Finding line bounding boxes

Aspose.OCR for .NET can automatically find the coordinates of image regions containing text lines. This can be useful for highlighting detected areas when previewing an image or extracting individual blocks of text.

To get bounding boxes of all lines in images, provided in OcrInput object, use Aspose.OCR.AsposeOcr.DetectRectangles method. Specify Aspose.OCR.AreasType.LINES as the areasType parameter of the method.

Line detection works differently depending on the detectAreas parameter of the method:

detectAreas	Behavior
true	The OCR engine tries to break the content into paragraphs and then extracts lines from the found paragraphs. Best suited for multi-column texts - adjacent lines in different columns will be treated as separate lines rather than a single line.
false	The OCR engine ignores the columns and combines adjacent lines from different columns into a single line. This can be useful when concatenating text from table rows.

The method returns a list of Aspose.OCR.RectangleOutput objects containing coordinates of each line in each image.

PDF documents can contain more than one image per page. Therefore, the resulting list can contain more Aspose.OCR.RectangleOutput objects than the number of pages in the document.

Property	Type	Description
Rectangles	List<Rectangle>	Coordinates of each line of an image (top-left corner, width and height), returned as a list of Rectangle objects.
ImageIndex	int	Sequence number of the image on the page. When working with single-page images, this value is always 0.
Page	int	Page number. When working with single-page images, this value is always 0.
Source	string	The full path or URL of the source file. If the file is provided as a MemoryStream object, an array of pixels, or a Base64 string, this value will be empty.

Example

The following code example shows how to detect lines in multiple images:

Aspose.OCR.AsposeOcr recognitionEngine = new Aspose.OCR.AsposeOcr();
// Add images to OcrInput object
Aspose.OCR.OcrInput input = new Aspose.OCR.OcrInput(Aspose.OCR.InputType.SingleImage);
input.Add("source1.png");
input.Add("source2.jpg");
// Detect lines
List<Aspose.OCR.RectangleOutput> results = recognitionEngine.DetectRectangles(input, Aspose.OCR.AreasType.LINES, true);
foreach(Aspose.OCR.RecognitionResult result in results)
{
	foreach(Rectangle region in result.Rectangles) Console.WriteLine($"File: {result.Source} | {region.Top}, {region.Left}, {region.Width}, {region.Height}");
}