OpenCV + Tesseract on Android

最近不务正业，决定做一个Android的小应用。
想起以前还曾经发誓，坚决不碰Java和移动开发。。。哎

有两个主要难点（对我来说）：

• OpenCV + Tesseract on Android
• 摄像头实时处理，包括读取和显示(read and display)

OpenCV + Tesseract on Android

Real time processing of Android camera

Android Camera API - Tutorial

- Using the camera on the Android device can be done via the integration of existing camera application. In this case you would start the existing Camera application via an intent and use the return data of the application to access the result.

- Alternatively you can also directly integrate the camera into your application via the Camera API.

Access camera by Intent

• Read from gallery (ACTION_PICK and ACTION_GET_CONTENT)

How to pick an image from gallery (SD Card) for my app?

With ACTION_PICK you specify a specific URI and with ACTION_GET_CONTENT you specify a mime_type.

Intent photoPickerIntent = new Intent(Intent.ACTION_PICK);
photoPickerIntent.setType("image/*");
startActivityForResult(photoPickerIntent, SELECT_PHOTO);
...
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent imageReturnedIntent) { 
    super.onActivityResult(requestCode, resultCode, imageReturnedIntent); 

    switch(requestCode) { 
    case SELECT_PHOTO:
        if(resultCode == RESULT_OK){  
            Uri selectedImage = imageReturnedIntent.getData();
            InputStream imageStream = getContentResolver().openInputStream(selectedImage);
            Bitmap yourSelectedImage = BitmapFactory.decodeStream(imageStream);
        }
    }
}

and Resize

private Bitmap decodeUri(Uri selectedImage) throws FileNotFoundException {

// Decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(getContentResolver().openInputStream(selectedImage), null, o);

// The new size we want to scale to
final int REQUIRED_SIZE = 140;

// Find the correct scale value. It should be the power of 2.
int width_tmp = o.outWidth, height_tmp = o.outHeight;
int scale = 1;
while (true) {
            if (width_tmp / 2 < REQUIRED_SIZE
               || height_tmp / 2 < REQUIRED_SIZE) {
                break;
            }
            width_tmp /= 2;
            height_tmp /= 2;
            scale *= 2;
        }

        // Decode with inSampleSize
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize = scale;
        return BitmapFactory.decodeStream(getContentResolver().openInputStream(selectedImage), null, o2);

}

• Read from camera

Intent to choose between the camera or the gallery in Android

Intent intent = new Intent(Intent.ACTION_PICK, null);
                intent.setDataAndType(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, IMAGE_UNSPECIFIED);
startActivityForResult(intent, PHOTOALBUM);

• Read from camera

Intent cameraIntent = new Intent(            android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(cameraIntent, TAKE_PICTURE);
.....
 if (requestcode == TAKE_PICTURE) {
picUri = intent.getData();
MediaStore.Images.Media.getBitmap(getContentResolver(), picUri);

• Read from camera and save

Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
File f = new File(android.os.Environment .getExternalStorageDirectory(), "MyImage.jpg");
intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(f));
startActivityForResult(intent, REQUEST_CAMERA);
...
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (resultCode == RESULT_OK) {
        Bitmap mBitmap;
        if (requestCode == REQUEST_CAMERA) {
            File camFile = new File(Environment.getExternalStorageDirectory()
                    .toString());
            for (File temp : camFile.listFiles()) {
                if (temp.getName().equals("MyImage.jpg")) {
                    camFile = temp;
                    break;
                }
            }
            try {

                BitmapFactory.Options btmapOptions = new BitmapFactory.Options();

                mBitmap = BitmapFactory.decodeFile(camFile.getAbsolutePath(),
                        btmapOptions);
                //Here you have the bitmap of the image from camera

            } catch (Exception e) {
                e.printStackTrace();
            }

• Do Both

Intent galleryintent = new Intent(Intent.ACTION_GET_CONTENT, null);
galleryintent.setType("image/*");

Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
Intent chooser = new Intent(Intent.ACTION_CHOOSER);
chooser.putExtra(Intent.EXTRA_INTENT, galleryintent);
chooser.putExtra(Intent.EXTRA_TITLE, "Select from:");

Intent[] intentArray = { cameraIntent };    chooser.putExtra(Intent.EXTRA_INITIAL_INTENTS, intentArray);
startActivityForResult(chooser, REQUEST_PIC);

Access camera by API