javafx-2 - 如何在 JavaFX Canvas 上绘制旋转的图像？

Question

我想在旋转的 Canvas 上绘制图像。与 drawImage(image, 0, 0)我可以绘制图像，但是如何将该图像旋转 45 度并绘制它，然后在同一 Canvas 上以 -50 度旋转绘制另一个图像？graphicContext2D对我不起作用，因为它会旋转所有 Canvas 内容。

Answer 1

这是一个示例，遵循与 Katona 的答案类似的原则，唯一的区别是它通过应用自定义变换围绕任意轴心点旋转图像。

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.canvas.*;
import javafx.scene.image.Image;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.transform.Rotate;
import javafx.stage.Stage;

/** Rotates images round pivot points and places them in a canvas */
public class RotatedImageInCanvas extends Application {
    /**
     * Sets the transform for the GraphicsContext to rotate around a pivot point.
     *
     * @param gc the graphics context the transform to applied to.
     * @param angle the angle of rotation.
     * @param px the x pivot co-ordinate for the rotation (in canvas co-ordinates).
     * @param py the y pivot co-ordinate for the rotation (in canvas co-ordinates).
     */
    private void rotate(GraphicsContext gc, double angle, double px, double py) {
        Rotate r = new Rotate(angle, px, py);
        gc.setTransform(r.getMxx(), r.getMyx(), r.getMxy(), r.getMyy(), r.getTx(), r.getTy());
    }

    /**
     * Draws an image on a graphics context.
     *
     * The image is drawn at (tlpx, tlpy) rotated by angle pivoted around the point:
     *   (tlpx + image.getWidth() / 2, tlpy + image.getHeight() / 2)
     *
     * @param gc the graphics context the image is to be drawn on.
     * @param angle the angle of rotation.
     * @param tlpx the top left x co-ordinate where the image will be plotted (in canvas co-ordinates).
     * @param tlpy the top left y co-ordinate where the image will be plotted (in canvas co-ordinates).
     */
    private void drawRotatedImage(GraphicsContext gc, Image image, double angle, double tlpx, double tlpy) {
        gc.save(); // saves the current state on stack, including the current transform
        rotate(gc, angle, tlpx + image.getWidth() / 2, tlpy + image.getHeight() / 2);
        gc.drawImage(image, tlpx, tlpy);
        gc.restore(); // back to original state (before rotation)
    }

    @Override public void start(Stage stage) {
        Image image = new Image(
            "http://worldpress.org/images/maps/world_600w.jpg", 350, 0, true, true
        );

        // creates a canvas on which rotated images are rendered.
        Canvas canvas = new Canvas(600, 400);
        GraphicsContext gc = canvas.getGraphicsContext2D();

        drawRotatedImage(gc, image,  40,   0,   0);
        drawRotatedImage(gc, image, -50, 400, 200);

        // supplies a tiled background image on which the canvas is drawn.
        StackPane stack = new StackPane();
        stack.setMaxSize(canvas.getWidth(), canvas.getHeight());
        stack.setStyle("-fx-background-image: url('http://1.bp.blogspot.com/_wV5JMD1OISg/TDYTYxuxR4I/AAAAAAAAvSo/a0zT8nwPV8U/s400/louis-vuitton-nice-beautiful.jpg');");
        stack.getChildren().add(
                canvas
        );

        // places a resizable padded frame around the canvas.
        StackPane frame = new StackPane();
        frame.setPadding(new Insets(20));
        frame.getChildren().add(stack);

        stage.setScene(new Scene(frame, Color.BURLYWOOD));
        stage.show();
    }

    public static void main(String[] args) { launch(RotatedImageInCanvas.class); }
}