当用户尝试下载pdf文件时将水印应用于pdf文件 [英] Applying watermarks on pdf files when users try to download the files

问题描述

我学校的作业解决方案都在PDF上印有水印，并在上面印有我们的用户名.

The solutions for my school's assignments all have waterstamps on the PDFs with our username on it.

我想知道你们是否知道如何使用PHP做类似的事情?他们在下载过程之前运行脚本吗?

I was wondering if you guys know how to do something like that using PHP? Do they run a script prior to the download process?

谢谢.

推荐答案

尽管有一些非常好的PHP PDF库，但是如果我正在编写这样的程序，我将直接运行

Although there are several very good PDF libs for PHP, if I were writing such a program I'd just shell out to run pdftk but you' still need to generate your watermark.

$tempfile=tempnam();
system("pdftk input_file.pdf background watermark.pdf output $tempfile dont_ask", $errcode);
if (!$errcode && $ih=fopen($tempfile, 'r')) {
    header('Content-Type: application/pdf');
    fpassthru($ih);
    fclose($ih);
} else {
    print "Whoops";
}
unlink($tempfile);

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