FPDF_ClosePage

FPDF_ClosePage(page)

Description

Closes a PDF page and releases all resources associated with it. This function must be called when you’re done with a page that was opened with FPDF_LoadPage.

Failing to call this function will result in memory leaks in your application.

Prerequisites

This example uses the initializePdfium helper function from our Getting Started guide. Make sure to include this function in your code before trying the examples below.

Parameters

Return Value

This function does not return a value.

Example

// Note: The initializePdfium function is a helper that initializes the PDFium library.
// For the full implementation, see: /docs/pdfium/getting-started
import { initializePdfium } from './initialize-pdfium';
 
async function renderPdfPage(pdfData: Uint8Array, pageIndex: number) {
  // Initialize PDFium
  const pdfium = await initializePdfium();
  
  // Allocate memory for the PDF data
  const filePtr = pdfium.pdfium.wasmExports.malloc(pdfData.length);
  pdfium.pdfium.HEAPU8.set(pdfData, filePtr);
  
  // Load the PDF document
  const docPtr = pdfium.FPDF_LoadMemDocument(filePtr, pdfData.length, 0);
  
  if (!docPtr) {
    const error = pdfium.FPDF_GetLastError();
    pdfium.pdfium.wasmExports.free(filePtr);
    throw new Error(`Failed to load PDF: ${error}`);
  }
  
  try {
    // Check page count
    const pageCount = pdfium.FPDF_GetPageCount(docPtr);
    
    if (pageIndex < 0 || pageIndex >= pageCount) {
      throw new Error(`Invalid page index: ${pageIndex}. Document has ${pageCount} pages.`);
    }
    
    // Load the page
    const pagePtr = pdfium.FPDF_LoadPage(docPtr, pageIndex);
    
    if (!pagePtr) {
      throw new Error(`Failed to load page ${pageIndex}`);
    }
    
    try {
      // Perform operations with the page...
      const width = pdfium.FPDF_GetPageWidthF(pagePtr);
      const height = pdfium.FPDF_GetPageHeightF(pagePtr);
      
      console.log(`Page ${pageIndex} dimensions: ${width} x ${height} points`);
      
      // More page operations...
      
    } finally {
      // Always close the page when done
      pdfium.FPDF_ClosePage(pagePtr);
    }
  } finally {
    // Clean up document resources
    pdfium.FPDF_CloseDocument(docPtr);
    pdfium.pdfium.wasmExports.free(filePtr);
  }
}
 
// Usage
fetch('sample.pdf')
  .then(response => response.arrayBuffer())
  .then(buffer => renderPdfPage(new Uint8Array(buffer), 0))
  .catch(error => console.error('Error:', error));

Best Practices

1. Always close pages: Call FPDF_ClosePage for every page you open, even if operations on the page fail. This prevents memory leaks.

2. Use try/finally blocks: Place your page operations inside a try block and the FPDF_ClosePage call in a finally block to ensure the page is closed even if exceptions occur:

   const pagePtr = pdfium.FPDF_LoadPage(docPtr, pageIndex);
   try {
     // Operate on the page...
   } finally {
     pdfium.FPDF_ClosePage(pagePtr);
   }

3. Close in the correct order: If you have opened multiple resources from a page (e.g., text pages), close them in the reverse order before closing the page:

   • Close text pages with FPDFText_ClosePage
   • Finally, close the page with FPDF_ClosePage

4. Don’t use the page after closing: After calling FPDF_ClosePage, the page handle is no longer valid. Any attempts to use it will result in undefined behavior and likely crashes.

5. Batch processing: When processing multiple pages, open and close them sequentially rather than keeping many pages open simultaneously, which can consume a lot of memory.

Common Issues

1. Memory leaks: The most common issue is forgetting to close pages, especially in error cases. This leads to memory leaks that can eventually crash your application.

2. Invalid page handles: Using a page handle after it has been closed can cause crashes or other unexpected behavior.

3. Rendering artifacts: If you’re rendering pages to a bitmap, make sure to close the page after rendering is complete. Not closing the page can sometimes lead to rendering artifacts when rendering subsequent pages.

Related Functions

• FPDF_LoadPage - Load a page from a document
• FPDF_LoadMemDocument - Load a PDF document from memory
• FPDF_CloseDocument - Close a document and release resources
• FPDFText_LoadPage - Load a page for text extraction