Anyone used QZXing for datamatrix reading?

[themts]

Hello guys,

I'm trying to decode some datamatrix-codes.
I thought QZXing looks easy to use but unfortunately I'm not able to decode a single code.
First I tried the simeple example application "QZXingDragNDropTest"
:: not able to decode my picture

Then I wrote 5 lines of code to test it myself

    QImage imageToDecode("img_6_1.bmp");
    QZXing decoder;
    decoder.setDecoder(QZXing::DecoderFormat_DATA_MATRIX);
    decoder.setSourceFilterType(QZXing::SourceFilter_ImageNormal);
    decoder.setTryHarderBehaviour(QZXing::TryHarderBehaviour_ThoroughScanning);

:: same result. Not able to decode my datamatrix-code. > ReedSolomonDecoder::findErrorLocations is failing

Strange thing is that if I upload my picture to zxing.org, it is working.

Is there anybody who can explain what's wrong?

here is one sample-image: