如何在Slick2D中检测到单击旋转的图像

Question

我有一个在绘制之前旋转的图像。图像由六角形的角度旋转。换句话说，图像基本上"突出显示"六角形的单个边缘。我需要检测到该旋转图像的内部是否单击鼠标。检测鼠标在无调图像的内部单击非常简单，但是我不知道如何在旋转点内检测单击。旋转后有没有办法获取图像角的点，以便我可以在图像顶部放置一个无形的多边形并使用polygon.contains（）？

                    Image highlightEdge = new Image("assets/img/highlightEdge.png");
                    if(angle == 90){
                        highlightEdge.setCenterOfRotation(highlightEdge.getWidth(), 0);
                        highlightEdge.rotate(new Float(angle));
                        highlightEdge.draw(testPoint.x - 56, testPoint.y);
                    } else if(angle == 210) {
                        highlightEdge.setCenterOfRotation(0, 0);
                        highlightEdge.rotate(new Float(angle));
                        highlightEdge.draw(lastSettlement.x - 72, lastSettlement.y - 32);
                    } else if( angle == 330){
                        highlightEdge.setCenterOfRotation(0, 0);
                        highlightEdge.rotate(new Float(angle));
                        highlightEdge.draw(lastSettlement.x - 8, lastSettlement.y - 32);
                    } else if(angle == 30){
                        highlightEdge.setCenterOfRotation(0, 0);
                        highlightEdge.rotate(new Float(angle));
                        highlightEdge.draw(lastSettlement.x-8, lastSettlement.y);
                    } else if(angle == 150){
                        highlightEdge.setCenterOfRotation(0, 0);
                        highlightEdge.rotate(new Float(angle));
                        highlightEdge.draw(lastSettlement.x-72, lastSettlement.y);
                    } else {
                        highlightEdge.setCenterOfRotation(0, 0);
                        highlightEdge.rotate(new Float(angle));
                        highlightEdge.draw(lastSettlement.x-40, lastSettlement.y - 48);
                    }

Answer 1

您可以创建一个Shape以与Image的形状完全匹配，然后使用其方法contains检测是否在内部单击鼠标。

考虑到Image的旋转，您可以将相应的旋转Transform应用于Shape。

我创建了这样做的方法shapeFromImage；它接收Image及其位置，并返回相应的Shape：

/**
 * Returns the Shape of an Image considering its rotation
 * @param image
 * @param x the x position of the Image
 * @param y the y position of the Image
 */
public static Shape shapeFromImage(Image image, float x, float y) {
    // create a rectangle with same position and size of the image
    Shape imageShape = new Rectangle(x, y, image.getWidth(), image.getHeight());
    // get the rotation angle of the image
    float angle = image.getRotation();
    // if the image is rotated, we also need to rotate our shape 
    if (angle != 0.f) {
        // convert the rotation angle in radians to use in Transform 
        float angleInRadians = (float) Math.toRadians(angle);
        // get the point of rotation to use in Transform.
        // image.getCenterOfRotation returns a point relative to the image.
        // for Transform we need an absolute point, so we add the image position to it
        float rotationX = image.getCenterOfRotationX() + x;
        float rotationY = image.getCenterOfRotationY() + y;
        // create the rotation Transform to match the image rotation
        Transform rotationTransform = Transform.createRotateTransform(angleInRadians, rotationX, rotationY);
        // apply the rotation Transform to our shape
        imageShape = imageShape.transform(rotationTransform);
    }
    return imageShape;
}

在您的示例中，您可以这样使用：

float positionX;
float positionY;
if (angle == 90) {
    highlightEdge.setCenterOfRotation(highlightEdge.getWidth(), 0);
    highlightEdge.rotate(new Float(angle));
    positionX = testPoint.x - 56;
    positionY = testPoint.y;
    highlightEdge.draw(positionX, positionY);
} 
...
// you can now use this Shape to use its method "contains"
imageShape = shapeFromImage(highlightEdge, positionX, positionY);