AffineTransform会截断图像，我该怎么办？

Question

我这里有一个尺寸为2156x1728的黑白png文件，我想使用AffineTransform旋转90度。生成的图像比例不正确。这是一些示例代码（假设我已将png文件成功加载到BufferedImage中）：

public BufferedImage transform(BufferedImage image){

    System.out.println("Input width: "+ image.getWidth());
    System.out.println("Input height: "+ image.getHeight());

    AffineTransform affineTransform = new AffineTransform();
    affineTransform.setToQuadrantRotation(1, image.getWidth() / 2, image.getHeight() / 2);

    AffineTransformOp opRotated = new AffineTransformOp(affineTransform, AffineTransformOp.TYPE_BILINEAR);
    BufferedImage transformedImage = opRotated.createCompatibleDestImage(image, image.getColorModel());
    System.out.println("Resulting width: "+ transformedImage.getWidth());
    System.out.println("Resulting height: "+ transformedImage.getHeight());

    transformedImage = opRotated.filter(image, transformedImage);
    return transformedImage;
}

输出如下：

输入宽度：2156

输入高度：1728

结果宽度：1942年

身高：1942

旋转如何返回如此完全无关的尺寸？

Answer 1

我不是专业人士，但是为什么不创建一个正确大小的BufferedImage？另请注意，您的旋转中心不正确。您将需要旋转[w / 2，w / 2]或[h /
2，h / 2]的中心（w是宽度，h是高度），具体取决于要旋转到的象限，是1还是3 ，以及图片的相对高度和宽度。例如：

import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JOptionPane;

public class RotateImage {
   public static final String IMAGE_PATH = "http://duke.kenai.com/"
         + "models/Duke3DprogressionSmall.jpg";

   public static void main(String[] args) {
      try {
         URL imageUrl = new URL(IMAGE_PATH);
         BufferedImage img0 = ImageIO.read(imageUrl);
         ImageIcon icon0 = new ImageIcon(img0);

         int numquadrants = 1;
         BufferedImage img1 = transform(img0, numquadrants );
         ImageIcon icon1 = new ImageIcon(img1);

         JOptionPane.showMessageDialog(null, new JLabel(icon0));
         JOptionPane.showMessageDialog(null, new JLabel(icon1));

      } catch (MalformedURLException e) {
         e.printStackTrace();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }

   public static BufferedImage transform(BufferedImage image, int numquadrants) {
      int w0 = image.getWidth();
      int h0 = image.getHeight();
      int w1 = w0;
      int h1 = h0;

      int centerX = w0 / 2;
      int centerY = h0 / 2;

      if (numquadrants % 2 == 1) {
         w1 = h0;
         h1 = w0;
      }

      if (numquadrants % 4 == 1) {
         if (w0 > h0) {
            centerX = h0 / 2;
            centerY = h0 / 2;
         } else if (h0 > w0) {
            centerX = w0 / 2;
            centerY = w0 / 2;
         }
         // if h0 == w0, then use default
      } else if (numquadrants % 4 == 3) {
         if (w0 > h0) {
            centerX = w0 / 2;
            centerY = w0 / 2;
         } else if (h0 > w0) {
            centerX = h0 / 2;
            centerY = h0 / 2;
         }
         // if h0 == w0, then use default
      }

      AffineTransform affineTransform = new AffineTransform();
      affineTransform.setToQuadrantRotation(numquadrants, centerX, centerY);

      AffineTransformOp opRotated = new AffineTransformOp(affineTransform,
            AffineTransformOp.TYPE_BILINEAR);

      BufferedImage transformedImage = new BufferedImage(w1, h1,
            image.getType());

      transformedImage = opRotated.filter(image, transformedImage);
      return transformedImage;
   }
}

编辑1
您询问：

您能向我解释为什么它必须为[w / 2，w / 2]或[h / 2，h / 2]吗？

为了更好地说明这一点，最好可视化并实际操作矩形：

切出矩形纸并将其放在纸上，使其左上角位于纸的左上角，这就是屏幕上的图像。现在，检查您需要旋转矩形1或3象限的位置，以使其新的左上角覆盖纸张的左上角，并且您将看到为什么需要使用[w
/ 2，w / 2]或[h / 2，h / 2]。