How to rotate JPEG images based on the orientation metadata?

If you want to rotate your images, I would suggest to use the metadata extractor library http://code.google.com/p/metadata-extractor/. You can get the image information with the following code:

// Inner class containing image information
public static class ImageInformation {
    public final int orientation;
    public final int width;
    public final int height;

    public ImageInformation(int orientation, int width, int height) {
        this.orientation = orientation;
        this.width = width;
        this.height = height;
    }

    public String toString() {
        return String.format("%dx%d,%d", this.width, this.height, this.orientation);
    }
}


public static ImageInformation readImageInformation(File imageFile)  throws IOException, MetadataException, ImageProcessingException {
    Metadata metadata = ImageMetadataReader.readMetadata(imageFile);
    Directory directory = metadata.getFirstDirectoryOfType(ExifIFD0Directory.class);
    JpegDirectory jpegDirectory = metadata.getFirstDirectoryOfType(JpegDirectory.class);

    int orientation = 1;
    try {
        orientation = directory.getInt(ExifIFD0Directory.TAG_ORIENTATION);
    } catch (MetadataException me) {
        logger.warn("Could not get orientation");
    }
    int width = jpegDirectory.getImageWidth();
    int height = jpegDirectory.getImageHeight();

    return new ImageInformation(orientation, width, height);
}

Then given the orientation you retrieve, you can rotate and/or flip the image to the right orientation. The Affine transform for the EXIF orientation is given by the following method:

// Look at http://chunter.tistory.com/143 for information
public static AffineTransform getExifTransformation(ImageInformation info) {

    AffineTransform t = new AffineTransform();

    switch (info.orientation) {
    case 1:
        break;
    case 2: // Flip X
        t.scale(-1.0, 1.0);
        t.translate(-info.width, 0);
        break;
    case 3: // PI rotation 
        t.translate(info.width, info.height);
        t.rotate(Math.PI);
        break;
    case 4: // Flip Y
        t.scale(1.0, -1.0);
        t.translate(0, -info.height);
        break;
    case 5: // - PI/2 and Flip X
        t.rotate(-Math.PI / 2);
        t.scale(-1.0, 1.0);
        break;
    case 6: // -PI/2 and -width
        t.translate(info.height, 0);
        t.rotate(Math.PI / 2);
        break;
    case 7: // PI/2 and Flip
        t.scale(-1.0, 1.0);
        t.translate(-info.height, 0);
        t.translate(0, info.width);
        t.rotate(  3 * Math.PI / 2);
        break;
    case 8: // PI / 2
        t.translate(0, info.width);
        t.rotate(  3 * Math.PI / 2);
        break;
    }

    return t;
}

The rotation of the image would be done by the following method:

public static BufferedImage transformImage(BufferedImage image, AffineTransform transform) throws Exception {

    AffineTransformOp op = new AffineTransformOp(transform, AffineTransformOp.TYPE_BICUBIC);

    BufferedImage destinationImage = op.createCompatibleDestImage(image, (image.getType() == BufferedImage.TYPE_BYTE_GRAY) ? image.getColorModel() : null );
    Graphics2D g = destinationImage.createGraphics();
    g.setBackground(Color.WHITE);
    g.clearRect(0, 0, destinationImage.getWidth(), destinationImage.getHeight());
    destinationImage = op.filter(image, destinationImage);
    return destinationImage;
}

In a server environment, don't forget to run with -Djava.awt.headless=true

The Thumbnailator library honors EXIF orientation flags. To read an image at full size with correct orientation:

BufferedImage image = Thumbnails.of(inputStream).scale(1).asBufferedImage();

This can be done surprisingly easily by using the image part of JavaXT core library :

// Browsers today can't handle images with Exif Orientation tag
Image image = new Image(uploadedFilename);
// Auto-rotate based on Exif Orientation tag, and remove all Exif tags
image.rotate(); 
image.saveAs(permanentFilename);

That's it!

I have tried Apache Commons Imaging, but that was a mess. JavaXT is way more elegant.