输出到\\u content（）的图像很可能是通过admin中的Media按钮手动添加的。您应该能够从此点添加自己的类。在插入介质模式中选择对齐等时，WP系统会添加默认类。

将图像插入帖子的那一刻，钩子image_send_to_editor 被调用。钩子的输入是html，也可能是标题短代码。像这样：

[caption id="attachment_999" align="alignright" width="150"]
<a href="http://www.example.com/wp-content/uploads/2016/06/my-image.jpg">
<img src="http://www.example.com/wp-content/uploads/2016/06/my-image-150x150.jpg" alt="My colourful image" width="150" height="150" class="size-thumbnail wp-image-101" />
</a>
Look at how colourful this is!
[/caption]

add_filter (\'image_send_to_editor\', \'wpse_209128_filter_image\');
function wpse_209128_filter_image ($html) {
    // first, remove the image and caption dimensions
    $html = preg_replace (\'/(width|height)=\\"\\d*\\"\\s/\', \'\', $html);
    // second, replace the class on the img tag
    $html = preg_replace (\'/class=\\"([^"]*)\\", \'class="img-responsive"\', $html);
return $html;
}