How to Add Featured Image Thumbnails to Your WordPress Theme

Guide to adding featured image thumbnails to WordPress themes

You may notice the "Featured Picture" box when editing an article or page. It allows you to upload or select images associated with the article. It usually appears as a thumbnail when viewing a list of articles (such as category indexes or search results). Thumbnail support must be enabled in the theme. You can add it to the plugin so that all themes can work, but this doesn't work in all cases. Therefore, you need to open or create the "functions.php" file in the theme folder (wp-content/themes/theme-name/).

To add thumbnail support to all article types, add the following code after the open <php></php> tag:

<code class="language-php">add_theme_support('post-thumbnails');</code>

Alternatively, you can enable thumbnails only for the article:

<code class="language-php">add_theme_support('post-thumbnails', array('post'));</code>

Or enable thumbnails only for the page:

<code class="language-php">add_theme_support('post-thumbnails', array('page'));</code>

Set thumbnail size

The default thumbnail size can be set in the Settings of WordPress > Media screen. However, you can also set the default height and width in functions.php, for example:

<code class="language-php">set_post_thumbnail_size(100, 75);</code>

This will generate a thumbnail with a width of 100 pixels and a height of 75 pixels (a pleasant 4:3 scale). But what happens when a user uploads an image with a different aspect ratio (e.g. 100 x 150)? In this case, the entire image will be scaled down to fit the space and the resulting thumbnail will be 50 x 75. Alternatively, you can define a hard crop by passing "true" as a third parameter:

<code class="language-php">set_post_thumbnail_size(100, 75, true);</code>

This will crop the image to match the aspect ratio. The generated thumbnail will always be 100 x 75, but the top and bottom or left and right edges will be removed.

The Featured Image box should now appear on your WordPress post/page editing screen. If it does not exist, check if it is enabled in "Screen Options", or check out your functions.php code.

Using thumbnails

Three main thumbnail commands can now be used in any WordPress loop. Typically, you need to use them in files named index.php, category.php, archive.php, author.php, taxonomy.php, or search.php:

• has_post_thumbnail() Return to "true" if the thumbnail has been set
• the_post_thumbnail() The output contains thumbnails<img src="/static/imghwm/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/174001393669976.jpg" class="lazy" alt="How to Add Featured Image Thumbnails to Your WordPress Theme ">

  That's it. Enjoy adding thumbnail support to all WordPress themes.

  (The following is the FAQ part. Since there are no pictures in the original FAQ part, only the text content is retained here)

  FAQs on Adding Featured Image Thumbnails in WordPress Themes (FAQ)

  How to add multiple featured images in WordPress?

  WordPress only allows you to add a featured image or article thumbnail by default. However, you can add multiple featured images using plugins like Dynamic Featured Image. After you install and activate the plugin, you can add multiple featured images to the article from the article editing screen. Remember to update your theme files to display these pictures correctly.

  Why is my featured image not displayed in WordPress?

  There may be several reasons why your featured image is not displayed. This may be due to theme or plugin conflicts, incorrect image size, or your theme may not support featured images. Try to deactivate your plugin one by one to see if any plugins are causing this issue. If this doesn't work, check your topic's functions.php file to make sure it supports article thumbnails.

  How to change the size of a featured image?

  You can change the size of the featured image by adding a custom function in the theme's functions.php file. Use the add_image_size() function to define the new image size. Then, use the the_post_thumbnail() function in your theme file to display the new image size.

  Can I add featured images to my old posts?

  Yes, you can add featured images to old posts. Just edit the article and set the featured picture from the article edit screen. If you have a lot of articles, you can use plugins like Quick Featured Images to set up featured images in batches.

  How to add default featured images in WordPress?

  You can add default featured images using plugins like Default Featured Image. After installing and activate the plugin, go to Settings > Media to set your default featured image. This image will be used whenever the article does not have a featured image.

  How to display featured pictures in RSS feed?

  WordPress does not include featured images in the RSS feed by default. However, you can add them using plugins like Featured Images in RSS & Mailchimp Email. Alternatively, you can add custom functions in the theme's functions.php file to include featured images in your RSS feed.

  Can I add featured images to my categories and tags?

  Yes, you can add featured images to your categories and tags using plugins like Categories Images. Once the plugin is installed and activated, you can set featured pictures for your categories and tags from the edit screen.

  How to add a featured image column in the WordPress admin panel?

  You can use plugins like Featured Image Admin Thumb to add featured image columns in the WordPress admin panel. This plugin adds a new column to the article list to display the featured images of each article.

  How to add a hover effect to my featured image?

  You can add hover effects to featured images using CSS. Add the hover selector to the style.css file of the theme and define the desired effect. For example, you can change the opacity when an image is hovered to create a fade effect.

  Can I add lightbox effects to my featured pictures?

  Yes, you can add lightbox effects to feature images using plugins like Simple Lightbox. After installing and activating the plugin, clicking your featured image will open in the light box.

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