JP2000299788A - Generating device and method for n-fold dense image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restore a dot pattern from a compressed code by previously preparing the dot layout data on every pixel included in a unit area, deciding a specific pixel position of the unit area to which an object pixel is corresponding, selecting the dot layout data corresponding to the pixel position and deciding the dot layout of the processing object pixel. SOLUTION: A compression part 1 receives the source data on a multi-tone image and converts the source data into a small-number-of-bit compressed code which can express a tone of a small number of steps of every pixel of the source data. An extension part 5 reads successively the 2-bit compressed codes of every pixel of the 3-fold dense image data out of a memory 3 and converts these compressed codes into the digital signals showing a dot pattern of every pixel of the 3-fold dense image. A dot layout rule of every pixel is also previously stored for a unit area, and a proper pattern is decided by the dot layout rule and generated when the compressed code of every pixel is converted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a laser printer,
Involved in digital image forming devices such as inkjet printers, copiers and bitmap display devices,
Also, the present invention relates to a computer system for performing digital image processing, and particularly to a binary image (N
Technology for generating double-density images).

[0002]

2. Description of the Related Art Many digital image forming apparatuses simulate an image in the form of binary data representing dots and blanks. In a multi-tone binary image formed by this type of device, each pixel, or pixel, is typically partitioned into a plurality of dot regions, and the tone of each pixel is reflected in the number of dots in each pixel.

In the example shown in FIG. 1, a pixel PC is divided into two dot areas D1 and D2, and three levels of tones P = 0, 1, and 2 are expressed by the number of dots in the pixel PC. In another example shown in FIG. 2, the pixel PC is divided into three dot areas D1, D2, and D3, and four levels of tones P = 0, 1, 2, and 3 are expressed.

More generally, by dividing one pixel into N dot areas, an N + 1-step tone P =
0 to N can be expressed. A multitone binary image in which one pixel is divided into N dot areas in this manner is referred to as an “N-fold dense” image in this specification.

In a primitive N-fold dense image, each pixel is represented as an N-bit code in which one bit corresponds to one dot area. However, since the N-fold density image has a huge amount of data and requires a large-capacity memory, several methods have been considered to reduce the amount of data by compressing the image.

The most basic of these compression methods is to use a compression code that can identify all possible dot patterns within a pixel. For example, in the case of the double-density image shown in FIG. 2, the possible dot patterns are the four types shown, and in the case of the triple-density image of FIG. 3, the possible dot patterns are the six types shown. is there. In general, a possible dot pattern in an N-fold dense image is 2N
Kind. A compression code that can identify the 2N types of dot patterns is used. For example, in the case of the double-density image shown in FIG. 2, a 2-bit compression code for identifying four types of patterns is used. In the case of the triple density image shown in FIG. 2, a 3-bit compression code that can identify six types of patterns is used. Further, in the case of a quadruple-density image, a 3-bit compression code that can identify eight types of patterns is used. The number of bits in a compressed code is called the "depth" of the compressed code. However, with this traditional basic compression method,
In the case of N = 2, 3, the compression code depth is the same as the number N of bits of the primitive pixel data, and the compression effect is not actually obtained. The compression effect is obtained only when N is 4 or more.

Japanese Patent Application Laid-Open No. 9-74485 discloses a compression technique having a higher compression effect in view of this problem. That is, the depth of the compressed code is only a sufficient number of bits necessary to identify the (N + 1) tone of the N-fold dense image. For example, in the case of N = 3, that is, a triple dense image, the depth of the compressed code is 2 which is necessary and sufficient to identify 3 + 1 = 4 tones.
It's just a bit. When restoring the dot pattern of each pixel from the compression code of each pixel, determine the number of dots from the compression code of each pixel, and further refer to the compression codes of two adjacent pixels on both sides of each pixel,
The dot pattern is restored by shifting the dots to the darker side of the adjacent pixels on both sides. FIG.
FIG. 4 shows an example of a triple-density image.
3 illustrates the principle of image compression and decompression of the technique of No. 4485.

[0008] As shown in FIG.
Assuming that C1, PC0, and PC-1 are arranged in a row,
Focus on the center pixel PC0. As shown in FIG.
There are four types of tones (density) P0 that the pixel PC0 can take, "0" to "3", and 2-bit compression codes "00" to "11" are assigned to these four types of tones, respectively. When the compression code is “01” or “10”, the same compression code is assigned to both the dot pattern in which the dots are shifted to the right and the dot pattern to which the dots are shifted to the left. Therefore, when the dot pattern is restored from the compressed code, the tone code of the pixels on both sides is referred to by referring to the compressed codes P1 and P2 of the pixels PC1 and PC-1 on both sides in addition to the compressed code of the pixel PC0. Automatically selects a dot pattern in which the dots are shifted to the side with the larger (darker).

As described above, 2 which can identify only 4 tones
All six types of dot patterns can be reproduced from the bit compression code. Also, since the dots in the dot pattern are joined to the dots of the adjacent pixels closer to the adjacent darker pixel side, the advantage that characters, diagrams, outlines of objects, etc. can be expressed clearly and smoothly. Can be

[0010]

SUMMARY OF THE INVENTION The above-mentioned JP-A-9-7
The compression technique of No. 4485 shifts the dots to the darker side of the adjacent pixels on both sides, which may restore the pattern in which the dots are shifted to the undesirable side. FIG. 5 shows an example. Paying attention to the pixel P3 in FIG. 5, the dot of the pixel P3 is shifted to the left side because the pixel P2 on the left side is darker than the pixel P4 on the right side. However, as a result, the dot of the pixel P3 is isolated, and the dot of the adjacent pixel P4 on the right side is also isolated. Such isolation of the dots of individual pixels is not preferable for achieving high image quality. A preferred dot arrangement is that the dot of pixel P3 is shifted to the right and joined with the dot of right pixel P4. On the other hand, adding a bit to the compression code of each pixel to indicate whether to shift the dot to the right or to the left solves this problem, but then the depth of the compression code (number of bits)
And the advantage of the high compression effect of the compression technique of Japanese Patent Application Laid-Open No. 9-74485 is lost.

Accordingly, an object of the present invention is to provide a technique for processing an N-fold dense image having a high compression effect and the ability to restore a high-quality dot pattern, particularly a technique for restoring a dot pattern from a compressed code. It is in.

[0012]

According to the present invention, the compression code of each pixel of the N-times dense image is calculated by the N-times of the N-times dense image.
A code having a necessary and sufficient depth to identify the +1 tone can be used. For example, in the case of an N = 3 triple-density image, 3 + 1 = 4 tones need only be identified, so a 2-bit depth of the compression code is sufficient. In this respect, a high compression effect equivalent to that of the compression technique disclosed in JP-A-9-74485 can be obtained.

The N-fold density image generating apparatus according to the first aspect of the present invention, when generating a dot pattern signal representing a dot pattern from the compression code of each pixel, generates a dot pattern signal of each pixel in accordance with the compression code of each pixel. Determine the size or number of dots in the dot pattern, and based on the relative position of each pixel with respect to the halftone dots applied to the N-fold dense image, the dot placement (eg, dot To the right or to the left)
To determine.

As described above, an appropriate dot pattern can be generated by determining the dot arrangement based on the relative positional relationship between each pixel and the halftone dot.

In a preferred embodiment, as a method of determining a dot arrangement, for a unit area of a halftone dot arrangement pattern on an N-fold dense image, dot arrangement data indicating a dot arrangement of each pixel included in the unit area is determined. Prepared in advance, for the pixel to be processed, determine which pixel position in the unit area it corresponds to, select dot arrangement data corresponding to the determined pixel position, and use the selected dot arrangement data to Determine the dot arrangement of the pickles to be processed.

In another preferred embodiment, as a method of determining a dot arrangement, position data of a growth nucleus of a halftone dot in this unit area is prepared in advance for a unit area of a halftone dot arrangement pattern on an N-fold dense image. Then, the position of the pixel to be processed in the unit area is determined, and the dot arrangement of each pixel is determined based on the relative relationship between the determined position and the position of the growth nucleus obtained from the nucleus position data means. I do.

An N-fold dense image generating apparatus according to a second aspect of the present invention, when generating a dot pattern for each pixel from a compressed code for each pixel, generates a dot pattern for each pixel in accordance with the compressed code for each pixel. The size or the number of the dots in the pixel is determined, and the dot arrangement in the dot pattern of each pixel is determined based on the compression code of the pixel one pixel before, one pixel and two pixels before each pixel.

In Japanese Unexamined Patent Application Publication No. 9-74485, the dot arrangement of the pixel to be processed is determined based on the compression codes of the pixels immediately before and after the pixel to be processed. The dot arrangement of the pixel to be processed is determined with reference to the compression code of the pixel two pixels before. By referring to the compression code of the pixel two pixels before, the dot arrangement of the pixel one pixel before can be known to some extent, so that a more appropriate dot arrangement can be determined accordingly.

The N-fold density image generating apparatus according to the third aspect of the present invention, when generating a dot pattern of each pixel from the compressed code of each pixel, generates a dot pattern of each pixel according to the compressed code of each pixel. Is determined, and the dot arrangement of each pixel is determined based on the compression code of the pixel one pixel before and one pixel after each pixel and the dot arrangement of the pixel one pixel before.

As described above, a more appropriate dot arrangement can be determined based on the determination of the dot arrangement of the pixel to be processed in consideration of the dot arrangement of the pixel one pixel before.

In the embodiment described below, the present invention is applied to image processing in a printer, but the present invention can also be applied to image processing in equipment other than a printer, for example, a computer or a copying machine. It is.

[0022]

FIG. 6 shows the configuration of an embodiment of an image processing system for a printer according to the present invention.

The compression section 1 receives source data of a multitone image. The value of each pixel of this source data is a multi-bit code capable of expressing multiple levels of tones (for example, an 8-bit code capable of expressing 256 levels of tones)
It is. The compression unit 1 converts the multi-bit code of each pixel of the source data into a small-bit compression code (for example, three-fold) capable of expressing a small number (N + 1) -step tone of each pixel of the small-number (N) double-density image. (A 2-bit-depth compressed code capable of expressing the four-stage tone of a dense image). Several methods can be used for this conversion, one of which is a method using a dither matrix as described in Japanese Patent Application Laid-Open No. 9-74485. The triple-density image data in the form of a 2-bit compression code from the compression unit 1 is stored in the memory 3.

The decompression unit 5 sequentially reads out the 2-bit compressed code of each pixel of the triple-density image data from the memory 3 and converts the code into a dot pattern of each pixel of the triple-density image (the six types of dots shown in FIG. 4). Digital signal (hereinafter, referred to as "dot pattern signal")
Convert to The print engine 7 receives the dot pattern signal, drives a drawing laser beam based on the dot pattern signal, and executes an electrophotographic process, thereby forming a dot pattern of each pixel on a sheet. As a result, a triple-density image in which the source multi-tone image is simulated by dots and blanks is printed out.

The compression section 1 may be provided in the printer, or may be provided in a printer driver of a host computer connected to the printer. The same applies to the extension unit 5. Each of the compression unit 1 and the decompression unit 5 may be a process realized by executing software, or may be a dedicated hardware circuit. In the present embodiment, the compression unit 1 is a process performed by a printer driver in the host computer or a controller in the printer, and the decompression unit 5 is a dedicated hardware circuit in the printer.

In the following, the expansion unit 5 in the above configuration will be described more specifically.

FIGS. 7 and 8 show the principle of the decompression process performed by the first embodiment of the decompression unit 5. FIG.

FIG. 7A shows a halftone cell which is generally used to represent a multi-step tone in an N-fold dense image, and is composed of a mass of a plurality of pixels 13 for forming a halftone dot (screen dot). 11 is shown. The illustrated halftone cell 11 is composed of five pixels 13 arranged in a cross. For a 3x dense image with N = 3,
Since one pixel 13 can represent four levels of tones, one halftone cell 11 can represent 4 × 5 = 20 levels of tones.

In this halftone cell 11, as the tone (density) increases, screen dots grow in each pixel 13 in the order of numbers 1, 2, 3, and 4 shown in each pixel 13. I will do it. In other words, when the tone gradually increases from the minimum value 0, the dots increase at the center pixel 13 of the number 1 first, and when the center pixel 13C is completely filled with the dots, the right side of the number 2 next The dot increases at the pixel 13R of the right pixel 13R.
When all of R are filled with dots, the dots increase at the upper pixel 13T of the number 3, and similarly, the dots increase in the order of the lower pixel 13B of the number 4 and the left pixel 13L of the number 5. To go. When the tone reaches the maximum value, the pixels 13L of number 5 are all filled with dots,
All the halftone cells 11 are filled with dots.

In one halftone cell 11, each dot increases as one lump (that is, as one screen dot). As shown in FIG. 7B, since the pixels 13 in the halftone cell 11 need to be formed into one lump, the pixels 13 in the halftone cell 11 determine whether the dots are arranged closer to the right side or the left side as shown in FIG. Specific rules apply. That is, in the right pixel 13R, the dots are arranged leftward (indicated by code 1), and in the other pixels 13C, 13T, 13B, 13L, the dots are arranged rightward (indicated by code 0). It should be noted that the screen cells 11 and the dot growth order shown in FIG. 7 are merely examples, and other screen cells 11 having various sizes and shapes and various dot growth orders can be adopted. On the other hand, there is a unique dot arrangement rule.

As shown in FIG. 8, a screen cell 11 is tiled and applied to an image composed of many pixels. In the case of the halftone cell 11 of 5 pixels illustrated in FIG. 7, a pattern obtained by tiled the halftone cell 11 (that is, an arrangement pattern of screen dots (halftone dots))
This is a pattern in which a rectangular area 15 of 5 × 5 pixels is surrounded by a broken line in FIG. 8 and the area 15 is simply repeatedly arranged in the horizontal and vertical directions. That is, the rectangular area 15 of 5 pixels × 5 pixels is a unit area of the arrangement pattern of the halftone dots on the image. Therefore, for this unit area 15, the dot arrangement rule of each pixel 13 as shown in FIG. 7B is stored in advance (FIG. 8 shows the arrangement rule of this unit area 15). When converting the compression code of the dot pattern signal into a dot pattern signal, it is possible to generate an appropriate dot pattern by deciding whether to shift the dots to the right or left according to the stored dot arrangement rules for each pixel. it can.

FIG. 9 shows the configuration of an embodiment of the decompression unit 5 that converts a 2-bit compression code of a triple-density image into a dot pattern signal using the above-described principle.

An address counter 21 for designating a read address of the memory 3 is provided. The read address counted by the address counter 21 is designated for the memory 3, and a 2-bit compression code of each pixel is sequentially read from the memory 3. The read 2-bit compression code is applied to a dot pattern signal generator 29 described later.

The expanding section 5 also has a dot arrangement data matrix 23. The dot arrangement data matrix 23 includes a 5 pixel × 5 pixel unit area 15 shown in FIG. 1-bit dot arrangement data (0 is rightward and 1 is leftward) defining dot arrangement according to the rule shown in FIG. 7B. The address of the data of each pixel in the dot arrangement data matrix 23 is the vertical position (0 to 0) of each pixel in the unit area 15 of 5 pixels × 5 pixels.
4) and the horizontal position (0 to 4). The horizontal counter 25 and the vertical counter 27 respectively determine the horizontal position and the vertical position of the pixel to be read in the unit area 15 from the read address output from the address counter 21, and transfer the horizontal address and the vertical address to the dot arrangement data matrix 23. The dot arrangement data of the designated address is extracted from the dot arrangement data matrix 23. Thereby, the dot arrangement data corresponding to the pixel read from the memory 3 is output from the dot arrangement data matrix 23. The output dot arrangement data is applied to the dot pattern signal generator 29.

The dot pattern signal generator 29 includes six types of dot pattern signals 31 and 33 representing six types of dot patterns that can be taken by the pixels of the triple density image.
R, 33L, 35R, 35L, and 37 are stored. The addresses of these dot pattern signals are specified by the 2-bit compression code read from the memory 3 and the dot arrangement data from the dot arrangement data matrix 23. You. Therefore, the dot pattern signal specified by the 2-bit compression code of the pixel read from the memory 3 and the dot position specification data corresponding to the pixel is output from the dot pattern signal generator 29.
For example, when the compression code is 00, a dot pattern signal 31 representing a dot pattern in which all pixels are blank is output regardless of the dot position designation data. When the compression code is 11, a dot pattern signal 37 representing a dot pattern in which all pixels are filled with dots is output regardless of the dot position designation data. When the compression code is 11, a dot pattern signal 37 representing a dot pattern in which all pixels are filled with three dots is output regardless of the dot position designation data. When the compression code is 01, one dot is shifted to the right if the dot position designation data is 0, and is a dot pattern signal 33R or 33L representing a dot pattern shifted to the left if the dot position designation data is 1. Is output. When the compression code is 10, the two dots are shifted to the right if the dot position designation data is 0, and are shifted to the left if the dot position designation data is 1; Is output. The output dot pattern signal is input to the print engine 7.

FIG. 10 shows the principle of a decompression process performed by the second embodiment of the decompression unit 5.

As shown in FIG. 10, in a rectangular area 41 of, for example, 4 pixels × 4 pixels on an image, a starting point (growth) of a halftone dot (screen dot) is located at two positions 43 and 45 at the upper left and the lower right. Nuclear). As the tone (density) increases, a cluster of screen dots grows (increases) starting from the upper left growth nucleus 43, and at the same time, another cluster of screen dots starts from the lower left growth nucleus 45. It grows (increases). The screen dots starting from the upper left growth nucleus 43 grow in such a manner that the horizontal width of the dot increases in the right and left directions centering on the growth nucleus 43 in the two rows where the vertical position is 0 and 1. I do. The screen dots starting from the lower right growth nucleus 45 are arranged such that the horizontal width of the dot increases in the right and left directions around the growth nucleus 45 in the two rows of vertical positions 2 and 3. grow up. On an image composed of a large number of pixels, this rectangular area 41 of 4 × 4 pixels
Are simply repeated in the horizontal and vertical directions. That is, the rectangular area 41 of 4 × 4 pixels is a unit area of the arrangement pattern of the halftone dots on the image.

In this unit area 41, there is a unique rule as to which of the right side and the left side of each pixel 13 the dots should be arranged. That is, as shown in FIG. 10 by codes 0 and 1 (0 is rightward and 1 is leftward) in each pixel, when the vertical position is 0 or 1, the code 0 (rightward) when the horizontal position is smaller than 1; If the horizontal position is 1 or more, the code is 1 (leftward). If the vertical position is 2 or 3, the code is 0 (rightward) if the horizontal position is smaller than 3. If the horizontal position is 3 or more, the code is 1 (rightward). (To the left). It should be noted that the size of the unit area 41 and the screen dot growth pattern in this area 41 shown in FIG. 10 are merely examples, and other various sizes of unit areas and various screen dot growth patterns can be adopted. There is a unique dot arrangement rule for each one.

For the rectangular area 41 shown in FIG. 10, the dot arrangement rule of each pixel shown in FIG. 10 is stored in advance, and the compressed code of each pixel is stored when the dot pattern signal is converted. An appropriate dot pattern can be generated by determining whether the dots are right-aligned or left-aligned in accordance with the dot arrangement rule of each pixel.

FIG. 11 shows the configuration of an embodiment of the decompression unit 5 that converts a 2-bit compression code of a triple-density image into a dot pattern signal using the above-described principle.

The expansion unit 5 has an address counter 21, a horizontal counter 25, and a vertical counter 27 similar to those shown in FIG. However, the horizontal position and the vertical position output from the horizontal counter 25 and the vertical counter 27 are the horizontal position (0 to 3) and the horizontal position (0 to 3) of the read target pixel read from the memory 3 in the 4 × 4 pixel 41 area shown in FIG. The vertical position (0-3).

The extension unit 5 also includes two growth nuclei 43 in a 4 pixel × 4 pixel 41 area 41 shown in FIG.
45 horizontal position (growth nucleus 43 is horizontal position 1, growth nucleus 45
Has a nuclear position table 51 storing nuclear position data indicating the horizontal position 3). The address of the nuclear position data in the nuclear position table 51 is designated by the vertical position from the vertical counter 27. For example, when the vertical position is 0 or 1, the nuclear position data at the horizontal position 1 is specified, and when the vertical position is 2 or 3, the nuclear position data at the horizontal position 3 is specified.
The nuclear position data specified by the vertical position is extracted from the nuclear position table 51 and input to the comparator 53.

The comparator 53 compares the horizontal position of the growth nucleus indicated by the nucleus position data input from the nucleus position table 51 with the horizontal position of the pixel to be read inputted from the horizontal counter 25, and compares the 1-bit data. The dot position data (0 is rightward and 1 is leftward) is output. If the value of the horizontal position of the pixel to be read is equal to or greater than the value of the horizontal position of the growth nucleus,
The dot position data is 1 (leftward), and if the value of the horizontal position of the pixel to be read is less than the value of the horizontal position of the growth nucleus, the dot position data is 0 (rightward). That is, dot position data having the values shown in FIG. 10 is output according to the horizontal position and the vertical position of the pixel to be read. The output dot position data is applied to the dot pattern signal generator 29.

The dot pattern signal generator 29 is the same as that shown in FIG. That is, the dot pattern signal generator 29 outputs a dot pattern signal indicating a dot pattern corresponding to the 2-bit compression code from the memory 3 and the dot position data from the dot pattern signal generator 29. As shown in FIG. 9, this dot pattern signal represents a dot pattern in which the number of dots indicated by the 2-bit compression code are arranged closer to the side specified by the dot position data. This dot pattern signal is input to the print engine 7, which draws the dot pattern.

FIGS. 12 and 13 show a decompression process performed by the decompression unit 5 according to the third embodiment.

The decompression unit 5 of this embodiment sequentially reads the 2-bit compression code of each pixel from the memory 3, and successively arranges the pixels 61, 63, 65, 67 on the same row as shown in FIG. Are sequentially processed from left to right, and assuming that the pixel 65 is to be processed, the density (value of the 2-bit compression code) c of the pixel 65 to be processed and the density of the pixels 63 and 65 on both sides are calculated. b, d,
With reference to the density a of the pixel 61 two pixels before in the processing order, the dot pattern of the processing target pixel 65 is determined according to the algorithm (rule) shown in FIG.

The principle of the dot pattern determination algorithm (rule) shown in FIG. 13 is as follows.

The number of dots in the processing target pixel 65 is determined by the value of the 2-bit compression code of the processing target pixel 65. Specifically, rule # 1: if the 2-bit compression code is 00, the number of dots is 0 (dot pattern 71). Rule # 2: If the 2-bit compression code is 11, the number of dots is three (dot pattern 73). Rule # 3: If the 2-bit compression code is 01, the number of dots is one (dot patterns 75R, 75L). rule#
4: If the 2-bit compression code is 10, the number of dots is 2 (dot patterns 77R and 77L).

When the number of dots is one or two (rules # 3 and # 4), the side to which the dot is shifted is the pixel 63 that is one pixel before the pixel 65 to be processed in the processing order (the dot pattern is already (Determined) is determined depending on which side the dot is shifted to. In other words, if the dot of the pixel 63 one pixel before is shifted toward the pixel 61 (left side) two pixels before, the dot of the pixel 65 to be processed becomes the pixel 6 one pixel behind.
7 (right side). On the other hand, if the dot of the pixel 63 immediately before the pixel 63 is shifted toward the pixel to be processed 65 (right side), the dot of the pixel to be processed 65 is shifted toward the pixel 63 immediately before the pixel (left side). In order to know on which side the pixel 63 one pixel before is shifted,
Pixels 61 and 65 on both sides of the pixel 63 before the pixel
Are referred to.

Specifically, when the number of dots of the pixel 65 to be processed is one, as shown in rule # 3, the densities a and c of the pixels 61 and 65 on both sides of the pixel 63 one pixel before are compared. If a ≧ c, the density b of the pixel 63 one pixel before is not 11 (unless the pixel 63 is filled with dots), and the dot of the pixel 63 one pixel before is shifted to the left. The dot of the processing target pixel 65 is shifted to the right (dot pattern 75
R) (except when the density of the pixel 67 on the right is 00 (complete blank)). Also, even if a ≧ c,
When the density b of the pixel 63 one pixel before is 11 (when the pixel 63 is filled with dots), the dot of the processing target pixel 65 is shifted to the left side in order to combine with the dot (dot pattern 75L). . Also,
In cases other than the above two cases, the processing target pixel 6
5. Compare the densities b and d of the pixels 63 and 67 on both sides of 5
If b <d, the dots of the processing target pixel 65 are shifted to the right (dot pattern 75R), and if b ≧ d, the dots of the processing target pixel 65 are shifted to the left (dot pattern 7).
5L).

When the number of dots of the pixel 65 to be processed is two, as shown in rule # 4, the side to which the dots are brought is determined by the same determination method as in rule # 3. However, in rule # 4, the number of dots is two (dot patterns 77R, 77L).

As described above, the pixel 61 two pixels before
By referring to the density of the pixel 63,
Is determined to which side the dot of the processing target pixel 65 is located, and a method of adjusting the side where the dot of the processing target pixel 65 is shifted in accordance with the result is introduced. Compared to the case where the side closer to the dot is determined only from the density of 63 and 67,
A more appropriate dot pattern can be determined.

The embodiment of the present invention has been described above.
These embodiments are merely examples for describing the present invention, and are not intended to limit the present invention only to these embodiments. Therefore, the present invention can be implemented in various modes other than the above-described embodiment.

[Brief description of the drawings]

FIG. 1 is a diagram showing a dot pattern of a double-density image.

FIG. 2 is a diagram showing a dot pattern of a triple-density image.

FIG. 3 is a diagram showing data of three consecutive pixels in the same row.

FIG. 4 is a diagram showing a correspondence relationship between a pixel tone, a compression code, and a dot pattern of a triple dense image according to the related art.

FIG. 5 is a diagram showing an example in which an inappropriate dot pattern occurs in the related art.

FIG. 6 is a block diagram showing a configuration of an embodiment of an image processing system for a printer according to the present invention.

FIG. 7 is a diagram illustrating a halftone cell for explaining the principle of the expansion process performed by the first embodiment of the expansion unit.

FIG. 8 is a diagram illustrating a tiled pattern of halftone cells for explaining the principle of expansion processing performed by the expansion unit according to the first embodiment.

FIG. 9 is a block diagram showing a configuration of a first embodiment of an extension unit.

FIG. 10 is a view showing the position of a growth nucleus of a halftone dot (screen dot) in a 4-pixel × 4-pixel rectangular area on an image, for explaining the principle of expansion processing performed by a second embodiment of an expansion unit. .

FIG. 11 is a block diagram showing a configuration of a second embodiment of the extension unit.

FIG. 12 is a diagram showing data of four consecutive pixels in the same row.

FIG. 13 is a diagram illustrating an algorithm (rule) of a decompression process according to a third embodiment of the decompression unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compression part 3 Memory 5 Decompression part 7 Print engine 11 Halftone cell 15 5 pixel x 5 pixel rectangular area 21 Address counter 23 Dot position data matrix 25 Horizontal counter 27 Vertical counter 29 Dot pattern signal generator 31, 33, 35, 37 dot pattern 41 rectangular area of 4 pixels × 4 pixels 43, 45 growth nucleus of halftone dot (screen dot) 51 nucleus position data table 53 comparator 61 pixel 2 pixels before 63 63 pixel 1 pixel before (pixel on the left) 65 pixel to be processed 67 pixel after one pixel (pixel on the right) 71, 73, 75, 77 dot pattern 65

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C262 AA02 AA05 AA24 AA26 BB06 BB10 BB14 BB20 DA17 5C077 LL18 MP01 NN04 NN05 NN07 NN08 PP68 PQ22 RR21 SS07 TT03 TT05 TT06 5C078 AA04 BA21 CA00 DA01 A02 DA02 DA02 DA02 DA02 DA02 DA02 9A001 EE04 HH27 KK42

Claims (8)

[Claims] 1. N + 1 possible values for each pixel of an N-fold dense image
Compression code storage means for storing a compression code of each pixel having a depth that can be represented by a tone; fetching the compression code of each pixel from the compression code storage means; Dot pattern signal generating means for generating a dot pattern signal representing a dot pattern formed by arranging dots or blanks, wherein the dot pattern signal generating means comprises: A dot arrangement determining unit that outputs dot arrangement data indicating a dot arrangement of each pixel based on a relative position of the pixel; and the dot pattern according to the compression code of each pixel fetched from the compression code storage unit. The size or the number of dots of each pixel is determined, and the pixel of each pixel output from the dot arrangement determining means is determined. An N-fold dense image generating apparatus, comprising: dot pattern determining means for determining the arrangement of dots in the dot pattern according to dot arrangement data. 2. The method according to claim 1, wherein said dot arrangement determining means includes a dot arrangement having dot arrangement data indicating a dot arrangement of each pixel included in the unit area of the halftone dot arrangement pattern on the N-fold dense image. Data means, for each pixel fetched from the compression code storage means, determine the position of each pixel in the unit area, obtain dot arrangement data corresponding to the determined position from the dot arrangement data means, 2. An apparatus for generating an N-fold density image according to claim 1, further comprising: means for outputting the dot arrangement data as the dot arrangement data. 3. A dot position determining means, comprising: for a unit area of a halftone dot arrangement pattern on the N-fold dense image, nuclear position data means having position data of a growth nucleus of a halftone dot in the unit area; For each pixel fetched from the compression code storage means, determine the position of each pixel in the unit area, and based on the relative relationship between the determined position and the position of the growth nucleus obtained from the nucleus position data means, 2. The apparatus according to claim 1, further comprising: means for determining and outputting dot arrangement data of pixels. 4. N + 1 possible values for each pixel of an N-fold dense image
Compression code storage means for storing a compression code of each pixel having a depth capable of expressing a tone; fetching the compression code of each pixel from the compression code storage means; Dot pattern signal generating means for generating a dot pattern signal representing a dot pattern formed by placing blanks, wherein the dot pattern signal generating means responds to a compression code of each pixel fetched from the compression code storage means. Determining the size or number of dots in the dot pattern of each pixel, and determining the dot pattern of each pixel based on the compression code of the pixel one pixel before, one pixel and two pixels before each pixel. For generating an N-fold dense image that determines the dot arrangement in the image. 5. N + 1 possible values for each pixel of an N-fold dense image
Compression code storage means for storing a compression code of each pixel having a depth capable of expressing a tone; fetching the compression code of each pixel from the compression code storage means; Dot pattern signal generating means for generating a dot pattern signal representing a dot pattern formed by placing blanks, wherein the dot pattern signal generating means responds to a compression code of each pixel fetched from the compression code storage means. Determining the size or number of dots in the dot pattern for each pixel, and based on the compressed code of the pixel one pixel before and one pixel after each pixel and the dot arrangement of the pixel one pixel before An N-fold dense image generation device for determining a dot arrangement of each pixel in the dot pattern. 6. N + 1 possible pixels of an N-fold dense image
Capturing a compressed code of each pixel having a depth that can be represented by a tone; and generating a dot pattern signal representing a dot pattern in which dots or blanks are arranged in N dot regions in each pixel. Generating the dot pattern signal, wherein a dot indicating a dot arrangement of each pixel based on a relative position of each of the captured pixels with respect to a halftone dot applied to the N-times dense image. Outputting arrangement data; and according to the compression code of each of the captured pixels,
Determining a size or number of dots in the dot pattern; and determining a dot arrangement in the dot pattern according to the dot arrangement data of each pixel output from the dot arrangement determining means. How to generate double-density images. 7. N + 1 possible values for each pixel of an N-fold dense image
Capturing a compressed code of each pixel having a depth that can be represented by a tone; and generating a dot pattern signal representing a dot pattern in which dots or blanks are arranged in N dot regions in each pixel. The step of generating the dot pattern signal comprises: determining the size or the number of dots in the dot pattern of each pixel according to the captured compression code of each pixel; Determining a dot arrangement in the dot pattern for each pixel based on a compression code of a pixel before, one pixel after, and two pixels before. 8. N + 1 possible values of each pixel of an N-fold dense image
Capturing a compressed code of each pixel having a depth that can be represented by a tone; and generating a dot pattern signal representing a dot pattern in which dots or blanks are arranged in N dot regions in each pixel. The step of generating the dot pattern signal comprises: determining the size or the number of dots in the dot pattern of each pixel according to the captured compression code of each pixel; and Determining a dot arrangement in the dot pattern for each pixel based on a compression code of a pixel one pixel before and one pixel after and a dot arrangement of the pixel one pixel before the pixel. .