How to change the catalog product image size by product id?

Question

I am wondering if I could change the size of one specific catalog product image.

I have many products with the same size (catalog images-not single product images, not even product thumbnails) and I want to change the size of a specific product, in order to be smaller than the other catalog images.

How can I do that?

Answer 1

You can use the single_product_archive_thumbnail_size filter to change which image size is used for a particular product:

function wpse_287488_product_thumbnail_size( $size ) {
    global $product;

    if ( $product->get_id() === 123 ) {
        $size = 'medium';
    }

    return $size;
}
add_filter( 'single_product_archive_thumbnail_size', 'wpse_287488_product_thumbnail_size' );

Just replace medium with the registered image size you want to use. See this codex article for an overview of image sizes and how to register your own.

Answer 2

Without going into too much detail..

global $product;

if($product->ID == '21'):
the_post_thumbnail('size');
else:
<default code for displaying product thumb>
endif;