Home > Code > C# > How to Extract Text From Part of an Image inside .NET Applications

How to Extract Text From Part of an Image inside .NET Applications

by sher azam   on Jul 15, 2014   Category: C#   |  Views: 2198    |  Points: 25   |  Gold 


This technical tip shows how to extract text from part of an image inside .NET Applications. Aspose.OCR for .NET provides OcrEngine class to extract text from a specific part of the image document. The OcrEngine class requires Source image, Language and Resource file for character recognition. The source image is the document on which OCR will be performed. The image can be a BMP, TIFF, JPEG, GIF or PNG file. The OcrEngine.Image property is used to set the source image. One or more languages must be specified before performing OCR. This is because the OcrEngine tries to recognize characters of the specified languages in the image. The OcrEngine recognizes text word by word. Each recognized word has a specific language which might be different from the language of the other words. Aspose.OCR for .NET also maintains the priority of each language. The language added first has the highest priority. Each language added afterwards has lower priority: the last added language has the least priority. The language priority matters when OCR is performed. Aspose.OCR for .NET first attempts to read characters as the highest priority language. If it doesn't recognize them, it tries to read them in the next language. If a word is identical in two or more languages, the OcrEngine assigns the highest priority language to the recognized word. The resource file is a ZIP archive that contains the data necessary to perform OCR. The OcrEngine.Resource property must be set and point to the resource file before starting an OCR process.

To run OCR on an image using the OcrEngine class:

• Create an instance of OcrEngine and initialize it using the default constructor.
• Set the image file using the OcrEngine.Image property.
• Add language(s) using the OcrEngine.Languages.AddLanguage method.
• Set the start point, width and height of the recognition block using the OcrConfig.AddRecognitionBlock method.
• Set the resource file using the OcrEngine.Resource property.
• Call the OcrEngine.Process method to perform OCR on the whole image.
• If OcrEngine.Process returns true, then get the recognized text with the IRecognitionBlock.Text property.

The sample code below shows how to use the steps above to run OCR on part of an image.

[C#]

const string resourceFileName = @"Aspose.OCR.Resources.zip";

try
{
//Create an instance of OcrEngine and assign
//image, language and image settings
OcrEngine ocrEngine = new OcrEngine();
ocrEngine.Image = ImageStream.FromFile("Sample.bmp");

ocrEngine.Languages.AddLanguage(Language.Load("english"));
ocrEngine.Config.UseDefaultDictionaries = true;

//Define the block in which to recognize text
int startX = 0, startY = 0, width = 120, height = 100;

//Clear recognition blocks
ocrEngine.Config.ClearRecognitionBlocks();

//Add 3 rectangle blocks to user defined recognition blocks
ocrEngine.Config.AddRecognitionBlock(RecognitionBlock.CreateTextBlock(startX, startY, width, height));

//Set the resource file name and extract OCR text
using (ocrEngine.Resource = new FileStream(resourceFileName, FileMode.Open))
{
try
{
if (ocrEngine.Process())
{
//Retrieve user defined blocks that determines the paye layout
var blocks = ocrEngine.Config.RecognitionBlocks;
//Loop over the list of blocks
foreach (var block in blocks)
{
//Display if block is set to be recognized
Console.WriteLine(block.ToRecognize);
//Check if block has recognition data
if (block.RecognitionData == null)
{
Console.WriteLine("Null{0}", Environment.NewLine);
continue;
}
//Display dimension & size of rectangle that defines the recognition block
Console.WriteLine("Block: {0}", block.Rectangle);
//Display the recognition results
Console.WriteLine("Text: {0}{1}", block.RecognitionData.Text, Environment.NewLine);
}
}
}
catch (Exception ex)
{
Console.WriteLine("Exception: " + ex.Message);
}
}
ocrEngine = null;
}
catch (Exception ex)
{
Console.WriteLine("Exception: " + ex.Message);
}



[VB.NET]

Const resourceFileName As String = "Aspose.OCR.Resources.zip"

Try
'Create an instance of OcrEngine and assign
'image, language and image settings
Dim ocrEngine As New OcrEngine()
ocrEngine.Image = ImageStream.FromFile("Sample.bmp")

ocrEngine.Languages.AddLanguage(Language.Load("english"))
ocrEngine.Config.UseDefaultDictionaries = True

'Define the block in which to recognize text
Dim startX As Integer = 0, startY As Integer = 0, width As Integer = 120, height As Integer = 100

'Clear recognition blocks
ocrEngine.Config.ClearRecognitionBlocks()

'Add 3 rectangle blocks to user defined recognition blocks
ocrEngine.Config.AddRecognitionBlock(RecognitionBlock.CreateTextBlock(startX, startY, width, height))

'Set the resource file name and extract OCR text
ocrEngine.Resource = New FileStream(resourceFileName, FileMode.Open)
Using ocrEngine.Resource
Try
If ocrEngine.Process() Then
'Retrieve user defined blocks that determines the paye layout
Dim blocks = ocrEngine.Config.RecognitionBlocks
'Loop over the list of blocks
For Each block In blocks
'Display if block is set to be recognized
Console.WriteLine(block.ToRecognize)
'Check if block has recognition data
If block.RecognitionData Is Nothing Then
Console.WriteLine("Null{0}", Environment.NewLine)
Continue For
End If
'Display dimension & size of rectangle that defines the recognition block
Console.WriteLine("Block: {0}", block.Rectangle)
'Display the recognition results
Console.WriteLine("Text: {0}{1}", block.RecognitionData.Text, Environment.NewLine)
Next block
End If
Catch ex As Exception
Console.WriteLine("Exception: " & ex.Message)
End Try
End Using
ocrEngine = Nothing
Catch ex As Exception
Console.WriteLine("Exception: " & ex.Message)
End Try



Overview: Aspose.OCR for .NET


Aspose.OCR for .NET is a character recognition component built to allow developers to add OCR functionality in their ASP .NET web applications, web services and Windows applications. It provides a simple set of classes for controlling character recognition tasks. It helps developers to work with image (BMP, TIFF) files from within their own applications. It allows developers to extract text from images quickly & easily, saving time & effort involved in developing an OCR solution from scratch.

- Homepage of Aspose.OCR for .NET: http://www.aspose.com/.net/ocr-component.aspx

-Download Aspose.OCR for .NET: http://www.aspose.com/community/files/51/.net-components/aspose.ocr-for-.net/default.aspx



Post Code  |  Code Snippet Home

User Responses


No response found, be the first to review this code snippet.

Submit feedback about this code snippet

Please sign in to post feedback

Latest Posts