如何在Java中从JPEG读取XMP面部数据

Question

我已经将Picasa的面部数据保存在我的JPEG文件中(在XMP中)，现在我正试图在Java中读取该信息。到目前为止，我失败了，希望你能帮助我。

我正在尝试使用元数据提取器库(尽管任何其他解决方案也会很好)。我可以读取基本信息(如日期，图像大小等)，但我在提取额外的数据丢失。这是我目前得到的:

File file -- this is my JPEG file
Metadata metadata = JpegMetadataReader.readMetadata(file);
XmpDirectory xmpDirectory = metadata.getDirectory(XmpDirectory.class); 
XMPMeta xmpMeta = xmpDirectory.getXMPMeta();
System.out.println(xmpMeta.dumpObject()); 

结果:

ROOT NODE
    http://www.metadataworkinggroup.com/schemas/regions/ = "mwg-rs:" (0x80000000 : SCHEMA_NODE)
        mwg-rs:Regions  (0x100 : STRUCT)
            mwg-rs:AppliedToDimensions  (0x100 : STRUCT)
                stDim:h = "2793"
                stDim:unit = "pixel"
                stDim:w = "2047"
            mwg-rs:RegionList   (0x200 : ARRAY)
                [1] (0x100 : STRUCT)
                    mwg-rs:Area (0x100 : STRUCT)
                        stArea:h = "0.69531"
                        stArea:unit = "normalized"
                        stArea:w = "0.790425"
                        stArea:x = "0.491451"
                        stArea:y = "0.41783"
                    mwg-rs:Name = "abcde"
                    mwg-rs:Type = "Face"
    http://ns.adobe.com/xap/1.0/ = "xmp:"   (0x80000000 : SCHEMA_NODE)
        xmp:ModifyDate = "2014-04-06T19:43:24+01:00"

我不明白如何到达这些stArea:w, mwg-rs:Type = "Face"等

Answer 1

像往常一样，在发布后我找到了一个解决方案。我把它列在下面。

try {
    Metadata metadata = ImageMetadataReader.readMetadata(imageFile);
    XmpDirectory xmpDirectory = metadata.getDirectory(XmpDirectory.class);
    XMPMeta xmpMeta = xmpDirectory.getXMPMeta();
    XMPIterator itr = xmpMeta.iterator();
    while (itr.hasNext()) {
        XMPPropertyInfo pi = (XMPPropertyInfo) itr.next();
        if (pi != null && pi.getPath() != null) {
            if ((pi.getPath().endsWith("stArea:w")) || (pi.getPath().endsWith("mwg-rs:Name")) || (pi.getPath().endsWith("stArea:h")))
                System.out.println(pi.getValue().toString());
        }
    }
} catch (final NullPointerException npe) {
  // ignore
}

这里我不喜欢的是它遍历所有属性，而不是只读取需要的属性。有更好(更快)的解决方案吗?