Java旋转图像将部分背景变为黑色

Question

当我尝试旋转图像时，背景的一部分似乎变黑（我的图像是透明的）

Background white
Part of background turns black

这是旋转图像的代码：

public BufferedImage rotate(int height, int width, BufferedImage originalImg, int angle) {
    BufferedImage rotateImage = null;
    try {
        rotateImage = new BufferedImage(height, width, BufferedImage.TYPE_INT_RGB);
        AffineTransform a90 = AffineTransform.getRotateInstance(Math.toRadians(angle), height / 2, width / 2);
        AffineTransformOp op90 = new AffineTransformOp(a90, AffineTransformOp.TYPE_BILINEAR);
        op90.filter(originalImg, rotateImage);
    }
    catch (Exception e) {
        System.err.println(e);
    }
    return rotateImage;
}

Answer 1

所以，我下载了你的“原始”图像（不是方形的），将它修改为方形，运行你的代码，得到一个java.awt.image.ImagingOpException: Unable to transform src image 异常，将BufferedImage.TYPE_INT_RGB 更改为BufferedImage.TYPE_INT_ARGB 并得到...

import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;

public class Main {

    public static void main(String[] args) {
        try {
            BufferedImage img = ImageIO.read(Main.class.getResource("/Block.jpg"));
            BufferedImage rotate = rotate(img.getHeight(), img.getWidth(), img, 90);

            JPanel panel = new JPanel();
            panel.add(new JLabel(new ImageIcon(img)));
            panel.add(new JLabel(new ImageIcon(rotate)));

            JOptionPane.showMessageDialog(null, panel);
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    public static BufferedImage rotate(int height, int width, BufferedImage originalImg, int angle) {
        BufferedImage rotateImage = null;
        try {
            rotateImage = new BufferedImage(height, width, BufferedImage.TYPE_INT_ARGB);
            AffineTransform a90 = AffineTransform.getRotateInstance(Math.toRadians(angle), height / 2, width / 2);
            AffineTransformOp op90 = new AffineTransformOp(a90, AffineTransformOp.TYPE_BILINEAR);
            op90.filter(originalImg, rotateImage);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return rotateImage;
    }

}

我的“直觉”感觉是也要修改 rotate 方法，因为它不应该需要 width 和 height 值；

public static BufferedImage rotate(BufferedImage originalImg, int angle) {
    BufferedImage rotateImage = null;
    try {
        rotateImage = new BufferedImage(originalImg.getWidth(), originalImg.getHeight(), BufferedImage.TYPE_INT_ARGB);
        AffineTransform a90 = AffineTransform.getRotateInstance(Math.toRadians(angle), originalImg.getWidth() / 2, originalImg.getHeight() / 2);
        AffineTransformOp op90 = new AffineTransformOp(a90, AffineTransformOp.TYPE_BILINEAR);
        op90.filter(originalImg, rotateImage);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return rotateImage;
}

它应该直接使用原始图像的尺寸。这将突出显示图像中可能存在的错误。这也假设您只想将图像旋转 90 度