Fix Windows file:// URL path handling in image processing

[adamhj]

Problem

When using html2pptx on Windows with relative image paths in HTML files (e.g., <img src="assets/icon.png">), the image loading fails with a "file not found" error.

Root Cause:

When Playwright renders HTML, relative image paths are automatically converted to absolute file:// URLs. For example:

• Input: assets/icon.png
• After Playwright: file:///D:/project/slides/assets/icon.png

The existing code strips the file:// prefix:

let imagePath = el.src.startsWith('file://') ? el.src.replace('file://', '') : el.src;

However, this leaves a path like /D:/project/slides/assets/icon.png (note the leading slash). When PptxGenJS processes this path, it interprets it as a relative path and prepends the current working directory, resulting in a malformed path:

d:\D:\project\slides\assets\icon.png

Solution

Added a check to detect and fix Windows-style paths that start with /[drive-letter]:/:

// Fix Windows file:// paths: /D:/path -> D:/path
if (imagePath.match(/^\/[A-Za-z]:\//)) {
  imagePath = imagePath.substring(1);
}

This removes the leading slash, producing a valid Windows absolute path like D:/project/slides/assets/icon.png.

Testing

• Tested with relative image paths on Windows 10
• Verified that images are correctly embedded in generated PowerPoint files
• No impact on Unix/Linux paths (which don't match the /[A-Z]:/ pattern)

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