I think you can do that by adding the function add_image_size in your functions.php file of the theme folder.
Read more on how to add add_image_size here: http://codex.wordpress.org/Function_Reference/add_image_size
Related Posts:
- The the_post_thumbnail without srcset?
- How to get gallery images?
- How can I get wp_head() as a string instead of echoing it?
- add_image_size is scaling, even though crop is set to true
- How do I get gallery thumbnail URL and change the default thumbnail size?
- How to remove header images from all pages except the home page? skeleton theme
- Add social icons in a theme through custom admin menu
- How can a Theme Contain no Header File or Footer File?
- Cannot get full thumbnail size using the_post_thumbnail
- Changing Header Image Every N Minutes/Seconds
- What is the meaning of WordPress’s recommended css classes and where are they applied?
- Set a featured image as a replacement to the header image
- Change image size depending on page
- Are seven additional image sizes are too many?
- Change Image Sizes for Mobile Theme
- Why is the `if else` not working?
- Is there a way to serve different resolution images to different devices?
- How do I remove header/page-title image in farvis theme? [closed]
- Change header image on a particular page
- Can’t upload images on new theme
- How to create full header but keep content narrow
- Custom Theme functions.php – Using add_settings_field and input type=”file” to set custom logo
- Sizing screenshot.png without losing aspect ratio
- WordPress Theme Preview Image
- How to add CSS class to custom logo?
- How to add custom css file in theme?
- theme path in javascript file
- get_template_part vs action hooks in themes
- wp_redirect() – headers already sent
- The proper way to include/require PHP files in WordPress
- Get the first image from post content (eg.: hotlinked images)
- after_setup_theme always runs
- Do I actually need to link my theme’s style.css in the theme files
- Using classes instead of global functions in functions.php
- WordPress API Menu/Submenu Order
- How to insert a logo in the header?
- How to move page template files like page-{slug}.php to a sub-directory?
- CSS classes for theme
- Add custom classes to anchor in wp_nav_menu
- How to remove search bar from a wordpress theme? [closed]
- Should `get_template_directory_uri()` be escaped?
- Get url of thumbnail from the media uploader
- My child theme doesn’t work Error: “The parent theme is missing. Please install your parent theme”
- Auto get_header and get_footer on every template?
- How To Add New Option Types To Option Tree?
- WP 3.4 – what action/hook is called when theme customisation is saved?
- What WP folder can I use to write files to?
- How to modify an image block in Gutenberg WordPress 5?
- How can I set image sizes and still have responsive images using the srcset attribute?
- Are the WordPress Core CSS styles really all nessesary?
- Add a dropdown to theme customizer
- Should I use set_transient or update_option?
- Why doesn’t default WordPress page view use force_balance_tags?
- Add default Backgrounds
- Page template in two level deep folder
- Edit srcset and sizes attributes in Gutenberg image, cover and gallery – blocks
- Theme Customizer : how to create multiple-level panel
- Why I can’t add a CSS style in this WordPress theme?
- Theme file for all pages that are a child of a specific page
- Allow Shortcode in Theme Customizer
- Where to post/upload the new theme for WordPress theme repository
- Setting multiple default background images?
- Template for individual post designs
- How to make a theme with more than one CSS file?
- Is it good to rename theme folder downloaded from WordPress.org?
- wp_get_attachment_image_attributes not working for me
- Best practice way to implement custom sections into a WordPress theme
- Editing the custom background CSS
- What is the problem if I use CDN in my WordPress parent theme(built using bootstrap)?
- Specify image dimensions
- register_sidebar ignores ‘id’ and ‘class’
- What, specifically, should be included in theme_name_setup()?
- Is it possible to use line break in theme description?
- Is the theme customizer slowing down my site?
- Display a different theme for not logged-in users
- Best practice (forward compatibility) for theme options
- Automatic Updates For Private And Commercial Themes?
- Add colors to existing color palette without replacing it
- Child Theme not loading parent CSS
- What can I hook into after_setup_theme?
- Where do I find the functions triggered within a hook?
- What does “Do not deregister the jquery script in the administration area” mean?
- What is the best book to learn how to make themes for wordpress?
- Grab the first paragraph of each post
- Use of undefined constant FS_CHMOD_DIR – assumed ‘FS_CHMOD_DIR’
- Featured Image in 4.4 should be larger on mobile device
- How to use the responsive images feature from WP 4.4 in your themes
- How to show next Post Thumbnail image in WordPress using current post id
- Symlink a directory to wp-content/themes
- Single Page WordPress Theme – Using page templates
- Confused about image sizing business in WordPress
- Unexpected width and srcset attributes for the_post_thumbnail();
- Pushing updates to your premium theme
- Registering Sidebars and Sidebar Widgets. Sidebar Widgets Not Displaying
- Where can I find a good reviewed collection of Twenty Ten child themes?
- How to check if post has any tag?
- What are WooCommerce starter themes? [closed]
- Front End Post Submit Form
- How do I “unhook” / de-register jQuery so that it’s not called as part of wp_footer();?
- How do I get a parent theme modification from a child theme?