JP2002036633A - Image processing method and apparatus - Google Patents

Abstract

(57) [Problem] To output a high-quality image with reduced graininess by maintaining the entire density in pseudo halftone processing of an image. SOLUTION: Binarization means (101 to 105) for binarizing image data by dots having a first recording area.
And binarizing means based on a predetermined number of dots of a second recording area larger than the first recording area so as to have the same density as the dots having the first recording area. The first method in which the dots of the first recording area in the converted image data are replaced with the dots of the previous second recording area
And a blank portion surrounded by the dots of the second recording area replaced by the first dot converting means, the dots of the third recording area smaller than the second recording area. And dot addition means (108) for adding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and apparatus for performing pseudo halftone processing using a variable dot diameter in order to output an image on a display device or a recording device.

[0002]

2. Description of the Related Art One of image processing methods is a pseudo-method for maintaining high-quality output results while expressing input multi-valued image data at a multi-valued level smaller than binary or input multi-valued image data. There is halftone processing. Regarding the error diffusion method which is a typical method of the pseudo halftone processing, for example, “An Adapt
ive Algorithm for Spatial Gray Scale ”in society f
or Information Display 1975 Symposium Digest of Te
The details are described in Chnical Papers, 1975, 36. Here, the pixel of interest is P, the density of the pixel is V, the non-binarized pixels P0, P1, P2, and P3 around the point P, and the densities are V0, V1, V2, V3, and binarized, respectively. The threshold of T
And The error diffusion method uses a binarization error E at the point of interest P.
Are weighted with the weighting coefficients W0, W1, W2, and W3 empirically obtained for the peripheral pixels P0, P1, P2, and P3. By adding the allocated error to the peripheral pixel data, the average density of the output image becomes equal to the density of the input image macroscopically. At this time, the output binary data is
Then, the peripheral pixels P0, P1, P2, and
Errors E0, E1, E2, and E3 with respect to P3 can be obtained. If V> = T, O = 1, E = V-Vmax If V <T, O = 0, E = V-Vmin where Vmax indicates the maximum density, Vmin indicates the minimum density, and the error is E0. = E × W0 E1 = E × W1 E2 = E × W2 E3 = E × W3 In the error diffusion method, the above operations are sequentially performed for each pixel.

[0003] Regarding the multi-level error diffusion method, for example,
Katoh, Y.Arai, Y.Yasuda National Conference of Comm
unication, Department in Showa53 Year, Society of
Electronic Communication in Japan (1973), pp. 504 (Ja
panese). The multi-level error diffusion method is
Instead of one fixed threshold, this is an error diffusion method in which a plurality of thresholds are provided, and multi-valued output value data corresponding to the plurality of thresholds is obtained. In order to print the multi-valued image data thus obtained by a printing device such as an ink jet printer, it is necessary to convert the multi-valued data into binary data. As one of the methods for converting multi-valued data into binary data, there is a method of replacing the data with a binary dot pattern that realizes a density corresponding to the multi-valued data. in this case,
Make dot pattern correspond to multi-value data one-to-one.
Convert to value data.

[0004]

When converting input multi-valued image data into binary data or the like and outputting the converted data, it is conceivable to reduce graininess as a means for obtaining a higher quality output result. That is, by forming an output image corresponding to certain input multi-valued image data at points as fine as possible, it becomes possible to smooth the contour portion and reduce the graininess of the highlight portion. However, if the size of the dot is reduced to improve the granularity, the dot diameter becomes smaller, and the dot is more likely to be affected by the accuracy of the landing position of the dot on the recording surface. For this reason, printing is performed with fine dots for parts where graininess is a problem, such as highlights, and high density parts or solid parts where little graininess is a problem can be printed with a large area at once. A method has been proposed in which printing is performed according to the size and a high-quality image is output in which the granularity is reduced by fine dots while minimizing unevenness and streaks.

[0005] However, when an area consisting of only dots having a large dot diameter is actually formed, the gap between the dots becomes large, and even if the density is the same as the case where the dot is formed only of the small dots, the solid portion becomes granular. There is a problem that image quality is deteriorated due to feeling.

The present invention has been made in view of such a problem. The purpose of the present invention is to perform printing with fine dots on a portion such as a highlight portion where graininess is a problem, and to print the High-density areas and solid areas where performance is not a problem are printed with a dot size that can print a large area at once, while filling the gaps between large dots with dots of another size, It is an object of the present invention to provide an image processing method and apparatus capable of outputting a high-quality image with reduced graininess by maintaining image quality.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to an image recording apparatus for recording an image by changing the recording area of dots attached to a recording surface. In the processing method, a binarizing step of binarizing image data with a dot having a first recording area; and the first predetermined step having a same density as the dot having the first recording area. The dots of the first recording area in the image data binarized in the binarization step are based on the number ratio of the dots of the second recording area larger than the recording area of the second recording area. A first dot conversion step for replacing dots,
A dot adding step of adding a dot having a third recording area smaller than the second recording area to a blank portion surrounded by the dots having the second recording area replaced in the dot conversion step. Features.

According to a second aspect of the present invention, the number of dots having a fourth recording area larger than the predetermined third recording area so as to have the same density as the dots having the third recording area. Based on the ratio, the dots having the third recording area added in the dot adding step are added to the fourth dots.
Characterized by a second dot conversion step of replacing dots with a dot having a recording area of.

According to a third aspect of the present invention, in the image processing method for recording an image by changing the recording area of the dots attached to the recording surface, the image data is binarized by the dots having the first recording area. A binarization step; a third dot having a second recording area larger than the first recording area and a third dot having a second recording area larger than the first recording area so as to have the same density as the dot having the first recording area. A third dot conversion step of determining a combination dot obtained by combining a dot of a recording area and replacing the dot of the first recording area in the image data binarized in the binarization step with the combination dot; It is characterized by having.

According to a fourth aspect of the present invention, in the third dot conversion step, a plurality of combination dots having the same density as the dots having the first recording area are replaced while being arbitrarily switched. I do.

According to a fifth aspect of the present invention, in an image processing apparatus for recording an image by changing the recording area of a dot attached to a recording surface, image data is binarized by a dot having a first recording area. The binarization means, based on a predetermined number of dots having a second recording area larger than the first recording area so as to have the same density as the dots having the first recording area, First dot conversion means for replacing the dots of the first recording area in the image data binarized by the binarization means with dots of the second recording area, and replacing the dots with the first dot conversion means; Dot adding means for adding a dot having a third recording area smaller than the second recording area to a blank portion surrounded by the dots having the second recording area.

The invention according to claim 6, wherein the number of dots having a fourth recording area larger than the predetermined third recording area so as to have the same density as the dots having the third recording area. And a second dot conversion unit that replaces the dot of the third recording area added by the dot addition unit with the dot of the fourth recording area based on the ratio.

According to a seventh aspect of the present invention, in an image processing apparatus for recording an image by changing the recording area of dots attached to a recording surface, image data is binarized by dots having a first recording area. Binarizing means, a dot having a second recording area larger than the first recording area, and a third dot smaller than the second recording area so as to have the same density as the dot having the first recording area. A third dot conversion unit that determines a combination dot obtained by combining a dot having a recording area and replaces the dot having the first recording area in the image data binarized by the binarization unit with the combination dot; It is characterized by having.

The invention according to claim 8 is characterized in that the third dot conversion means replaces a plurality of combination dots having the same density as the dots having the first recording area while arbitrarily switching. I do.

According to a ninth aspect of the present invention, in an image processing apparatus for recording an image by changing the recording area of dots attached to a recording surface, image data is binarized by dots having a first recording area. A binarizing step; and a second step which is larger than the first recording area and is predetermined so as to have the same density as the dots having the first recording area.
The first data in the image data binarized in the binarization step based on the dot ratio of the dots having the recording area of
A first dot conversion step of replacing the dots of the recording area with the dots of the second recording area, and a blank portion surrounded by the dots of the second recording area replaced in the first dot conversion step. And a dot addition step of adding a dot having a third recording area smaller than the second recording area. A computer-readable recording medium recording a program for causing a computer to execute the image processing method. And

According to a tenth aspect of the present invention, in an image processing apparatus for recording an image by changing the recording area of a dot attached to a recording surface, image data is binarized by a dot having a first recording area. A binarizing step;
So as to have the same density as a dot having a recording area of
A combination dot is determined by combining a dot having a second recording area larger than the first recording area and a dot having a third recording area smaller than the second recording area, and binarizing in the binarizing step. A third step of replacing the dots of the first recording area in the obtained image data with the combination dots;
And a computer-readable recording medium in which a program for causing a computer to execute the image processing method including the dot conversion step is recorded.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic block diagram showing an image processing unit in an image processing apparatus according to a first embodiment of the present invention. The image processing unit includes an output value data generator 101 that determines multi-tone multi-valued data to be output according to the input multi-valued image data, and data obtained by adding an error to the input multi-valued image data and an output value. Comparator 102 for comparing
And a selector 103 for selecting output data and error data
And an accumulation error buffer 104 for accumulating error data
And a divider 105 for distributing the sum of the accumulated error data to peripheral pixels, and a dot having a minimum dot diameter size (hereinafter, referred to as a small dot) is divided into a minimum dot diameter dot and a maximum dot diameter dot. And a medium dot conversion unit 106 that replaces the medium dot with a dot having an intermediate dot diameter (hereinafter referred to as a medium dot). , A large dot).
7 and a small dot adding unit 108 for arranging small dots in gaps between large dots when converted to large dots.

With such a configuration, the input multi-valued image data (In) is subjected to error diffusion processing assuming small dot size dots. The integrated error data generated by the error diffusion processing is added to the input multi-valued image data (In). The output value data generator 101 outputs a multi-level error diffusion output value (Out) according to the input value. Comparator 102
Is a multi-level error diffusion output value (Out) and input data (In
+ DIn). In the first embodiment, the output value of the error diffusion process is a binary output. The selector 103
Error data (In + dIn-Out) obtained by subtracting the multi-level error diffusion output value (Out) from the value (In + dIn) obtained by adding the integrated error data to the input multi-level image data is stored together with the multi-level error diffusion output value (Out). The data is accumulated in the error buffer 104. The divider 105 distributes the accumulated error data (In + dIn-Out) to peripheral pixels by a weighting process. The distributed error data is added to the input multi-level image data for each corresponding peripheral pixel.

The selector 103 selects a small dot 2
Outputs the value output value. The medium dot conversion unit 106 converts a binary output value assuming a small dot into a medium dot according to a predetermined conversion rule. The large dot conversion unit 107 converts only medium dots into large dots according to a predetermined conversion rule for image data in which small dots and medium dots are mixed. Usually, when replaced by large dots, a gap is created in a portion surrounded by the large dots. The blank portion of the gap increases as the diameter of the large dot increases. Therefore, even if the dot densities are equal before and after the conversion, the solid portion deteriorates in image quality due to the granularity. Therefore, the small dot adding unit 108
Small dots are arranged in the gaps between the large dots to reduce blank portions of the gaps, thereby preventing image quality deterioration due to granularity. In this way, the image processing unit generates image data in which small dots, medium dots, and large dots are mixed, from the output value of the error diffusion processing composed of only small dots. In a printer capable of printing in a multi-dot size, a high-quality image can be obtained by outputting the image data.

FIG. 2 is a diagram showing a conversion rule between small dots and medium dots, and between medium dots and large dots. The relationship between small dot and medium dot, medium dot and large dot is
When a certain small area is formed by each dot, the conversion ratio of the number of dots is determined so as to realize the same density value. In the first embodiment, the medium dot is composed of four small dots, and the large dot is composed of four medium dots.

FIG. 3 is a diagram showing conversion from small dots to medium dots and from medium dots to large dots. First,
The conversion from small dots to medium dots is performed by sequentially discriminating small dot groups satisfying the conversion rules from small dots to medium dots shown in FIG. 2 for image data of error diffusion output values composed of small dots. , A small dot group within a predetermined rectangular range is converted into a medium dot. Image data (a) composed of only small dots is converted to image data (b) in which small dots and medium dots are mixed. Next, in the conversion from the medium dot to the large dot, the medium dot group satisfying the conversion rule from the medium dot to the large dot shown in FIG. A medium dot group within a predetermined rectangular range is converted into a large dot. Image data (b) in which small dots and medium dots are mixed is converted to image data (c) in which small dots, medium dots, and large dots are mixed. Although four medium dots are replaced with one large dot, a combination of not only a plurality of medium dots but also a plurality of small dots may be converted to a large dot.

FIG. 4 is a diagram showing a state where small dots are further arranged in the gaps between large dots. As shown in FIG. 3, there is a gap between the large dots. Therefore, when a dot having an appropriate dot diameter is arranged in this gap, a blank portion between large dots is reduced. In Example 1, a dot having the same size as a small dot was added.

FIG. 5 is a diagram showing a state in which a plurality of small dots arranged between large dots are converted into medium dots. In the first embodiment, since four small dots are replaced with one medium dot, when four added small dots are collected, they can be converted into one medium dot.

Originally, the initial density is already guaranteed at the time of replacement with a large dot. Therefore, adding a small dot or a medium dot to fill a gap later increases the density of that portion. There is nothing else. However, the portion converted to the large dot is a portion where the small dot and the medium dot existed without a gap, and is considered to be a solid portion. Therefore, although the density of a portion converted into a large dot is higher than that of the original image data, the solid portion has little effect on the image quality due to the solid portion.

As described above, a portion where graininess such as a highlight portion is a problem is printed with small dots, and a portion where the graininess is not a problem such as a high density portion or a solid portion is a large number at a time. Printing is performed using large dots that can print the area. Large dots can suppress unevenness and streaks, and small dots can reduce the granularity of highlights. Further, image quality degradation caused by the granularity caused by the gap between the large dots is prevented by adding small dots to the gap between the large dots, and a high-quality image can be output.

In the first embodiment, the small dot group within the rectangular range is converted into a medium dot, but this can be applied to a small dot group of any shape. In addition, although it is assumed that the entirety of the rectangular area is filled with small dots, if there are several small dots in the rectangular area, they may be converted to medium dots. Further, the present invention does not matter even if the center position of the dot diameter of the medium dot to be replaced is set to any of the center positions of the small dots in the rectangular range. The restriction on the conversion from small dots to medium dots described above can be applied to the restriction on conversion from medium dots to large dots as it is.

In the first embodiment, a dot having the same size as a small dot is added to fill a gap between large dots. However, the present invention is not limited to this dot size. Good. In addition, although the three dot sizes of the large dot, the medium dot, and the small dot have been described, the same holds when there are more dot sizes.

(Embodiment 2) FIG. 6 is a schematic block diagram showing an image processing section in an image processing apparatus according to Embodiment 2 of the present invention. The image processing unit according to the second embodiment is the large dot conversion unit 107 of the image processing unit (FIG. 1) according to the first embodiment.
In place of the small dot addition unit 108, an additional small dot position determination unit 601 and a combination dot conversion unit 602 are provided. The additional small dot position determination unit 601 determines the arrangement positions of the small dots of the combination dots that realize the same density as the four medium dots and the density of the large dot that should be originally converted. The combination dot conversion unit 602 converts a predetermined number of medium dots.

The input multi-valued image data is subjected to (In) error diffusion processing assuming small dot size dots.
The integrated error data generated by the error diffusion processing is added to the input multi-valued image data (In). The output value data generator 101 outputs a multi-level error diffusion output value (O
ut). The comparator 102 compares the multi-level error diffusion output value (Out) with the input data (In + dIn). In the second embodiment, the output value of the error diffusion process is a binary output. The selector 103 obtains the error data (In + dIn-Out) obtained by subtracting the multi-level error diffusion output value (Out) from the value (In + dIn) obtained by adding the integrated error data to the input multi-level image data, and outputs the multi-level error diffusion output value ( O
ut) and accumulates in the accumulation error buffer 104. The divider 105 calculates the accumulated error data (In + dIn-
Out) is distributed to peripheral pixels by a weighting process.
The distributed error data is added to the input multi-level image data for each corresponding peripheral pixel.

On the other hand, the selector 103 outputs a binary output value assuming a small dot. The medium dot conversion unit 106
A binary output value assuming a small dot is converted into a medium dot according to a predetermined conversion rule. Originally, for image data in which small dots and medium dots are mixed, medium dots are converted to large dots in accordance with the conversion rules. However, simply replacing them with large dots causes gaps between the large dots. The blank portion of the gap increases as the large dot diameter increases. Therefore, even if the density is equal before and after the conversion, the image quality of the solid portion deteriorates due to the granularity. Example 2
Then, the medium dot is converted by a combination dot that achieves the same density as the large dot that should be replaced. The combination dot is configured by combining a plurality of dots of a certain appropriate size and a plurality of smaller dots.

FIG. 7 is a diagram exemplifying combination dots having the same density as large dots according to the arrangement of added small dots. That is, this is an example showing how small dots in combination dots are arranged in order to realize the density closest to the density of a large dot that should be replaced. In Example 2, a dot having the same dot diameter as the small dot was used. The density adjustment realized by the combination dots may be controlled by the number of small dots to be added. The position of the small dot to be added is determined by the additional dot position determining unit 601 with respect to the combination dot thus obtained.

FIG. 8 is a diagram showing a dot arrangement of combination dots having the same density and different positions of added small dots. When actually converting a plurality of medium dots into combination dots, a random number may be selected from the patterns shown in FIG. 8 or may be limited to one of the patterns. By the determined combination dot,
The combination dot conversion unit 602 converts the plurality of medium dots by combination dots instead of the large dots that should be replaced.

FIG. 9 is a diagram showing a state in which medium dots are converted into combination dots. By being converted into combination dots, small dots are arranged in the gaps between large dots, thereby reducing the space in the gaps and preventing image quality deterioration due to granularity. Further, unlike the first embodiment, since the combination dot is realized by combining the same density as that of the large dot to be originally converted, the solid portion has a higher density than the original image in the first embodiment. In Example 2, the original density is maintained.

As described above, printing is performed with small dots in portions where graininess is a problem, such as highlight portions, and combination dots are used in high density portions and solid portions where graininess is not a problem. Accordingly, it is possible to reduce the granularity of the highlight portion with minute dots while suppressing unevenness and streaks by using combination dots that can print a large area relatively at once. In addition, image quality deterioration due to graininess caused by gaps generated between large dots is prevented by reducing the gap area solidified in one place by combination dots, thereby reducing graininess and outputting a high-quality image. It becomes possible. In addition, the solid portion also maintains the original density of the combination dots, so that the density of the entire image is faithfully reproduced. Here, in the second embodiment, the small dot group within the rectangular range is converted into medium dots.
This is applicable to small dot groups of any shape. Further, it is assumed that all of the rectangular area is filled with small dots. However, if there are several small dots in the rectangular area, the area may be converted to medium dots. Further, the present invention does not matter even if the center position of the dot diameter of the medium dot to be replaced is set to any of the center positions of the small dots in the rectangular range. Furthermore, the diameter of the dot located at the center of the combination dot is not particularly described. In the second embodiment, the dots added to the combination dots are described as having the same size as the small dots, but are not limited to the same dot diameter as the small dots.

In the second embodiment, a description has been given of the three-stage dot sizes of large, medium, and small. However, the same holds when there are more dot sizes.

[0037]

As described above, according to the present invention,
A binarizing means for binarizing the image data with the dots having the first recording area; and a binarizing means having a larger than the predetermined first recording area so as to have the same density as the dots having the first recording area. A first dot conversion unit that replaces a dot having a first recording area with a dot having a second recording area in the image data binarized by the binarizing unit based on the number ratio of dots having a recording area of 2; A dot adding means for adding a dot having a third recording area smaller than the second recording area to a blank portion surrounded by the dots having the second recording area replaced by the first dot converting means. Therefore, the granularity is reduced by forming the low-density portions with print dots having a small dot diameter. Preventing and graininess is reduced, it is possible to form a high-quality image by being reduced by also adding the between-dot graininess due space between large dots.

Further, according to the present invention, based on the ratio of the number of dots of the fourth recording area larger than the predetermined third recording area so as to have the same density as that of the dot having the third recording area. Since the second dot converting means for replacing the dots of the third recording area added by the dot adding means with the dots of the fourth recording area is provided, a blank space generated between the large dots with a smaller number of additional dots is provided. And a high-quality image can be formed.

Further, according to the present invention, the binarizing means for binarizing the image data with the dots having the first recording area, and the binarizing means for having the same density as the dots having the first recording area are provided. Image data binarized by binarization means by determining a combination dot obtained by combining a dot having a second recording area larger than the first recording area and a dot having a third recording area smaller than the second recording area. And a third dot conversion means for replacing the dots having the first recording area with the combination dots in the above-mentioned method, so that the blank portion generated between the dots having a certain dot diameter or more can be removed while maintaining the density of the original image. By filling, low-density parts are formed with print dots with a small dot diameter to reduce graininess, and high-density parts are printed with dots with a large dot diameter to reduce dot landing errors. That unevenness and streaks preventing and graininess is reduced, it is possible to form a high-quality image by being reduced by also adding the between-dot graininess due space between large dots. Further, since the combination dots maintain the original image density, it is possible to form an image in which the solid portions have different densities.

Further, according to the present invention, the third dot conversion means replaces a plurality of combination dots having the same density as the dots having the first recording area while switching them arbitrarily. Are prevented from appearing regularly, and a higher quality image can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram illustrating an image processing unit in an image processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating conversion rules for small dots and medium dots, and for medium dots and large dots.

FIG. 3 is a diagram illustrating conversion from small dots to medium dots and from medium dots to large dots.

FIG. 4 is a diagram showing a state in which small dots are further arranged in gaps between large dots.

FIG. 5 is a diagram showing a state in which a plurality of small dots arranged between large dots are converted into medium dots.

FIG. 6 is a schematic block diagram illustrating an image processing unit in the image processing apparatus according to the second embodiment of the present invention.

FIG. 7 is a diagram exemplifying combination dots having the same density as large dots in accordance with the arrangement of small dots to be added.

FIG. 8 is a diagram showing a dot arrangement of combination dots having the same density and different positions of added small dots.

FIG. 9 is a diagram showing a state in which medium dots are converted into combination dots.

[Explanation of symbols]

 Reference Signs List 101 output value data generator 102 comparator 103 selector 104 accumulation error buffer 105 divider 106 medium dot conversion unit 107 large dot conversion unit 108 small dot addition unit 601 additional small dot position determination unit 602 combination dot conversion unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C262 AA02 AA24 AA26 AA27 AB13 BB01 BB08 BB10 BB14 BB18 5B057 AA11 BA29 CA02 CA07 CA12 CA16 CB02 CB07 CB12 CB16 CC02 CE13 CH18 DA08 DA17 DC04 5C074 AA20 CC01 DD01 DD DD NN05 NN11 PP43 PQ08 RR02 SS02

Claims (10)

[Claims] 1. An image processing method for recording an image by changing the recording area of dots attached to a recording surface, comprising: a binarizing step of binarizing image data with dots having a first recording area; In the binarizing step, the binarization step is performed based on a predetermined ratio of the number of dots having a second recording area larger than the first recording area so as to have the same density as the dots having the first recording area. A first dot conversion step of replacing the dots of the first recording area in the converted image data with dots of the second recording area; and the second dot conversion step replaced by the first dot conversion step.
A dot adding step of adding a dot having a third recording area smaller than the second recording area to a blank portion surrounded by the dots having the recording area. 2. The method according to claim 1, wherein the third density is the same as that of the third recording area.
Based on the ratio of the number of dots in the fourth recording area larger than the recording area of
2. The image processing method according to claim 1, further comprising a second dot conversion step of replacing a dot having a recording area with a dot having the fourth recording area. 3. An image processing method for recording an image by changing a recording area of a dot attached to a recording surface, comprising: a binarizing step of binarizing image data with a dot having a first recording area; A combination of a dot having a second recording area larger than the first recording area and a dot having a third recording area smaller than the second recording area so as to have the same density as the dot having the first recording area. The combination dot is determined, and
A third dot conversion step of replacing dots of the first recording area in the image data binarized in the value conversion step with the combination dots. 4. The method according to claim 3, wherein in the third dot conversion step, a plurality of combination dots having the same density as the dots having the first recording area are replaced while being arbitrarily switched. Image processing method. 5. An image processing apparatus for recording an image by changing the recording area of dots attached to a recording surface, comprising: a binarizing means for binarizing image data with dots having a first recording area; The binarizing means uses the binarization means based on a predetermined number ratio of dots having a second recording area larger than the first recording area so as to have the same density as the dots having the first recording area. First dot conversion means for replacing the dots of the first recording area in the converted image data with dots of the second recording area; and the second recording means replaced by the first dot conversion means. In the blank portion surrounded by dots of area, the second
A dot adding unit for adding a dot having a third recording area smaller than the recording area. 6. A method according to claim 3, wherein the third density is the same as the density of the dot having the third recording area.
The second dot conversion for replacing the dots of the third recording area added by the dot adding means with the dots of the fourth recording area based on the number ratio of the dots of the fourth recording area larger than the recording area of The image processing apparatus according to claim 5, further comprising a unit. 7. An image processing apparatus for recording an image by changing a recording area of a dot attached to a recording surface, comprising: a binarizing unit for binarizing image data by using a dot having a first recording area; A combination of a dot having a second recording area larger than the first recording area and a dot having a third recording area smaller than the second recording area so as to have the same density as the dot having the first recording area. The combination dot is determined, and
An image processing apparatus comprising: a third dot conversion unit that replaces dots of the first recording area in the image data binarized by the value conversion unit with the combination dots. 8. The method according to claim 1, wherein the third dot conversion unit is configured to perform the first
8. The image processing apparatus according to claim 7, wherein a plurality of combination dots having the same density as the dots having the recording area are replaced while being arbitrarily switched. 9. An image processing apparatus for recording an image by changing the recording area of a dot attached to a recording surface, wherein the binarizing step binarizes image data by using a dot having a first recording area. In the binarizing step, the binarization step is performed based on a predetermined ratio of the number of dots having a second recording area larger than the first recording area so as to have the same density as the dots having the first recording area. A first dot conversion step of replacing the dots of the first recording area in the converted image data with dots of the second recording area, and the second recording step replaced by the first dot conversion step A dot adding step of adding a dot having a third recording area smaller than the second recording area to a blank portion surrounded by dots having an area. A computer-readable recording medium that records a program to be executed by a computer. 10. An image processing apparatus for recording an image by changing the recording area of a dot attached to a recording surface.
A binarizing step of binarizing the image data with dots having a recording area of the following, and a second recording area larger than the first recording area so as to have the same density as the dots having the first recording area. And a dot having a third recording area smaller than the second recording area are determined, and the first recording area in the image data binarized in the binarization step is determined. And a third dot conversion step of replacing dots with the combination dots. A computer-readable recording medium recording a program for causing a computer to execute an image processing method.