Detailed explanation of the steps to dynamically crop images using PHP in nginx

/**
 * Author pony_chiang
 * 高性能图像裁剪方案
 * 需要php-imagick扩展
 */
 ini_set ( "memory_limit", "80M" );
// 请求地址比如  http://yourdomain.com/resize.php?site=www&width=300&height=200&mode=2&path=uploadfile/helloworld.png
// nginx重写规则  rewrite ^([^\.]*)/s/(.*)/(\d+)x(\d+)-(\d)/(.*) $1/s/resize.php?site=$2&width=$3&height=$4&mode=$5&path=$6 last;
$path = trim ( $_GET ['path'] );
$mode = intval ( $_GET ['mode'] );
$site = trim ( $_GET ['site'] );
$width = intval ( $_GET ['width'] );
$height = intval ( $_GET ['height'] );
$site_list = array ('www' => '/mnt/webroot/test/' );
$orig_dir = dirname ( FILE );
if (! array_key_exists ( $site, $site_list )) {
    header ( 'HTTP/1.1 400 Bad Request' );
    exit ();
}
if ($mode > 3 || $mode < 0) {
    header ( 'HTTP/1.1 400 Bad Request' );
    exit ();
}
$orig_file = $site_list [$site] . $path;
if (! file_exists ( $orig_file )) {
    header ( 'HTTP/1.1 404 Not Found' );
    exit ();
}
$file_ext = '.' . pathinfo ( $path, PATHINFO_EXTENSION );
$file_name = basename ( $path, $file_ext );
$save_path = "{$orig_dir}/{$site}/{$width}x{$height}-{$mode}/{$path}";
$save_dir = dirname ( $save_path );
if (! file_exists ( $save_dir ))
    wpx_mkdir ( $save_dir );
$target_width = $width;
$target_height = $height;
$new_width = $target_width;
$new_height = $target_height;
$image = new Imagick ( $orig_file );
list ( $orig_width, $orig_height, $type, $attr ) = getimagesize ( $orig_file );
if ($mode == "0") {
    //等比缩放图像
    $new_height = $orig_height * $new_width / $orig_width;
    if ($new_height > $target_height) {
$new_width = $orig_width * $target_height / $orig_height;
$new_height = $target_height;
    }
} else if ($mode == "2") {
    // 放大并裁剪图像
    $desired_aspect = $target_width / $target_height;
    $orig_aspect = $orig_width / $orig_height;
    if ($desired_aspect > $orig_aspect) {
$trim = $orig_height - ($orig_width / $desired_aspect);
$image->cropImage ( $orig_width, $orig_height - $trim, 0, $trim / 2 );
error_log ( "HEIGHT TRIM $trim" );
    } else {
$trim = $orig_width - ($orig_height * $desired_aspect);
$image->cropImage ( $orig_width - $trim, $orig_height, $trim / 2, 0 );
    } www.jbxue.com
}
$image->resizeImage ( $new_width, $new_height, imagick::FILTER_LANCZOS, 1 );
$image->writeImage ( $save_path );
header ( 'Content-Type: image/jpeg' );
header ( 'Last-Modified: ' . gmdate ( 'D, d M Y H:i:s' ) . ' GMT' );
echo file_get_contents ( $save_path );
return true;
// 循环生成目录
function wpx_mkdir($dir, $mode = 0777) {
    if (is_dir ( $dir ) || @mkdir ( $dir, $mode ))
return true;
    if (! wpx_mkdir ( dirname ( $dir ), $mode ))
return false;
    return @mkdir ( $dir, $mode );
}

server {
listen       80;
server_name test.yourdomain.com;
root   /mnt/webroot/test;
index  index.php;
expires 30d;
location /s {
   #只有当没有生成这张图片时才调用动态裁剪
   if (!-e $request_filename) {
     rewrite ^([^\.]*)/s/(.*)/(\d+)x(\d+)-(\d)/(.*) $1/s/resize.php?site=$2&width=$3&height=$4&mode=$5&path=$6 last;
     break;
   }
}
error_page   404 403 402 500 502 503 504  /404.html;
location = /404.html {
}
location ~ \.php$ {
    fastcgi_pass   127.0.0.1:9000;
    fastcgi_index  index.php;
    fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;
    includefastcgi_params;
}
}

header('Last-Modified: ' .gmdate('D, d M Y H:i:s') . ' GMT' );