Java Path2D.curveTo方法代码示例

import java.awt.geom.Path2D; //导入方法依赖的package包/类
private Shape renderCurvePath(int[] xPoints, int[] yPoints) {
    Path2D path = new Path2D.Double();
    path.moveTo(xPoints[0], yPoints[0]);

    int curveIndex;
    for (curveIndex = 0; curveIndex <= xPoints.length - 3; curveIndex += 3) {
        path.curveTo(xPoints[curveIndex], yPoints[curveIndex], xPoints[curveIndex + 1], yPoints[curveIndex + 1], xPoints[curveIndex + 2], yPoints[curveIndex + 2]);
    }

    if (xPoints.length >= 3 && xPoints.length - curveIndex == 2) {
        path.curveTo(xPoints[xPoints.length - 3], yPoints[xPoints.length - 3], xPoints[xPoints.length - 2], yPoints[xPoints.length - 2], xPoints[xPoints.length - 1], yPoints[xPoints.length - 1]);
    } else {
        path.lineTo(xPoints[xPoints.length - 1], yPoints[xPoints.length - 1]);
    }

    return path;
}
 

import java.awt.geom.Path2D; //导入方法依赖的package包/类
/**
 * Converts an arc to cubic Bezier segments and records them in p.
 *
 * @param p The target for the cubic Bezier segments
 * @param cx The x coordinate center of the ellipse
 * @param cy The y coordinate center of the ellipse
 * @param a The radius of the ellipse in the horizontal direction
 * @param b The radius of the ellipse in the vertical direction
 * @param e1x E(eta1) x coordinate of the starting point of the arc
 * @param e1y E(eta2) y coordinate of the starting point of the arc
 * @param theta The angle that the ellipse bounding rectangle makes with the horizontal plane
 * @param start The start angle of the arc on the ellipse
 * @param sweep The angle (positive or negative) of the sweep of the arc on the ellipse
 */
private static void arcToBezier(Path2D p, double cx, double cy, double a,
        double b, double e1x, double e1y, double theta, double start,
        double sweep) {
    // Taken from equations at:
    // http://spaceroots.org/documents/ellipse/node8.html
    // and http://www.spaceroots.org/documents/ellipse/node22.html

    // Maximum of 45 degrees per cubic Bezier segment
    int numSegments = Math.abs((int) Math.ceil(sweep * 4 / Math.PI));

    double eta1 = start;
    double cosTheta = Math.cos(theta);
    double sinTheta = Math.sin(theta);
    double cosEta1 = Math.cos(eta1);
    double sinEta1 = Math.sin(eta1);
    double ep1x = (-a * cosTheta * sinEta1) - (b * sinTheta * cosEta1);
    double ep1y = (-a * sinTheta * sinEta1) + (b * cosTheta * cosEta1);

    double anglePerSegment = sweep / numSegments;
    for (int i = 0; i < numSegments; i++) {
        double eta2 = eta1 + anglePerSegment;
        double sinEta2 = Math.sin(eta2);
        double cosEta2 = Math.cos(eta2);
        double e2x = cx + (a * cosTheta * cosEta2)
                - (b * sinTheta * sinEta2);
        double e2y = cy + (a * sinTheta * cosEta2)
                + (b * cosTheta * sinEta2);
        double ep2x = -a * cosTheta * sinEta2 - b * sinTheta * cosEta2;
        double ep2y = -a * sinTheta * sinEta2 + b * cosTheta * cosEta2;
        double tanDiff2 = Math.tan((eta2 - eta1) / 2);
        double alpha = Math.sin(eta2 - eta1)
                * (Math.sqrt(4 + (3 * tanDiff2 * tanDiff2)) - 1) / 3;
        double q1x = e1x + alpha * ep1x;
        double q1y = e1y + alpha * ep1y;
        double q2x = e2x - alpha * ep2x;
        double q2y = e2y - alpha * ep2y;

        p.curveTo((float) q1x, (float) q1y, (float) q2x, (float) q2y,
                (float) e2x, (float) e2y);
        eta1 = eta2;
        e1x = e2x;
        e1y = e2y;
        ep1x = ep2x;
        ep1y = ep2y;
    }
}
 

import java.awt.geom.Path2D; //导入方法依赖的package包/类
static Path2D addCubics(Path2D p2d) {
    for (int i = 0; i < 10; i++) {
        p2d.curveTo(1.1 * i, 1.2 * i, 1.3 * i, 1.4 * i, 1.5 * i, 1.6 * i);
    }
    return p2d;
}
 

import java.awt.geom.Path2D; //导入方法依赖的package包/类
static void addCubic(Path2D p2d, int i) {
    p2d.curveTo(1.1 * i, 1.2 * i, 1.3 * i, 1.4 * i, 1.5 * i, 1.6 * i);
}