JPS6175478A - Image processing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a dot-based halftone rendering method that allows gradual concealment.

[Prior art]

Methods of expressing intermediate tones using graduated densities include a method in which each pixel corresponds to the dot number 91 that is closest to the input clearness data, and a method in which each pixel is represented by one dot, and a method in which each pixel is represented by a 2X2.5X5 dot.
．． A method such as arranging dots with different levels of serenity in a matrix such as 4X4, preparing patterns in advance that can take a sufficient number of density values for the entire J-Trix, and selecting and expressing patterns according to the AA data. There is.

The former method is very simple, but has the disadvantage that smooth expression cannot be achieved if the output dots do not have a sufficient N function.

In the latter method, if the matrix is small, the halftones obtained will be insufficient, and if the matrix is made large, the output image will inevitably be large, and the lack of resolution will become noticeable. In addition, in this method, a so-called pseudo-contour, where discontinuous halftone boundaries are connected, appears, resulting in poor quality.

〔the purpose〕

The present invention was made to eliminate these drawbacks, and aims to express smooth intermediate tones using dots having only a limited number of density values.

〔Features〕

In order to achieve this purpose, the present invention expresses one pixel with one dot, and as a method of determining its density value, the density data of the pixel of interest and the error data of a plurality of surrounding pixels are combined. It is characterized by classifying and determining the sum with a weighted average, and calculating error data at that pixel from the value of the sum and the determined one-time value.

[Meikyu example]

The present invention will be explained in detail below. First, consider a weight matrix for a plurality of pixels surrounding the pixel of interest. This can be considered in various ways, as shown in Figures 1 (α), (A), and (c). Letting this be W, the weighted average A m,s of the error data is determined.

Here, t is a subscript indicating the row and column of the weight matrix, and Ek,l is error data in the range of the weight matrix. This error data is obtained by the method described later.

Further, if the data of the pixel of interest is set to 0, 0 (0 ≦ 1, outside 1), the density value determination data Pm of this pixel,
n to P lip 1% = A m, outside + engineering door, outside...-(
2). The density value of a dot representing that pixel is determined by the values of Pm and s. In other words, the output dot varies from 0 to t
If it is possible to express i+1 gradations up to a density of , then 26 +1 (P s * s≦/+.

,,"'+1 <'%, 0 depending on which of t+1 of 11 holds true.
．． The density value is determined as follows: 1...-. The errors E% and S are determined by the formula E m , % = P 1% - m ( ] is the density value determined by the above method).

For example, when expressing four levels of concentration using dots, 0≦1'rI&+ n≦12 αz (p 1%≦[L4 α4 (P m , %≦16 11L6pm, %≦[L8 −8 The pixels are divided into five different densities, %≦1, and densities from 0 to 4 are determined, and the pixels output dots with the determined densities.

The above procedure is repeated for all pixels. Furthermore, in the case of a color image, the same procedure may be performed independently for the number of colors to be used, and the images may be combined at the time of output.

〔effect〕

As described above, according to the present invention, since one pixel is expressed as one dot, a smooth image can be obtained without reducing the resolution. Also for processing color images.

Since each color can be processed independently, the same hardware can handle multiple colors, or hardware can be prepared in parallel and processed simultaneously, giving a high degree of freedom.

[Brief explanation of the drawing]

The first [1ii1(α)(A)(C) is an example of the weight matrix in the present invention. that's all

Claims (1)

[Claims] In an image processing method that converts an image consisting of a set of density data of multiple pixels into data expressed by dots that can take on graded densities, the overlap between the density data of the pixel of interest and the error data of multiple surrounding pixels is used. It consists of a procedure of determining the density value of a dot representing the pixel from the sum with the average value of the detection, and a procedure of calculating error data of the pixel from the sum value and the determined density value of the dot. Image processing method.