Android中的OpenCv:来自文件的图像中的关键点检测

Question

我是OpenCv和StackOverflow的新手,对Android编程几乎不熟悉所以请原谅我,如果我的问题很愚蠢.

我试图将从相机获取的图像与某些图像文件进行匹配,以查看哪个图像文件与相机图像更相似.所以我使用DescriptorExtractor.compute获取文件图像的关键点和带有SURF的摄像机图像(我也尝试过SIFT)以匹配它们但是...应用于文件图像的方法总是返回一个空的关键点列表,而如果我在相机图像上使用它,我总是得到一个非空列表(平均一百个点).让我最困惑的是,即使使用相同的图像,首先从相机加载,然后从文件,我得到这种行为.

你能帮我弄清楚我做错了什么吗？这是一些测试代码(仅适用于文件部分,但我使用相同的方法getKp来从相机中提取关键点).

public class HelloOpenCvActivity extends Activity {
    private static final int FILE_REQUEST = 400;
    /** Called when the activity is first created. */

    ImageView img;
    TextView txt;
    Bitmap logo;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        img = (ImageView) findViewById(R.id.image);
        txt = (TextView) findViewById(R.id.kp);

        img.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                chooseFile();               
            }
        });
    }

    private void chooseFile(){
        Intent fileIntent = new Intent(Intent.ACTION_GET_CONTENT);
        fileIntent.addCategory(Intent.CATEGORY_OPENABLE);
        fileIntent.setType("image/*");
        startActivityForResult(Intent.createChooser(fileIntent,"prova"), FILE_REQUEST); 
    }

    /*Quando ho il risultato della chiamata al file explorer, viene invocata questa callback */
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {  
        if (requestCode == FILE_REQUEST) {  
            // obtain the filename
            Uri uri = data.getData();
            String filePath = null;
            if (uri != null) {
                if (uri.toString().startsWith("file:")) {
                    filePath = uri.getPath();
                } else { // uri.startsWith("content:")
                    Cursor c = getContentResolver().query(uri, null, null, null, null);
                    if (c != null && c.moveToFirst()) {
                        int id = c.getColumnIndex(Images.Media.DATA);
                        if (id != -1) {
                            filePath = c.getString(id);
                        }
                    }
                }
            }
            if (filePath != null) {
                logo = BitmapFactory.decodeFile(filePath);
                img.setImageBitmap(logo);
                txt.setText(""+getKp(logo).size());
            }
        }  
    }

    private List<KeyPoint> getKp(Bitmap bm){
        Mat image = Utils.bitmapToMat(bm);

        List<KeyPoint> kp = new ArrayList<KeyPoint>();
        FeatureDetector fd = FeatureDetector.create(FeatureDetector.SURF);
        fd.detect(image, kp);


        return kp;
    }

}

非常感谢你.

麦酒

Answer 1

经过几个小时的研究和头痛;-)我发现了问题.来自摄像机和文件的图像都可以存储在位图对象中,但它们的配置(Bitmap.Config)是不同的:ARGB_8888用于摄像机图像,RGB_565用于文件图像.使用Bitmap.copy方法将文件映像中的位图配置更改为ARGB_8888是解决方案.

private List<KeyPoint> getKp(Bitmap bm){
    //scale bitmap (otherwise the program crashes due to memory lack)
    int MAX_DIM = 300;
    int w, h;       
    if (bm.getWidth() >= bm.getHeight()){
        w = MAX_DIM;
        h = bm.getHeight()*MAX_DIM/bm.getWidth();
    }
    else{
        h = MAX_DIM;
        w = bm.getWidth()*MAX_DIM/bm.getHeight();
    }
    bm = Bitmap.createScaledBitmap(bm, w, h, false);

    //change bitmap config <- THAT'S THE POINT!
    Bitmap img = bm.copy(Bitmap.Config.ARGB_8888, false);           

    Mat image = Utils.bitmapToMat(img);

    List<KeyPoint> kp = new ArrayList<KeyPoint>();
    FeatureDetector fd = FeatureDetector.create(FeatureDetector.SURF);
    fd.detect(image, kp);

    return kp;
}

希望这可以帮助任何遇到同样问题的人.:-)