How to Change Size of Featured Images

Jannah theme defines several image sizes for the featured images. WordPress will crop your uploaded image to all these sizes when you set a featured image. The theme will then use these different sized images on various locations in the theme.

If you want to change the size of any of these generated images, Add this code to your child theme’s  functions.php file or via a plugin that allows custom functions to be added, such as the Code snippets plugin. Avoid adding custom code directly to your parent theme’s functions.php file, as this will be wiped entirely when you update the theme.

add_action( 'init', 'tie_custom_image_sizes' );
function tie_custom_image_sizes(){

	add_image_size( TIELABS_THEME_SLUG.'-image-small', 220, 150, true );
	add_image_size( TIELABS_THEME_SLUG.'-image-large', 390, 220, true );
	add_image_size( TIELABS_THEME_SLUG.'-image-post',  780, 470, true );

Change the values of the width and height.

you will need to run the “Regenerate Thumbnails” plugin to regenerate thumbnails in the new sizes.