Working with Vector Graphics
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In this chapter, we’ll explore how to use the powerful GraphicsAbsorber class to interact with vector graphics within PDF documents. Whether you need to move, remove, or add graphics, this guide will show you how to perform these tasks effectively.
Introduction
Vector graphics are a crucial component of many PDF documents, used to represent images, shapes, and other graphical elements. Aspose.PDF provides the GraphicsAbsorber class, which allows developers to programmatically access and manipulate these graphics. By using the Visit method of GraphicsAbsorber, you can extract vector graphics from a specified page and perform various operations, such as moving, removing, or copying them to other pages.
Extracting Graphics with GraphicsAbsorber
The first step in working with vector graphics is to extract them from a PDF document. Here’s how you can do it using the GraphicsAbsorber class:
private static void UsingGraphicsAbsorber()
{
// Step 1: The path to the document directory
var dataDir = RunExamples.GetDataDir_AsposePdf_Images();
// Step 2: Open the document using 'using' block to ensure proper disposal
using (var document = new Aspose.Pdf.Document(dataDir + "DocumentWithVectorGraphics.pdf"))
{
// Step 3: Create an instance of GraphicsAbsorber
using (var graphicsAbsorber = new Aspose.Pdf.Vector.GraphicsAbsorber())
{
// Select the first page of the document
var page = document.Pages[1];
// Step 4: Use the `Visit` method to extract graphics from the page
graphicsAbsorber.Visit(page);
// Step 5: Display information about the extracted elements
foreach (var element in graphicsAbsorber.Elements)
{
Console.WriteLine($"Page Number: {element.SourcePage.Number}");
Console.WriteLine($"Position: ({element.Position.X}, {element.Position.Y})");
Console.WriteLine($"Number of Operators: {element.Operators.Count}");
}
}
}
}
- Create a Document Object: A new
Documentobject is instantiated with the path to the target PDF file. - Create an Instance of
GraphicsAbsorber: This class captures all graphics elements from a specified page. - Visit Method: The
Visitmethod is called on the first page, allowingGraphicsAbsorberto absorb the vector graphics. - Iterate Through Extracted Elements: The code loops through each extracted element, printing information such as page number, position, and the number of drawing operators involved.
Moving Graphics
Once you have extracted the graphics, you can move them to a different position on the same page. Here’s how you can achieve this:
private static void MoveGraphics()
{
// The path to the document directory
var dataDir = RunExamples.GetDataDir_AsposePdf_Images();
// Open document using 'using' block to ensure proper disposal
using (var document = new Aspose.Pdf.Document(dataDir + "DocumentWithVectorGraphics.pdf"))
{
// Create a GraphicsAbsorber instance using 'using' block
using (var graphicsAbsorber = new Aspose.Pdf.Vector.GraphicsAbsorber())
{
// Select the first page of the document
var page = document.Pages[1];
// Extract graphic elements from the page
graphicsAbsorber.Visit(page);
// Temporarily suspend updates to improve performance
graphicsAbsorber.SuppressUpdate();
// Loop through each extracted graphic element and shift its position
foreach (var element in graphicsAbsorber.Elements)
{
var position = element.Position;
// Move graphics by shifting its X and Y coordinates
element.Position = new Aspose.Pdf.Point(position.X + 150, position.Y - 10);
}
// Resume updates and apply changes
graphicsAbsorber.ResumeUpdate();
}
// Save the modified document
document.Save(dataDir + "DocumentWithVectorGraphics_out.pdf");
}
}
- SuppressUpdate: This method temporarily suspends updates to improve performance when making multiple changes.
- ResumeUpdate: This method resumes updates and applies changes made to the graphics’ positions.
- Element Positioning: The position of each graphic is adjusted by changing its
XandYcoordinates.
Removing Graphics
There are scenarios where you might want to remove specific graphics from a page. Aspose.PDF offers two methods to accomplish this:
Method 1: Using Rectangle Boundary
private static void RemoveGraphicsMethod1()
{
// The path to the document directory
var dataDir = RunExamples.GetDataDir_AsposePdf_Images();
// Open the document using 'using' block to ensure proper disposal
using (var document = new Aspose.Pdf.Document(dataDir + "DocumentWithVectorGraphics.pdf"))
{
// Create an instance of GraphicsAbsorber using 'using' block
using (var graphicsAbsorber = new Aspose.Pdf.Vector.GraphicsAbsorber())
{
// Get the first page of the document
var page = document.Pages[1];
// Extract graphic elements from the page
graphicsAbsorber.Visit(page);
// Define the rectangle where graphics will be removed
var rectangle = new Aspose.Pdf.Rectangle(70, 248, 170, 252);
// Temporarily suspend updates for better performance
graphicsAbsorber.SuppressUpdate();
// Iterate through the extracted graphic elements and remove elements inside the rectangle
foreach (var element in graphicsAbsorber.Elements)
{
// Check if the graphic's position falls within the rectangle
if (rectangle.Contains(element.Position))
{
// Remove the graphic element
element.Remove();
}
}
// Resume updates and apply changes
graphicsAbsorber.ResumeUpdate();
}
// Save the modified document with '_out' suffix
document.Save(dataDir + "DocumentWithVectorGraphics_out.pdf");
}
}
Method 2: Using a Collection of Removed Elements
private static void RemoveGraphicsMethod2()
{
// The path to the document directory
var dataDir = RunExamples.GetDataDir_AsposePdf_Images();
// Open document using 'using' block to ensure proper disposal
using (var document = new Aspose.Pdf.Document(dataDir + "DocumentWithVectorGraphics.pdf"))
{
// Create an instance of GraphicsAbsorber using 'using' block
using (var graphicsAbsorber = new Aspose.Pdf.Vector.GraphicsAbsorber())
{
// Get the first page of the document
var page = document.Pages[1];
// Define the rectangle where graphics will be removed
var rectangle = new Aspose.Pdf.Rectangle(70, 248, 170, 252);
// Extract graphic elements from the page
graphicsAbsorber.Visit(page);
// Create a collection for the removed elements
var removedElementsCollection = new Aspose.Pdf.Vector.GraphicElementCollection();
// Add elements within the rectangle to the collection
foreach (var item in graphicsAbsorber.Elements.Where(el => rectangle.Contains(el.Position)))
{
removedElementsCollection.Add(item);
}
// Temporarily suppress updates for better performance
page.Contents.SuppressUpdate();
// Delete the selected graphic elements
page.DeleteGraphics(removedElementsCollection);
// Resume updates and apply changes
page.Contents.ResumeUpdate();
}
// Save the updated document with '_out' suffix
document.Save(dataDir + "DocumentWithVectorGraphics_out.pdf");
}
}
- Rectangle Boundary: Define a rectangle area to specify which graphics to remove.
- Suppress and Resume Updates: Ensure efficient removal without intermediate rendering.
Adding Graphics to Another Page
Graphics absorbed from one page can be added to another page within the same document. Here are two methods to achieve this:
Method 1: Adding Graphics Individually
private static void AddToAnotherPageMethod1()
{
// The path to the document directory
var dataDir = RunExamples.GetDataDir_AsposePdf_Images();
// Open document using 'using' block to ensure proper disposal
using (var document = new Aspose.Pdf.Document(dataDir + "DocumentWithVectorGraphics.pdf"))
{
// Create a GraphicsAbsorber instance using 'using' block
using (var graphicsAbsorber = new Aspose.Pdf.Vector.GraphicsAbsorber())
{
// Get the first and second pages
var page1 = document.Pages[1];
var page2 = document.Pages[2];
// Extract graphic elements from the first page
graphicsAbsorber.Visit(page1);
// Temporarily suppress updates for better performance
page2.Contents.SuppressUpdate();
// Add each graphic element from the first page to the second page
foreach (var element in graphicsAbsorber.Elements)
{
element.AddOnPage(page2); // Add each graphic element to the second page.
}
// Resume updates and apply changes
page2.Contents.ResumeUpdate();
}
// Save the updated document with '_out' suffix
document.Save(dataDir + "DocumentWithVectorGraphics_out.pdf");
}
}
Method 2: Adding Graphics as a Collection
private static void AddToAnotherPageMethod2()
{
// The path to the document directory
var dataDir = RunExamples.GetDataDir_AsposePdf_Images();
// Open document using 'using' block to ensure proper disposal
using (var document = new Aspose.Pdf.Document(dataDir + "DocumentWithVectorGraphics.pdf"))
{
// Create a GraphicsAbsorber instance using 'using' block
using (var graphicsAbsorber = new Aspose.Pdf.Vector.GraphicsAbsorber())
{
// Get the first and second pages
var page1 = document.Pages[1];
var page2 = document.Pages[2];
// Extract graphic elements from the first page
graphicsAbsorber.Visit(page1);
// Temporarily suppress updates for better performance
page2.Contents.SuppressUpdate();
// Add all graphics at once from the first page to the second page
page2.AddGraphics(graphicsAbsorber.Elements);
// Resume updates and apply changes
page2.Contents.ResumeUpdate();
}
// Save the updated document with '_out' suffix
document.Save(dataDir + "DocumentWithVectorGraphics_out.pdf");
}
}
- SuppressUpdate and ResumeUpdate: These methods help in maintaining performance while making bulk changes.
- AddOnPage vs. AddGraphics: Use
AddOnPagefor individual additions andAddGraphicsfor bulk additions.