在Android拍照后保存缩略图

Question

我有一个应用程序可以通过底部的完整代码拍照。我的问题是如何访问存储在jpeg中的缩略图或生成新的缩略图。将代码放入此类或检查基于事件或计划的文件夹并生成缩略图的单独类都可以。

具体来说，我设置了缩略图，但无法以任何方式访问它。我尝试实现ExifInterface并手动调整照片大小。我能够将其他参数放入Jpeg Exif（为纬度和经度输入一些随机数字）。查看文件确认数字已写入。非常感谢。

    public void surfaceChanged(SurfaceHolder holder,int format, int width, int height) {
        Camera.Parameters parameters=camera.getParameters();

        parameters.setPreviewSize(width, height);
        parameters.setPictureFormat(PixelFormat.JPEG);
        parameters.setJpegThumbnailQuality(50);
        parameters.setJpegThumbnailSize(192, 256);

        camera.setParameters(parameters);
        camera.startPreview();
    }

这是我尝试使用Exif接口失败的内容：

                ExifInterface myEI = new ExifInterface(photo.getPath());
                byte[] thumbArray = myEI.getThumbnail();

                File thumbFolder = new File(appFolder.getPath(), "thumbnails");
                if (!thumbFolder.exists())
                {
                    thumbFolder.mkdirs();
                }
                File thumbnail=new File(thumbFolder, picFile.getName());
                if (thumbnail.exists()) {
                    thumbnail.delete();
                }

                Bitmap bitmap = BitmapFactory.decodeByteArray(thumbArray, 0, thumbArray.length);
                FileOutputStream fos = openFileOutput(thumbnail.getPath(), MODE_WORLD_READABLE);
                bitmap.compress(CompressFormat.JPEG, 50, fos);
                fos.close();

类的完整代码。

public class PictureTaker extends Activity {
private static final String TAG = "PictureTaker";
private SurfaceView preview=null;
private SurfaceHolder previewHolder=null;
private Camera camera=null;
String filename;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.camera);
    preview=(SurfaceView)findViewById(R.id.preview);
    previewHolder=preview.getHolder();
    previewHolder.addCallback(surfaceCallback);
    previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode==82 || keyCode==KeyEvent.KEYCODE_SEARCH) {
        takePicture();
        return(true);
    }
    return super.onKeyDown(keyCode, event);
}

private void exitCamera() {
    finish();
    super.onStop();
}

private void takePicture() {
    camera.takePicture(null, null, photoCallback);
}

SurfaceHolder.Callback surfaceCallback=new SurfaceHolder.Callback() {
    public void surfaceCreated(SurfaceHolder holder) {
        camera=Camera.open();

        try {
            camera.setPreviewDisplay(previewHolder);
        }
        catch (Throwable t) {
            Log.d(TAG, "Exception in setPreviewDisplay()", t);
        }
    }

    public void surfaceChanged(SurfaceHolder holder,int format, int width, int height) {
        Camera.Parameters parameters=camera.getParameters();

        parameters.setPreviewSize(width, height);
        parameters.setPictureFormat(PixelFormat.JPEG);
        parameters.setJpegThumbnailQuality(50);
        parameters.setJpegThumbnailSize(192, 256);

        camera.setParameters(parameters);
        camera.startPreview();
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        camera.stopPreview();
        camera.release();
        camera=null;
    }
};

Camera.PictureCallback photoCallback=new Camera.PictureCallback() {
    public void onPictureTaken(byte[] data, Camera camera) {
        new SavePhotoTask().execute(data);
        camera.startPreview();
    }
};

class SavePhotoTask extends AsyncTask<byte[], String, String> {
    @Override
    protected String doInBackground(byte[]... jpeg) {
        filename = Utilities.getTimeString() + ".jpg";

        File photo=new File(filename);
        if (photo.exists()) {
            photo.delete();
        }
        try {
            FileOutputStream fos=new FileOutputStream(photo.getPath());
            fos.write(jpeg[0]);
            fos.close();

        }
        catch (java.io.IOException e) {
            Log.d(TAG, "Exception in photoCallback", e);
        }
        return(null);
    }
}

}

- Adam

Answer 1

我知道这听起来很傻，但我唯一与你不同的是使用文件对象初始化FileOutputStream，而不是文件名字符串。所以你有

FileOutputStream fos = openFileOutput(thumbnail.getPath(), MODE_WORLD_READABLE);
FileOutputStream fos=new FileOutputStream(photo.getPath());

试试这个：

FileOutputStream fos = openFileOutput(thumbnail, MODE_WORLD_READABLE);
FileOutputStream fos=new FileOutputStream(photo);

我记得这让之前无法正常工作的东西对我有用，尽管我想不出为什么会有任何区别。

- Mike

Answer 2

不要使用

FileOutputStream fos = openFileOutput(thumbnail.getPath(), MODE_WORLD_READABLE);
FileOutputStream fos=new FileOutputStream(photo.getPath());

试一下这个

FileOutputStream fos = openFileOutput(thumbnail.getPath(), MODE_WORLD_READABLE);
FileOutputStream fos=new FileOutputStream(new File(photo.getPath()));

- ritz