Great question! WordPress缺少一些更高级别的图像管理功能，这些功能可以使文件维护变得更加简单。WordPress的核心团队一直威胁要为许多版本添加增强图像功能；最终他们可能真的会这么做！在此之前，您必须使用插件和/或自定义代码的补丁。

更多好消息和坏消息：good news WordPress与PHP的结合是否具有大量较低级别的图像处理功能，但bad news 它有大量的低级图像处理功能，您必须从中决定使用哪种功能！不久前我发布了list of image handling functions found in WordPress 如果你扫描一下，你可能会看到有几种不同的方法可以剥这只猫的皮。

尽管如此，我选择了一种方法，下面给出了大量的评论，而不是在本文中进行解释。您可以将其复制到网站的根目录/downsize-images.php 并从浏览器中调用它。如果超时，不要担心；我写它是为了跟踪它已经做了什么，所以只要继续运行它，直到你看到它打印出来“完成！”

NOTE: 您需要设置常量MAX_RESIZE_IMAGE_TO 无论你想要你的最大维度是什么；我举了一个例子640 像素。运行后，您将有一组图像文件，扩展名为.save 已附加。一旦你对它按照你想要的方式运行感到满意，你就可以删除那些.save 文件。我没有自动删除它们，以防脚本出错。

(IMPORTANT: 是SURE TO BACKUP 你的数据库和上传目录BEFORE 你来运行这个。它在我的机器上工作，但你可能有我没有测试的东西，它可能会导致损坏，所以备份！DO NOT 晚点回来说我没有警告你！！！）：

<?php

include "wp-load.php";                 // Need this to load WordPress core
include "wp-admin/includes/image.php"; // Needed for wp_create_thumbnail()

define(\'MAX_RESIZE_IMAGE_TO\',640);     // SET YOUR MAX DIMENSION HERE!!!!

// Check our "queue" to see if we\'ve previously only run to partial competion.
$attachment_ids = get_option(\'attachment_ids_to_resize\');
if ($attachment_ids==\'Done!\') { // Make sure we don\'t do it again
  echo \'Already done.\';
} else {
  if (empty($attachment_ids)) { // If this is the first time, this array will be empty. Get the IDs.
    global $wpdb;
    $attachment_ids = $wpdb->get_col("SELECT ID FROM {$wpdb->posts} WHERE post_type=\'attachment\'");
  }
  foreach($attachment_ids as $index => $attachment_id) {
    // Get metadata: [width,height,hwstring_small,file,sizes[file,width,height],image_meta[...]]:
    $metadata = wp_get_attachment_metadata($attachment_id);
    // Get upload_dir: [path,url,subdir,basedir,baseurl,error]:
    $upload_dir = wp_upload_dir();
    // Get full path to original file
    $filepath = "{$upload_dir[\'basedir\']}/{$metadata[\'file\']}";
    // Make a smaller version constrained by largest dimension to MAX_RESIZE_IMAGE_TO
    $smaller_file = wp_create_thumbnail( $filepath, MAX_RESIZE_IMAGE_TO);
    // If the file was really created
    if (@file_exists($smaller_file)) {
      // Append a ".save" to original file name, just in case (you can manually delete *.save)
      rename($filepath,"{$filepath}.save");
      // Get this smaller files dimensions
      list($width,$height) = getimagesize($smaller_file);
      // Strip the base directory off the filename (i.e. \'/Users/username/Sites/sitename/wp-content/uploads/\')
      $metadata[\'file\'] = str_replace("{$upload_dir[\'basedir\']}/",\'\',$smaller_file);
      $metadata[\'height\'] = $height;
      $metadata[\'width\'] =  $width;
      // Get the the small size, 128x96 or smaller if need be
      list($uwidth,$uheight) = wp_constrain_dimensions($metadata[\'width\'], $metadata[\'height\'], 128, 96);
      $metadata[\'hwstring_small\'] = "height=\'$uheight\' width=\'$uwidth\'";
      // Make sure none of the sizes are larger than the new size
      foreach($metadata[\'sizes\'] as $size => $size_info) {
        if (intval($size_info[\'height\'])>intval($height) ||
            intval($size_info[\'width\'])>intval($width)) {
          // If too large get the full file path of the sized image
          $old_file = "{$upload_dir[\'path\']}/{$size_info[\'file\']}";
          // Tack a ".save" extension on it, just in case (you can manually delete *.save)
          rename($old_file,"{$old_file}.save");
          // Remove it from the metadata since it\'s too large
          unset($metadata[\'sizes\'][$size]);
        }
      }
      // Update the attachement metadata with the new smaller values
      wp_update_attachment_metadata($attachment_id,$metadata);
      // Update the name of the other place the orginal file name is stored
      update_attached_file($attachment_id,$metadata[\'file\']);
    }
    // Remove this attachment from our "queue"
    unset($attachment_ids[$index]);
    // Save the new smaller "queue" in case we need to run this again.
    update_option(\'attachment_ids_to_resize\',$attachment_ids);
  }
  // If we\'ve actually processed them all
  if (count($attachment_ids)==0) {
    // Store a marker so we won\'t accidentally run this again
    update_option(\'attachment_ids_to_resize\',\'Done!\');
  }
  echo \'Done!\';
}