How to Create a Universal Barcode Reader on Windows 10 with C/C++ Legacy Code

Probably many Windows developers have upgraded operating systems to Windows 10. On Windows 10, Microsoft suggests developers create Universal Windows Apps (UWP) for a variety of devices, including PC, tablet, mobile phone, Hololens and so on. For development, I wonder whether legacy C/C++ SDKs can also seamlessly work on Windows 10, such as Dynamsoft Barcode SDK, which does not officially support UWP development yet. The answer is yes. Let’s see the tricks.

Prerequisites

• Enable developer mode on Windows 10.
• Install Visual Studio 2015.
• Install Dynamsoft Barcode SDK.

Where do We Start?

Follow Microsoft’s tutorial to write your first “Hello World” App:

https://msdn.microsoft.com/en-us/library/windows/apps/dn996906.aspx

What’s the difference between Universal Windows app and desktop app?

Unlike Windows desktop app, Universal app is compiled into a package appx, which contains all resources, configurations and executable file. The application can only run in the context of an app container.

How to Invoke C/C++ APIs of Dynamsoft Barcode SDK in UWP App?

Create a new Universal Windows App.

Add Image, Button and TextBlock to MainPage.xaml:

<ScrollViewer Grid.Row="1" VerticalScrollMode="Auto" VerticalScrollBarVisibility="Auto" VerticalAlignment="Top">
                <StackPanel>
                    <Grid x:Name="Image" Margin="0,0,0,5" VerticalAlignment="Top">
                        <Image x:Name="PreviewImage" HorizontalAlignment="Left" VerticalAlignment="Top" MaxWidth="600"/>
                    </Grid>
                    <StackPanel Orientation="Horizontal" Margin="0, 0, 0, 5" VerticalAlignment="Top">
                        <Button x:Name="button" Margin="0, 0, 5, 0" Click="button_Click" VerticalAlignment="Top">
                            <Viewbox MaxHeight="40" MaxWidth="40">
                                <SymbolIcon Symbol="OpenFile"/>
                            </Viewbox>
                        </Button>
                        <TextBlock x:Name="BarcodeResults" Margin="0,0,0,10" TextWrapping="Wrap" Text="Results:" Height="600" Width="300" VerticalAlignment="Stretch" HorizontalAlignment="Left" />
                    </StackPanel>
                </StackPanel>
            </ScrollViewer>

Loading barcode images with FileOpenPicker:

FileOpenPicker^ picker = ref new FileOpenPicker();
picker->FileTypeFilter->Append(".bmp");
picker->SuggestedStartLocation = PickerLocationId::PicturesLibrary;

To get the C++ pointer of the image data buffers from WriteableBitmap, we can refer to the article – Obtaining pointers to data buffers. Here is the code:

byte* GetPointerToPixelData(IBuffer^ pixelBuffer, unsigned int *length)
{
	if (length != nullptr)
	{
		*length = pixelBuffer->Length;
	}
	// Query the IBufferByteAccess interface.
	ComPtr<IBufferByteAccess> bufferByteAccess;
	reinterpret_cast<IInspectable*>(pixelBuffer)->QueryInterface(IID_PPV_ARGS(&bufferByteAccess));

	// Retrieve the buffer data.
	byte* pixels = nullptr;
	bufferByteAccess->Buffer(&pixels);
	return pixels;
}

We’ll use the API DecodeBuffer, but the underlying required data structure is different. We need to construct the data buffer (BITMAPINFOHEADER + Image data) ourselves:

char *total = (char *)malloc(len + 40);
BITMAPINFOHEADER bitmap_info = { 40, width, height, 0, 32, 0, len, 0, 0, 0, 0 };
memcpy(total, &bitmap_info, 40);
char *data = total + 40;
memcpy(data, buffer, len);

Read barcode image and return results:

iRet = reader.DecodeBuffer((unsigned char*)total, len + 40);

	// Output barcode result
	pszTemp = (char*)malloc(4096);
	if (iRet != DBR_OK)
	{
		sprintf(pszTemp, "Failed to read barcode: %s\r\n", DBR_GetErrorString(iRet));
		free(pszTemp);
		return nullptr;
	}

	pBarcodeResultArray paryResult = NULL;
	reader.GetBarcodes(&paryResult);

After getting the barcode results, convert C String to Platform::String^. I found the solution from StackOverflow.

results = ref new Array<String^>(paryResult->iBarcodeCount);
	for (iIndex = 0; iIndex < paryResult->iBarcodeCount; iIndex++)
	{
		sprintf(pszTemp, "Barcode %d:\r\n", iIndex + 1);
		sprintf(pszTemp, "%s    Page: %d\r\n", pszTemp, paryResult->ppBarcodes[iIndex]->iPageNum);
		sprintf(pszTemp, "%s    Type: %s\r\n", pszTemp, GetFormatStr(paryResult->ppBarcodes[iIndex]->llFormat));
		pszTemp1 = (char*)malloc(paryResult->ppBarcodes[iIndex]->iBarcodeDataLength + 1);
		memset(pszTemp1, 0, paryResult->ppBarcodes[iIndex]->iBarcodeDataLength + 1);
		memcpy(pszTemp1, paryResult->ppBarcodes[iIndex]->pBarcodeData, paryResult->ppBarcodes[iIndex]->iBarcodeDataLength);
		sprintf(pszTemp, "%s    Value: %s\r\n", pszTemp, pszTemp1);

		// http://stackoverflow.com/questions/11545951/how-to-convert-from-char-to-platformstring-c-cli
		std::string s_str = std::string(pszTemp);
		std::wstring wid_str = std::wstring(s_str.begin(), s_str.end());
		const wchar_t* w_char = wid_str.c_str();
		OutputDebugString(w_char);
		barcode_result = ref new String(w_char);
		results->set(iIndex, barcode_result);
		free(pszTemp1);
	}

Copy DynamsoftBarcodeReaderx86.dll from <Dynamsoft Barcode SDK>\Redist\C_C++ to DynamsoftBarcodeReader\Debug\DynamsoftBarcodeReader\AppX.

Run the UWP Barcode Reader directly from Visual Studio by CTRL+F5 or the Start menu:

See the screenshot:

Known Issues

• Because some CRT functions are not applicable to UWP apps, such as fopen, the API DecodeFile cannot work. Please refer to CRT functions not supported in Universal Windows Platform apps.
• Only 1D barcode detection works.
• Only BMP image file is supported.

Source Code

https://github.com/dynamsoftsamples/universal-windows-barcode-reader