wordpress可用的缩略图函数

<?php//缩略图技术by：http://www.bgbk.org
if( !defined( 'THEME_THUMBNAIL_PATH' ) ) define( 'THEME_THUMBNAIL_PATH', '/cache/theme-thumbnail' ); //存储目录
function biji_build_empty_index( $path ){ //生成空白首页
    $index = $path . '/index.php';
    if( is_file( $index ) ) return;
    wp_mkdir_p( $path );
    file_put_contents( $index, "<?php\n// Silence is golden.\n" );
}
function biji_crop_thumbnail( $url, $width, $height = null ){ //裁剪图片
    $width = (int) $width;
    $height = empty( $height ) ? $width : (int) $height;
    $hash = md5( $url );
    $file_path = constant( 'WP_CONTENT_DIR' ) . constant( 'THEME_THUMBNAIL_PATH' ) . "/$hash-$width-$height.jpg";
    $file_url = content_url( constant( 'THEME_THUMBNAIL_PATH' ) . "/$hash-$width-$height.jpg" );
    if( is_file( $file_path ) ) return $file_url;
    $editor = wp_get_image_editor( $url );
    if( is_wp_error( $editor ) ) return $url;
    $size = $editor->get_size();
    $dims = image_resize_dimensions( $size['width'], $size['height'], $width, $height, true );
    //if( !$dims ) return $url;
    $cmp = min( $size['width'] / $width, $size['height'] / $height );
    if( is_wp_error( $editor->crop( $dims[2], $dims[3], $width * $cmp, $height * $cmp, $width, $height ) ) ) return $url;
    biji_build_empty_index( constant( 'WP_CONTENT_DIR' ) . constant( 'THEME_THUMBNAIL_PATH' ) );
    return is_wp_error( $editor->save( $file_path, 'image/jpg' ) ) ? $url : $file_url;
}
//缩略图获取post_thumbnail
function post_thumbnail($width = 275,$height = 170 )
{
    global $post;
    //如果有特色图片则取特色图片
    if( has_post_thumbnail( $post->ID ) ){
        $thumbnail_ID = get_post_thumbnail_id( $post->ID );
        $thumbnailsrc = wp_get_attachment_image_src( $thumbnail_ID, 'full' );
        return biji_crop_thumbnail($thumbnailsrc[0],$width,$height);
    } else {
        $content = $post->post_content;
        preg_match_all('/<img.*?(?: |\\t|\\r|\\n)?src=[\'"]?(.+?)[\'"]?(?:(?: |\\t|\\r|\\n)+.*?)? >/sim', $content, $strResult, PREG_PATTERN_ORDER);
        if(count($strResult[1]) > 0) return biji_crop_thumbnail($strResult[1][0],$width,$height);
        else{
            return false;
        }
    }
}
?>

<?php if (post_thumbnail(110, 110)){ ?>
  <img src="<?php echo post_thumbnail(110, 110); ?>" srcset="<?php echo post_thumbnail(220, 220); ?> 2x"/>
<?php }else{
   echo '<i class="icon-file-text2"></i>';
  }?>