Scaling PDF Pages by 70% using losLab PDF Library, in Delphi, C# & VB.Net

Problem Statement

We need to scale down each page of a PDF document by 70% while maintaining the original page order. This requires:

Loading the PDF file.
Capturing and scaling each page.
Saving the scaled pages into a new PDF file.

Steps to Achieve the Goal

Initialize the Environment:
- Load the original PDF file.
- Delete any previously existing output file to avoid conflicts.
Set Up the Scaling Parameters:
- Define the scaling factor (70%).
- Calculate the borders required to center the scaled content.
Process Each Page in a Loop:
- Select the first page.
- Capture the page content.
- Create a new page with the original dimensions.
- Draw the captured, scaled content onto the new page.
- Repeat for all pages.
Save the New PDF and Open it:
- Save the modified pages into a new PDF file.
- Automatically open the new PDF to review the results.

Code Implementation

Here is the C# code that performs the above steps:

private void button_Click(object sender, EventArgs e)
{
    // Delete the old file if it exists to avoid any conflicts.
    File.Delete("newpages.pdf");

    // Define variables for page dimensions and scaling factors.
    double pageWidth, pageHeight, horizBorder, vertBorder;
    double scaleFactor = 0.70; // 70% scaling reduction.
    int capturedPageId;
    int ret;

    // Load the original PDF document.
    PDFL.LoadFromFile("Pages.pdf");
    PDFL.SetOrigin(1);

    // Get the total number of pages in the document.
    int numPages = PDFL.PageCount();

    // Loop through all pages to process each one.
    for (int i = 1; i <= numPages; i++)
    {
        // Always select the first page as the pages get deleted after capture.
        PDFL.SelectPage(1);

        // Retrieve the dimensions of the current page.
        pageWidth = PDFL.PageWidth();
        pageHeight = PDFL.PageHeight();

        // Calculate the borders to center the scaled page content.
        horizBorder = pageWidth * (1.0 - scaleFactor) / 2;
        vertBorder = pageHeight * (1.0 - scaleFactor) / 2;

        // Capture the content of the first page. This action deletes the page from the document.
        capturedPageId = PDFL.CapturePage(1);

        // Create a new page with the original dimensions.
        int pageId = PDFL.NewPage();
        PDFL.SetPageDimensions(pageWidth, pageHeight);

        // Draw the captured page content onto the new page with the specified scaling.
        ret = PDFL.DrawCapturedPage(capturedPageId, horizBorder, vertBorder, pageWidth - 2 * horizBorder, pageHeight - 2 * vertBorder);
    }

    // Save the modified document as a new PDF file.
    PDFL.SaveToFile("newpages.pdf");

    // Open the newly created PDF file for review.
    System.Diagnostics.Process.Start(@"newpages.pdf");

private void button_Click(object sender, EventArgs e)

{

// Delete the old file if it exists to avoid any conflicts.

File.Delete("newpages.pdf");

// Define variables for page dimensions and scaling factors.

double pageWidth, pageHeight, horizBorder, vertBorder;

double scaleFactor = 0.70; // 70% scaling reduction.

int capturedPageId;

int ret;

// Load the original PDF document.

PDFL.LoadFromFile("Pages.pdf");

PDFL.SetOrigin(1);

// Get the total number of pages in the document.

int numPages = PDFL.PageCount();

// Loop through all pages to process each one.

for (int i = 1; i <= numPages; i++)

{

// Always select the first page as the pages get deleted after capture.

PDFL.SelectPage(1);

// Retrieve the dimensions of the current page.

pageWidth = PDFL.PageWidth();

pageHeight = PDFL.PageHeight();

// Calculate the borders to center the scaled page content.

horizBorder = pageWidth * (1.0 - scaleFactor) / 2;

vertBorder = pageHeight * (1.0 - scaleFactor) / 2;

// Capture the content of the first page. This action deletes the page from the document.

capturedPageId = PDFL.CapturePage(1);

// Create a new page with the original dimensions.

int pageId = PDFL.NewPage();

PDFL.SetPageDimensions(pageWidth, pageHeight);

// Draw the captured page content onto the new page with the specified scaling.

ret = PDFL.DrawCapturedPage(capturedPageId, horizBorder, vertBorder, pageWidth - 2 * horizBorder, pageHeight - 2 * vertBorder);

}

// Save the modified document as a new PDF file.

PDFL.SaveToFile("newpages.pdf");

// Open the newly created PDF file for review.

System.Diagnostics.Process.Start(@"newpages.pdf");

Explanation and Justification

File Deletion: Ensures that any previous output is cleared to prevent errors or outdated content.
Scaling Factor: Set to 0.70, this reduces the size of the content to 70% of the original.
Border Calculation: Centers the scaled content within the original page dimensions.
Page Processing Loop: Iterates through all pages, capturing, scaling, and drawing each one in sequence.
File Saving and Opening: Finalizes the new document and opens it for the user to verify the changes.

By following this structured approach, we ensure that each page in the PDF is scaled consistently and maintains its original order, resulting in a professionally processed document.

Delphi edition:

Use Delphi to Scale PDF pages by 70%:

procedure TForm1.ButtonClick(Sender: TObject);
var
  pageWidth, pageHeight, horizBorder, vertBorder: Double;
  scaleFactor: Double;
  capturedPageId, ret: Integer;
  numPages, pageId, i: Integer;
begin
  // Delete the old file if it exists to avoid any conflicts.
  if FileExists('newpages.pdf') then
    DeleteFile('newpages.pdf');

  // Define the scaling factor (70%).
  scaleFactor := 0.70; // 70% scaling reduction.

  // Load the original PDF document.
  PDFL.LoadFromFile('Pages.pdf');
  PDFL.SetOrigin(1);

  // Get the total number of pages in the document.
  numPages := PDFL.PageCount();

  // Loop through all pages to process each one.
  for i := 1 to numPages do
  begin
    // Always select the first page as the pages get deleted after capture.
    PDFL.SelectPage(1);

    // Retrieve the dimensions of the current page.
    pageWidth := PDFL.PageWidth();
    pageHeight := PDFL.PageHeight();

    // Calculate the borders to center the scaled page content.
    horizBorder := pageWidth * (1.0 - scaleFactor) / 2;
    vertBorder := pageHeight * (1.0 - scaleFactor) / 2;

    // Capture the content of the first page. This action deletes the page from the document.
    capturedPageId := PDFL.CapturePage(1);

    // Create a new page with the original dimensions.
    pageId := PDFL.NewPage();
    PDFL.SetPageDimensions(pageWidth, pageHeight);

    // Draw the captured page content onto the new page with the specified scaling.
    ret := PDFL.DrawCapturedPage(capturedPageId, horizBorder, vertBorder, pageWidth - 2 * horizBorder, pageHeight - 2 * vertBorder);
  end;

  // Save the modified document as a new PDF file.
  PDFL.SaveToFile('newpages.pdf');

  // Open the newly created PDF file for review.
  ShellExecute(0, 'open', 'newpages.pdf', nil, nil, SW_SHOWNORMAL);
end;

procedure TForm1.ButtonClick(Sender: TObject);

var

pageWidth, pageHeight, horizBorder, vertBorder: Double;

scaleFactor: Double;

capturedPageId, ret: Integer;

numPages, pageId, i: Integer;

begin

// Delete the old file if it exists to avoid any conflicts.

if FileExists('newpages.pdf') then

DeleteFile('newpages.pdf');

// Define the scaling factor (70%).

scaleFactor := 0.70; // 70% scaling reduction.

// Load the original PDF document.

PDFL.LoadFromFile('Pages.pdf');

PDFL.SetOrigin(1);

// Get the total number of pages in the document.

numPages := PDFL.PageCount();

// Loop through all pages to process each one.

for i := 1 to numPages do

begin

// Always select the first page as the pages get deleted after capture.

PDFL.SelectPage(1);

// Retrieve the dimensions of the current page.

pageWidth := PDFL.PageWidth();

pageHeight := PDFL.PageHeight();

// Calculate the borders to center the scaled page content.

horizBorder := pageWidth * (1.0 - scaleFactor) / 2;

vertBorder := pageHeight * (1.0 - scaleFactor) / 2;

// Capture the content of the first page. This action deletes the page from the document.

capturedPageId := PDFL.CapturePage(1);

// Create a new page with the original dimensions.

pageId := PDFL.NewPage();

PDFL.SetPageDimensions(pageWidth, pageHeight);

// Draw the captured page content onto the new page with the specified scaling.

ret := PDFL.DrawCapturedPage(capturedPageId, horizBorder, vertBorder, pageWidth - 2 * horizBorder, pageHeight - 2 * vertBorder);

end;

// Save the modified document as a new PDF file.

PDFL.SaveToFile('newpages.pdf');

// Open the newly created PDF file for review.

ShellExecute(0, 'open', 'newpages.pdf', nil, nil, SW_SHOWNORMAL);

end;

VB.Net edition

Here is the VB.Net code to perform the task:

Private Sub button_Click(sender As Object, e As EventArgs) Handles button.Click
    ' Delete the old file if it exists to avoid any conflicts.
    If File.Exists("newpages.pdf") Then
        File.Delete("newpages.pdf")
    End If

    ' Define variables for page dimensions and scaling factors.
    Dim pageWidth, pageHeight, horizBorder, vertBorder As Double
    Dim scaleFactor As Double = 0.70 ' 70% scaling reduction.
    Dim capturedPageId, ret As Integer

    ' Load the original PDF document.
    PDFL.LoadFromFile("Pages.pdf")
    PDFL.SetOrigin(1)

    ' Get the total number of pages in the document.
    Dim numPages As Integer = PDFL.PageCount()

    ' Loop through all pages to process each one.
    For i As Integer = 1 To numPages
        ' Always select the first page as the pages get deleted after capture.
        PDFL.SelectPage(1)

        ' Retrieve the dimensions of the current page.
        pageWidth = PDFL.PageWidth()
        pageHeight = PDFL.PageHeight()

        ' Calculate the borders to center the scaled page content.
        horizBorder = pageWidth * (1.0 - scaleFactor) / 2
        vertBorder = pageHeight * (1.0 - scaleFactor) / 2

        ' Capture the content of the first page. This action deletes the page from the document.
        capturedPageId = PDFL.CapturePage(1)

        ' Create a new page with the original dimensions.
        Dim pageId As Integer = PDFL.NewPage()
        PDFL.SetPageDimensions(pageWidth, pageHeight)

        ' Draw the captured page content onto the new page with the specified scaling.
        ret = PDFL.DrawCapturedPage(capturedPageId, horizBorder, vertBorder, pageWidth - 2 * horizBorder, pageHeight - 2 * vertBorder)
    Next

    ' Save the modified document as a new PDF file.
    PDFL.SaveToFile("newpages.pdf")

    ' Open the newly created PDF file for review.
    Process.Start("newpages.pdf")
End Sub

Private Sub button_Click(sender As Object, e As EventArgs) Handles button.Click

' Delete the old file if it exists to avoid any conflicts.

If File.Exists("newpages.pdf") Then

File.Delete("newpages.pdf")

End If

' Define variables for page dimensions and scaling factors.

Dim pageWidth, pageHeight, horizBorder, vertBorder As Double

Dim scaleFactor As Double = 0.70 ' 70% scaling reduction.

Dim capturedPageId, ret As Integer

' Load the original PDF document.

PDFL.LoadFromFile("Pages.pdf")

PDFL.SetOrigin(1)

' Get the total number of pages in the document.

Dim numPages As Integer = PDFL.PageCount()

' Loop through all pages to process each one.

For i As Integer = 1 To numPages

' Always select the first page as the pages get deleted after capture.

PDFL.SelectPage(1)

' Retrieve the dimensions of the current page.

pageWidth = PDFL.PageWidth()

pageHeight = PDFL.PageHeight()

' Calculate the borders to center the scaled page content.

horizBorder = pageWidth * (1.0 - scaleFactor) / 2

vertBorder = pageHeight * (1.0 - scaleFactor) / 2

' Capture the content of the first page. This action deletes the page from the document.

capturedPageId = PDFL.CapturePage(1)

' Create a new page with the original dimensions.

Dim pageId As Integer = PDFL.NewPage()

PDFL.SetPageDimensions(pageWidth, pageHeight)

' Draw the captured page content onto the new page with the specified scaling.

ret = PDFL.DrawCapturedPage(capturedPageId, horizBorder, vertBorder, pageWidth - 2 * horizBorder, pageHeight - 2 * vertBorder)

' Save the modified document as a new PDF file.

PDFL.SaveToFile("newpages.pdf")

' Open the newly created PDF file for review.

Process.Start("newpages.pdf")

End Sub

Both VB.Net and Delphi versions of the code achieve the same result as the original C# code, ensuring that each page in the PDF is scaled down by 70% while maintaining the original order.

losLab Software