我的 java 代码旋转 jpeg 照片有什么问题？

Question

我只是想让我的网站用户将提交的照片的方向从水平更改为垂直。这是我的代码：

public static final void rotatePhoto(String jpgFilename){
      BufferedImage originalImage = null, newImage=null;
      try{
         File file = new File(jpgFilename);
         originalImage = ImageIO.read(file);
System.out.println("Photo.rotatePhoto(" +jpgFilename +") originalImage.getWidth(null)=" +originalImage.getWidth(null) +" originalImage.getHeight(null)=" +originalImage.getHeight(null)  );
         java.awt.image.AffineTransformOp opRotated = new java.awt.image.AffineTransformOp( java.awt.geom.AffineTransform.getQuadrantRotateInstance(1), null );
         newImage = opRotated.createCompatibleDestImage(originalImage, originalImage.getColorModel());
         opRotated.filter(originalImage, newImage);
      }catch (IOException e){
      }
      /// Write result to file::::::::::::::::::::::::::::::::::::::::::::::::::::
      try{
         File outputfile = new File(testFilename);
         ImageIO.write(newImage, "jpg", outputfile);
      }catch(IOException ioE){
      }
   }

问题是，即使System.out.println显示宽度和高度为640x480 ，我也会收到这个错误

java.awt.image.RasterFormatException: Transformed width (0) is less than or equal to 0.
    java.awt.image.AffineTransformOp.createCompatibleDestImage(AffineTransformOp.java:447)
    base.Photo.rotatePhoto(Photo.java:135)
    base.ProcessContent.handleInput(ProcessContent.java:245)
    servlets.ProcessServlet.doPost(ProcessServlet.java:74)
    servlets.ProcessServlet.doGet(ProcessServlet.java:33)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

有什么想法或解决办法吗？

Answer 1

尝试从头开始创建一个新的AffineTransform，并在AffineTransformOp构造函数中使用它：

AffineTransform tx = new AffineTransform();
tx.rotate(Math.PI / 2, originalImage.getWidth() / 2, originalImage.getHeight() / 2);
AffineTransformOp op = new AffineTransformOp(tx, AffineTransformOp.TYPE_BILINEAR);
newImage = op.filter(originalImage, newImage);

您还必须确保newImage包含filter()方法返回的数据。

奇怪的是，只有当您将ImageIO.write()中的formatName设置为"png"时，这才会起作用。我尝试使用jpg，结果是一张黑色图片。

Answer 2

使用：AffineTransform.getQuadrantRotateInstance(1);

仿射变换按轴旋转了正数个象限。这将打乱"变换操作"，因为无论何时创建兼容图像，它都取决于x和y。

    int w = r.x + r.width;
    int h = r.y + r.height;
    if (w <= 0) {
        throw new RasterFormatException("Transformed width ("+w+
                                        ") is less than or equal to 0.");
    }

我建议你自己做：

public final void rotatePhoto(String jpgFilename) throws IOException {
    File file = new File(jpgFilename);
    BufferedImage originalImage = ImageIO.read(file);
    // You could use Math.PI / 2, depends on your input.
    AffineTransform affineTransform = new AffineTransform();
    affineTransform.rotate(Math.toRadians(90), originalImage.getWidth() / 2, originalImage.getHeight() / 2);
    // Now lets make that transform an operation, and we use it.
    AffineTransformOp opRotated = new AffineTransformOp(affineTransform, AffineTransformOp.TYPE_BILINEAR);  
    BufferedImage newImage = opRotated.filter(originalImage, null);
    // Save the image.
    File outputfile = new File("rotated.jpg");
    ImageIO.write(newImage, "jpg", outputfile);
}

更新：顺便说一句，我之前在"如何编写一个旋转图像的servlet？"？