JPH09191405A - Gradation processing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate lines where dots are continuously off and to prevent void even if a user executes oblique line printing with the duty of 50% (45 degrees direction to right and left) or vertically ruled line printing and laterally ruled line printing, which frequently exist in general application software, in any condition. SOLUTION: At the time of executing printing with the duty of 50%, threshold data '1'-'16' whose values are less than half a maximum value and threshold data '17'-'32' whose values are larger than half the maximum value among thirty two threshold data from the maximum value '32' to a minimum value '1' coexist and arranged in any of vertical/lateral directions and the direction of line screen 45 deg. in a dither matrix. Even if oblique line printing with the duty of 50% is executed in any line of the lines 101-108, a place on which the line dots exists, and therefore void is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation processing method, and more particularly to a gradation processing method for expressing density by changing a dot ratio in a pixel.

[0002]

2. Description of the Related Art To record image information in a printer or the like, gradation processing is performed in which the ratio of dots in pixels of the image information is changed to express density. As this gradation processing method, for example, one pixel is decomposed into a matrix, each pixel of the matrix is further divided into n in the scanning line direction, and when reproducing gradation, a line is formed in a direction at a predetermined angle with respect to the scanning line direction. A gradation processing method has been conventionally known in which dots are thickened in the scanning line direction as they are formed and the gradation increases (Japanese Patent Laid-Open No. 62-91076).

2A and 2B are views for explaining an example of the above-mentioned conventional gradation processing method. In the above-described conventional gradation processing method, a dither matrix indicating the dot generation order is used. In FIG. 2A, for simplification, 4 × 4 pixels are used, the multivalue is set to three values (0, 1/2, and 1), and the angle of the line screen is 4.
The dither matrix for 5 ° is shown.

In FIG. 2B, first, four 1/2 dots are formed to form a line screen, and then half of the dots 200 is formed.
In the diagram in which the dots are thickened to 1 dot, dots are generated in accordance with the density in the order of the numbers of the dither matrix shown in FIG. Further, since the dither matrix is two-dimensionally repeated, the line 201 of 45 ° is in the right direction (main scanning direction) by the dither matrix of FIG.
Will occur. Thus, in this conventional gradation processing method, it is attempted to improve both the gradation and the resolution when the angle of the line screen is 45 °.

[0005]

However, in this conventional gradation processing method, since the line screen angle is two-dimensionally repeated as a dither matrix having a line screen angle of 45 °, the duty 5 which is common in general application software is used.
There is a problem that white spots may occur when 0% diagonal printing is performed.

This problem will be concretely described with reference to FIG. The dots of the dither matrix are turned on when (input data) ≧ (threshold data) and turned off when (input data) <(threshold data). Figure 2 (c)
In the line 202, diagonal lines with a duty of 50% are printed.
Let's do it. The duty of 50% means that the dots where the threshold data are 1 to 16 are turned on here,
This means that the dots at 17 to 32 are turned off. Therefore, all dots are turned off on the line 202, and nothing is printed (that is, white spots are generated).

[0007] The present invention has been made in view of the above points,
It is an object of the present invention to provide a gradation processing method that does not cause white spots in any line when oblique line printing with a duty of 50%, which is common in general application software, is performed.

[0008]

In order to achieve the above object, the present invention binarizes each pixel of an input image having gradation by sequentially comparing it with corresponding threshold data in a dither matrix by area gradation. In a gradation processing method for obtaining a pseudo gradation image by using a dither matrix, a threshold value data of a minimum value among a plurality of threshold value data having different values The threshold value data of the maximum value and the threshold value data of a large value in the vicinity of the threshold value are arranged in the peripheral part of the matrix and in the vicinity thereof. The gradation processing is performed so that the dots are turned off when the data is less than the data.

Here, the dither matrix is two-dimensionally repeated, and when printing with a duty of 50%, a plurality of threshold value data is obtained in any of the vertical direction, the horizontal direction, and the line screen angle of 45 °. The maximum of 1
It is characterized in that threshold data having a value of / 2 or less and threshold data having a value larger than ½ of the maximum value are arranged in a mixed manner.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is an explanatory diagram of an embodiment of a gradation processing method according to the present invention. In this embodiment, the dot generation order is determined using a dither matrix as shown in FIG. FIG. 1A shows the above dither matrix when the number of gradations is 33 including white and is binary (dot on and dot off) and the angle of the line screen is 45 ° for simplification. In the gradation processing method using binary area gradation, dots are turned on when the input data supplied is equal to or larger than the threshold data (number of generation order) of the dither matrix.

When the given input data is smaller than the threshold data of the dither matrix, the dot is turned off. That is, if printing with a duty of 50% is performed on one side,
In the case of the 33-gradation dither matrix of this embodiment,
The location of the dither matrix having the threshold data of “1” to “16” shown in FIG. 1A is dot-on,
The location of the dither matrix having the threshold data of "17" to "32" is dot-off.

In this embodiment, when the dither matrix prints at a duty of 50%, the dither matrix shown in FIG.
As shown in, among the 32 pieces of threshold value data from the maximum value “32” to the minimum value “1”, the threshold value data “1” to “16” having a value of 1/2 or less of the maximum value and the maximum value Of the threshold data “17” to “32” having a value greater than ½ of the vertical direction,
The feature is that they are arranged in a mixed manner in both the horizontal direction and the line screen angle of 45 °.

Now, let us consider a case of performing diagonal line printing with a duty of 50%, which is often seen in general application software. Since the user performs this work in his or her preferred way, he does not know in which line of the dither matrix the diagonal printing will be performed. That is, there is a possibility that diagonal lines may be printed on any line.

In the gradation processing method according to the embodiment of the present invention, a case where the above-mentioned diagonal line printing with a duty of 50% is performed will be described with reference to FIG. 45 to the right
When performing the diagonal line printing with a duty of 50% on the diagonal line 101 of 0 °, the dither matrix location of the threshold data “10” is dot-on, and the threshold data “26” and “29”.
And "31" dither matrix locations are doted off. When performing diagonal line printing with a duty of 50% on the diagonal line 102 of 45 ° to the right, the threshold value data “1” is set.
The locations of the dither matrix "3" are dot-on, and the locations of the threshold data "17", "21", and "24" are dot-off. When performing diagonal line printing with a duty of 50% on the diagonal line 45 of 45 ° to the right, the dither matrix locations of the threshold data “5”, “12”, and “15” are dot-on, and the threshold data “2”.
8 "dither matrix locations are doted off.

Also, a diagonal line 104 of 45 ° to the right
When performing diagonal line printing with a duty of 50%, the dither matrix locations of the threshold data “4”, “6” and “7” are dot-on, and the dither matrix locations of the threshold data “19” are dot-off. When performing diagonal line printing with a duty of 50% on the diagonal line 105 of 45 ° to the right, the dither matrix locations of threshold data “1”, “3”, and “9” are dot-on, and the threshold data “20”.
The dither matrix locations of are dot off. Also,
Duty 50% at diagonal line 106 of 45 ° to the right
When performing the diagonal line printing, the locations of the threshold data “2”, “11” and “16” in the dither matrix are dot-on, and the locations of the threshold data “27” in the dither matrix are dot-off.

Furthermore, a slanted line 107 extending 45 ° to the right
When performing diagonal line printing with a duty of 50% at, the dither matrix location of the threshold data “14” is dot-on,
The locations of the threshold data “18”, “22”, and “23” in the dither matrix are dot-off. Furthermore, when performing diagonal line printing with a duty of 50% on the diagonal line 108 of 45 ° to the right, the location of the threshold data “8” in the dither matrix is dot-on, and the threshold data “25” and “3” are displayed.
The 0 "and" 32 "dither matrix locations are doted off.

Since the dither matrix is two-dimensionally repeated, it can be said that the above eight types of lines are all lines. Therefore, no matter which of the lines 101 to 108 is printed with diagonal lines with a duty of 50%, white spots will not occur because there is a dot-on place.

Since the dither matrix is two-dimensionally repeated, the threshold data "30" of another dither matrix is arranged in the upward direction of the threshold data "26" shown in FIGS. 1 (a) and 1 (b), for example. , "18", "2",
"3". . . Since they are arranged in this order, there is no blank even in the vertical direction.

Although the present invention has been described in the above embodiment by taking the case of the oblique line of 45 ° in the upper right direction as an example, the present invention is not limited to this. With respect to the vertical ruled lines and the horizontal ruled lines, white spots do not occur in 50% duty printing.

[0020]

As described above, according to the present invention,
The dither matrix for performing gradation processing is two-dimensionally repeated, and the dither matrix is arranged in the vertical direction, the horizontal direction, and the line screen 4.
In any of the 5 ° directions, the threshold data for dot on and the threshold data for dot off are mixed,
Diagonal line printing with a duty of 50% (45 ° horizontal direction) or vertical ruled lines, which is common in general application software
Regardless of the situation in which the user makes the horizontal ruled lines, it is possible to prevent a line in which dots are continuously turned off and a white spot from being lost.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an embodiment of the system of the present invention.

FIG. 2 is a diagram illustrating an example of a conventional method and its problem explanation diagram.

[Explanation of reference numerals] 101 to 108: 45 ° diagonal line to the right

Claims (2)

[Claims] 1. A gradation processing method in which each pixel of an input image having a gradation is sequentially compared with corresponding threshold data in a dither matrix by area gradation and binarized to obtain a pseudo gradation image, wherein the dither Of the plurality of threshold value data having different values, the matrix is arranged in the central portion of the matrix and the vicinity thereof, and the threshold value data of the minimum value and the vicinity thereof, and the threshold data of the maximum value and the vicinity thereof. The gradation data having a large threshold value is arranged in the peripheral portion of the matrix and in the vicinity thereof, and the dot is turned on when the input pixel data is equal to or more than the threshold data, and is turned off when the input pixel data is less than the threshold data. A gradation processing method characterized by performing processing. 2. The dither matrix is two-dimensionally repeated, and when printing with a duty of 50%, the plurality of thresholds are set in any of the vertical direction, the horizontal direction, and the line screen angle of 45 °. 2. The threshold data having a value less than or equal to ½ of the maximum value and the threshold data having a value greater than ½ of the maximum value are mixedly arranged in the data. Gradation processing method.