JPH01142879A - Interpolating device for digital image - Google Patents

Abstract

PURPOSE:To obtain excellent picture quality by a simple circuit by executing interpolation/enlargement processing respectively independently in the main scanning direction and the sub-scanning direction and inputting one processed result to the other processing. CONSTITUTION:The title device is provided with digital differential analyzers (DDAs) 14, 15 for setting up optional interpolating positions, selecting 2mX2n image data surrounding the interpolating positions around the set interpolating positions and finding out distances (x), (y) from the set interpolating positions up to the selected image data. The device is also provided with 1st interpolation image data forming means 16-18 forming intermediate interpolation image data I(Y) by the distance (y), a factor omega(y) uniquely determined based on the distance (y) and 2n image data in the Y direction, and 2nd interpolation image data forming means 19-21 forming the final interpolation image data I by the distance (x), a factor omega(x) uniquely determined based on the distance (x) and 2m 1st interpolation image data I(Y) formed in the X direction. Consequently, excellent interpolation processing can be rapidly executed by the simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital image interpolation device, and more particularly to a digital image interpolation device that forms interpolated image data to be provided to an image output device.

[Prior Art] Generally, this type of device can perform image enlargement and interpolation processing. However, when outputting to a laser beam printer (LBP) or the like, it is necessary to output the processing results in synchronization with a high-speed pixel clock signal.

For this reason, in the past, the same pixel was simply read out a number of times corresponding to the enlargement ratio, or the enlarged and interpolated image data was stored in a memory and then read out again and transferred. However, in the former case, the magnification is 2x, 3x, 4x 180
．． As the image size increased, the image became mosaic-like and its quality became extremely poor. Furthermore, in the latter case, as printers become higher in definition or larger in size, the memory capacity for holding processed image data becomes enormous, which poses a problem in terms of cost.

[Problems to be Solved by the Invention] The present invention eliminates the drawbacks of the prior art described above, and its purpose is to provide a digital image interpolation device that can perform high-quality interpolation processing at high speed with a simple configuration. Our goal is to provide the following.

[Means for Solving the Problems] In order to achieve the above object, the digital image interpolation device according to the present invention includes an image memory that stores a plurality of image data at integer addresses of orthogonal addresses X and Y; interpolation position setting means for setting an arbitrary interpolation position in the real addresses X and Y; and image data selection means for selecting 2m×2n pieces of image data surrounding the interpolation position with the set interpolation position as the approximate center. , distance calculation means for calculating distances x and y from the set interpolation position to the selected image data; and the distance y and the distance l! a first interpolated image data forming means that forms intermediate interpolated image data I (Y) from a coefficient ω(y) uniquely determined based on 1y and 2n pieces of image data in the Y direction; and the distance @x;
The coefficient ω(X) that is uniquely determined based on the distance 1lix and the 2m pieces of first interpolated image data I (
Y) to form the final interpolated image data
The outline of the system is to include an interpolated image data forming means.

Preferably, the first interpolation image data forming means calculates the interpolation coefficient I from the distance y and the coefficient ω(y) determined by the distance y.
(y) is obtained according to the following formula, πy, and the multiplication of the interpolation coefficient I (y) obtained above and the image data corresponding to the interpolation coefficient I (y) is taken,
Intermediate interpolated image data I (Y) is formed by the sum of the obtained 2n products, and the second interpolated image data forming means calculates the distance X and the coefficient ω(X) determined by the distance 1x.
The interpolation coefficient I (x) is determined according to the following formula, π One aspect of this is to take the multiproducts of 2m products and form the final interpolated image data (2) by the sum of the 2m products obtained.

Preferably, the coefficients ω(×) and ω(y) are each expressed by the following equations, One aspect of this is that it is determined by the relationship.

Preferably, the coordinate Y corresponds to the sub-scanning direction of the image output device, and the coordinate X corresponds to the main scanning direction of the image output device.

[Operation] In such a configuration, the image memory has orthogonal addresses X, Y
A plurality of image data is stored at an integer address. The interpolation position setting means sets an arbitrary interpolation position at the real addresses of the orthogonal addresses X and Y. The image data selection means selects 2m×2n pieces of image data so as to surround the set interpolation position approximately at the center. The distance calculation means calculates the distance 1efix, y from the set interpolation position to the selected image data. The first interpolated image data forming means sequentially generates intermediate interpolated image data I (Y) using the distance 1ily, a coefficient ω(y) uniquely determined based on the distance y, and 2n pieces of image data in the Y direction. Form. Preferably, the coefficient ω(y) is determined by the following equation. Then, the first interpolation image data forming means generates an interpolation coefficient from the distance may and the coefficient ω(y) determined by the distance y. (y) is obtained according to the following formula, πy, and various types of image data corresponding to the interpolation coefficient r (y) obtained above and the interpolation coefficient I (y) are obtained,
Intermediate interpolated image data I (Y) is formed by the sum of the 2n products obtained.

The second interpolated image data forming means determines the distance aX,
The coefficient ω(x) that is uniquely determined based on the distance lIx and the 2m pieces of first interpolation image data I (Y
) to form the final interpolated image data ■. Preferably, the coefficient ω(x) is determined by the following equation, m. Then, the second interpolation image data forming means calculates the interpolation coefficient I (x) from the distance @x and the coefficient ω(x) determined by the distance x according to the following formula, π ) and the intermediate interpolated image data I (Y) formed above corresponding to the interpolation coefficient 1 (x), and the final interpolated image data (2) is formed by the sum of the obtained 2m products.

In this case, preferably the coordinate Y corresponds to the sub-scanning direction of the image output device, and the coordinate X corresponds to the main scanning direction of the image output device.

In this way, by configuring the output of one as the input of the other, the processing is pipelined and the processing in each part is simplified, making it possible to perform high-speed processing with good image quality with a relatively simple configuration. do.

[Description of Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[First Embodiment] FIG. 1 is a block diagram of a digital image interpolation device according to a first embodiment of the present invention. The first embodiment relates to one in which an NTSC video signal of a television is digitally converted, interpolation processing according to the present invention is performed, and the resulting interpolated image data is output to an image printer.

In FIG. 1, 1 is a video signal source, which generates an NTSC video signal VS used, for example, in television. Reference numeral 2 denotes a luminance signal extraction circuit, which extracts a zedeo luminance signal VLS from the video signal vs using, for example, a known color subcarrier removal filter. Reference numeral 3 denotes a synchronization signal extraction circuit, which extracts a video frame synchronization signal V from the video signal vS using a known circuit in, for example, a conventional television receiver.
FDS (vertical synchronization signal) and video scanning line synchronization signal V
Extract HDS (horizontal synchronization signal). 4 is a sampling period generating circuit, which generates the extracted synchronization signal VFDS.
, based on VHDS, for example, the video luminance signal VLS is converted to A/
A data sampling signal DSS (for example, 640 pixels/scanning line) for D conversion is generated. 5 is an A/D conversion circuit which A/D converts the input video luminance signal VLS and outputs digital luminance data LD. 6 is a γ conversion circuit which converts the input luminance data LD to an appropriate density level and outputs density data ND. In general, a television signal is a signal having a γ characteristic of (1/2.2), which matches the characteristics of a display surface fluorescent material for image reception.

Therefore, the γ conversion circuit 6 converts the luminance data LD having this characteristic.
is linearly converted into density data ND having an appropriate density level matching the printer characteristics. A frame memory 7 stores one page of input density data ND. A write address control circuit 11 controls the write address WAD and write timing of the density data ND to the frame memory 7. Specifically, the data sampling signal DSS is counted to calculate which pixel position (X coordinate) it corresponds to in the video scanning line, and the video scanning line synchronization signal VHDS is counted to calculate which pixel position (X coordinate) it corresponds to in the screen. It is calculated whether it corresponds to the th video scanning line (Y coordinate).

With the above configuration, each density data NI) (image data G
D) are written in a continuous manner onto the integer addresses of the frame memory 7 in synchronization with the data sampling signal DSS.

FIG. 6 is a diagram showing one storage mode of image data in the frame memory 7. As shown in FIG. In the figure, a series of image data G
D (density data ND) is stored as raster data corresponding to a printing scanning line (raster). For example, first, the first pixel, second pixel, . . . , Nth pixel of the first rask are stored in order.

If necessary, a margin for the first rask is stored between the first rask and the second rask. This simplifies eight-way control of the X and Y addresses. Next, the first pixel, second pixel, ..., Nth pixel of the second rask are stored in order,
In this way, finally, the 341st pixel of the Mth raster, the second pixel,
. . , the Nth pixel is stored in order. In this case, the frame memory 7 continuously stores image data GD having a number of pixels corresponding to a power of 2, for example, for each rask. The size of one image stored in this way is, for example, 640 (pixels/raster) x 4.80 (raster/image), and the memory space for this may be 1024 x 512 = 512 bytes.

In FIG. 1, reference numeral 10 denotes an image printer, which sends out a print page synchronization signal PPDS indicating the top of the page when printing starts, and sends out a print page synchronization signal PPDS (sub-scanning synchronization signal ) and a print pixel synchronization signal PGDS (main scan synchronization signal) in each print scan line. These synchronization signals are input to an interpolation processing circuit 8, which will be described later, via a printer I/F circuit 9. 8 is an interpolation processing circuit which sets an interpolation position (real number coordinates) by counting various synchronization signals from the image printer 10 and also outputs synchronization signals (various carry signals) for updating the integer read address of the frame memory 7. CA
R), and together with these, the sum of the products of the interpolation coefficient I and the original image data (interpolated image data HGD) is generated.

A read address control circuit 12 updates the integer read address RAD of the frame memory 7 in synchronization with various carry signals CAR from the interpolation processing circuit 8. With the above configuration, the image data GD on the frame memory 7 is interpolated by the interpolated image data HGD and output to the image printer 10. Reference numeral 13 denotes a sequence control section, which controls the operating procedure of the entire apparatus.

FIG. 3 is a flowchart of the image data processing procedure by the sequence control circuit 13 of the first embodiment. In the figure, in step S1, it is determined whether or not there is a print instruction from an operation unit (not shown).

If there is no print instruction, the process advances to step S2 and other processing is performed. Other processing includes, for example, the image printer 1
This refers to checking the status of the video signal source 1 (such as power off) or checking the status of the video signal source 1 (whether the signal is being transmitted or not). If there is no abnormality in this check, the process immediately returns to step S1. Further, if there is a print instruction in step S1, the process advances to step S3, where the write address control circuit 11 is initialized, and then the density data ND write function is activated to store a series of density data ND in the frame memory. Start writing to 7. In step S4, it is determined whether writing to the frame memory 7 is complete. If writing is not completed, step S5
, and perform other processing in the same manner as described above. When the writing of all density data ND is completed, the process advances to step S6, and the data writing function of the write address control circuit 11 is disabled. In step S7, it is determined whether the image printer 10 is ready to start printing. If it is not ready to start printing, the process advances to step S8, and other processing is performed in the same manner as described above. Further, if the printing can be started, the process advances to step S9, and the interpolation processing circuit 8 is initialized.

Specifically, setting of each constant value (initial value, increment value) in the differential analysis circuit (DDA) 14 and DDA 15, which will be described later, clearing various buffer groups (F I FO, latch, etc.), and data flow (not shown) Initializes control counters and clears various gates, etc.

In step S10, the read address control circuit 12 is initialized and then placed in a data read operation enabled state.

Specifically, the counter and the like that hold the image data read address RAD of the frame memory 7 are initialized, and the first image data GD is made readable. Step Stt
Now, the printer I/F circuit 9 is initialized. in particular,
Reception of control commands and status signals with the image printer 10 initializes the I10 circuit for control information necessary for transfer, etc., and sends and receives the information, etc., as well as various synchronization signals related to image interpolation processing and transfer. initialization, and initialization of gate circuits and the like related to these signals are performed. In this way, from now on, the read address control circuit 12 and the interpolation processing circuit 8 operate in synchronization with the operation clock signal (various synchronization signals) from the image printer 10, and the image data GD is transferred from the frame memory 7.
are sequentially read out, subjected to interpolation processing, and the generated interpolated image data HGD is sent to the image printer 10 via the printer I/F circuit 9. On the other hand, the sequence control circuit 13 waits for printing completion in step S12. That is, it is determined in step S12 whether or not printing has been completed, and if printing has not been completed, the process advances to step S13 and other processing is performed in the same manner as described above. When printing is eventually completed, the process proceeds to step 314, where the image data read function of the read address control circuit 12 is disabled.

FIG. 2 is a block diagram showing details of the interpolation processing circuit 8 of the first embodiment. In the figure, 14 is D D A (
Digital Differential Anal
yzer) and performs digital differential analysis of the printer sub-scanning direction address (Y coordinate). Specifically, it generates a sub-scan carry signal VCAR for updating the integer read address (Y coordinate) of the frame memory 7, and also generates a sub-scan carry signal VCAR for updating the integer read address (Y coordinate) of the frame memory 7, and also
coordinates). 15 is a DDA, which performs digital differential analysis of the printer main scanning direction address (X coordinate).

Specifically, the integer read address (X
It generates a main scanning carry signal HCAR for updating the coordinates), and also generates a real address (X coordinate of the interpolated position) located between the integer read addresses. Reference numeral 16 denotes a group of raw data scanning line buffers, which can store seven scanning lines of image data GD sequentially read out from the frame memory 7 in parallel. Reference numeral 17 denotes a sub-scanning direction interpolation table group, which is set to obtain the product of the temporary sub-scanning direction component interpolation coefficient 7 and the input image data for the eight image data GD arranged in one row in the sub-scanning direction. Interpolated position and distance between each image data! Each generates a value of a predetermined coefficient 7 based on Iy, and the product of the value of the coefficient 7 and the image data is calculated. Reference numeral 18 denotes a sub-scanning direction interpolation adder group, which calculates the sum of the multiproducts by the interpolation table group 17 and obtains the sum of the products of I7 and human image data as a temporary interpolation result in the sub-scanning direction.

19 is a main scanning direction interpolation data buffer group, which stores temporary interpolation results of the output of the sub scanning direction interpolation adder group 18;
Seven total products of the input image data and the input image data can be sequentially stored in the main scanning direction.

20 is a main scanning direction interpolation table group, in which 8 interpolation coefficients arranged in a line in the main scanning direction ■ The final interpolation result for 7 ■ To obtain the sum of the products of the input image data, set interpolation Each generates a predetermined value of coefficient IX based on the distance 1[tx between the position and each interpolated image data, and calculates the product of the value of coefficient 8 and the above-mentioned temporary interpolation result. 21 is a group of interpolation adders in the main scanning direction, which calculates the sum of multiproducts by the interpolation table group 20 and calculates the final interpolated image data V o
Find ut.

FIG. 13 is a diagram showing tables 17 and 20 of the embodiment. These are realized by a ROM, and the upper side of the address input corresponds to interpolation position information (ΔX or Δy), and the lower side of the address input corresponds to the value of the human pixel. The contents of the table are preset as the product of the interpolation coefficient at the interpolation position corresponding to each address and the corresponding pixel value.

Next, details of the operation of the interpolation processing circuit 8 will be explained.

When the page synchronization signal PPDS is input to the DDA 14, the selector 14-4 changes to a mode in which the contents of the initial value register 14-2 are selectively output. As a result, the adder 14-5 outputs the initial value of the initial value register 14-2 and the increment value register 14.
-1 increment value is added and the addition result is output. When the first scanning line synchronization signal PSDS is input to the 0th order, the adder 14
The addition output of -5 is taken into the current value register 14-3, and at the same time the selector 14-4 changes to a mode for selectively outputting the contents of the current value register 14-3.

Therefore, from now on, each time the scanning line synchronization signal PSDS is input, the contents of the current value register 14-3 are updated by the value obtained by adding the increment value to the previous value. Also, each time an addition carry occurs in the adder 14-5 during this update cycle, a carry signal VCAR is generated and outputted to the read address control circuit 12. From the above, the output of the adder 14-5 can be considered to be the remaining fractional part when the carry is normalized to 1, excluding the carry signal VCAR. Therefore, when the distance of the sampling interval in the sub-scanning direction of the video signal vS is considered to be a unit distance mi, the output of the adder 14-5 is the real distance lI measured from each sampling position in the sub-scanning direction.
It represents y.

Similarly, when the scanning line synchronization signal psDS is input to the DDA 15, the selector 15-4 changes to a mode in which the contents of the initial value register 15-2 are selectively output. As a result, the adder 14-5 adds the initial value of the initial value register 15-2 and the increment value of the increment value register 15-1, and outputs the addition result. Next, when the first pixel synchronization signal PGDS is input manually, the addition output of the adder 15-5 is taken into the current value register 15-3, and at the same time, the selector 15-4 enters a mode for selectively outputting the contents of the current value register 15-3. Change. Therefore, from now on, each time the pixel synchronization signal PGDS is input manually, the contents of the current value register 15-3 are updated by the value obtained by adding the increment value to the previous value. Also, when an addition carry occurs in the adder 15-5 during this update cycle, a carry signal HCAR is generated each time, and this is sent to the read address control circuit 1.
Output to 2. From the above, the output of the adder 15-5 can be considered to be the remaining fractional part when the carry is normalized to 1, excluding the carry signal HCAR. Therefore, when the distance of the sampling interval in the main scanning direction of the video signal vS is considered as a unit distance 11, the output of the adder 15-5 represents the real distance wix measured from each sampling position in the main scanning direction.

FIG. 5 is a schematic diagram illustrating the operation mode of the DDA of the first embodiment. FIG. 5 shows, as an example, the operation of the DDA when an original image is enlarged by 130% and subjected to interpolation processing. 1
When enlarging by 30%, a value of 1/1.3 is expressed in binary and 15 bits below the decimal point are used as the increment value. When the decimal part is expressed in hex, it is "313B". On the other hand, the initial value becomes the current value (decimal part) when the 8th carry signal CAR is generated by adding the increment value "313B".
Set a value such that the value is "O". The initial value in this case is "13B2". As a result, FIG. 5 shows a relationship in which the first carry signal CAR is generated when the first 10 clock signals are input from the printer 10 side.

Here, if the clock signal on the image printer 10 side is the pixel synchronization signal PGDS, then FIG. 5 shows an example of the operation of the main scanning direction DDA 15. This shows a relationship in which eight pieces of input image data GD are read out during output. Furthermore, if the clock signal is the scanning line synchronization signal PSDS, then FIG. 5 shows an example of the operation of the sub-scanning direction DDA14. The relationship is shown in which eight lines of input image data GD are read out. Note that it is not necessary to perform the addition using the FULL 15 bits, and the addition may be performed using the upper several bits.

In FIG. 2, the read address control circuit 12 is reset by the page synchronization signal PPDS, and thereafter the DDA
The lower read address (main scanning direction address) of the frame memory 7 is obtained by counting the carry signal HCAR from 15.
and carry signal VCAR from DDA14.
is counted and the upper read address of the frame memory 7 (
(sub-scanning direction address). The read address signals R and AD sent to the frame memory 7 are a combination of the upper and lower read addresses.

The raw data scanning line buffer group 16 includes seven shift registers (PIFo, 16-1 to 16-7), and contains seven scanning lines of image data G that cannot be read from the frame memory 7.
Save D. That is, the image data GD read from the frame memory 7 is input to the FIFO 16-1 and shifted by 1024 pixels. Next, the output of PIFO16-1 is FI
It becomes the input of FO16-2, and in the same way, FIFO1
The output of 6-6 becomes the input of PIF016-7. Furthermore, the image data GD input to PIF016-7 is 10
When shifted by 24 pixels, the image data GD of the eighth scanning line is read out from the frame memory 7 in synchronization with this. If this 8th scanning line read raster is the current read raster, then any PIFO 16-i (i-1, 2,
....

The content stored in 7) is the read raster i lines before.

The sub-scanning direction interpolation table group 17 includes eight look-up tables (LUTs) 1 to 17-8. Each LOT is the image data GD of the corresponding readout raster and the real number path 1 measured in the sub-scanning direction from the current sampling position.
1ty (output of adder 14-5) as input, the contribution rate (sub-scanning Directional partial interpolation coefficient Iy
) and the corresponding input pixel value.

For example, the LUT 17-1 is the image data GDO of the current read raster and the current interpolated position y of the output of the adder 14-5.
is used as the address input, and this causes the LUT17-
1 is a predetermined interpolation coefficient Iy corresponding to the current interpolation position y
o (partial interpolation coefficient) and the value of the image data CD (
The product value I'J o G Do is internally generated and output.

Similarly, LUT17-8 is set to 7 of PIF016-7 output.
The image data GD7 before the line and the interpolation position y of the adder 14-5 are used as address inputs, so that the LUT
17-8 is a predetermined coefficient I3'? corresponding to the interpolation position y7, which is the current interpolation position y plus 7 scanning line intervals. The value Iyy of the product of the value (partial interpolation coefficient) and the value of the image data GD7
Generate and output GDy internally. In this way, the contents of the image data GD are sequentially updated in synchronization with the generation of the carry signal (ICAR), and the product of the aforementioned partial interpolation coefficient Iyn and the human image data GD is sequentially calculated. On the other hand, the contents of the read raster are sequentially updated one line at a time in synchronization with the generation of the carry signal VCAR. During this period, scan synchronization signals PSDS are normally generated at a rate of one or more (1, 2, 1, 3, etc.), and the interpolation position y in the sub-scanning direction is updated in synchronization with this. As a result, image data GD is enlarged and interpolated in the sub-scanning direction.

In the above embodiment, the calculation of the partial interpolation coefficient ry is performed simultaneously using the current readout raster and the preceding 7 lines of readout rasters, but in reality, the calculation of the partial interpolation coefficient ry is performed using the current readout raster and the preceding 7 lines of readout raster, but in reality, the image is calculated on four lines above and below approximately centered on the current interpolation position. You may want to perform interpolation processing depending on the data.

In this case, for example, the adder 14-5 output and each LUTl
The phase of the current interpolation position may be delayed by inserting a four-stage shift register between 7-1 and 17-8.

The sub-scanning direction interpolation adder group 18 includes LUT17-1 to LUT
Add all outputs of I 7-8 and output the sum. Thus, the output of the adder 18-7 is a temporary partial interpolation value GDv based on the sub-scanning direction image data GD at the current interpolation position.

Next, interpolation processing in the main scanning direction will be explained. The main scanning direction interpolation processing data buffer group 19 sequentially stores (latches) partial interpolation values in the sub scanning direction in synchronization with the carry signal HCAR.
do. This memory is stored from latch 19-1 to latch 19-2,
The latch 19-2 to latch 19-3 are latched in a shift register format in synchronization with the carry signal HCAH.

Therefore, if the current point is when the output of the adder 18-7 becomes valid, the latch 19-7 will hold the partial interpolation value GDY of seven columns before.
7, and latch 19-6 is 6 rows in front...
Similarly, latch 19-1 is the partial interpolation value GDY of the previous column.
, holds.

The main scanning direction interpolation table group 20 includes eight look-up tables (LUTs) 20-1 to 20-8. Each LUT has a corresponding partial interpolation value GDY and a real number distance 1! measured in the main scanning direction from the current sampling position! Ix
(adder 15-5 output) as input and the corresponding partial interpolated value G
Interpolated image data HG with the density of DY to be generated at the interpolated position
The product of the contribution rate (partial interpolation coefficient Ix in the main scanning direction) indicating how much contribution should be made from the main scanning direction to the density of I) and the corresponding partial interpolation value GDY is output. For example, LUTZ
O-1 is the current partial interpolation value GDY0 and adder 15-
The current interpolated position
The value of the product of the value of a predetermined coefficient 1x (partial interpolation coefficient) corresponding to 1x and the value (density) of the partial interpolation value GDyo is internally generated and output. Similarly, LUTZO-8 is FIFO
The partial interpolated value GDY7 of the 7th column before the output of 19-7 and the interpolated position The predetermined coefficient Ix, (
A value of the product of the value of the partial interpolation coefficient) and the value of the partial interpolation value GDY7 is internally generated and output. In this way, the partial interpolation value GDY is sequentially updated in synchronization with the generation of the carry signal HCAFt, and the product with the aforementioned partial interpolation coefficient Ixn is sequentially calculated. During this period, the pixel synchronization signal PGDS is normally used at one or more ratios (1, 2, 1, 3, etc.)
occurs, and in synchronization with this, the interpolated position X in the main scanning direction is updated. As a result, image data GD is enlarged and interpolated in the main scanning direction.

In the above embodiment, the calculation of the partial interpolation coefficient lx is performed simultaneously by using 8 pixels of the current partial interpolation value GDY and the preceding 7 partial interpolation values GDY, but in reality, the calculation of the partial interpolation coefficient lx is performed approximately at the current interpolation position. Partial interpolation value of 4 pixels before and after 1. There are cases where it is desired to perform interpolation by t. In this case, for example, the adder 15-5 output and each LUT 20-1 to 2
By inserting a four-stage shift register between 0 and 8, the phase of the current interpolation position may be delayed.

The main scanning direction interpolation adder group 21 includes LUTs 20-1 to LU
Add all outputs of T 20-8 and output the sum.

Thus, the output of adder 21-7 is the final interpolated value V at the current interpolated position. ut (interpolated image data I(G
D).

FIGS. 4(A) and 4(B) are operation timing charts illustrating the manner of synchronization between the interpolation processing circuit 8 and the image printer 10. In FIG. 4(A), when the image printer 10 becomes ready, the sequence control circuit 13 outputs a read address enable signal and the image printer 10 is actually printing. Subsequently, the page synchronization signal P is sent from the image printer 10.
PDS and scanning line synchronization signal PSDS are output, and interpolation processing is performed in synchronization with these.

FIG. 4(B) is an enlarged view of one scanning line period in FIG. 4(A). In FIG. 4(B), a pixel synchronization signal PGDS is generated at predetermined intervals within one scanning line period, and a carry signal HCAR is normally generated at a constant rate smaller than this. On the other hand, the interpolated image data HGD is the pixel synchronization signal PGD.
It is output in synchronization with S.

Next, the enlarging interpolation process for the original image will be explained in detail.

FIG. 7(A) is a diagram showing the original image of a person, and FIG.
B) is a diagram showing an image obtained by enlarging and interpolating the original image of FIG. 7(A). The enlargement ratio of the image in the figure is, for example, 5.75 times in the main scanning direction and 4.25 times in the sub-scanning direction. Such image enlargement can be realized by increasing the number of pixels of the original image using the interpolation method according to the present invention.

FIG. 8(A) is a diagram showing a partial area of the original image.
Figure (B) shows the partial area of Figure 8 (A) in the main scanning direction.
75 times, and 4.25 times in the sub-scanning direction. 8th
The pixel pitch in Figure (A) corresponds to the data sampling pitch when the video image signal vS is sampled, and Figure 8 (B) shows the partial area that has been relatively enlarged using this sampling pitch as the minimum unit. It is shown.

Therefore, the partial area a of the original image corresponds to the partial area a' of the enlarged image, and the assumed interpolation position in the original image corresponds to the output pixel position b' in the enlarged partial area a'. Therefore, interpolated image data HGD is formed at the output pixel position b', and the value (density) of the interpolated image data HGD is determined by selecting a plurality of predetermined image data surrounding the output pixel position b'. This is performed by using the value of GD, weighting the contribution rate (interpolation coefficient) determined by the distance from the pixel position b' to each image data GD, and calculating the sum of the weights.

Next, the case of determining the value of the output pixel position b' in FIG. 8(B) will be explained. This is equivalent to finding the real value corresponding to the interpolated position in FIG. 8(A). Therefore, Figure 8 (A
) is rewritten as shown in Figure 9. In FIG. 9, the position of the x mark is point b.

Here, the pixel positions of the original image are indicated by O marks, and the sampling pitch of the image data GD is equal in both the main scanning and sub-scanning directions. In addition, in Fig. 9, the pixel interval of the original image is considered to be a unit distance (for example, distance 1), and the coordinates in the main scanning direction are set with the interpolation position of the X mark as the origin, the right direction is positive, the left direction is negative, and For the coordinates in the sub-scanning direction, another coordinate system is introduced in which the origin is the interpolated position of the X mark, and the downward direction is positive and the upward direction is negative. Therefore, in the new coordinate system, the position of the original image can be expressed by applying ±ΔX and ±Δy, respectively. 5ΔX and Δy are the pixel positions C of the original image whose coordinate values do not exceed the interpolated position in the main scanning direction and the sub-scanning direction, respectively.
is the distance from

Now, let the distance in the main scanning direction between the pixel position and the interpolation position of a certain original image be X, and similarly let the distance in the sub-scanning direction be y, and then It is assumed that the contribution rate (interpolation coefficient) I(y) in the scanning direction is expressed by the following formulas.

πx 2 4 πy 2 4Here m=4. A multiple of 2 was chosen, such as n=4. Next this I
(x) and I (y) are multiplied by the value of the input image data GD, this operation is obtained for all input image data GD within the range used for interpolation, and the sum of these is taken as the interpolated value I.

That is, the value of interpolated value I (interpolated image data HGD) is set to V 0
When LIT is assumed, and considering that the interpolation point is interpolated using surrounding 8 pixels x 8 rasters, totaling 64 pixel data, as shown in Fig. 9, v outT is expressed as follows, xI (i - Δx) x I
(j-Δy)). This is done after calculating all the values multiplied by the interpolation coefficients for each of the 64 pixels.
means to calculate the sum of the values. However, attempting to realize this as is would require enormous amounts of hardware and would be impractical. Also, if it is performed using software, sufficient processing speed cannot be obtained. Therefore, the above formula for V OUT is modified as follows.

out xl(i-ΔX) Thus, first performing interpolation in the sub-scanning direction and then using the result to perform interpolation in the main scanning direction is equivalent to the above. The first embodiment described above is realized according to this method.

FIG. 10 is a diagram showing details of the interpolation principle in the main scanning direction. In the figure, the symbol (V+-ΔX) is the coordinate (i-ΔX)
This is the value of the image data GD at the point.

Based on these, the value v0 of the interpolated image data HGD is obtained as follows.

Also, ω5inc (i, ΔX) ==ω(i, Δx) ・5inc (i, ΔX)
π(i-ΔX) = 172[1+cos(27E/N (L-ΔX))
]π(i−ΔX). The LUT instantly performs the equivalent of this calculation.

Figures 11 (A) to (C) are diagrams showing how image data increases (how the number of pixels increases) when the original image data is interpolated in the sub-scanning direction and then interpolated in the main scanning direction. . In FIG. 11(A), a scanning line interpolated only in the sub-scanning direction is created using 8 consecutive scanning lines in the human image, that is, using pixels at the same position in the sub-scanning direction on each scanning line. do. In FIG. 11(B), interpolation is performed in the main scanning direction using pixels on the scanning line interpolated only in the sub-scanning direction. This results in an output scan line with an increased number of pixels in one scan line and an increased number of scan lines in the image as shown in FIG. 11(C).

[Second Embodiment] The second embodiment relates to generalization of manual selection of pixel regions required for calculating interpolated values. That is, in the second embodiment, for example, each correction coefficient formula I(x) for integers m and n
, I (y) are taken as follows, and the input pixel area is expanded from the 8×8 described in the first embodiment to 2m×2n.

[Third example] The third embodiment relates to a modification of the configuration shown in FIG.

That is, the LUT groups of the interpolation table groups 17 and 20 may be configured as an LUT that outputs only a predetermined coefficient ω(X) or ω(y) and a multiplier that calculates the product of the LUT output and the pixel value. .

In this way, it is possible to significantly reduce the capacity of the LUT. Incidentally, in the third embodiment, the size can be determined by a trade-off between image quality and circuit scale, and this also shows that the present invention itself does not depend on size.

[Fourth example] The fourth embodiment relates to a modification of the configuration shown in FIG.

That is, in the first embodiment, the DDA 14.15 was configured to add and hold only the decimal part and output the carry signal CAR, but by further expanding the bit length of the DDA,
It may also be configured such that an integer part can also be held and the input pixel position can be specified using this integer part.

[Fifth example] The fifth embodiment relates to a modification of the configuration shown in FIG.

That is, in the first embodiment, the increment value and initial value of DDA14.15 are initialized by the control unit of the image printer 10, but there are other methods as well. You can also do it in 4th grade. This embodiment is shown in FIG.

[Sixth Example] The sixth embodiment relates to a modification of the configuration shown in FIG.

That is, in the first embodiment, the DDA 14.15 was configured to hold the initial value and the current value separately, and input the selector to the adder using the selector, but it also has a register that holds the current value. For example, in the case of DDA in the main scanning direction, reinitialization may be performed in synchronization with the scan line synchronization signal PSDS, and in the case of ODA in the sub-scanning direction, reinitialization may be performed in synchronization with the page synchronization signal PPDS. In this case, an initial value holding circuit and a selector are not required, but scanning such as returning an interrupt signal to the sequence control circuit using a synchronization signal or resetting the holding circuit with a synchronization signal is required.

[Seventh Example] The seventh embodiment relates to another aspect of the interpolation coefficient formula.

That is, assuming that interpolation is preferably performed at 2mXZn points surrounding the interpolation position, the interpolation coefficient equation 1 (X), I (y
) may be as follows.

Although values can be determined more easily in the seventh embodiment than in the second embodiment, the density stripes occurring at pixel intervals are strong.

[Eighth Example] The eighth embodiment relates to another aspect of the interpolation coefficient formula.

That is, assuming that interpolation is preferably performed at 2mxZn points surrounding the interpolation position, the interpolation coefficient formulas r (x), I (y
) may be as follows.

π x
mπy
In this way, ω(X) and ω(y) can be diversified.

According to this, the occurrence of dark and light stripes is weaker than in the first embodiment.

Furthermore, if the same number of interpolation points is obtained, the sharpness of the image after processing is reduced, albeit slightly. Therefore, there is room for different uses depending on the purpose.

[Ninth Example] The ninth embodiment relates to another aspect of the interpolation coefficient formula.

That is, assuming that interpolation is preferably performed at 2mXZn points surrounding the interpolation position, the interpolation coefficient formula r(x), I(y)
may be as follows.

π x m
mπy
n n In this way, ω(X) and ω(y) can be diversified.

According to this, the occurrence of dark and light stripes is weaker than in the first embodiment.

In addition, the sharpness of the processed image deteriorates, albeit slightly, when performing interpolation in which the same number of interpolation points is obtained.

Therefore, there is room for different uses depending on the purpose.

[Tenth Example] The tenth example relates to another aspect of the interpolation coefficient formula. That is,
Preferably, interpolation is performed at 2mXZn points surrounding the interpolation position, and the interpolation coefficient is expressed as 1 (x).

I(y) may be as follows.

πx 1. [ωa m]πy
Io[ωb nl where Io[]
is a modified zero-order Bessel function of the first kind, and ω1. ωb is a setting parameter, and a value in the range of m m − ω, <− nn is selected and used. ■. [X] can be approximately determined by, for example, etc.

In this way, ω(X) and ω(y) can be diversified.

The occurrence of dark and light stripes is weaker than in the first embodiment. Furthermore, if the same number of interpolation points is obtained, the sharpness of the image after processing is reduced, albeit slightly. Therefore, there is room for different uses depending on the purpose.

[Eleventh Example] The eleventh example relates to another aspect of the interpolation coefficient formula. That is,
Assuming that interpolation is performed using 4x4 points surrounding the interpolation position, the interpolation coefficient formulas I (X) and I (y) may be as follows.

1(x)-(a+2)x'-(a+3)x2+1
(0≦IX+<1) 1(x)-ax'-5ax2+8a
x-4a (1≦IXI(2)1 (x) −
0 (2≦1×1) where a is a real constant.

The same applies to I(y).

[Effects of the Invention] As described above, according to the present invention, interpolation and
By performing enlargement processing independently in the main scanning direction and the sub-scanning direction, and configuring the processing results of one to be used as the human power for processing the other, interpolation processing that provides good image quality can be achieved with a relatively simple circuit. It is possible to achieve the enlargement processing that has been applied.

Furthermore, processing that can sufficiently cope with the output speed to an LBP printer or the like can be realized, and a memory such as a printer buffer for holding output image data can be eliminated.

Preferably, by configuring the printer to perform interpolation enlargement processing in the sub-scanning direction prior to that in the main scanning direction, it is possible to reduce the capacity of the line buffer memory required during processing, and the circuit of the present invention can be realized. When constructed using a super LSIC or the like, the number of required gates is reduced, making implementation extremely easy.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram of a digital image interpolation device according to a first embodiment of the present invention. FIG. 2 is a block diagram showing details of an interpolation processing circuit 8 of the first embodiment. FIG. 3 is a block diagram of a digital image interpolation device according to a first embodiment. A flowchart of the image data processing procedure by the sequence control circuit 13 of FIG.
B) is an operation timing chart explaining the synchronization mode between the interpolation processing circuit 8 and the image printer 10, FIG. 5 is a schematic diagram explaining the operation mode of the DDA of the first embodiment, and FIG. A diagram showing a storage mode of image data; FIG. 7(A) is a diagram showing an original image of a person; FIG. 7(B) is a diagram showing an image obtained by enlarging and interpolating the original image of FIG. 7(A). , Fig. 8(A) is a diagram showing a partial area of the original image, Fig. 8(B) is a diagram showing a partial area of the original image.
) is a diagram showing the partial area of Figure 8(A) multiplied by 5.75 times in the main scanning direction and 4.25 times in the sub-scanning direction, Figure 9 is a diagram showing details of Figure 8(A), Figure 10 is a diagram showing details of the principle of interpolation in the main scanning direction, and Figures 11 (A) to (C) are image data obtained when interpolation is performed in the main scanning direction after interpolation in the sub-scanning direction using original image data. 12 is a block diagram showing a part of the configuration of the ODA of the fifth embodiment. FIG. 13 is a diagram showing tables 17 and 20 of the embodiment. be. In the figure, 1... Video signal source, 2... Luminance signal extraction circuit, 3... Synchronization signal extraction circuit, 4... Sampling cycle generation circuit, 5... A/D conversion circuit, 6... ... γ conversion circuit, 7... Frame memory 7.8... Interpolation processing circuit, 9... Printer I/F circuit, 10... Image printer, 11... Write address control circuit, 12 ...
Read address control circuit, 13... Sequence control circuit.

Claims (4)

[Claims] (1) A digital image interpolation device for providing interpolated image data to an image output device, comprising: an image memory that stores a plurality of image data at integer addresses of orthogonal addresses X and Y; and real numbers of the orthogonal addresses X and Y. interpolation position setting means for setting an arbitrary interpolation position in the address; image data selection means for selecting 2m×2n pieces of image data so as to surround the interpolation position with the set interpolation position as the approximate center; Distance calculation means for calculating the distance x, y from the interpolation position to the selected image data; the distance y; a coefficient ω(y) uniquely determined based on the distance y; and a Y direction 2n.
intermediate interpolated image data I(Y)
a first interpolated image data forming means that forms a first interpolated image data forming means, the distance x, and a coefficient ω( uniquely determined based on the distance x);
x) and a second interpolated image data forming means for forming final interpolated image data I from the formed 2m pieces of first interpolated image data I(Y) in the X direction. interpolator. (2) The first interpolation image data forming means calculates the interpolation coefficient I(y) from the distance y and the coefficient ω(y) determined by the distance y using the following formula: I(y)=ω(y)・(sinπy /πy), and the interpolation coefficient I(y) obtained above and the interpolation coefficient I(y)
The second interpolated image data forming means calculates each product with the image data corresponding to the distance x, and forms intermediate interpolated image data I(Y) by the sum of the obtained 2n products. From the coefficient ω(x) determined by the distance ) and the interpolation coefficient I(x)
The intermediate interpolated image data I(Y) formed above corresponding to
2. The digital image interpolation device according to claim 1, wherein the final interpolated image data I is formed by the sum of the 2m products obtained. (3) The coefficients ω(x) and ω(y) are each expressed as follows, ω(x)=
1/2(1+cos[πx/m])ω(y)=1/2(
3. The digital image interpolation device according to claim 1 or 2, wherein the interpolation method is determined by the relationship: 1+cos[πy/n]). (4) The digital image interpolation device according to claim 1, wherein the coordinate Y corresponds to the sub-scanning direction of the image output device, and the coordinate X corresponds to the main scanning direction of the image output device.