Extract Border In PDF File

In this tutorial, we are going to learn how to extract the border in PDF file using Aspose.PDF for .NET. We will explain the source code in C# step by step. At the end of this tutorial, you will know how to extract the border from a PDF document and save it as an image. Let’s start!

Step 1: Setting up the environment

First, make sure you’ve set up your C# development environment with Aspose.PDF for .NET. Add the reference to the library and import the necessary namespaces.

Step 2: Loading the PDF Document

In this step, we load the PDF document from the specified file.

Document doc = new Document(dataDir + "input.pdf");

Be sure to replace “YOUR DOCUMENT DIRECTORY” with the actual directory where your PDF file is located.

Step 3: Edge Extraction

We will extract the border from the PDF document by iterating over the operations contained in the document.

Stack graphicsState = new Stack();
System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap((int)doc.Pages[1].PageInfo.Width, (int)doc.Pages[1].PageInfo.Height);
System.Drawing.Drawing2D.GraphicsPath graphicsPath = new System.Drawing.Drawing2D.GraphicsPath();
System.Drawing.Drawing2D.Matrix lastCTM = new System.Drawing.Drawing2D.Matrix(1, 0, 0, -1, 0, 0);
System.Drawing.Drawing2D.Matrix inversionMatrix = new System.Drawing.Drawing2D.Matrix(1, 0, 0, -1, 0, (float)doc.Pages[1].PageInfo.Height);
System.Drawing.PointF lastPoint = new System.Drawing.PointF(0, 0);
System.Drawing.Color fillColor = System.Drawing.Color.FromArgb(0, 0, 0);
System.Drawing.Color strokeColor = System.Drawing.Color.FromArgb(0, 0, 0);

using (System.Drawing.Graphics gr = System.Drawing.Graphics.FromImage(bitmap))
{
     // Process all content operations
     foreach(Operator op in doc.Pages[1].Contents)
     {
         // Check the type of operation
         // ...
         // Add code to process each operation
     }
}

We create a graphicsState stack to store graphics states, a bitmap image to capture the extracted border, a GraphicsPath object to store drawing paths, and other variables to track state and colors.

Step 4: Transaction Processing

In this step, we process each operation of the document to extract the border.

// Check the type of operation
if (opSaveState != null)
{
     // Save the previous state and push the current state to the top of the stack
     graphicsState.Push(((System.Drawing.Drawing2D.Matrix)graphicsState.Peek()).Clone());
     lastCTM = (System.Drawing.Drawing2D.Matrix)graphicsState.Peek();
}
else if (opRestoreState != null)
{
     // Delete the current state and restore previous state
     graphicsState. Pop();
     lastCTM = (System.Drawing.Drawing2D.Matrix)graphicsState.Peek();
}
else if (opCtm != null)
{
     // Retrieve the current transformation matrix
     System.Drawing.Drawing2D.Matrix cm = new System.Drawing.Drawing2D.Matrix(
         (float)opCtm.Matrix.A,
         (float)opCtm.Matrix.B,
         (float)opCtm.Matrix.C,
         (float)opCtm.Matrix.D,
         (float)opCtm.Matrix.E,
         (float)opCtm.Matrix.F);

     // Multiply the current matrix with the state matrix
     ((System.Drawing.Drawing2D.Matrix)graphicsState.Peek()).Multiply(cm);
     lastCTM = (System.Drawing.Drawing2D.Matrix)graphicsState.Peek();
}
else if (opMoveTo != null)
{
     // Update the last drawing point
     lastPoint = new System.Drawing.PointF((float)opMoveTo.X, (float)opMoveTo.Y);
}
else if (opLineTo != null)
{
     // Process the drawing of a line
     // ...
     // Add code to handle drawing a line
}
// ...
// Add else if blocks for other operations

We check the type of operation using conditions and run the appropriate code for each operation.

Step 5: Backup Image

Finally, we save the bitmap image containing the extracted border to a specified file.

dataDir = dataDir + "ExtractBorder_out.png";
bitmap.Save(dataDir, ImageFormat.Png);

Be sure to specify the correct directory and filename to save the output image.

Example source code for Extract Border using Aspose.PDF for .NET

// The path to the documents directory.
string dataDir = "YOUR DOCUMENT DIRECTORY";

Document doc = new Document(dataDir + "input.pdf");

Stack graphicsState = new Stack();
System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap((int)doc.Pages[1].PageInfo.Width, (int)doc.Pages[1].PageInfo.Height);
System.Drawing.Drawing2D.GraphicsPath graphicsPath = new System.Drawing.Drawing2D.GraphicsPath();
// Default ctm matrix value is 1,0,0,1,0,0
System.Drawing.Drawing2D.Matrix lastCTM = new System.Drawing.Drawing2D.Matrix(1, 0, 0, -1, 0, 0);
// System.Drawing coordinate system is top left based, while pdf coordinate system is low left based, so we have to apply the inversion matrix
System.Drawing.Drawing2D.Matrix inversionMatrix = new System.Drawing.Drawing2D.Matrix(1, 0, 0, -1, 0, (float)doc.Pages[1].PageInfo.Height);
System.Drawing.PointF lastPoint = new System.Drawing.PointF(0, 0);
System.Drawing.Color fillColor = System.Drawing.Color.FromArgb(0, 0, 0);
System.Drawing.Color strokeColor = System.Drawing.Color.FromArgb(0, 0, 0);

using (System.Drawing.Graphics gr = System.Drawing.Graphics.FromImage(bitmap))
{
	gr.SmoothingMode = SmoothingMode.HighQuality;
	graphicsState.Push(new System.Drawing.Drawing2D.Matrix(1, 0, 0, 1, 0, 0));

	// Process all the contents commands
	foreach (Operator op in doc.Pages[1].Contents)
	{
		Aspose.Pdf.Operators.GSave opSaveState = op as Aspose.Pdf.Operators.GSave;
		Aspose.Pdf.Operators.GRestore opRestoreState = op as Aspose.Pdf.Operators.GRestore;
		Aspose.Pdf.Operators.ConcatenateMatrix opCtm = op as Aspose.Pdf.Operators.ConcatenateMatrix;
		Aspose.Pdf.Operators.MoveTo opMoveTo = op as Aspose.Pdf.Operators.MoveTo;
		Aspose.Pdf.Operators.LineTo opLineTo = op as Aspose.Pdf.Operators.LineTo;
		Aspose.Pdf.Operators.Re opRe = op as Aspose.Pdf.Operators.Re;
		Aspose.Pdf.Operators.EndPath opEndPath = op as Aspose.Pdf.Operators.EndPath;
		Aspose.Pdf.Operators.Stroke opStroke = op as Aspose.Pdf.Operators.Stroke;
		Aspose.Pdf.Operators.Fill opFill = op as Aspose.Pdf.Operators.Fill;
		Aspose.Pdf.Operators.EOFill opEOFill = op as Aspose.Pdf.Operators.EOFill;
		Aspose.Pdf.Operators.SetRGBColor opRGBFillColor = op as Aspose.Pdf.Operators.SetRGBColor;
		Aspose.Pdf.Operators.SetRGBColorStroke opRGBStrokeColor = op as Aspose.Pdf.Operators.SetRGBColorStroke;

		if (opSaveState != null)
		{
			// Save previous state and push current state to the top of the stack
			graphicsState.Push(((System.Drawing.Drawing2D.Matrix)graphicsState.Peek()).Clone());
			lastCTM = (System.Drawing.Drawing2D.Matrix)graphicsState.Peek();
		}
		else if (opRestoreState != null)
		{
			// Throw away current state and restore previous one
			graphicsState.Pop();
			lastCTM = (System.Drawing.Drawing2D.Matrix)graphicsState.Peek();
		}
		else if (opCtm != null)
		{
			System.Drawing.Drawing2D.Matrix cm = new System.Drawing.Drawing2D.Matrix(
				(float)opCtm.Matrix.A,
				(float)opCtm.Matrix.B,
				(float)opCtm.Matrix.C,
				(float)opCtm.Matrix.D,
				(float)opCtm.Matrix.E,
				(float)opCtm.Matrix.F);

			// Multiply current matrix with the state matrix
			((System.Drawing.Drawing2D.Matrix)graphicsState.Peek()).Multiply(cm);
			lastCTM = (System.Drawing.Drawing2D.Matrix)graphicsState.Peek();
		}
		else if (opMoveTo != null)
		{
			lastPoint = new System.Drawing.PointF((float)opMoveTo.X, (float)opMoveTo.Y);
		}
		else if (opLineTo != null)
		{
			System.Drawing.PointF linePoint = new System.Drawing.PointF((float)opLineTo.X, (float)opLineTo.Y);
			graphicsPath.AddLine(lastPoint, linePoint);

			lastPoint = linePoint;
		}
		else if (opRe != null)
		{
			System.Drawing.RectangleF re = new System.Drawing.RectangleF((float)opRe.X, (float)opRe.Y, (float)opRe.Width, (float)opRe.Height);
			graphicsPath.AddRectangle(re);
		}
		else if (opEndPath != null)
		{
			graphicsPath = new System.Drawing.Drawing2D.GraphicsPath();
		}
		else if (opRGBFillColor != null)
		{
			fillColor = opRGBFillColor.getColor();
		}
		else if (opRGBStrokeColor != null)
		{
			strokeColor = opRGBStrokeColor.getColor();
		}
		else if (opStroke != null)
		{
			graphicsPath.Transform(lastCTM);
			graphicsPath.Transform(inversionMatrix);
			gr.DrawPath(new System.Drawing.Pen(strokeColor), graphicsPath);
			graphicsPath = new System.Drawing.Drawing2D.GraphicsPath();
		}
		else if (opFill != null)
		{
			graphicsPath.FillMode = FillMode.Winding;
			graphicsPath.Transform(lastCTM);
			graphicsPath.Transform(inversionMatrix);
			gr.FillPath(new System.Drawing.SolidBrush(fillColor), graphicsPath);
			graphicsPath = new System.Drawing.Drawing2D.GraphicsPath();
		}
		else if (opEOFill != null)
		{
			graphicsPath.FillMode = FillMode.Alternate;
			graphicsPath.Transform(lastCTM);
			graphicsPath.Transform(inversionMatrix);
			gr.FillPath(new System.Drawing.SolidBrush(fillColor), graphicsPath);
			graphicsPath = new System.Drawing.Drawing2D.GraphicsPath();
		}
	}
}
dataDir = dataDir + "ExtractBorder_out.png";
bitmap.Save(dataDir, ImageFormat.Png);

Console.WriteLine("\nBorder extracted successfully as image.\nFile saved at " + dataDir);

Conclusion

In this tutorial, we learned how to extract the border from a PDF document using Aspose.PDF for .NET. You can use this step-by-step guide to extract border from other PDF documents.

FAQ’s for extract border in PDF file

Q: What is the purpose of extracting the border from a PDF file?

A: Extracting the border from a PDF file can be useful for various purposes. It allows you to isolate and analyze the structural elements of the document, such as tables, diagrams, or graphical elements. You can use the extracted border to identify the layout, dimensions, and positioning of the content within the PDF document.

Q: Can I extract the border from specific pages or areas within the PDF document?

A: Yes, you can modify the provided C# source code to extract the border from specific pages or regions within the PDF document. By manipulating the doc.Pages collection and specifying custom criteria, you can choose to extract the border from particular pages or areas of interest.

Q: How can I customize the output image format and quality?

A: In the provided C# code, the extracted border is saved as a PNG image. If you want to change the output image format, you can modify the ImageFormat.Png parameter in the bitmap.Save method to other supported image formats, such as JPEG, BMP, or GIF. Additionally, you can adjust the image quality or compression settings based on your requirements.

Q: What other operations can I perform on the extracted border?

A: Once you have extracted the border as an image, you can further process it using image processing libraries or algorithms. You can analyze the image, apply image filters, detect patterns, or perform OCR (Optical Character Recognition) to extract text from the image if needed.

Q: Are there any limitations or considerations when extracting borders from complex PDF documents?

A: The extraction process may vary depending on the complexity of the PDF document. Complex PDFs with multiple layers, transparency, or advanced graphics might require additional processing or adjustments to accurately extract the border. It’s essential to thoroughly test the extraction process on various PDF documents to ensure reliable results.

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