Convert the first n pages of a pdf file to a single png Image file using PHP ImageMagick library-CodePudding

I'm working with the PHP ImageMagick Library to convert uploaded pdf files to single png files so I can display the pdf as a single image on my Laravel webpage. So far I'm able to convert an entire pdf to a single image with this code:

<?php
  $imagick = new Imagick();
  $file = new File;
  // other lines of code
  // ...
  $imgPath = Storage::path($file->file_path);
  $imgSavePath = Storage::path('uploads/buffer/'.Str::beforeLast($file->name, '.').'.png');
  $imagick->readImage($imgPath);
  $imagick->resetIterator();
  $imagick = $imagick->appendImages(true);
  $imagick->writeImages($imgSavePath, true);

This works by producing a single png image. However, I find this to be resource intensive (storage wise) and time consuming because I'm delivering the functionality through an ajax call.

I want my web application to convert only the first n pages of the pdf (say first 5 pages) into a single image to act as a preview on the site - thereafter the user can download the entire pdf to view on their local system. The function should work regardless of the number of pages in an uploaded pdf document.

So far, I only find in the documentation where I can read a page at a particular index from the Imagick object and convert to an image using:

...
$imgPath = Storage::path($file->file_path);
$index = 5;
$imagick->readImage($imgPath. '[' . $index . ']');

However, I'm finding it difficult to refactor this so that the application can read the first n pages.

CodePudding user response：

Intuitively, the readImage() function seems to work in a similar way as the command line syntax. Thanks to the hint from @MarkSetchell in the comments:

<?php
  $imagick = new Imagick();
  $file = new File;
  // other lines of code
  // ...
  $imgPath = Storage::path($file->file_path);
  $imgSavePath = Storage::path('uploads/buffer/'.Str::beforeLast($file->name, '.').'.png');
  $imagick->readImage($imgPath.'[0-4]'); // read only the first 5 pages
  $imagick->resetIterator();
  $imagick = $imagick->appendImages(true);
  $imagick->writeImages($imgSavePath, true);

I'm using ImageMagick 6.9.10-68 and PHP 8.1.12