process in the sub-scanning direction by the product-sum process of the result and the image data, the result of the main scanning direction projection surface side length calculation unit and the sub-scanning direction projection surface side length calculation unit Image sync signal from Gosuru pixel density conversion apparatus characterized by comprising a synchronization signal control unit. 18. The first product-sum processing unit has image data storage means for at least one pixel, and performs the product-sum process on a pixel-by-pixel basis using the side length of the converted image in the main scanning direction as a product-sum section. 18. The pixel density changing device according to claim 17, which is characterized in that. 19. The second sum-of-products processing unit has image data storage means for at least one line, and performs sum-of-products processing on a line-by-line basis using the side length of the converted image in the sub-scanning direction as a sum-of-products section. The pixel density conversion device according to claim 17, which is characterized in that.