How to Efficiently Merge Multiple PDFs While Removing Excess Whitespace?

How to Remove Whitespace on Merge

When merging PDF documents, often there is a need to remove the vertical or horizontal whitespace between pages to create a seamless document. This question discusses a scenario where three separate PDF documents are merged, but each document is considered a full page even if it only contains a small amount of content, resulting in large amounts of whitespace. The goal is to eliminate this whitespace while preserving the content of each document.

Solution: PdfVeryDenseMergeTool

To achieve the desired result, a custom tool named PdfVeryDenseMergeTool is introduced. This tool aims to densely merge the contents of multiple pages onto a single page, even if they do not completely fit. The tool operates as follows:

1. Vertical Analysis: The tool analyzes each page vertically to identify the sections containing content and any empty space above or below it.
2. Splitting Pages: If a page cannot fit entirely onto the target page, the tool intelligently splits the page at a horizontal line that does not intersect any content.
3. Reassembling Pages: The split sections from multiple pages are then reassembled onto a single target page, minimizing the amount of whitespace while optimizing content placement.

Comparison to PdfDenseMergeTool

The PdfVeryDenseMergeTool shares similarities with the PdfDenseMergeTool mentioned in the original question. Both tools attempt to merge PDF pages densely. However, the PdfVeryDenseMergeTool offers enhancements by:

• Splitting pages horizontally to allow for even denser merging.
• Prioritizing content placement over attempting to squeeze everything onto a single page, resulting in a more readable and usable merged document.
• Handling cases where pages are rotated or have complex content.

Code Example

Here's a simplified example of how to use the PdfVeryDenseMergeTool in Java:

PdfVeryDenseMergeTool tool = new PdfVeryDenseMergeTool(PageSize.A4, 18, 18, 10);
List<byte[]> files = ... // Load the three PDF byte arrays here

try (MemoryStream ms = new MemoryStream()) {
  List<PdfReader> readers = new List<PdfReader>();
  foreach (byte[] ba in files) {
    readers.Add(new PdfReader(ba));
  }

  tool.Merge(ms, readers);

  // Save the final merged document using ms.GetBuffer()
}

Note: Translating this tool to C# and integrating it with iTextSharp should be straightforward.

By utilizing the PdfVeryDenseMergeTool, you can efficiently merge multiple PDF documents while eliminating unnecessary whitespace and preserving the integrity of the content. This results in a seamless and optimized merged document that is easier to read and navigate.

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