OCR Usage Basics Leave feedback
GroupDocs.Parser doesn’t contain OCR functionality as a part of its distributable. Instead of it API for integrating any paid or free OCR solution is provided. See this article for details how to integrate OCR soluton to GroupDocs.Parser.
To use OCR functionality, Parser object must be properly initialized:
- Instantiate ParserSettings object with the instance of class that implements OCR functionality;
- Instantiate Parser object with ParserSettings object.
The following example shows how to create an instance of Parser class with Aspose.OCR on-premise API connector:
// Create an instance of ParserSettings class with the implementation of Aspose.OCR on-premise API connector
ParserSettings settings = new ParserSettings(new AsposeOCR());
// Create an instance of Parser class with the parser settings
Parser parser = new Parser(fileName, settins);
GetText and GetTextAreas methods from Parser class are used to recognize a text from images.
To extract a text from image files or non-text PDF documents GetText method is used:
- Instantiate ParserSettings object with the instance of class that implements OCR functionality;
- Instantiate Parser object with ParserSettings object;
- Instantiate TextOptions object with useOcr = true;
- Call GetText(TextOptions) method with TextOptions parameter and obtain TextReader object;
- Check if the reader isn’t null (text extraction is supported for the document);
- Read a text from the reader.
The following example shows how to extract a text from the image file:
// Create an instance of ParserSettings class with OCR Connector
ParserSettings settings = new ParserSettings(new AsposeOcrOnPremise());
// Create an instance of Parser class with settings
using (Parser parser = new Parser(Constants.SampleScan, settings))
{
// Create an instance of TextOptions to use OCR
TextOptions options = new TextOptions(false, true);
// Extract a text using OCR
using(TextReader reader = parser.GetText(options))
{
// Print a text or 'not supported' message
Console.WriteLine(reader == null ? "Text extraction isn't supported" : reader.ReadToEnd());
}
}
To extract text areas from image files or non-text PDF documents GetTextAreas method is used:
- Instantiate ParserSettings object with the instance of class that implements OCR functionality;
- Instantiate Parser object with ParserSettings object;
- Instantiate PageTextAreaOptions object with useOcr = true;
- Call GetTextAreas(PageTextAreaOptions) method and obtain the collection of PageTextArea objects;
- Check if the collection isn’t null (text areas extraction is supported for the document);
- Iterate through the collection and get rectangles and texts.
The following example shows how to extract text areas from the image file:
// Create an instance of ParserSettings class with OCR Connector
ParserSettings settings = new ParserSettings(new AsposeOcrOnPremise());
// Create an instance of Parser class with settings
using (Parser parser = new Parser(Constants.SampleScan, settings))
{
// Create an instance of PageTextAreaOptions to use OCR
PageTextAreaOptions options = new PageTextAreaOptions(true);
// Extract text areas
IEnumerable<PageTextArea> areas = parser.GetTextAreas(options);
// Check if text areas extraction is supported
if (areas == null)
{
Console.WriteLine("Text areas extraction isn't supported");
return;
}
// Iterate over text areas
foreach (PageTextArea a in areas)
{
// Print a text, position and size for each text area
Console.WriteLine(a.Text);
Console.WriteLine("\tPosition: ({0}; {1})", a.Rectangle.Left, a.Rectangle.Top);
Console.WriteLine("\tSize: ({0}; {1})", a.Rectangle.Size.Width, a.Rectangle.Size.Height);
}
}
TextOptions and PageTextAreaOptions classes have the property OcrOptions. OcrOptions class has the following members:
| Member | Description |
|---|---|
| Rectangle | Is used to pass a rectangular area to restrict the area of the text recognition. |
| Handler | An instance of OcrEventHandler class to handle any warnings which occur while the text recognition. |
The following sections describe how to use this property.
To restrict an area of the image for the text recognition OcrOptions class is used. Set Rectangle property to restrict the rectangular area for the text recognition.
The following example shows how to restrict the text recognition by the rectangular area:
// Create an instance of ParserSettings class with OCR Connector
ParserSettings settings = new ParserSettings(new AsposeOcrOnPremise());
// Create an instance of Parser class with settings
using (Parser parser = new Parser(Constants.SampleScan, settings))
{
// Create an instance of OcrOptions to set a rectangle
OcrOptions ocrOptions = new OcrOptions(new Data.Rectangle(0, 0, 400, 200));
// Create an instance of TextOptions to use OCR
TextOptions options = new TextOptions(false, true, ocrOptions);
// Extract a text using OCR
using (TextReader reader = parser.GetText(options))
{
// Print a text or 'not supported' message
Console.WriteLine(reader == null ? "Text extraction isn't supported" : reader.ReadToEnd());
}
}
To restrict an area of the image for the text recognition OcrOptions class is used. Set Handler property to handle warning messages. HasWarnings property of OcrEventHandler class is used to indicate if any warnings occur. Use Warnings to get all warnings or GetWarnings method for warnings for the page. the empty list returns if no warning occurs during the text recognition.
The following example shows how to handle warning messages:
// Create an instance of ParserSettings class with OCR Connector
ParserSettings settings = new ParserSettings(new AsposeOcrOnPremise());
// Create an instance of Parser class with settings
using (Parser parser = new Parser(Constants.SampleScan, settings))
{
// Create an instance of OcrEventHandler to handle warnings
OcrEventHandler handler = new OcrEventHandler();
// Create an instance of OcrOptions to set a handler
OcrOptions ocrOptions = new OcrOptions(handler);
// Create an instance of TextOptions to use OCR
TextOptions options = new TextOptions(false, true, ocrOptions);
// Extract a text using OCR
using (TextReader reader = parser.GetText(options))
{
// Print a text or 'not supported' message
Console.WriteLine(reader == null ? "Text extraction isn't supported" : reader.ReadToEnd());
}
if (handler.HasWarnings)
{
Console.WriteLine("The following warnings occur while the text recognition:");
foreach (string w in handler.Warnings)
{
Console.WriteLine("\\t* " + w);
}
}
else
{
Console.WriteLine("the text recognition was performed without any warning.");
}
}
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