AffineTransform截断图像 [英] AffineTransform truncates image

问题描述

我有一个图像，我必须旋转45度，90度，135度，180度。我在做什么：

I have an image and I have to rotate it by 45, 90, 135, 180 degrees. What I am doing:

try {
    BufferedImage src = ImageIO.read(new File("src.png"));
    double ang = Math.toRadians(90);

    AffineTransform t = new AffineTransform();
    t.setToRotation(ang, src.getWidth() / 2, src.getHeight() / 2);

    AffineTransformOp op = new AffineTransformOp(t, null);
    BufferedImage dst = new BufferedImage(src.getWidth(), src.getHeight(), src.getType());
    op.filter(src, dst);

    ImageIO.write(dst, "png", new File("output.png"));
} catch(Exception ex) { ex.printStackTrace();
}

问题是图像改变了位置并超出了目标图像的范围：

The problem is that image changes its position and gets out of bounds of destination image:

问题http： //img32.imageshack.us/img32/3328/resultcs.png

我用谷歌搜索了这个问题并找到了这个问题的解决方案： AffineTransform截断图片，我有什么不对？但我完全不明白它只适用于象限。我试图将目标的宽度和高度相乘两倍，但它失败了：

I've googled this and found the solution in this question: AffineTransform truncates image, what do I wrong? But I quite don't understand it and it works only for quadrants. I've tried to multiply twice width and height of destination, but it failed:

另一个失败http://img401.imageshack.us/img401/2417/result2a.png

如何解决这个问题？目标图像不应具有任何额外的（对角线旋转所需的除外）空白或截断区域。角度问题（0 == 180或顺时针方向）并不重要。

How to fix this? The destination image shouldn't have any extra (except required for diagonal rotation) whitespace or truncated area. Angle problems (0 == 180 or is it clockwise) aren't important.

感谢您的帮助。

推荐答案

编辑：现在它适用于一般情况。

旋转是围绕中心，并且中心位于目标图像中与源图像中相同的位置（正确行为）。

The rotation is performed around the center, and the center is placed at the same position in the destination image as it was in the source image (correct behavior).

我已修改您的代码以进行转换源图像矩形，以便我们可以轻松获得新的尺寸/图像偏移。这用于构造正确尺寸的目的地 BufferedImage ，并将翻译附加到 AffineTransform ，以便图像center位于目标图像的中心。

I've modified your code to transform the source image rectangle so we can easily get the new dimensions/image offset. This is used to construct a destination BufferedImage of the correct dimensions, and to append a translation to your AffineTransform so the image center is placed at the center of the destination image.

        BufferedImage src = ImageIO.read(new File(INPUT));
        int w = src.getWidth();
        int h = src.getHeight();

        AffineTransform t = new AffineTransform();
        double ang = Math.toRadians(35);
        t.setToRotation(ang, w / 2d, h / 2d);

        // source image rectangle
        Point[] points = {
            new Point(0, 0),
            new Point(w, 0),
            new Point(w, h),
            new Point(0, h)
        };

        // transform to destination rectangle
        t.transform(points, 0, points, 0, 4);

        // get destination rectangle bounding box
        Point min = new Point(points[0]);
        Point max = new Point(points[0]);
        for (int i = 1, n = points.length; i < n; i ++) {
            Point p = points[i];
            double pX = p.getX(), pY = p.getY();

            // update min/max x
            if (pX < min.getX()) min.setLocation(pX, min.getY());
            if (pX > max.getX()) max.setLocation(pX, max.getY());

            // update min/max y
            if (pY < min.getY()) min.setLocation(min.getX(), pY);
            if (pY > max.getY()) max.setLocation(max.getX(), pY);
        }

        // determine new width, height
        w = (int) (max.getX() - min.getX());
        h = (int) (max.getY() - min.getY());

        // determine required translation
        double tx = min.getX();
        double ty = min.getY();

        // append required translation
        AffineTransform translation = new AffineTransform();
        translation.translate(-tx, -ty);
        t.preConcatenate(translation);

        AffineTransformOp op = new AffineTransformOp(t, null);
        BufferedImage dst = new BufferedImage(w, h, src.getType());
        op.filter(src, dst);

        ImageIO.write(dst, "png", new File(OUTPUT));

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