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Optimizing PNG images and keeping resolution in PHP using free API:

<?php
$url = 'http://server.com/image.png';
$data = json_decode(file_get_contents('http://api.rest7.com/v1/png_lossy.php?url=' . $url));

if (@$data->success !== 1)
{
    die('Failed');
}
$image = file_get_contents($data->file);
file_put_contents('optimized.png', $image);