在WordPress中通过编程方式上传多尺寸图片

require_once( ABSPATH . 'wp-admin/includes/image.php' );
require_once( ABSPATH . 'wp-admin/includes/file.php' );
require_once( ABSPATH . 'wp-admin/includes/media.php' );

if ( ! function_exists( 'wp_handle_upload' ) ) {
    require_once( ABSPATH . 'wp-admin/includes/file.php' );
}

$uploadedfile = $_FILES['your_image_field']; // 你的图片上传字段名
$upload_overrides = array( 'test_form' => false );

$movefile = wp_handle_upload( $uploadedfile, $upload_overrides );

if ( $movefile && ! isset( $movefile['error'] ) ) {
    echo "File is valid, and was successfully uploaded.\n";
    var_dump( $movefile);

    $filename = $movefile['file'];
    $wp_filetype = wp_check_filetype( basename( $filename ), null );
    $attachment = array(
        'post_mime_type' => $wp_filetype['type'],
        'post_title' => preg_replace('/\.[^.]+$/', '', basename( $filename )),
        'post_content' => '',
        'post_status' => 'inherit'
    );

    $attach_id = wp_insert_attachment( $attachment, $filename);

    // you must first include the image.php file
    // for the function wp_generate_attachment_metadata() to work
    $attach_data = wp_generate_attachment_metadata( $attach_id, $filename );
    wp_update_attachment_metadata( $attach_id,  $attach_data );

    // 现在你可以使用 $attach_id 获取不同尺寸的图片
    // 例如：
    // $image_src = wp_get_attachment_image_src( $attach_id, 'thumbnail' );
    // echo '<img src="' . $image_src[0] . '" />';


} else {
    /**
     * Error generated. Possible error values:
     * 'file' - filename was missing.
     * 'test' - the PHP temporary upload folder is missing.
     * 'test_size' - the file exceeds the maximum upload size.
     * 'upload_max_filesize' - the file exceeds the upload_max_filesize directive in php.ini.
     * 'max_file_uploads' - the file exceeds the max_file_uploads directive in php.ini.
     * 'post_max_size' - the post exceeds the post_max_size directive in php.ini.
     * 'size' - the file exceeds the MAX_FILE_SIZE directive that was specified in the html form.
     * 'type' - the file does not match the accepted file types.
     * 'ext' - the file extension does not match the accepted file types.
     */
    echo $movefile['error'];
}

$attachment_id = get_the_ID(); // 假设在文章页面获取附件 ID
$thumbnail_size = 'thumbnail'; // 默认缩略图尺寸
$medium_size = 'medium'; // 中等尺寸
$large_size = 'large'; // 大尺寸
$full_size = 'full'; // 原始尺寸

// 获取缩略图
$thumbnail_image = wp_get_attachment_image( $attachment_id, $thumbnail_size );
echo $thumbnail_image;

// 获取中等尺寸图片
$medium_image = wp_get_attachment_image( $attachment_id, $medium_size );
echo $medium_image;

// 获取大尺寸图片
$large_image = wp_get_attachment_image( $attachment_id, $large_size );
echo $large_image;

// 获取原始尺寸图片
$full_image = wp_get_attachment_image( $attachment_id, $full_size );
echo $full_image;

add_image_size( 'custom-size', 200, 200, true ); // 创建一个 200x200 的裁剪尺寸

// 在主题的 functions.php 文件中添加以下代码
add_action( 'after_setup_theme', 'my_theme_setup' );
function my_theme_setup() {
    add_image_size( 'my-custom-size', 300, 200, true ); // 300像素宽，200像素高，裁剪模式
}