JPH0134423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a character image processing system in which contour specifying information of characters, images, etc. is stored as data, and furthermore, the stored data is decoded to output an approximate curve signal for character/image reproduction. Regarding the data processing method, in particular, it is possible to reproduce a character image with a smooth contour shape simply by storing coefficients obtained from the coordinate information of sample points set on the contour and the slope information between each sample point as stored data. This provides a method that does this.

It is well known that binary data obtained by decomposing characters, images, etc. (hereinafter referred to as characters) into dots has extremely high redundancy. Therefore, various data compression methods have been proposed to reduce this redundancy.

On the other hand, in general, the outline shape of a character is not only continuous, but also, when viewed excluding special points such as the intersections of character lines and the tips of "springs", It has the characteristic that the first derivative (the slope of the contour) changes continuously.

However, in the conventional data compression method using the contour method, although some improvement can be achieved at the expense of the data compression rate, theoretically and practically, character images reproduced based on the compressed data However, there are problems in that unnaturalness (discontinuity in inclination) occurs, and in any case, it is difficult to faithfully reproduce character contours.

These problems with the conventional method are described in detail in the specification of Patent Application No. 16884 filed in 1982 by the present applicant, but the present application proposes a method different from that of the earlier application. Therefore, the present invention is intended to further improve the data compression rate and shorten the processing time required to encode the compressed data, thereby overcoming the drawbacks of the conventional method.

Therefore, the first object of the present invention is to provide a character image data processing method using improved contour method data compression, and the second object is to provide a contour approximation curve that faithfully reproduces the smoothness of character contours. The third objective is to provide a data compression method that can obtain a signal, and the third purpose is to provide character image data that can obtain a sufficiently high data compression rate while faithfully reproducing the smoothness of character contours. The fourth object is to provide a character image data processing method that achieves the first to third purposes above while reducing the processing time required to create compressed data. It is something to do.

First, basic matters that enable the character image data processing method according to the present invention will be explained based on FIG.

FIG. 1 is an explanatory diagram in which an arbitrary contour curve 1 is developed on the X and Y coordinates.

In the figure, point P _i ( _{i =} 1 to
n) is a sample point arbitrarily set on the curve 1, and S _i is a segment corresponding to the interval (x _i ≦x≦x _i+1 ).

Also, m _i is the slope between sample points P _i and P _i+1 , that is, m _i =
(y _i+1 −y _i )/(x _i+1 − x _i ) is shown.

Now, suppose that the function f _i (x) is a piecewise cubic polynomial in the interval (x _i ≦x≦x _i+1 ), and the contour curve corresponding to the segment S _i is approximated by y=f _i (x). In this case, this piecewise cubic polynomial f _i (x) can be specified by giving four independent conditions.

Therefore, as the passage conditions and inclination conditions at both end points P _i and P _i+1 of segment S _i , the following 4.
Let us give two conditions. That is, y _i = f _i (x _i ) ...(1) y _i+1 = f _i (x _i+1 ) ...(2) f _i ′(x _i )=t _i ...(3) f _i ′ (x _i+1 )=t _i+1 ...(4) At this time, the value of t _i in equations (3) and (4) can be obtained by substituting the value of m _i above into equation (5) below. t _i =
｜m _i+1 −m _i ｜・m _i-1 ＋｜m _i-1 −m _i-2 ｜・m _i ／｜m _i+1 −m _i
|＋｜m _i-1 −m _i-2 | ...(5) However, when m _i+1 = m _i ≠m _i-1 = m _i-2 , t _i =(m _i-1
+m _i )/2.

Assume that

Incidentally, the piecewise cubic polynomial f _i (x) can generally be expressed as shown in equation (6) below.

f _i (x)=a _i +b _i (x−x _i ) +c _i (x− _i ) ² +d _i (x− _i ) ³ ……(6) Therefore, its first derivative f _i ′( x) becomes f _i ′(x)=b _i +2c _i (x−x _i )+3d _i (x−x _i ) ² ……(7).

Therefore, by substituting the conditional expressions (1) to (4) above into equations (6) and (7) to find the values of each coefficient a _i , b _i , c i , d _{i ,} a _i = y _i ……(8) b _i ＝t _i ……(9) c _i ＝3m _i −2t _i −t _i+1 ／x _i+1 −x _i ……(10) d _i ＝t _i ＋t _{i +1} −2m _i /(x _i+1 −x _i ) ² ...(11).

In this case, since the value of t _i can be calculated from the value of the slope m _i as is clear from equation (5), each value a _i , b _i , c _i on the left side of equations (8) to (11) , d _i can be determined relatively easily if the coordinate values (x _i , y _i ) of the sample point P _i and the value of the slope m _i are known.

Therefore, by substituting the values of each of the obtained coefficients into equation (6), the value of y=f _i (x) corresponding to x in the interval (x _i ≦x≦x _i+1 ) is found. I can do it.

Next, in Fig. 1, the adjacent segment S _i-1
For two piecewise curves y=f _i-1 (x) and y=f _i (x) corresponding to and S _i , the continuity of the slope at the sample point P _i will be examined.

That is, the slope of each piecewise curve at point P _i ,
f _i-1 ′(x _i ) and f _i ′(x _i ) are expressed by equations (9) to (11) in equation (7) above.
By substituting the formula, f _i-1 ′(x _i )=b _i-1 +2c _i-1 (x _i −x _i-1 ) +3d _i-1 (x _i −x _i-1 ) ² = t _i ...(12) and f _i ′(x _i )=b _i =t _i ...(13), and in the end, f _i-1 ′(x _i )=f _i ′(x _i )=t _i becomes.

That is, a _i , b _i , which are obtained from the above equations (8) to (11),
Any two adjacent piecewise curves y= specified by a piecewise cubic polynomial f _i (x) with coefficients c _i and d _i respectively
f _i-1 (x) and y=f _i (x) are curves with continuous slopes at the point P _i (x _i , y _i ). The continuity of such inclination matches the characteristics of the character image contour as described above.

The above are the basic matters that enable the character image data processing method of the present invention.

Next, an embodiment of the method of the present invention will be described based on the drawings.

FIG. 2 is an explanatory diagram schematically showing an arbitrary character outline 2 on the X and Y coordinates, and as in the case of FIG. 1,
P _i is the sample point set on contour 2, S _i is the sample point P _i ,
This is a segment between P _i+1 .

In the method of the present invention, first, sample points P _i (i=1 to n) are set as appropriate on the character contour 2, and the X, Y
Find the coordinate values (x _i , y _i ).

With this sampling point setting method, it is generally possible to set arbitrary points on the contour, but this method requires too much or too little data to reproduce a faithful character image or to generate a contour approximation curve signal. occurs. Therefore, in order to prevent the storage data per character from increasing unnecessarily while maintaining the reproducibility of the approximate curve signal to be output, that is, the reproducibility of the reproduced character image, for example, the present invention It is appropriate to adopt the sampling point setting method as described in Patent Application No. 16886 and No. 16887 filed by the applicant.

The method of the present invention first sets a sample point in this way, calculates its X and Y coordinate values (x _i , y _i ), and then
The slope between adjacent sample points P _i and P _i+1 is m _i = (y _i+1 −
Find y _i )/(x _i+1 − x _i ).

Then, based on the value of this slope information m _i ,
As shown in equations (9) to (11) above, b _i =t _i ...(9)' c _i =3m _i −2t _i −t _i+1 /x _i+1 −x _i ...(10 )′ d _i =t _i +t _i+1 −2m _i /(x _i+1 −x _i ) ² …(11)′ (However, t _i = |m _i+1 −m _i |・m _{i- 1} +｜m _i-1
−m _i-2 ｜・m _i ／｜m _i+1 −m _i ｜＋｜m _i-1 −m _i-2 ｜……(5)
′) Find the values of b _i , c _i , d _i and
The coordinate values (x _i , y _i ) of the sample points are stored in an appropriate storage medium as specific information of the character contour 2.

As already mentioned as a basic matter, the stored data obtained in this way is composed of a plurality of piecewise cubic curves that pass through each sample point P _i and whose slope changes continuously at the point P _i . The character outline 2 of any shape can be specified by such a set of piecewise cubic curves. Moreover, the creation of these memory data is
Based on equations (5)' and (9)' to (11)', it can be obtained in a relatively short time.

The first invention of the present application relates to the creation and storage of contour specifying information as described above.

Next, the second invention of the present application relates to a method of outputting an approximate curve signal of a character/image outline based on the stored data.

That is, in this case, first, the contour specifying information x _i , y _i , b _i , c _i , d _i stored in the storage medium is read out sequentially for i=1 to n, and then the section (x _i ≦x≦x _i+1 ), and then following equation (6), y=y _i +b _i (x-x _i ) +c _i (x-x _i ) ² + d _i (x-x _i ) Find the value of y that is ³ . By outputting the determined y value as an approximate curve signal of the character/image, a reproduced image faithful to the desired character/image can be obtained.

Note that the approximation curve signal obtained by the second method of the present application is used, for example, in the sample point setting method related to Patent Application No. 16886 of 1982, etc., for the ideal character image separately given. This signal can be used as a comparison signal for simulating the difference between the contour and the contour.

Another application is to supply this approximate curve signal as a character signal to scanning type character image generating means such as a CRT display tube, CRT phototypesetting machine, or laser printer, and use the supplied y value to determine the luminance of each scanning line. By using a modulated position signal, it becomes possible to display or print a desired character image.

As described above, the character image data processing method according to the present invention uses contour specifying information of characters, images, etc. as stored data, decodes the stored data, and outputs an approximate curve signal of the character/image contour. In the character image data processing method, the coordinate values (x _i , y _i ) of the sample point P _i (i=1 to n) set on the outline of the character/image and the adjacent sample points P _i , P _{i+ 1} slope m _i
After finding = (y _i+1 −y _i )/(x _i+1 −x _i ), b _i =t _i c _i =3m _i −2t _i −t _i+1 /x _i+1 −x _i d _i = t _i + t _i+1 −2m _i /(x _i+1 −x _i ) ² (however, t _i =｜m _i+1 −m _i ｜・m _i-1 +｜m _i-1
−m _i-2 ｜・m _i ／｜m _i+1 −m _i ｜＋｜m _i-1 −m _i-2 ｜)
Furthermore, the values of b _i , c _i , d _i and the coordinate values (x _i , y _i ) of the sample points are stored in an appropriate storage medium as outline identification information of characters, images, etc. Furthermore, the stored data is read out and, corresponding to x in the interval (x _i ≦x≦x _i+1 ), y=y _i +b _i (x−x _i ) +c _i The y value of (x-x _i ) ² + d _i (x-x _i ) ³ is determined, and this y value is output as an approximate curve signal of the character/image outline passing through the sample point P _i . It is characterized by things. By doing this, the present invention guarantees reproduction of character images with smooth contours, and
The memory data for contour identification required for this purpose can be created in a short time with relatively simple calculations.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the basic matters that enable the method of the present invention, and FIG. 2 is an explanatory diagram schematically showing an arbitrary character outline on the X and Y coordinates regarding an embodiment of the method of the present invention. 1...Arbitrary curve, 2...Arbitrary character outline, P _i
...sample point, S _i ...segment.

Claims (1)

[Scope of Claims] 1. In a character image data processing method in which contour specifying information of characters, images, etc. is stored data, sample points Pi(i
= 1 to n) coordinate values (x _i , y _i ) and the slope between adjacent sample points P _i , P _i+1 = (y _i+1 − _{y i )} /(x _i+1 − x _i )
After finding, b _i =t _i c _i =3m _i −2t _i −t _i+1 /x _i+1 −x _i d _i =t _i +t _i+1 −2m _i /(x _i+1 − x _i ) ² (however, t _i =｜m _i+1 −m _i |・m _i-1 +｜m _i-1
−m _i-2 ｜・m _i ／｜m _i+1 −m _i ｜＋｜m _i-1 −m _i-2 ｜)
Furthermore, the values of b _i , c _i , d _i and the coordinate values (x _i , y _i ) of the sample points are stored in an appropriate storage medium as outline identification information of characters, images, etc. A character image data processing method designed to 2. In a character image data processing method in which contour identification information of characters, images, etc. is stored as stored data, and the stored data is decoded to output an approximate curve signal of the character/image contour, a signal is set on the contour of the character/image. sample point Pi(i
= 1 to n) coordinate values (x _i , y _i ) and the slope between adjacent sample points P _i , P _i+1 = (y _i+1 − _{y i )} /(x _i+1 − x _i )
After finding, b _i =t _i c _i =3m _i −2t _i −t _i+1 /x _i+1 −x _i d _i =t _i +t _i+1 −2m _i /(x _i+1 − x _i ) ² (however, t _i =｜m _i+1 −m _i |・m _i-1 +｜m _i-1
−m _i-2 ｜・m _i ／｜m _i+1 −m _i ｜＋｜m _i-1 −m _i-2 ｜)
Furthermore, the values of b _i , c _i , d _i and the coordinate values (x _i , y _i ) of the sample points are stored in an appropriate storage medium as outline identification information of characters, images, etc. Then, the stored data is read out and the interval (x _i ≦
Corresponding to x where x≦x _i+1 ), find the value of y where y=y _i +b _i (x-x _i ) +c _i (x-x _i ) ² +d _i (x-x _i ) ³ . , A character image data processing method that outputs this y value as an approximate curve signal of a character/image outline passing through the sample point P _i .