JPS6375881A - Dot picture screen line-number converter - Google Patents

Abstract

PURPOSE:To obtain a converted picture without generating disturbance in a gradation or screen line number by substituting a dot picture with representative values, executing the data conversion based on a conversion ratio, then generating the dot picture again. CONSTITUTION:A representative calculating means 1 divides the target picture of screen line number conversion input square areas whose one side is a signal dot, and calculates the number of black dots in each square area as its representative value. A representative value conversion means 2 enlarges/reduces the representative value groups calculated by the representative calculating means 1 by using an area function determined by the degree of overlapping of the square area before and after the conversion, thereafter the means 2 converts the representative values by using area ratios to generate the representative value groups after the screen line number conversion. A dot picture forming means 3 forms a dot picture after the screen line number conversion from the representative value groups after screen line number conversion generated by the representative value conversion means 2.

Description

[Detailed Description of the Invention] [Summary] In order to convert the screen line number of a halftone dot image represented by black and white pixels, the halftone dot image is divided into small areas, and the number of black pixels in the small area is calculated based on the number of black pixels in the small area. After converting the representative value according to the conversion ratio, the target halftone image is created, and conversion without disturbing the gradation and the number of screen lines is possible.

[Industrial Field of Application] The present invention relates to an apparatus for converting pseudo gradation data of a halftone image.

2. Description of the Related Art A method called a halftone image is used to output a grayscale image such as a photograph using an output device capable of only binary recording, such as a printing device.

The halftone image is created by using a halftone dot pattern table as shown in FIG. This is to obtain pseudo gradation as a pixel. For example, if the gradation is "20", the portion of the table with a numerical value of 20 or less is set as a black pixel.

Pseudo gradation (dot formation) of grayscale images is performed at the time of image input to match the line density of the output device, but when outputting to an output device with a different line density, the roughness of the pseudo gradation and cropping may occur. There is a problem that this occurs, and a solution to this problem is desired.

[Prior Art] Conventionally, in order to output halftone image data to output devices with different linear densities, the halftone image data has been subjected to a combination of simple thinning, logical thinning, and simple enlargement. I am trying to create the desired halftone image data.

Simple thinning is simply thinning out one line out of several lines, and logical thinning is upper thinning in which a logical sum is calculated to prevent the omission of important pixels.

For example, 2/3 expansion was performed by combining thinning and simple expansion.

[Problems to be Solved by the Invention] Conventional image data conversion processing is performed by a combination of simple thinning, logical thinning, and simple enlargement, resulting in disturbances in gradation and screen line number. There is also a problem in that coordinate values exceed a predetermined range and trimming occurs.

The present invention aims to provide a novel halftone image screen line number conversion device that solves the above-mentioned conventional problems.

[Means for Solving the Problems] FIG. 1 shows a block diagram of the principle of the halftone image screen line number conversion device of the present invention.

In the figure, 1 is a representative value calculation means, which divides the image to be converted into screen line number into square areas with the dot period as one side, and calculates the number of black pixels in each square area as the representative value of the area. do.

Reference numeral 2 denotes a representative value converting means, which enlarges or reduces the representative value group calculated by the representative value calculating means 1 by an area function determined by the overlap of the square v4 area before and after conversion, and then converts the representative value by an area ratio. Create a group of representative values after screen frequency conversion.

For example, 70% of the area of one square area after conversion is included in square area A before conversion, 30% is included in square area B, the representative value of area A is 10, and area B If the representative value of the square area is 12, then the representative value of the square area is 1
Expand or contract as 0x0.7 +12x0.3 = 10.6, and the area ratio of the square area before and after conversion is 100.
: If it is 64, 10.6 X (64/100)
=6.8#7.

This conversion is performed to match the ratio of the number of expression gradations before and after conversion.

Reference numeral 3 denotes a halftone dot image generation means, which creates a halftone dot image after screen line number conversion from the representative value group after screen line number conversion created by the representative value converting means 2.

[Operation] The configuration of the present invention replaces the halftone dot image with a representative value, performs data conversion based on the conversion ratio, and then generates the halftone image again, so that conversion without disturbing the gradation and screen line number is possible. You can get the image.

[Example] The present invention will be described in more detail below with reference to Examples shown in FIGS. 2 to 8.

FIG. 2 is a circuit configuration block diagram of an embodiment of the present invention.

In FIG. 2, a black pixel counter 11 counts the number of black pixels from input halftone image scanning data and writes the count value into the memory 14.

By the pixel counter 2 and line counter 13,
The black pixel counter 11 calculates a small area with one side having a halftone dot period.
control the count range. The memory 14 stores the number of black pixels in each small area as a representative value.

FIG. 3 is a diagram showing an example of a halftone dot image to be converted according to this embodiment, and is a halftone dot image with a screen line count called 45 degrees/64 lines (64 lines per inch in the 45 degree direction). It is. As shown in the figure, the halftone dot period is 10 pixels.

FIG. 4 shows a group of representative values for each microcephalic region obtained in the memory 14, that is, a representative surface image.

Returning to FIG. 2 again, reference numeral 21 is an enlargement/reduction calculation table, which is used to perform calculations for converting and enlarging representative values in accordance with the overlap of small areas caused by screen number conversion, and 22a, 22b, 22c. , 22d is a multiplier that multiplies the area of each mold by its representative value, and 23
is an adder that adds the multiplication results of these multipliers, and the expanded representative value group calculated thereby is stored in the memory 24.

25 is a representative value conversion table, which is a table for converting the representative value stored in the memory 24 according to an area ratio, and 26 is a multiplier that performs the calculation.

The obtained representative surface image after conversion is stored in the memory 27.

Figure 5 shows the 45 degree/64 line halftone image shown in Figure 3,
FIG. 7 is a diagram showing the overlap of small areas of a 45 degree/80 line halftone image (with a UII point period of 8 pixels) to be converted.

FIG. 6 is a diagram showing representative plane image conversion from 45 degrees/64 lines to 45 degrees/80 lines.

The area is calculated and enlarged according to the overlap of the small areas, and then the representative value is converted according to the area ratio, that is, 64/100.

Returning to FIG. 2 again, 31 is a halftone pattern generator;
From the converted representative surface image stored in the memory 27, a 45 degree/80 line halftone dot image is created by arranging white pixels and black pixels using a 45 degree/80 line halftone dot table.

The created halftone dot pattern is stored in the memory 32.

FIG. 7 shows a 45 degree/80 line representative surface image converted according to this embodiment.

FIG. 8 shows a 45 degree/80 line halftone image converted according to this embodiment.

As can be seen from FIG. 8, a high-quality halftone image without any disturbance in gradation or screen line number can be obtained.

[Effects of the Invention] As described above, according to the present invention, halftone image screen line number conversion can be performed without disturbance of gradation and screen line number, and its practical effects are extremely large.

[Brief explanation of the drawing]

Fig. 1 is a principle block diagram of the present invention, Fig. 2 is a circuit configuration block diagram of an embodiment of the present invention, Fig. 3 is a diagram showing a halftone image before conversion according to the present invention, and Fig. 4 is a diagram of the present invention. FIG. 5 is a diagram showing the overlap of small areas before and after conversion according to the present invention. FIG. 6 is a diagram showing the representative surface image conversion procedure according to the present invention. FIG. 7 8 is a diagram showing a representative surface image after conversion according to the present invention, FIG. 8 is a diagram showing a halftone dot image after conversion according to the present invention, and FIG. 9 is a diagram illustrating a halftone dot pattern table. In the drawing, l is a representative value calculation means, 2 is a representative value conversion means, 3 is a halftone image reproduction means, 11 is a black pixel counter, 12 is a pixel counter, 13 is a line counter, 14
, 24, 27, and 32 are memories, 21 is an expansion/reduction operation table, 22a to 22d are multipliers, 23 is an adder, 25
26 represents a representative value conversion table, 26 represents a multiplier, and 31 represents a halftone dot pattern generator. 10 (fsa)] Moon Ji Shishi Phosphorus Leopard I~shi 5zu L Stone Oath Wise,
Ya T”El Kororo C Kororo 0 Ama Kororo mouth

[Koroguchi C Koroguchi [ ] 00 [ Koroguchi [ Koro O [ Koroguchi C Su γK, published by To Nakato l2, 2nd term H month 8) Madai, ゐ Elephant ≦, Hosu 4 U = F ] 1 Thousand-colored bar 2-shitabu> The bud of the butt row

Claims (1)

[Scope of Claims] Representative value calculation means (1) that divides an image to be converted into screen line number into square regions each side having a halftone dot period, and calculates the number of black pixels in each square region as a representative value of the region; , a representative value converting means (2) that expands or reduces the representative value group calculated by the representative value calculating means (1) using an area function, and then converts it using an area ratio; and a representative value converted by the representative value converting means (2). A halftone image screen line comprising a halftone image generating means (3) for creating a halftone image after converting the screen line number from a value group, and configured to convert the screen line number of the halftone image. Number converter.