Compress image file to specified filesize using PHP ImageMagick

compressIMagick.php

<?php

/**
 * Sample to compress image file in PHP.
 * 
 * This will compress all files in *input* directory and store the result in *output* directory.
 * 
 * To run this code, PHP extension *imagemagick* should be enabled.
 * 
 * Syntax
 * ```shell
 *    php compressIMagick.php
 * ```
 */

// Get files in directory input, ignore '.' and '..'.
$files = array_diff(scandir('input'), ['.', '..']);

// Convert files to output/small_<input name>.jpeg
foreach ($files as $file) {
    compress("input/$file", "output/small_{$file}.jpeg", '500kb');
}

/**
 * Compress image file to jpeg file.
 * 
 * @param string $source Image file of type jpeg/gif/png
 * @param string $destination Output image
 * @param string $fileSize File size to be converted. Default to 500kb
 */
function compress($source, $destination, $fileSize = '500kb')
{
    $im = new IMagick($source);
    $im->setOption('jpeg:extent', $fileSize);
    $im->writeImage($destination);
}