java - 使用 AffineTransform Java 旋转图像时出现偏移错误

Question

我正在尝试使用 AffineTransform 类旋转图像。但是，当旋转例如 90 度时，图像会更改其宽度和高度值，从而导致我想要删除的偏移。

这是我尝试过的

OpRotate.java

    public BufferedImage filter(BufferedImage src, BufferedImage dest) {

        // Parameter auswerten
        float rotationAngle = ((float) attributes.getAttributeByName("Desired rotation angle").getValue());

        AffineTransform rotationTransformation = new AffineTransform();
        double middlePointX = src.getHeight() / 2;
        double middlePointY = src.getWidth() / 2;


        rotationTransformation.setToRotation(Math.toRadians(rotationAngle), middlePointX, middlePointY);

        operation = new AffineTransformOp(rotationTransformation, AffineTransformOp.TYPE_BILINEAR);

        return operation.filter(src, dest);

    }

将图像向右旋转 90 度后，结果如下所示:

Answer 1

使用 AffineTransformOp 旋转图像(在我看来)有点违反直觉...旋转本身很容易，但正如您可能已经发现的那样，困难的部分是正确平移，以便图像的左上角部分(或者它的边界框，如果是非象限旋转)旋转后完美地击中原点。

如果您需要旋转任意角度，可以使用以下非常通用的代码:

public static BufferedImage rotate(BufferedImage src, double degrees) {
    double angle = toRadians(degrees); // Allows any angle

    double sin = abs(sin(angle));
    double cos = abs(cos(angle));

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

    // Compute new width and height
    double newWidth = width * cos + height * sin;
    double newHeight = height * cos + width * sin;

    // Build transform
    AffineTransform transform = new AffineTransform();
    transform.translate(newWidth / 2.0, newHeight / 2.0);
    transform.rotate(angle);
    transform.translate(-width / 2.0, -height / 2.0);

    BufferedImageOp operation = new AffineTransformOp(transform, AffineTransformOp.TYPE_BILINEAR);

    return operation.filter(src, null);
}

但是，如果您只想旋转 90 度的倍数，则可以使用这个稍快的变体:

public static BufferedImage rotate90(BufferedImage src, int quadrants) {
    // Allows any multiple of 90 degree rotations (1, 2, 3)

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

    // Compute new width and height
    boolean swapXY = quadrants % 2 != 0;
    int newWidth = swapXY ? height : width;
    int newHeight = swapXY ? width : height;

    // Build transform
    AffineTransform transform = new AffineTransform();
    transform.translate(newWidth / 2.0, newHeight / 2.0);
    transform.quadrantRotate(quadrants);
    transform.translate(-width / 2.0, -height / 2.0);

    BufferedImageOp operation = new AffineTransformOp(transform, AffineTransformOp.TYPE_NEAREST_NEIGHBOR); // 1:1 mapping

    return operation.filter(src, null);
}