zxing And Aforge aztec Barcode Reading

Question

private readonly IBarcodeReader barcodeReader;
barcodeReader = new BarcodeReader {
    AutoRotate = true,
    Options = new DecodingOptions {
        TryHarder = true,
        PossibleFormats = new List < BarcodeFormat {
            BarcodeFormat.AZTEC
        }
    }
};
currentBitmapForDecoding = new Bitmap(@ "F:\Aztec-Code-Scandit.png");
Result result = barcodeReader.Decode(currentBitmapForDecoding);

it working when i read image from physical path.but when i assign current frame of webcam to currentBitmapForDecoding it unabel to reade Aztec Barcode.pls anyone how help me to read aztec barcode from web cam.i also make frame size small but not work.