下面这个脚本能使wordpress生成一个大幅图片，并用该图片代替用户所上传的图片（如果所上传图片尺寸大于用户的后台设置），以节省服务器空间，如果你链接到的是原始图片的缩略图，还可以节省带宽，效果和lightBox插件一样。

只要将以下代码添加到functions.PHP文件并保存即可。

function replace_uploaded_image($image_data) {

// if there is no large image : return

if (!isset($image_data['sizes']['large'])) return $image_data;

// paths to the uploaded image and the large image

$upload_dir = wp_upload_dir();

$uploaded_image_location = $upload_dir['basedir'] . '/' .$image_data['file'];

$large_image_location

= $upload_dir['path'] . '/'.$image_data['sizes']['large']['file'];

// delete the uploaded image

unlink($uploaded_image_location);

// rename the large image

rename($large_image_location,$uploaded_image_location);

// update image Metadata and return them

$image_data['width'] = $image_data['sizes']['large']['width'];

$image_data['height'] = $image_data['sizes']['large']['height'];

unset($image_data['sizes']['large']);

return $image_data;

}

add_filter('wp_generate_attachment_Metadata',

'replace_uploaded_image');

注意：不同主题对该代码的支持程度会有所不同

原文：How to automatically use resized images instead of originals

出处：http://www.wordpress.la/