PDF 生成中的绘图和圆弧

Question

基本上我需要使函数 drawArc 来创建 PDF 文件。

drawArc(int x, int y, int width, int height, int startAngle, int arcAngle)

我在PDF specification but does not talk about a command to draw an Arc (like in PostScript)中搜索过...所以我想我需要以某种方式用曲线模拟Arc，但它似乎太难了。

任何帮助将不胜感激，谢谢！

编辑。我找到了解决 drawEllipse here 问题的答案，但我需要实现方法 drawArc（而不是 drawEllipse）。

Answer 1

所以，最后我编写了一个分为两个函数的解决方案：

pdfDrawArc

private void pdfDrawArc(int x, int y, int width, int height, int startAngle, int arcAngle) {
    System.out.println("Arc");
    width -= 1;
    height -= 1;
    int n = (int)(Math.ceil(Math.abs(arcAngle / maxAnglePerCurve())));
    int i;
    double currentStartAngle = startAngle;
    double actualArcAngle = ((double)arcAngle) / n;
    for (i = 0; i < n; i++) {
        double[] bezier = bezierCurve(this.x + x, this.y + y, width, height, currentStartAngle, actualArcAngle);
        if (i == 0)
            this.pdfMoveTo(bezier[0], bezier[1]);
        this.pdfCurveTo(bezier [2], bezier [3], bezier [4], bezier [5], bezier [6], bezier [7]);
        this.pdfStroke();
        currentStartAngle += actualArcAngle;
    }
}

贝泽曲线 基于 L. Maisonobe solution.

private double[] bezierCurve(double x, double y, double width, double height, double startAngle, double arcAngle) {
    double pi = 3.141592;

    double a = width / 2;
    double b = height / 2;

    //center
    double cx = x + a;
    double cy = y + b;

    //calculate trigonometric operations so we don't need to repeat the calculus
    double cos1 = Math.cos(startAngle * pi / 180);
    double sin1 = Math.sin(startAngle * pi / 180);
    double cos2 = Math.cos((startAngle + arcAngle) * pi / 180);
    double sin2 = Math.sin((startAngle + arcAngle) * pi / 180);

    //point p1. Start point
    double p1x = cx + a * cos1;
    double p1y = cy - b * sin1;

    //point d1. First derivative at start point.
    double d1x = -a * sin1;
    double d1y = -b * cos1;

    //point p2. End point
    double p2x = cx + a * cos2;
    double p2y = cy - b * sin2;

    //point d2. First derivative at end point
    double d2x = -a * sin2;
    double d2y = -b * cos2;

    //alpha constant
    double aux = Math.tan((arcAngle / 2) * pi / 180);
    double alpha = Math.sin(arcAngle * pi / 180) * (Math.sqrt(4 + 3 * aux * aux) - 1.0) / 3.0;

    //point q1. First control point
    double q1x = p1x + alpha * d1x;
    double q1y = p1y + alpha * d1y;

    //point q2. Second control point.
    double q2x = p2x - alpha * d2x;
    double q2y = p2y - alpha * d2y;
    return new double[] { p1x, p1y, q1x, q1y, q2x, q2y, p2x, p2y };
}

PDF 生成中的绘图和圆弧

Draw and Arc in PDF generation

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