在Android OpenCV 2.4.4中，选择好匹配项的好方法是什么

我正在写一个识别钞票的程序。下面是我查找匹配项的函数。我有5张来自手机存储器的图像和一张通过摄像头拍摄的图像。此代码在for循环中执行，以查找匹配数量最多的图像。从变量匹配中获得好匹配的好方法是什么

object_desc = new Mat();
scene_desc = new Mat();

object_keys = new MatOfKeyPoint();
scene_keys = new MatOfKeyPoint();

matches = new MatOfDMatch();
good_matches = new MatOfDMatch();

Utils.bitmapToMat(image, object); 
surf = FeatureDetector.create(FeatureDetector.FAST);
surf.detect(object, object_keys);
surf.detect(mRgba, scene_keys);

surfEX = DescriptorExtractor.create(DescriptorExtractor.FREAK);
surfEX.compute(object, object_keys, object_desc);
surfEX.compute(mRgba, scene_keys, scene_desc);
dm = DescriptorMatcher.create(DescriptorMatcher.BRUTEFORCE_HAMMING);

dm.match(object_desc, scene_desc, matches);

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在这里，你可以看一些挑选好对手的例子。有什么发现吗？