围绕参考点旋转图像

Question

我正在尝试使用 BufferedImage 和 AffineTransform 围绕 Java 中的参考点旋转图像，起初它似乎正是我需要的，但事实证明它没有按预期运行。我需要做一些基本的旋转，90 的倍数，所以我尝试做 getQuadrantRotateInstance，但是，如果参考点在 0,0，那么我得到一个 RasterFormatException：Transformed height (0) is less than or equal to 0.

var rotation = switch (transform) {
    case TRANS_NONE -> 0;
    case TRANS_ROT90 -> 1;
    case TRANS_ROT180 -> 2;
    case TRANS_ROT270 -> 3;
    default -> throw new NotImplementedException();
};
var transform = AffineTransform.getQuadrantRotateInstance(rotation, referenceX, referenceY);
var operation = new AffineTransformOp(transform, AffineTransformOp.TYPE_BILINEAR);
var rotated = operation.filter(source, null);

从外观上看，图像旋转出 canvas（进入负坐标），导致上述异常。

创建图像的旋转变体的正确解决方案是什么而不像现有解决方案那样裁剪或绕中心点旋转？

Answer 1

围绕中心点旋转图像一个角度：

private BufferedImage rotateImage(BufferedImage buffImage, double angle) {
    double radian = Math.toRadians(angle);
    double sin = Math.abs(Math.sin(radian));
    double cos = Math.abs(Math.cos(radian));

    int width = buffImage.getWidth();
    int height = buffImage.getHeight();

    int nWidth = (int) Math.floor((double) width * cos + (double) height * sin);
    int nHeight = (int) Math.floor((double) height * cos + (double) width * sin);

    BufferedImage rotatedImage = new BufferedImage(nWidth, nHeight, BufferedImage.TYPE_INT_ARGB);

    Graphics2D graphics = rotatedImage.createGraphics();

    graphics.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
    graphics.translate((nWidth - width) / 2, (nHeight - height) / 2);
    // This is the rotation around the center point - change this line
    graphics.rotate(radian, (double) (width / 2), (double) (height / 2));
    graphics.drawImage(buffImage, 0, 0, null);
    graphics.dispose();

    return rotatedImage;
}

要更改旋转的原点，请参阅方法 javadoc rotate。

来源：Creating simple captcha.

围绕参考点旋转图像

Rotating an image around a reference point

java

rotation

image-rotation

graphics2d