PHP图像魔术师图像没有正确调整大小

So I was adding some image upload functionality to my website and I decided to go with the PHP Image Magician Library by Jarrod Oberto

Resizing a 1080 pixel wide image to 480 pixels works like a charm. However resizing the image to 720 pixels results in an unexpected crop.

Whatever shall I do to make the 720 pixel image resize perfectly?

The code Im using for he resize is;

    <?php
    $magicianObj = new imageLib("original.jpg");
    $magicianObj -> resizeImage(480, 800);
    $magicianObj -> saveImage("480.jpg", 100);
    $magicianObj -> resizeImage(720, 1280);
    $magicianObj -> saveImage("720.jpg", 100);

Here are the images:

  1. 480 pixels

480 pixels

  1. 720 pixels

enter image description here

Does it make any difference if you resize firstly to 720 and save it then resize to 480 and save?

$magicianObj = new imageLib("original.jpg");
$magicianObj -> resizeImage(720, 1280);
$magicianObj -> saveImage("720.jpg", 100);

$magicianObj -> resizeImage(480, 800);
$magicianObj -> saveImage("480.jpg", 100);