Extract invoice data with C# and OCR

Nutrient .NET SDK’s (formerly GdPicture.NET) key-value pair (KVP) extraction engine enables you to recognize related data items in a document and export them to an external destination like a spreadsheet.

To extract data items from an invoice, follow the steps below:

Create a GdPictureOCR object and a GdPictureImaging object.
Select the invoice by passing its path to the CreateGdPictureImageFromFile method of the GdPictureImaging object.
Configure the OCR process with the GdPictureOCR object in the following way:
- Set the invoice with the SetImage method.
- Set the path to the OCR resource folder with the ResourceFolder property. The default language resources are located in GdPicture.NET 14\Redist\OCR. For more information on adding language resources, see the language support guide.
- With the AddLanguage method, add the language resources that Nutrient .NET SDK uses to recognize text in the image. This method takes a member of the OCRLanguage enumeration.
Run the OCR process with the RunOCR method of the GdPictureOCR object.
Get the number of key-value pairs detected during the OCR process with the GetKeyValuePairCount method of the GdPictureOCR object, and loop through them.
Get the key-value pairs, the data types, and the confidence scores with the following methods:
Write the output to the console.
Release unnecessary resources.

The example below retrieves key-value pairs from the following invoice.

Download the sample invoice and run the code below, or check out our demo.

using GdPictureOCR gdpictureOCR = new GdPictureOCR();
using GdPictureImaging gdpictureImaging = new GdPictureImaging();
// Load the source document.
int imageId = gdpictureImaging.CreateGdPictureImageFromFile(@"C:\temp\source.png");
// Configure the OCR process.
gdpictureOCR.ResourceFolder = @"C:\GdPicture.NET 14\Redist\OCR";
gdpictureOCR.AddLanguage(OCRLanguage.English);
gdpictureOCR.SetImage(imageId);
// Run the OCR process.
string ocrResultId = gdpictureOCR.RunOCR();
string keyValuePairsData = "";
for (int pairIndex = 0; pairIndex < gdpictureOCR.GetKeyValuePairCount(ocrResultId); pairIndex++)
{
    keyValuePairsData += $"| Key: {gdpictureOCR.GetKeyValuePairKeyString(ocrResultId, pairIndex)} | " +
                         $"Value: {gdpictureOCR.GetKeyValuePairValueString(ocrResultId, pairIndex)} | " +
                         $"Document Type: {gdpictureOCR.GetKeyValuePairDataType(ocrResultId, pairIndex).ToString()} | " + 
                         $"Confidence Level: {Math.Round(gdpictureOCR.GetKeyValuePairConfidence(ocrResultId, pairIndex), 1).ToString()}% |\n";
}
// Write the output to the console.
Console.WriteLine(keyValuePairsData);
// Release unnecessary resources.
gdpictureImaging.ReleaseGdPictureImage(imageId);
gdpictureOCR.ReleaseOCRResults();

Using gdpictureOCR As GdPictureOCR = New GdPictureOCR()
Using gdpictureImaging As GdPictureImaging = New GdPictureImaging()
    ' Load the source document.
    Dim imageId As Integer = gdpictureImaging.CreateGdPictureImageFromFile("C:\temp\source.png")
    ' Configure the OCR process.
    gdpictureOCR.ResourceFolder = "C:\GdPicture.NET 14\Redist\OCR"
    gdpictureOCR.AddLanguage(OCRLanguage.English)
    gdpictureOCR.SetImage(imageId)
    ' Run the OCR process.
    Dim ocrResultId As String = gdpictureOCR.RunOCR()
    Dim keyValuePairsData = ""
    For pairIndex As Integer = 0 To gdpictureOCR.GetKeyValuePairCount(ocrResultId) - 1
        keyValuePairsData += $"| Key: {gdpictureOCR.GetKeyValuePairKeyString(ocrResultId, pairIndex)} | Value: {gdpictureOCR.GetKeyValuePairValueString(ocrResultId, pairIndex)} | Document Type: {gdpictureOCR.GetKeyValuePairDataType(ocrResultId, pairIndex).ToString()} | Confidence Level: {Math.Round(gdpictureOCR.GetKeyValuePairConfidence(CStr(ocrResultId), CInt(pairIndex)), CInt(1)).ToString()}% |" & vbLf
    Next
    ' Write the output to the console.
    Console.WriteLine(keyValuePairsData)
    ' Release unnecessary resources.
    gdpictureImaging.ReleaseGdPictureImage(imageId)
    gdpictureOCR.ReleaseOCRResults()
End Using
End Using

Used methods and properties

Related topics

Format the output to obtain the following table:

Key	Value	Document type	Confidence level
Billing date	20/09/2022	DateTime	100%
Order date	20/09/2022	DateTime	100%
Republic of PDF	+100 847 738 227	PhoneNumber	77.2%
IBAN	AT13 2060 4236 6111 5994	IBAN	100%
Customer	Vandelay Industries Around the Corner 13 NBC City	String	69.8%
Delivery address	Vandelay Industries Around the Corner 13 NBC City	String	69.9%
Invoice number	No 00162	String	70.9%
Ref. number	34751	Number	92.9%
No	00162	Number	100%
Reference	P00201	UID	100%
Quantity total (excl. VAT)	320.00€	Currency	59%
Subtotal	1,220.00€	Currency	100%
Discount (10%)	-122.00€	Currency	90.6%
VAT (5.5%)	+6710€	Currency	66.9%
Shipping cost	0.00€	Currency	75%
TOTAL	1,165.10€	Currency	100%
Description	Lake Mirror	String	99.6%
VAT	5.5%	Percentage	66.6%
Price per unit (excl. VAT)	320.00€	Currency	80%
Tax No.	AT98765321	UID	73.8%
#	[email protected]	EmailAddress	65.6%
#	www.bruuuk.com	URL	65.6%