Scaning QRcode from image (not from camera) using ZXing

I am using the ZXing library for barcode scanning.

I want to scan a barcode using this library from an image (e.g., on the SD card) rather than from the camera.

How can I do this using the ZXing library?

Answer

I wanted to test it out before posting it so it took me a while, I’m also using ZXing right now so this comes handy for me as well:

First of course, read the image from the gallery (this can be in your activity):

        Intent pickIntent = new Intent(Intent.ACTION_PICK);
        pickIntent.setDataAndType( android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI, "image/*");

        startActivityForResult(pickIntent, 111);

After that, just get the image uri on the activity result and then ZXing will do the magic:

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        switch (requestCode) {
            //the case is because you might be handling multiple request codes here
            case 111:
                if(data == null || data.getData()==null) {
                    Log.e("TAG", "The uri is null, probably the user cancelled the image selection process using the back button.");
                    return;
                }
                Uri uri = data.getData();
                try
                {
                    InputStream inputStream = getContentResolver().openInputStream(uri);
                    Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                    if (bitmap == null)
                    {
                        Log.e("TAG", "uri is not a bitmap," + uri.toString());
                        return;
                    }
                    int width = bitmap.getWidth(), height = bitmap.getHeight();
                    int[] pixels = new int[width * height];
                    bitmap.getPixels(pixels, 0, width, 0, 0, width, height);
                    bitmap.recycle();
                    bitmap = null;
                    RGBLuminanceSource source = new RGBLuminanceSource(width, height, pixels);
                    BinaryBitmap bBitmap = new BinaryBitmap(new HybridBinarizer(source));
                    MultiFormatReader reader = new MultiFormatReader();
                    try
                    {
                        Result result = reader.decode(bBitmap);
                        Toast.makeText(this, "The content of the QR image is: " + result.getText(), Toast.LENGTH_SHORT).show();
                    }
                    catch (NotFoundException e)
                    {
                        Log.e("TAG", "decode exception", e);
                    }
                }
                catch (FileNotFoundException e)
                {
                    Log.e("TAG", "can not open file" + uri.toString(), e);
                }
                break;
        }
    }

I tested this and it works, cheers.