JPH0263268A - Method and apparatus for reducing picture - Google Patents

Abstract

PURPOSE:To obtain a reduced picture at a high speed in a form preserving thin line information by detecting whether or not an object is an interleave object based on an interleaved data, a split area, a density data of picture element to be converted and a divided area so as to calculate the density of the conversion picture element. CONSTITUTION:A division area designation means 2 designates to which division area set on a plane of a picture element to be converted the conversion picture element is located and a density data of a picture element group to be converted is inputted sequentially by a converted picture element input means 1. An interleave data generating means 3 generates an interleaved data required to detect whether or not the picture element to be converted is an interleave object picture element based on the division area and the reduction rate. A split area decision means 4 based on the reduction rate discriminates to which split area the conversion picture element at present time is located. Then a conversion picture element density calculation means 6 calculates the density of the conversion picture element based on the interleave data, the split area to which a decided conversion picture element is located and the density data of the converted picture element group. Thus, a reduced picture is obtained without erasing thin lines.

Description

[Detailed description of the invention] (Table of contents) Overview Background of the industrial application field technology (Figures 12, 13, and 14) Prior art (Figures 11 and 14) Problems to be solved by the invention (Figures 1 and 2) Figure) Means for solving the problem (Figures 1 and 2) Effect (Figures 1 and 2) Example (Figures 3 to 10) Effects of the invention [Summary] On a plane on which pixels to be converted are arranged, A pixel reduction device that sets divided regions according to a reduction ratio and determines the density of each converted pixel from the density of neighboring converted pixels according to a logical formula corresponding to the divided region in which the converted pixels projected on the plane are located; Regarding the method, the object is to provide an image reduction device and method that performs conversion so that thin lines do not disappear, and the converted pixel is located in a segmented area set on the plane and determined based on the reduction rate. Sequentially specify the segmented areas, sequentially input the density data of a predetermined group of converted pixels located near the converted pixel based on the segmented area, and perform reduction from among the group of converted pixels based on the segmented area and the reduction rate. Generates the thinning data necessary to detect thinning target pixels on the thin line to be thinned out, determines the divided area where the converted pixel is located based on the reduction ratio, and generates the thinned data, divided area, and density data of the converted pixel. The density of the converted pixel is calculated by detecting whether or not the converted pixel is to be thinned out based on the segmented area.

[Industrial application field]

The present invention relates to an image reduction device and method in pixel resolution conversion from high density to low density, such as in conversion from G4 facsimile to 03 facsimile, or image editing processing, and in particular to a plane on which pixels to be converted are arranged. Set the divided areas above according to the desired reduction ratio, and determine the density of each converted pixel from the density of neighboring converted pixels according to the logical formula corresponding to the divided area where the converted pixels projected on the plane are located. The present invention relates to a pixel reduction device and method.

[Technology background]

Conventionally, when reducing an image, SPC (Select
tive Processing Conversio
n) method, disjunction method, nine-part method, high-speed projection method
-97958) and the like have been proposed, all of which are methods for determining the density of a converted pixel from four converted pixels in the vicinity of the converted pixel.

In the S2O method, the image tends to become thinner when reduced, and missing white and black pixels are noticeable.

Furthermore, the logical sum method and the nine-division method have the disadvantage that the image becomes thicker and the black pixels increase.

On the other hand, the high-speed projection method is known as a method that causes less omission and collapse of white and black pixels. The high-speed projection method realizes high-speed processing by replacing arithmetic operations with logical operations when determining the density of converted pixels.

In the high-speed projection method, as shown in Fig. 14, a divided area is set in the plane of the converted pixel according to the conversion magnification, and a logical formula is used to determine the density of the converted pixel from the converted pixel within the divided area. was prepared in advance, and the density of the converted pixel was to be determined based on the logical formula assigned to the divided area where the conversion is located.

FIG. 12 shows the principle of the projection method. As shown in the figure, first, four pixels A and B near a predetermined converted pixel.

Divide the pixels to be converted including C and D into four equal parts. Let the pixel densities of four neighboring pixels be I, , 1. , I.C., I. When the converted pixel R is projected onto the pixel surface to be converted, the area ratios projected onto the four equally divided areas are expressed as WA, Wa, Wc, and Wn.

In the projection method, the density of the converted pixel R is IR=Σif*w.

Since it is binarized as i*A, B, C, D, IR≧0.5
→ IR-1 (black'), 1. <0.5→IR
=0 (white). Note that p and q in FIG. 12 are conversion/reduction magnifications in the X-axis and Y-axis directions.

Furthermore, since this projection method requires arithmetic to determine the density of the converted pixel R, high-speed processing is not possible. Therefore, in the high-speed projection method, the arithmetic operations are replaced with logical operations to increase the speed. The curve in FIG. 13 shows a boundary where the density of the converted pixel R can be determined by only one pixel among the four pixels. For example, the curve that separates G3 and 07 is given by the following equation.

(p X +0.5) (q Y +0.5)
= 0.5 Therefore, as shown in Table 1, the logical expression takes into consideration only one pixel in the regions G□ to G, and the combination with the other three pixels in the regions G and G8.

Table 1. Logical formula for high-speed projection method [Prior art] When reducing an image using a higher-speed projection method than conventional technology, each density of a group of converted pixels located near a converted pixel is calculated as shown in FIG. Converted pixel input means 21 that sequentially inputs data; divided area determination means 24 that determines to which area the converted pixel belongs based on a desired reduction rate;
An image reduction device is used, which has a converted pixel density calculation means 25 that calculates the density of the converted pixel based on the density data of the group of converted pixels inputted by the converted pixel group 21 and the divided area to which each converted pixel belongs. The image was reduced.

[Problem to be solved by the invention]

By the way, in image reduction apparatuses using conventional methods such as the SPC method and the high-speed projection method, during reduction, vertical lines with a line width perpendicular to the X-axis direction of less than 1/p (p is the reduction ratio in the X-axis direction), There has been a problem in which horizontal lines with a line width of less than 1/q (q is the reduction ratio in the Y-axis direction) perpendicular to the Y-axis direction disappear.

FIG. 14 shows the positional relationship between the pixel to be converted and the pixel to be converted when reducing the size to 273 on both the X and Y axes. Converted pixel Si
For t~S33, the converted pixel R11°R1□, R20,
The regions where R22 is located are G5°G6. G,, G8. Therefore, the value of the converted pixel R11 becomes "0" from the logical formula in Table 4, that is, At(B+C+D)+BtC. Hereinafter, since the converted pixels R, 2, R2, and R2□ are also "0°', the converted pixels S1□→S2□→S
32 or S21→S2□→S23, when a black and white pattern with a line width of 1 appears, the above-mentioned thin line pattern is not expressed in the converted pixel, but becomes a thinned out form.

In addition, in the high-speed projection method, in addition to quadrangulating the area, it is necessary to divide the area using the formula
This method requires two additions, two additions, and one comparison, and has the drawback of increasing the circuit scale.

The technical objective of the present invention is to solve the above-mentioned problems, and it simplifies area division and is subject to thinning according to the reduction ratio (there is a possibility of thin lines disappearing).
It is an object of the present invention to provide an image reduction device and method that detects pixels to be converted and reproduces thin lines.

(Means for Solving the Problems) In order to solve the above-mentioned technical problems, the present invention has a first aspect of the present invention, as shown in FIG. In the pixel reduction device, the density of each converted pixel is determined from the density of neighboring pixels to be converted according to a logical formula corresponding to the divided area in which the converted pixel projected on the plane is located. a segmented area specifying means 2 for sequentially specifying a segmented area in which the converted pixel is located among segmented areas set on a plane and determined based on a reduction ratio; and a predetermined area located near the converted pixel based on the segmented area. a pixel input means 1 to be converted which sequentially inputs density data of a group of pixels to be converted; and a pixel to be thinned out on a thin line to be thinned out by reduction from among the group of pixels to be converted based on the segmented area and the reduction rate. A thinning data generating means 3 generates the thinning data necessary for the reduction, a divided area determining means 4 determines the divided area in which the converted pixel is located based on the reduction ratio, and a divided area determining means 4 generates the thinned data, divided area, and converted pixel. The converted pixel density calculation means 5 calculates the density of the converted pixel by detecting whether or not the converted pixel is to be thinned out based on the density data and the segmented area.

As shown in FIG. 2, the second invention is to set divided areas according to a desired reduction ratio on a plane on which pixels to be converted are arranged, and to divide areas in which converted pixels projected onto the plane are located. In a pixel reduction method that determines the density of each converted pixel from the density of neighboring pixels to be converted according to a logical formula corresponding to the area, the converted pixel is located in a segmented area set on the plane and determined based on a reduction rate. a step (S1) of sequentially specifying segmented areas to be converted and sequentially inputting density data of a predetermined group of converted pixels located in the vicinity of the converted pixel based on the segmented area; A process (S2) of generating thinning data necessary for detecting thinning target pixels on a thin line thinned out by reduction from among a group of converted pixels, and determining a divided area in which converted pixels are located based on the reduction rate. A process of determining (S3), and a process (S4) of calculating the density of the converted pixel by detecting whether or not it is a thinning target based on the thinning data, the divided area, the density data of the converted pixel, and the divided area. It is.

[Effect]

The present invention will be described in detail. When reducing an image according to the present invention, in step S1, the divided area specifying means 2 selects the converted pixel whose density is to be determined based on the reduction ratio (conversion magnification). In addition to specifying which of the segmented areas set on the pixel plane the converted pixel is located, the density data of a predetermined group of converted pixels located in the vicinity of the converted pixel is sequentially input using the converted pixel input means 1. do.

Here, the purpose of specifying the segmented area is to select only the necessary reference pixels from the group of converted pixels in the subsequent thin line pattern detection process, and select the converted pixels that are required when performing the detection process. This is to reduce the number of

Here, "predetermined" is a group of converted pixels that affects the density of the converted pixel, and the number of the converted pixel group is limited by using the designation result of the segmented area, Processing will be simplified.

Note that the process of inputting the converted pixel and the process of specifying the segmented area in step S1 are not necessarily limited to this order. The area specifying means 2 may specify a divided area, and the input means 1 may send limited pixels to be converted to the converted pixel density calculating means 5 based on the specified area.

In step S2, the thinning data generating means 3 generates thinning data necessary for detecting whether or not the pixel to be converted is a pixel to be thinned out based on the segmented area and the reduction rate.

At that time, the segmented area is also included as part of the thinning data.

Here, "pixel to be thinned out" means that the pixel to be converted forms a thin line (black or white pixels arranged continuously in a line) having a line width less than one of the reduction weight. conventional s
Pixels to be converted are erased during reduction conversion using the PC method or high-speed projection method, and thinning data is the data necessary to determine whether or not the pixel to be converted is a pixel to be thinned out. It is originally determined based on the reduction rate. This means that whether or not a certain pixel to be converted is thinned out is determined by the position of the adjacent converted pixel.
This is because, after determining the coordinates of the starting point, the converted pixel position can be uniquely determined based on the desired reduction ratio.

In the present invention, the generation of thinned data is facilitated by taking into account the divided areas when generating the thinned data.

In step S3, the divided area determining means 4 determines in which divided area the current converted pixel is located based on the reduction ratio.

If the divided area is divided by the same boundary as the divided area as shown in the example, the divided area will be judged under the same conditions (logic) as the divided area, making the judgment easier. Become something.

Further, in step S4, the converted pixel density calculation means 5 calculates the density of the converted pixel based on the thinned-out data, the divided area in which the determined converted pixel is located, and the density data of the converted pixel group. , the above procedure is repeated for each converted pixel.

That is, in step S4, even if it is determined based on the thinning data that a pixel to be thinned out exists among the converted pixels, if the pixel to be thinned out does not form a thin line based on the density data of the group of converted pixels. The density of the converted pixel is determined using the same method as before, but in order to avoid erasing the thin line that would be thinned out due to reduction from the density data of the converted pixel group, the thin line pattern is determined by the density of the converted pixel. If the pixel to be converted is not to be thinned out, or if it is to be thinned out but does not form a thin line, the density of the converted pixel is output according to a conventional method.

〔Example〕

Examples according to the present invention will be described.

FIG. 3 shows an image reduction device according to an embodiment.

This device is a device that reduces the image while preventing thin lines from disappearing in the X-axis and Y-axis directions, and the reduction ratio is 1<p, q.
This corresponds to ≦1/2.

Note that p is the reduction rate in the X-axis direction, and q is the reduction rate in the Y-axis direction.

This device includes a converted pixel input means 11 which sequentially inputs each density data of a group of converted pixels located in the vicinity of the converted pixel when the current converted pixel is projected onto the converted pixel plane.
and a two-dimensional image memory 10 in which density data of pixels to be converted of the original image are stored.

Furthermore, access control to the two-dimensional image memory 10, control to the converted pixel input means 11, the divided area specifying means 2, the divided area determining means 4, and the thinning data generating means 3 are performed based on the current position information of the converted pixels. It has a control section 12 that specifies a divided area, determines a divided area, and generates thinned-out data, and a logic circuit 15 for determining a converted pixel density as the converted pixel density calculation means 5.

As shown in FIG. 3, the converted pixel input means 11 has six shift registers lla to llf. The shift registers lla and llb hold the pixels to be converted existing in the first line. Similarly, shift register l
lc, lid are on the second line, shift register 11e,
The shift register llf holds the pixel to be converted existing on the third line.

The control unit 12 determines the divided area to which the current converted pixel belongs based on the desired reduction ratios p and q in the X-axis direction and the Y-axis direction, and also determines the divided area to which the current converted pixel belongs, as well as each converted area located near the converted pixel. It generates the thinning data necessary to detect whether or not a pixel is to be thinned out, and specifies each of the divided areas where the current converted pixel is located.

Here, as shown in FIG. 4, the thinned-out data is the coordinate position X of the immediately preceding converted pixel R1o within the converted image plane in the X-axis direction. >0.0, current converted pixel R1□
Whether or not the following conditions are satisfied: the coordinate position X□>0.0 of the next converted pixel R□2, and the coordinate position x2>0.0 of the next converted pixel R□2, and the converted pixel R process. The number of converted pixels that pass when moving from to R1□xshifto, converted pixels R□, to R
1 Number of pixels to be converted that pass when transitioning to □xshif
This is 1-bit or 2-bit data that indicates the value of tl, and in the Y-axis direction, it is the coordinate position y of the previous converted pixel R in the converted image plane. 〉0.0. Whether or not the following conditions are satisfied: Coordinate position y of the current converted pixel R〉0.01 Coordinate position y2 of the next converted pixel R2〉o, o, and transition from the converted pixel Ro to R□1 The number of converted pixels passing through when moving from converted pixel R11 to R2□ ysif
This is data that displays the value of t01.

Furthermore, in this embodiment, the divided area is a square area formed by four converted pixels surrounding the current converted pixel, which is divided into four squares (hereinafter referred to as "four divided area"). , and data indicating in which area the converted pixel is located is also used as thinning data.

The purpose of specifying the divided areas is to detect the thin line pattern to be thinned out without significantly increasing the number of converted pixels to be referred to.

That is, as shown in FIGS. 5 and 6, the converted pixels are in the area g
If it is located at g4, then n, n+1. The n+2nd line data is sufficient, and the converted pixels are in the area g2. When located at g3, the data to be thinned out can be detected by reading out the data on the n-1, n, and n+1 lines.

In other words, the converted pixels are in the segmented area g1. If located at gs, pixels A, B, C, D, E, F.

Referring to the 10 pixels of I, J, and L, if the converted pixel is located in the segmented areas gt and g3, the pixel A.

Ten pixels B, C, D, E, F, G, H, I, and J are referenced.

As described above, FIG. 7 shows a thin line pattern to be thinned out in a manner in which the reference pixels are limited using the information of the four divided regions. This is a thin line pattern corresponding to a reduction ratio of 1>p and q≧1/2, and a pattern with a line width of 1 is targeted. Furthermore, whether or not the thin line pattern in FIG. 7 is to be thinned out is determined according to the thinning detection conditions in Table 2. Next, the current density of the converted pixel is calculated based on the conditions, the density of the pixel to be converted, and the divided area.

Table 2-1.1>p, q≧l/Table 2-2.1>p, Q≧1/2 Detection conditions for pixels to be thinned out When p, Q≧1/2 In this example, the divided areas are shown in FIG. As shown in FIG. 4, the same four-part area as shown in FIG. 4 is applied.

That is, g□→G1 g2→Gz, g3→G3. g<
→G4 As a result, division area designation, division area determination, and thinning data generation (partially) can all be realized under the conditions of four division areas, and processing can be greatly simplified.

The converted pixel density determination logic circuit 15 is connected to the control section 12.
The divided regions determined in and the converted pixel input means 11
The density of the converted pixel is calculated based on the density of the converted pixel input by using the logical formulas shown in Tables 3 and 4. Table 3 shows the results obtained by applying the present invention to the conventional SpC method, and Table 4 shows the results obtained by applying the present invention to 05 to G8 of the high-speed projection method (Table 1). (By applying Table 4, as the reduction ratio moves away from 1, the same converted pixels as in the fast projection method can be obtained in a simpler form.) Table 31 Logical formula 1 according to this embodiment (1>p , when q≧1/2) (when t>p, Q≧1/2) Pl/Yl wheel (pattern No., I): Corresponds to thin line pattern 1 in Fig. 7 P2-Yl search (pattern No., 2) :
ffs 7 Corresponds to thin line pattern 2 of U2 P3-X+Kin pattern No., 3); Corresponds to thin line pattern 3 of Fig. 7 P
4.×1 quintillion (pattern No. 4); Corresponds to thin line pattern 4 in Fig. 7 Based on the conditions in Table 2 for Y, pattern No. l
, 2 is the target = 1. Others = OX1 + According to the conditions in Table 2, if pattern No. 3.4 is the target = 1. Others: 0 Now, the operation of the apparatus according to this embodiment will be explained.

Let us take as an example a case where pixels to be converted stored in the two-dimensional pixel memory 10 are reduced at a reduction rate p, q = 2/3. The control unit 12 controls the two-dimensional image memory 10, which stores the current image to be reduced, in units of a certain word length (4 bits/word in FIG. 3).
The density data of the converted pixel group located in the vicinity of each current converted pixel is read out to shift registers lla, llc, and lie which function as the converted pixel input means 11 and sequentially hold up to three lines of each density data. Let them input.

In other words, as shown in FIGS. 6 and 7, when projecting the current converted pixel onto a grid composed of converted pixels A, B, C, and D in the converted pixel plane, each converted pixel A-L
Each density data of each line (n-1, n, n+1
, n+2), each of the shift registers lla, ll
c, lie.

The control unit 12 controls the shift register l at a predetermined timing.
The density data of each pixel to be converted held in la, llc, lie is transferred to the shift registers 11b, lid, ll.
f and sends it to the logic circuit 15.

At this time, as shown in FIG. 5, the control unit 12 divides the lattice formed by the four pixel groups located near the currently converted pixel into four sections. Each quadrant area g□+ g2 r g3
! g4, and sends 2-bit data to the logic circuit 15 to distinguish the area. This data also serves as a criterion for determining divided regions. Further, the control unit 12 sends thinning data (see Table 2) created to detect and store thin lines to be thinned out according to a desired reduction rate to the logical operation circuit 15. Note that if the thinned data is output as is, 4 bits (xshift, yshift, x:>O, y>0 distinction) are required, so in Fig. 3, the thin line target pattern shown in Fig. 7 is distinguished. Therefore, it is transmitted in a condensed form of 2 bits. Next, the logical operation circuit 15 detects whether or not it is a thinning target based on the information about the four divided areas g-g4 outputted by the control unit 12, the thinning data, and the density data of the pixel group to be converted. Then, the density of the pixel to be converted is calculated according to the logical formula in Table 3 or Table 4.

Hereinafter, the case where both the reduction ratios p and q are 273 will be explained separately into (1) a case where a thin line pattern perpendicular to the X axis exists, and (2) a case where a thin line pattern perpendicular to the Y axis exists.

Table 4 is used as the logical formula.

■ When there is a thin line pattern perpendicular to the
(black) and all other converted pixels are 0'' (white). In this case, the conditions in Table 2, the thin line pattern in Figure 7, and the logical formula in Table 4 correspond.The current converted pixel R1
The surrounding four pixels A, B, C, and D for 1 are each 5H2S□
2. S2□+S2□. The position of the converted pixel R □ belongs to the divided area G1, and xshiftl=1. yshift
l=1°×2)0.0. Y2) 0.0. This corresponds to condition G□-4 in Table 2-1. Therefore, the target thin line pattern is gl-No. 1-4 in FIG. Since g□-No.3 appears in the thin line pattern in the above example, it is set to "1'' from the logical formula in Table 4. Similarly, in the converted pixel R1□, from the condition G4-4 in Table 2-2, the thin line pattern g4 -No
,') becomes a thin line pattern. However, S engineering 2. S2□
The thin line pattern existing in , has already been expressed by pixel R, so the density of pixel R is not recognized as the target thin line and becomes 0.The above process is for pixels R2 and R22. The same is true.

Conversely, the converted pixel S12→S2□→S3□ is “0”
(white) and all other pixels to be converted are “1” (black),
For the converted pixel R□□, the thin line pattern g1-No.4 corresponds to the condition G1-4.

Therefore, the density of converted pixel R1□ is "0" from the logical formula in Table 4.
shall be. As in the previous example, the density of the converted pixel R02 is not regarded as a thin line pattern, and is 1.

The above process is the same for pixels R, , R2□.

■ When a thin line pattern perpendicular to the Y axis exists According to Figure 9, the converted pixel S2□→S2□→523II 111
(black) and all other pixels to be converted are "0" (white). In this case, the conditions in Table 2, the thin line pattern in FIG. 7, and the logical formula in Table 4 correspond. Current conversion pixel R
The surrounding four pixels A, B, C, and D for 11 are each S□4.
S□2°S2□+S2□. The position of the converted pixel R0□ belongs to the divided area G, and xshfftl=1. yshi
ftl=1. X2) 0.0. Y2) 0.0. From Table 2-
This corresponds to condition G4-4 of No. 1. Therefore, the target thin line pattern is g□-No. 1-4 in FIG. The thin line pattern in the above example becomes g1-No.1. Therefore, the density of the converted pixel R□1 is g for the thin line pattern, -No.
, 1 appears, so it is determined as "1'' from the logical formula in Table 4. Similarly, in the converted pixel R12, it corresponds to condition G4-4 in Table 2-2, and g4-No. 1 in FIG. 7 is a thin line. However, since the thin line pattern existing in S12 and S22 is already expressed by the pixel R1□, the density of the pixel R1□ is not recognized as the target thin line and becomes “0”.The above process The same holds true for pixels R2, , R2□.

Conversely, the converted pixel S21→S2□→S23 is “0°
If all other pixels to be converted are "1" (black), the thin line pattern g, -No., 2 corresponds to the conversion pixel R, according to the condition G knee 4. Therefore, the density of the converted pixel R1□ is set to "0"' from the logical formula in Table 4. Conversion pixel R engineering. As in the previous example, the density of
It becomes ゛′. The above process is the same for pixels R2, , R2□.

As described above, according to this embodiment, a simple area division process of four divided areas can be used, and a thin white or black line pattern can be created under the same conditions, without increasing the line width, and with fewer pixels to be converted (
8 pixels), it is possible to reproduce thin lines in the converted image.

Moreover, as shown in FIG. 10, the desired reduction ratio is 1>p
, q≧1/n (n=2″I, m=o, 1,2.・
...), (m-1) circuits according to this embodiment specifying a reduction rate of 1/2 are connected in series in multiple stages, and the reduction rate is 2111-1*p, 2FT1-1*q. A magnification of 172 or less can be realized with the same circuit configuration by connecting the specified circuits according to this embodiment or by looping the same circuit.

Furthermore, in this embodiment, since the divided area is divided by the same boundary as the divided area, the determination of the divided area is performed under the same conditions (logic) as the divided area, making the determination easier. processing can be performed at high speed.

〔Effect of the invention〕

As explained above, in the present invention, the converted pixel group and thinning data necessary to detect converted pixels having a thin line pattern whose line width is less than one of the reduction weight due to reduction of the current image. is input and generated based on the segmented area, and when the converted pixel density calculation means calculates the converted pixel, the segmented area is used to automatically reproduce the thin line pattern of the converted pixel. .

As a result, a reliable reduced image with thin line information preserved can be obtained at high speed with a simple circuit configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the principle of the first invention, FIG. 2 is a flowchart of the principle of the second invention, FIG. 3 is a circuit block diagram of an image reduction device according to an embodiment, and FIG. 4 is a thinning-out diagram according to an embodiment. An explanatory diagram of the thinning data necessary to detect the target pixel to be converted, FIG. 5 is a diagram showing a four-section area, and FIG. 6 is a reference in the case of reduction ratio 1>p, q≧172 according to the embodiment. A diagram showing pixels, FIG. 7 shows the reduction ratio according to the embodiment 1) p I q≧172
FIG. 8 is a diagram showing the divided area according to the example, and FIG. 9 is a diagram showing the thin line pattern according to the example.
A diagram showing the positional relationship between the converted pixel and the converted pixel in the case of , FIG. 10 is a block diagram in the case of reduction ratio 1) p and q≧1/n according to the embodiment, and FIG. 11 is a block diagram according to the conventional example. Figure 12 is a diagram showing the principle of the projection method, Figure 13 is a diagram showing the divided areas of the high-speed projection method, and Figure 14 is a diagram showing the converted pixels and the converted pixels when the reduction rate is 2/3 according to the high-speed projection method. FIG. 3 is a diagram showing the positional relationship of pixels. 1.11...Transformed pixel input means 2 (12)...Segmented area designation means (control unit) 3 (12)
)... Thinning data generation means (control unit) 4 (12)... Divided area determination means (control unit) 5 (15
)...Converted pixel density calculation means (logic circuit for determining converted pixel density)

Claims (6)

[Claims] (1) Set divided areas according to the desired reduction ratio on the plane where the converted pixels are arranged, and follow the logical formula corresponding to the divided area where the converted pixels projected onto the plane are located In an image reduction device that determines the density of each converted pixel from the density of the pixel, segmented area designation that sequentially specifies a segmented area in which the converted pixel is located among segmented areas set on the plane and determined based on a reduction rate. means (2); converted pixel input means (1) for sequentially inputting density data of a predetermined group of converted pixels located in the vicinity of the converted pixel based on the segmented area; and based on the segmented area and reduction rate. a thinning data generating means (3) for generating thinning data necessary for detecting thinning target pixels on a thin line thinned out by reduction from a group of converted pixels; a divided area determining means (4) for determining a divided area to be converted, and a conversion for calculating the density of a converted pixel by detecting whether or not it is a target for thinning based on the thinning data, the divided area, the density data of the converted pixel, and the divided area. An image reduction device comprising: pixel density calculation means (5). (2) Set divided areas according to the desired reduction ratio on the plane where the converted pixels are arranged, and follow the logical formula corresponding to the divided area where the converted pixels projected onto the plane are located In a pixel reduction method in which the density of each converted pixel is determined from the density of the pixel, a segmented area in which the converted pixel is located is sequentially specified among segmented areas set on the plane and determined based on the reduction rate, and a step (S1) of sequentially inputting density data of a predetermined group of converted pixels located in the vicinity of the converted pixel based on the segmented area; A process (S2) of generating thinning data necessary to detect pixels to be thinned out on the thin line to be drawn, a process (S3) of determining a divided area in which a converted pixel is located based on the reduction ratio, and a process (S3) of generating thinning data. , a step (S4) of calculating the density of the converted pixel by detecting whether or not it is to be thinned out based on the divided area, the density data of the converted pixel, and the divided area. (3) As the thinning data generating means (3), when the horizontal axis is the X axis and the vertical axis is the Y axis as a coordinate plane based on the four converted pixels surrounding the converted pixel, in the X axis direction, Position coordinate x_0 of the immediately preceding converted pixel on the pixel surface to be converted, position coordinate x_1 of the current converted pixel
, by the position coordinate x_2 of the next converted pixel, the truth or falsity of the inequality x_0>coordinate reference value, x_1>coordinate reference value, x_2>coordinate reference value, and the converted pixel that exists between the above-mentioned immediately before and the current converted pixel. The number of pixels or the number of converted pixels existing between the converted pixel at the above point and the next converted pixel is generated as thinning data, and the position coordinates of the immediately previous converted pixel on the converted pixel surface in the Y-axis direction. y_0, current position coordinate of the converted pixel y_1
, by the position coordinate y_2 of the next converted pixel, the truth or falsity of the inequality y_0>coordinate reference value, y_1>coordinate reference value, y_2>coordinate reference value, and the converted pixel that exists between the immediately preceding and current converted pixel. 2. The image reduction apparatus according to claim 1, wherein the pixel or the number of converted pixels existing between the converted pixel at the time and the next converted pixel is generated as thinning data. (4) As the divided area determination means (4), when the horizontal axis is the X axis and the vertical axis is the Y axis as a coordinate plane based on the four converted pixels surrounding the converted pixel, the X axis direction is , the current position coordinate x of the converted pixel on the converted pixel surface
For the Y-axis direction, the truth or falsity of the inequality x_1 by _1>coordinate reference value, the current position coordinate of the converted pixel on the pixel surface to be converted y_1>coordinate reference value, is used. An image reduction device according to claim 1. (5) As the converted pixel density calculation means (5), a logical formula for preserving a thin line based on the thinning data is added to a logical formula that takes into account the connection with the nearest converted pixel or the nearest neighboring pixel. An image reduction device according to claim 1, characterized in that: (6) The reduction rate in the X-axis direction is p, the reduction rate in the Y-axis direction is q,
When n = 2^m (m = 0, 1, 2, ...), if the desired reduction rate is 1>p, q≧1/n, then the magnification is 1/n.
2 reduction processing (m-1) times and magnification 2^m^-^1*p
, 2^m^-^1*q reduction processing is performed once.