post_thumbnails_divi.php

<?php
add_theme_support( 'post-thumbnails' );

global $et_theme_image_sizes;

$et_theme_image_sizes = array(
	'400x250'  => 'et-pb-post-main-image',
	'1080x675' => 'et-pb-post-main-image-fullwidth',
	'400x284'   => 'et-pb-portfolio-image',
	'510x382'   => 'et-pb-portfolio-module-image',
	'1080x9999' => 'et-pb-portfolio-image-single',
	'400x516'   => 'et-pb-gallery-module-image-portrait',
	'2880x1800' => 'et-pb-post-main-image-fullwidth-large',
);

$et_theme_image_sizes = apply_filters( 'et_theme_image_sizes', $et_theme_image_sizes );
$crop = apply_filters( 'et_post_thumbnails_crop', true );

if ( is_array( $et_theme_image_sizes ) ){
	foreach ( $et_theme_image_sizes as $image_size_dimensions => $image_size_name ){
		$dimensions = explode( 'x', $image_size_dimensions );

		if ( in_array( $image_size_name, array( 'et-pb-portfolio-image-single' ) ) )
			$crop = false;

		add_image_size( $image_size_name, $dimensions[0], $dimensions[1], $crop );

		$crop = apply_filters( 'et_post_thumbnails_crop', true );
	}
}

if ( function_exists( 'et_screen_sizes' ) && function_exists( 'et_is_responsive_images_enabled' ) && et_is_responsive_images_enabled() ) {
	// Register responsive image sizes.
	$et_screen_sizes = et_screen_sizes();
	if ( $et_screen_sizes && is_array( $et_screen_sizes ) ) {
		foreach ( $et_screen_sizes as $breakpoint => $width ) {
			$height = round( ( $width * ( 56.25/100 ) ) ); // 16:9 aspect ratio.
			add_image_size( "et-pb-image--responsive--{$breakpoint}", $width, $height, $crop );
		}
	}
}