裁剪裁剪但不保持纵横比

Question

我正在裁剪图像，图像裁剪得很好，但在我查看裁剪后的图像时，它会从一些随机位置裁剪图像，我不知道为什么会发生这种情况。我关注此帖http://mrbool.com/jquery-crop-cropping-images-with-jcrop/26243

       <form id="crop_form" action="crop.php" method="post">
                                <input type="hidden" id="x" name="x" />
                                <input type="hidden" id="y" name="y" />
                                <input type="hidden" id="w" name="w" />
                                <input type="hidden" id="h" name="h" />
                                <input type="hidden" name="src" id="src"/>
                                <input type="hidden" name="original_width" id="original_width" value="<?php echo $row['width']; ?>"/>
                                <input type="hidden" name="original_height" id="original_height" value="<?php echo $row['height']; ?>"/>
                                <a id="image_crop" name="image_crop" >
                                    <img src="images/icon-01.png" width="41" height="41"  alt="" />
                                </a>
                            </form>

                        </div> 
                        <?php
                            $width = $row['width'];  
                            $height = $row['height'];
                        ?>
                        <img title="" id="main_image" src="<?php echo "patternimages/" . $row['img_name'] ?>" width="<?php echo $width; ?>" height="<?php echo $height; ?>"> </div>

以下是我的JS代码

  $(function() {

        var main_image_src = jQuery('#main_image').attr('src');
        jQuery('#src').val(main_image_src);
        jQuery('#image_crop').on('click', function() {
//            checkCoords();
            jQuery('#crop_form').submit();
        });

        $('#main_image').Jcrop({
            aspectRatio: 1,
            onSelect: updateCoords,
        });

    });

    function updateCoords(c)
    {
        $('#x').val(c.x);
        $('#y').val(c.y);
        $('#w').val(c.w);
        $('#h').val(c.h);
    }

这里是Crop.php

<?php

session_start();
$targ_w = $targ_h = 150;
$jpeg_quality = 90;

$src = $_POST['src'];
$img_r = imagecreatefromjpeg($src);
$dst_r = ImageCreateTrueColor($targ_w, $targ_h);

imagecopyresampled($dst_r, $img_r, 0, 0, $_POST['x'], $_POST['y'], $targ_w, $targ_h, $_POST['w'], $_POST['h']);

header('Content-type: image/jpeg');
imagejpeg($dst_r, 'dummy.jpg', $jpeg_quality);

exit;