JPH04346391A - Vector font plotting device - Google Patents

Abstract

PURPOSE:To provide a vector font plotting device capable of calculating increment to variable (t) of a tertiary Bezier curve at high speed by means of a hardware. CONSTITUTION:A vector font plotting device is provided with the first, the second, the third and the fourth selecting means 1, 2, 7 and 13, an adding/ subtracting means 3, an absolute value converting means 4, the first, the second and the third holding means 5, 6, and 8, a left shift operation means 9, a comparison means 10, a knurling value holding means 11 and a right shift operation means 12, and increment to variable (t) of a tertiary Bezier curve is calculated at high speed by means of a hardware without using a multiplying/dividing means, so that contour of a character can be plotted at high speed.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a vector font drawing device that draws the outline of a character (vector font) defined by a plurality of vectors, and in particular to a vector font drawing device that quickly calculates and draws the outline of a curved line. It is related to the device.

0002

2. Description of the Related Art A character pattern generation method is known in which a high-quality character pattern is generated by drawing the outline of a character (vector font) defined by a plurality of vectors and filling the inside thereof. The outline of a character is mainly composed of straight lines and curved lines, and when drawing a curved outline, a cubic Bezier curve is usually employed.

A cubic Bezier curve is defined by four points: a starting point A, an ending point B, and control points C and D. The curve is the following 3
It can be drawn by calculating the following equation. x(t)=axt3 +bxt2 +cxt+x0y(
t)=ayt3 +byt2 +cyt+y0(0≦t
≦1) By displacing the variable t from 0 to 1, the coordinates of the curve from the starting point A to the ending point B can be calculated. A beautiful curve can be drawn by optimizing the increment of the variable t, but if the increment of the variable t is large, the curve will deviate from the actual curve.

The geometrical properties of the cubic Bezier curve are that the points that internally divide the line segments AC, CD, and DB into m:n are E, F, and G.
, let H and I be the points that internally divide the line segments EF and FG into m:n, and let J be the point that internally divide the line segment HI into m:n, then the cubic Bezi
The er curve touches line segment HI at point J. (See FIG. 2) In this type of method, the optimum increment (δ) of the variable t is determined by software using the following calculation method.

[0005]t=kδ(k=1,2,3...,n-1
) is the interpolation point of the approximate break point. (See FIG. 3) Furthermore, P, M, a, b, and c described below are vectors. Pk-1 = P ((k-1) δ) = (k-1)3 δ3
a+(k-1)2 δ2 b+(k-1)δcPk
=P(kδ)=k3 δ3 a+k2 δ2 b+kδ
Let M be the midpoint between both points c (see Figure 4), then M = (2k
3 -3k2 +3k-1) δ3 a/2+(2k2
-2k+1)δ2 b/2+(2k-1)δc/2 Also, if the point at t=(tk-1 +tk)/2 is P', then P'=((2kδ-δ)/2)=( 8k3 -12k2
+6k-1) δ3 a/23+(4k2 -4k+1
) δ2 b/22 + (2k-1) δc/2 Now, if we substitute D=MP' for the approximation error d (see Figure 5), Dk = | 3 (2k-1)/23 × δ3 a+1/2
2 × δ2 b|=(9|a|2 /26 ×(2k−
1) 2 δ6 + 6ab/25 × (2k-1) δ5 +
|b|2/24×δ4)1/2 D takes the maximum value at k=1 or k=1/δ.

[0006]D0=|b|/22×δ2...
・(1) D1/δ = |3(2/δ-1)/23 ×δ
3 a+b/22 ×δ2 |=|3a+b|/22
×δ2 −|3a|/23 ×δ3 ...(2) To find the optimal increment of variable t, set the left side of equation (2) to 0.
Therefore, it was necessary to calculate δ.

[0007] Conventionally, the above calculations were performed using software.

[0008]

As described above, conventionally, the increment δ of t of a cubic Bezier curve has been calculated by software. However, today there is a growing need to draw character outlines at high speed, and it has become necessary to calculate the increment of the variable t using hardware to speed up the calculation.However, the above calculation involves multiplication and division. It was difficult to realize this with hardware.

The present invention solves the above problem by calculating the length from the starting point to the control point, the length from the control point to the control point, and the length from the control point to the end point.
It is an object of the present invention to provide a vector font drawing device that can quickly calculate the increment of a variable t without using a multiplier or the like and draw a curved outline at high speed.

0010

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a first and a second method that receives x, y coordinates input from the outside and internal data, and selects the two data.
a selection means, an addition/subtraction means for adding and subtracting the data output from the two selection means, an absolute value conversion means for taking the absolute value of the value output from the addition/subtraction means, and a first and second holding means that hold a value and output the held data to the first and second selection means; and a third holding means that receives 0, 1 and internal data and selects the three data. a selection means, a third holding means for holding data output from the third selection means, and a third holding means for holding data output from the third selection means;
a left shift calculation means for shifting the data output from the holding means to the left by one position and outputting the calculation result to the third selection means; a comparison means for comparing the magnitude of the values; a step value holding means for inputting the comparison result output from the comparison means and holding the data output from the third holding means; The present invention includes right shift calculation means for shifting, and selection means for selecting data output from the right shift calculation means and 0.

[0011]

[Operation] With the above configuration, the increment of the variable t can be calculated at high speed simply by using the comparison means and the shift calculation means.
Further, the length from the starting point to the control point, the length from the control point to the control point, and the length from the control point to the end point can be easily calculated using hardware.

0012

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. FIG. 1 is a block diagram of a vector font drawing device showing one embodiment of the present invention.

As shown in FIG. 1, the vector font drawing device receives x, y coordinates 21 input from the outside and one piece of internal data 27, selects the two data, and outputs a selection result 23. a first selection means 1; a second selection means 2 which receives an externally input x, y coordinate 22 and one internal data 28, selects the two data and outputs a selection result 24; Addition and subtraction means 3 receives the selection results 23 and 24 outputted from the first and second selection means 1 and 2, performs addition and subtraction on the two data, and outputs the results; and a value 25 outputted from this addition and subtraction means 3. an absolute value conversion means 4 that takes the absolute value of , first and second holding means 5 and 6 that hold the absolute value 26 output from the absolute value conversion means 4, and inputs 0, 1, and internal data 31. year,
a third selection means 7 for selecting the three data and outputting the selection result 29; a third holding means 8 for holding the data 29 output from the third selection means 7 as input; As an input, the value 30 output from the holding means 8 of
The left shift calculation means 9 shifts the input data 30 to the left by one bit and outputs the result, and the data 28 outputted from the second holding means 6 and the data 30 outputted from the third holding means 8 are compared. , a comparing means 10 that outputs a step value detection signal 32 when the value of the second holding means 6≦the value of the third holding means 8; Step value holding means 1 that holds when is output
1, a right shift calculation means 12 which performs a right shift using the step value 32 outputted from the step value holding means 11 and outputs a shift result 34, and a shift result 34 outputted from this right shift calculation means 12 and 0. As input, selection result 3
A fourth selection means 13 that outputs 5 and a selection result 35 output from this fourth selection means 13 are input, and based on this selection result 35, x and y coordinates are calculated and a curve is drawn. It is composed of a cubic Bezier curve calculation means 14.

In the above configuration, the first selection means 1 selects the x, y coordinates 21 of the starting point A (see FIG. 2 below) inputted from the outside, and outputs it to one input of the addition/subtraction means 3. Further, the second selection means 2 selects the x, y coordinates 22 of the first control point C input from the outside, and outputs it to the other input of the addition/subtraction means 2. The addition/subtraction means 3 outputs the difference between the two data to the absolute value conversion means 4. Length (d1) from the starting point A to the first control point C output from the absolute value conversion means 4
is held by the first holding means 5. Next, the first selection means 1 selects the x, y coordinates 21 of the first control point C input from the outside, and outputs it to the addition/subtraction means 3. Further, the second selection means 2 selects the x, y coordinates 22 of the second control point D inputted from the outside, and outputs it to the addition/subtraction means 3. The addition/subtraction means 3 outputs the difference between the two data to the absolute value conversion means 4. The length (d2) from the first control point C to the second control point D output from the absolute value conversion means 4 is determined by the second holding means 6.
is maintained. Furthermore, the first selection means 1 and the second selection means 2 are connected to the first holding means 5 and the second holding means 6, respectively.
selects d1 and d2 outputted from , calculates d1+d2, and stores it in the first holding means 5 through the absolute value conversion means 4.

x of the second control point D input from the outside,
The first selection means 1 selects the y-coordinate 21, and the addition/subtraction means 3
Output to. Also, x, y of the end point B input from the outside
The second selection means 2 selects the coordinate 22 and outputs it to the other input of the subtraction means 2. The addition/subtraction means 3 outputs the difference between the two data to the absolute value conversion means 4. The length from the end point B output from the absolute value conversion means 4 to the second control point D (d3
) is held by the second holding means 6. Finally, the first selection means 1 and the second selection means 2 output d1+d2 and d from the first holding means 5 and the second holding means 6, respectively.
3 is selected, d1+d2+d3 is calculated, and the result is stored in the second holding means 6 through the absolute value conversion means 4.

The third selection means 7 first selects 0, and the third holding means 8 holds the value of 0. Comparison means 10 is
The value of d1+d2+d3 held by the second holding means 6 and the value held by the third holding means 8 are compared, and d1
When the value of +d2+d3≦the value of the third holding means 8, the step value detection signal 32 is output. If not output, the third
The selection means 7 then selects 1, and the third holding means 8 selects 1.
Holds the value of . The comparison means 10 compares the value of d1+d2+d3 held by the second holding means 6 and the third holding means 8.
Compare the values held by and find the value of d1+d2+d3≦
When the third holding means 8 holds the value, the step value detection signal 32 is output. If not output, the third selection means 7 shifts the value of the third holding means 8 to the left by shifting it to the left and calculating means 9.
Select the value 31 shifted left by 1 bit with
The holding means 8 holds. The comparison means 10 compares the value of d1+d2+d3 held by the second holding means 6 with the value held by the third holding means 8, and calculates d1+d2+d3.
When the value of ≦the value of the third holding means 8, the step value detection signal 32
Output. From this point on, the third selection means 8 selects the value 31 output from the left shift calculation means 10, and the comparison means 1
0 is d1+d2+d held by the second holding means 6
3 and the value held by the third holding means 9, and when the value of d1+d2+d3≦the value of the third holding means 8,
A step value detection signal 32 is output. When the step value detection signal 32 is output, the step value holding means 11 takes in the value 30 held by the third holding means 9.

Value 33 held by step value holding means 11
When is 0, the fourth selection means 13 selects 0 and outputs it as the fourth selection result 35 to the cubic Bezier curve calculation means 14. Further, when the value 33 held by the step value holding means 11 is other than 0, the fourth selection means 13 selects the shift result 34 output from the right shift calculation means 13, and selects the shift result 34 outputted from the right shift calculation means 13.
As the selection result 35, cubic Bezier curve calculation means 1
Output to 4. Using the selection result 35 which is the increment of the variable t, the cubic Bezier curve calculating means 14 calculates the x, y of the curve.
Perform coordinate calculations. In this way, the increment of the variable t can be calculated at high speed, and the length from the starting point A to the control point C, the length from the control point C to the control point D, and the length from the control point D to the end point B can be calculated at high speed. The length can be easily calculated using hardware.

[0018]

As described above, according to the present invention, x and y coordinates input from the outside and internal data are input, and the above two
first and second selection means for selecting one data;
an addition/subtraction means for adding and subtracting data output from the two selection means; an absolute value conversion means for taking the absolute value of the value output from the addition/subtraction means; 1. first and second holding means for outputting held data to the second selection means; third selection means for inputting 0, 1 and internal data and selecting the three data; A third holding means holds the data output from the selection means, and the data output from the third holding means is shifted to the left by one position, and the calculation result is transferred to the third holding means.
a left shift calculation means for outputting to the selection means; a comparison means for comparing the magnitudes of the values output from the second holding means and the third holding means; and inputting the comparison result output from the comparison means. and a step value holding means for holding the data output from the third holding means, a right shift calculation means for shifting the data to the right by the value of the step value, and selecting 0 as the data output from the right shift calculation means. and a selection means for
Cubic Be can be easily calculated by using comparison means and shift calculation means.
The increment of the variable t of the Zier curve can be calculated at high speed by hardware, and the outline of a character can be drawn at high speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a vector font drawing device according to an embodiment of the present invention.

FIG. 2 is a diagram regarding the geometric properties of a cubic Bezier curve.

FIG. 3 is a diagram regarding the incremental calculation of the variable t of a cubic Bezier curve.

FIG. 4 is a diagram regarding the incremental calculation of the variable t of a cubic Bezier curve.

FIG. 5 is a diagram regarding approximation errors of cubic Bezier curves.

[Explanation of symbols]

1 First selection means 2 Second selection means 3 Addition and subtraction means 4 Absolute value conversion means 5 First holding means 6 Second holding means 7 Third selection means 8 Third holding means 9 Left shift calculation means 10 Comparison means 11 Step value holding means 12 Right shift calculation means 13 Fourth selection means

Claims (1)

[Claims] Claims: 1. A vector font drawing device for drawing the outline of a character defined by a plurality of vectors; , a second selection means, an addition/subtraction means for adding and subtracting the data output from the two selection means, an absolute value conversion means for taking the absolute value of the value output from the addition/subtraction means, and the absolute value conversion means. first and second holding means that hold the values output from and output the held data to the first and second selection means;
and a shift result as input and selects the three data; a third holding means that holds the data output from the third selection means; a left shift calculation means for shifting the output data to the left by one and outputting the calculation result to the third selection means; and the size of the values output from the second holding means and the third holding means. step value holding means for holding the data output from the third holding means according to the comparison result output from the comparing means; and right shift calculation means for shifting the data to the right by the step value. and a selection means for selecting data output from the right shift calculation means and 0.