缩略图大小基于中定义的尺寸WordPress Dashboard > Settings > Media, 除非你的主题覆盖了它。

如何使我的主题覆盖它？

要更改默认的后期缩略图大小，您需要使用set_post_thumbnail_size. 将此添加到函数中。php文件：

if ( function_exists( \'add_theme_support\' ) ) {
    add_theme_support( \'post-thumbnails\' );
    set_post_thumbnail_size( W, H, true ); //change to false to disable hard cropping
}

更改W 和H 要为缩略图设置的尺寸（以像素为单位）。例如set_post_thumbnail_size( 150, 150 ); 将缩略图大小设置为150 x 150像素。

NOTE: 检查主题是否已经add_theme_support( \'post-thumbnails\' ); — 如果有，只需添加set_post_thumbnail_size( W, H ); 在它下面。

因为我需要的图库缩略图大小与帖子缩略图不同，所以没有专门针对图库的其他功能。

选项1：（所有代码都进入functions.php）

首先，让我们为库缩略图注册新的图像大小：

if ( function_exists( \'add_image_size\' ) ) {

    // set gallery thumbnail image\'s size to 250 x 250 pixels
    add_image_size( \'ilyad-gallery-thumb\', 250, 250, true ); //change to false to disable hard cropping

}

现在，让我们用自己的代码修改默认的WordPress图库代码（以便我们可以为图库中的图像设置自己的缩略图大小）-下面的所有代码都是默认的图库短代码，取自wp-includes/media.php. 我改变了\'size\' => \'thumbnail\' 到\'size\' => \'gallery-thumb\' 要让画廊使用我们新注册的画廊图像大小。

// Modified Gallery Shortcode

add_filter("post_gallery", "wpse56909_post_gallery",10,2);
function wpse56909_post_gallery($output, $attr) {
    global $post;

    static $instance = 0;
    $instance++;

    // We\'re trusting author input, so let\'s at least make sure it looks like a valid orderby statement
    if ( isset( $attr[\'orderby\'] ) ) {
        $attr[\'orderby\'] = sanitize_sql_orderby( $attr[\'orderby\'] );
        if ( !$attr[\'orderby\'] )
            unset( $attr[\'orderby\'] );
    }

    extract(shortcode_atts(array(
        \'order\'      => \'ASC\',
        \'orderby\'    => \'menu_order ID\',
        \'id\'         => $post->ID,
        \'itemtag\'    => \'dl\',
        \'icontag\'    => \'dt\',
        \'captiontag\' => \'dd\',
        \'columns\'    => 3,
        \'size\'       => \'gallery-thumb\',
        \'include\'    => \'\',
        \'exclude\'    => \'\'
    ), $attr));

    $id = intval($id);
    if ( \'RAND\' == $order )
        $orderby = \'none\';

    if ( !empty($include) ) {
        $include = preg_replace( \'/[^0-9,]+/\', \'\', $include );
        $_attachments = get_posts( array(\'include\' => $include, \'post_status\' => \'inherit\', \'post_type\' => \'attachment\', \'post_mime_type\' => \'image\', \'order\' => $order, \'orderby\' => $orderby) );

        $attachments = array();
        foreach ( $_attachments as $key => $val ) {
            $attachments[$val->ID] = $_attachments[$key];
        }
    } elseif ( !empty($exclude) ) {
        $exclude = preg_replace( \'/[^0-9,]+/\', \'\', $exclude );
        $attachments = get_children( array(\'post_parent\' => $id, \'exclude\' => $exclude, \'post_status\' => \'inherit\', \'post_type\' => \'attachment\', \'post_mime_type\' => \'image\', \'order\' => $order, \'orderby\' => $orderby) );
    } else {
        $attachments = get_children( array(\'post_parent\' => $id, \'post_status\' => \'inherit\', \'post_type\' => \'attachment\', \'post_mime_type\' => \'image\', \'order\' => $order, \'orderby\' => $orderby) );
    }

    if ( empty($attachments) )
        return \'\';

    if ( is_feed() ) {
        $output = "\\n";
        foreach ( $attachments as $att_id => $attachment )
            $output .= wp_get_attachment_link($att_id, $size, true) . "\\n";
        return $output;
    }

    $itemtag = tag_escape($itemtag);
    $captiontag = tag_escape($captiontag);
    $columns = intval($columns);
    $itemwidth = $columns > 0 ? floor(100/$columns) : 100;
    $float = is_rtl() ? \'right\' : \'left\';

    $selector = "gallery-{$instance}";

    $gallery_style = $gallery_div = \'\';
    if ( apply_filters( \'use_default_gallery_style\', true ) )
        $gallery_style = "
        <style type=\'text/css\'>
            #{$selector} {
                margin: auto;
            }
            #{$selector} .gallery-item {
                float: {$float};
                margin-top: 10px;
                text-align: center;
                width: {$itemwidth}%;
            }
            #{$selector} img {
                border: 2px solid #cfcfcf;
            }
            #{$selector} .gallery-caption {
                margin-left: 0;
            }
        </style>
        <!-- see gallery_shortcode() in wp-includes/media.php -->";
    $size_class = sanitize_html_class( $size );
    $gallery_div = "<div id=\'$selector\' class=\'gallery galleryid-{$id} gallery-columns-{$columns} gallery-size-{$size_class}\'>";
    $output = apply_filters( \'gallery_style\', $gallery_style . "\\n\\t\\t" . $gallery_div );

    $i = 0;
    foreach ( $attachments as $id => $attachment ) {
        $link = isset($attr[\'link\']) && \'file\' == $attr[\'link\'] ? wp_get_attachment_link($id, $size, false, false) : wp_get_attachment_link($id, $size, true, false);

        $output .= "<{$itemtag} class=\'gallery-item\'>";
        $output .= "
            <{$icontag} class=\'gallery-icon\'>
                $link
            </{$icontag}>";
        if ( $captiontag && trim($attachment->post_excerpt) ) {
            $output .= "
                <{$captiontag} class=\'wp-caption-text gallery-caption\'>
                " . wptexturize($attachment->post_excerpt) . "
                </{$captiontag}>";
        }
        $output .= "</{$itemtag}>";
        if ( $columns > 0 && ++$i % $columns == 0 )
            $output .= \'<br style="clear: both" />\';
    }

    $output .= "
            <br style=\'clear: both;\' />
        </div>\\n";

    return $output;
}

这些更改不会影响您的旧帖子。如果你认为应该，你需要重新生成所有帖子的缩略图，这是最受欢迎的插件-AJAX Thumbnail Rebuild.

[Source]

选项2：（所有代码都进入functions.php）

假设您希望库中缩略图的大小为250 x 250像素。转到WordPress Dashboard > Settings > Media 并设置Thumbnail size 宽度和高度分别为250和250。完成一半！

现在，我们需要修改代表您帖子的缩略图的大小。允许首先注册新的缩略图大小：

if ( function_exists( \'add_image_size\' ) ) { 
    add_image_size( \'ilyad-post-thumb\', 150, 150, true ); //change to false to disable hard cropping
}

现在，应该修改主题文件中帖子缩略图的所有代码实例，以使用ilyad-post-thumb 大小这里有两个例子。

• CASE - 1: 如果您的主题使用以下内容：

  <?php
  if ( \'\' != get_the_post_thumbnail() ) :
          $thumbnail = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), thumbnail );
  ?>
  <div class="entry-image">
      <a href="<?php the_permalink(); ?>" title="<?php printf( esc_attr__( \'Permalink to %s\', \'reddle\' ), the_title_attribute( \'echo=0\' ) ); ?>" rel="bookmark">
          <img class="featured-image" src="<?php echo $thumbnail[0]; ?>" alt="">
      </a>
  </div>
  

  应修改为：

  <?php
  if ( \'\' != get_the_post_thumbnail() ) :
          $thumbnail = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), ilyad-post-thumb );
  ?>
  <div class="entry-image">
      <a href="<?php the_permalink(); ?>" title="<?php printf( esc_attr__( \'Permalink to %s\', \'reddle\' ), the_title_attribute( \'echo=0\' ) ); ?>" rel="bookmark">
          <img class="featured-image" src="<?php echo $thumbnail[0]; ?>" alt="">
      </a>
  </div>
  

  在上面，我们只是更改thumbnail （图像大小）至ilyad-post-thumb.

• CASE - 2: 如果您的主题使用以下内容：

  <?php 
  if ( has_post_thumbnail() ) { // check if the post has a Post Thumbnail assigned to it.
    the_post_thumbnail();
  } 
  ?>
  

  将其更改为：

  <?php 
  if ( has_post_thumbnail() ) { // check if the post has a Post Thumbnail assigned to it.
    the_post_thumbnail(\'ilyad-post-thumb\');
  } 
  ?>
  

  这两个例子应该给你一个想法，告诉你应该如何去做

  PS: 这个答案是在我的知识范围内写的