Wie man PDF-Dateien in C# zuschneidet

IronPDF Installation

There are multiple ways to install IronPDF:

1. You can download IronPDF from the NuGet Package Manager solution in your C# project, which is created using Visual Studio. Access the NuGet Package Manager via Tools or by right-clicking on Solution Explorer. Browse for the IronPDF package and install it.
2. Another way to install IronPDF is by directly downloading it from the IronPDF NuGet Page.

Step 1: Load PDF Document

To load a PDF file from a local location into this project, IronPDF provides a FromFile method present in the PdfDocument class. The following code example demonstrates how to open an existing PDF file:

// Load an existing PDF document from a file
PdfDocument pdf = PdfDocument.FromFile("Input.pdf");

// Load an existing PDF document from a file
PdfDocument pdf = PdfDocument.FromFile("Input.pdf");

' Load an existing PDF document from a file
Dim pdf As PdfDocument = PdfDocument.FromFile("Input.pdf")

The loaded document is as follows:

A sample PDF barcode file

Step 2: Load a Specific Page from a PDF Document

Now that the file is opened for editing, create a separate PdfDocument object and store the specific page that needs to be cropped using the CopyPage method. Simply pass the index of the page that needs to be cropped. Here, the code sample will crop the first page of the PDF document.

// Copy the first page of the loaded PDF document
PdfDocument loadedPage = pdf.CopyPage(0);

// Copy the first page of the loaded PDF document
PdfDocument loadedPage = pdf.CopyPage(0);

' Copy the first page of the loaded PDF document
Dim loadedPage As PdfDocument = pdf.CopyPage(0)

Step 3: Convert the Loaded PDF Page to an Image

The Convert PDF Page to High-Resolution Image method provides the facility to save the PDF page to a high-resolution image file. The following code helps to convert the selected page to an image for cropping.

// Convert the PDF page to a high-resolution PNG image
loadedPage.RasterizeToImageFiles(@"C:\Image\Page_to_be_Cropped.png");

// Convert the PDF page to a high-resolution PNG image
loadedPage.RasterizeToImageFiles(@"C:\Image\Page_to_be_Cropped.png");

' Convert the PDF page to a high-resolution PNG image
loadedPage.RasterizeToImageFiles("C:\Image\Page_to_be_Cropped.png")

Now the page will be converted to an image file. The output is a high-quality PNG image.

The output high-quality PNG image file

Now, the specific page is separate from the original document and ready to be cropped.

Step 4: Retrieve the Dimensions of the Loaded Page

To crop the PDF, it is necessary to create a crop box with a certain width and height. For this purpose, a new document will be created using the ChromePdfRenderer class. It provides the option to customize the PDF page size according to the needs, and data is split evenly across pages.

Before creating a ChromePdfRenderer, first, get the dimensions of the loaded page in step 2. Then, use these dimensions while setting the custom page size for creating a crop box. The following code sample will help you to get the width and height of the page:

// Retrieve dimensions of the loaded PDF page
PdfPagesCollection pages = loadedPage.Pages;
PdfPage pdfPage = pages[0];

// Dimensions retrieved in mm
float width = pdfPage.Width;
float height = pdfPage.Height;

// Retrieve dimensions of the loaded PDF page
PdfPagesCollection pages = loadedPage.Pages;
PdfPage pdfPage = pages[0];

// Dimensions retrieved in mm
float width = pdfPage.Width;
float height = pdfPage.Height;

' Retrieve dimensions of the loaded PDF page
Dim pages As PdfPagesCollection = loadedPage.Pages
Dim pdfPage As PdfPage = pages(0)

' Dimensions retrieved in mm
Dim width As Single = pdfPage.Width
Dim height As Single = pdfPage.Height

Firstly, retrieve the total number of pages in the loaded PDF file using PdfPagesCollection. Then, pass that page to a PdfPage instance to get the page dimension values from the Width and Height properties of the page. All done! Now, let's move to the next step to create a custom crop box.

Step 5: Set the Custom PDF Page Size

The following code will help create a custom PDF paper size that will work as a crop box, to crop the content in different page segments.

// Create a ChromePdfRenderer to set up a custom paper size
ChromePdfRenderer pdfRenderer = new ChromePdfRenderer();
pdfRenderer.RenderingOptions.PaperSize = IronPdf.Rendering.PdfPaperSize.Custom;
pdfRenderer.RenderingOptions.SetCustomPaperSizeInMillimeters(width, height / 4);
pdfRenderer.RenderingOptions.ForcePaperSize = true;

// Create a ChromePdfRenderer to set up a custom paper size
ChromePdfRenderer pdfRenderer = new ChromePdfRenderer();
pdfRenderer.RenderingOptions.PaperSize = IronPdf.Rendering.PdfPaperSize.Custom;
pdfRenderer.RenderingOptions.SetCustomPaperSizeInMillimeters(width, height / 4);
pdfRenderer.RenderingOptions.ForcePaperSize = true;

' Create a ChromePdfRenderer to set up a custom paper size
Dim pdfRenderer As New ChromePdfRenderer()
pdfRenderer.RenderingOptions.PaperSize = IronPdf.Rendering.PdfPaperSize.Custom
'INSTANT VB WARNING: Instant VB cannot determine whether both operands of this division are integer types - if they are then you should use the VB integer division operator:
pdfRenderer.RenderingOptions.SetCustomPaperSizeInMillimeters(width, height / 4)
pdfRenderer.RenderingOptions.ForcePaperSize = True

In the above code, a ChromePdfRenderer is created, which is used to create a new PDF document. Then, the PdfPaperSize property value is set to Custom. Lastly, a custom page margin is set using the dimensions retrieved in step 4.

Set the width to the original page width and decrease the height by 1/4th of the original page length. This makes the page work as a rectangle-shaped media box for the content.

Note: You can use ForcePaperSize = true to make sure the custom size is applied. For setting custom margins, please visit this Customize PDF Margins Guide.

Step 6: Create a New Document using HTML

Now, this final step will create a new document using the custom page size PDF and the image saved from the loaded page.

// Render HTML to a PDF document with a custom paper size using the cropped image
var croppedPdf = pdfRenderer.RenderHtmlAsPdf("<img src='Page_to_be_Cropped.png'/>", @"C:\Image\");

// Render HTML to a PDF document with a custom paper size using the cropped image
var croppedPdf = pdfRenderer.RenderHtmlAsPdf("<img src='Page_to_be_Cropped.png'/>", @"C:\Image\");

' Render HTML to a PDF document with a custom paper size using the cropped image
Dim croppedPdf = pdfRenderer.RenderHtmlAsPdf("<img src='Page_to_be_Cropped.png'/>", "C:\Image\")

Now let's save the document using the SaveAs method.

// Save the newly cropped document
croppedPdf.SaveAs("Cropped.pdf");

// Save the newly cropped document
croppedPdf.SaveAs("Cropped.pdf");

' Save the newly cropped document
croppedPdf.SaveAs("Cropped.pdf")

Output

The cropped PDF file

From the output, you can see that a single image is now split into multiple pages with the custom trim box created. You can copy a specific page you need using the following code:

// Copy and save a specific page from the cropped document
croppedPdf.CopyPage(1).SaveAs("Cropped_Page1.pdf");

// Copy and save a specific page from the cropped document
croppedPdf.CopyPage(1).SaveAs("Cropped_Page1.pdf");

' Copy and save a specific page from the cropped document
croppedPdf.CopyPage(1).SaveAs("Cropped_Page1.pdf")