如何在Woocommerce中显示条件图像缩略图大小

Question

As I'm developing a stock photo site I want to show my visitors a large preview of he image. To avoid image theft I have watermarked my images except for the full size. To serve a large preview I created a custom thumbnail size and change the code accordingly. See the thread here .

The case is that sometimes an image is uploaded with smaller dimensions as the 3072 px (width or height). What I want is that there is a fallback in this case to the thumbnail called 'large' which is one of the default Wordpress image sizes. As it is right now it is falling back to the full size image. It appears that no thumbnail of size 3072 px is generated when the full size image is smaller then 3072px.

I have tried to get it done by the piece of code below but can't get it right. What's wrong?

$filemeta = wp_get_attachment_metadata( $post_thumbnail_id, FALSE ); 

$image_width       = $filemeta['width'];
$image_height      = $filemeta['height'];


if ($image_width < 3072 || $image_height < 3072){
$thumbnail_size    = apply_filters( 'woocommerce_product_thumbnails_large_size', 'large' );
} else {
$thumbnail_size    = apply_filters( 'woocommerce_product_thumbnails_large_size', 'preview' );
}

Answer 1

Found it.

Changed this line in product_image.php

$thumbnail_size    = apply_filters( 'woocommerce_product_thumbnails_large_size', 'preview' );

in

add_image_size( 'preview', $width = 3072, $height =3072, $crop = false ); 

$post_thumbnail_id = get_post_thumbnail_id( $post->ID );
$filemeta = wp_get_attachment_metadata( $post_thumbnail_id, FALSE );

if ($filemeta['width']>3071 || $filemeta['height']>3071){
    $thumbnail_size    = apply_filters( 'woocommerce_product_thumbnails_large_size', 'preview' );
}else{
    $thumbnail_size    = apply_filters( 'woocommerce_product_thumbnails_large_size', 'large' );
}

Maybe there is a smarter way but this works for me.

EDIT 2018-06-26 I picked this project up after a while and noticed that it is not working anymore due to the WooCommerce update to 3.3. WooCommerce has changes the way it handles product images. For me it means that I'm back at square one. WooCommerce displays the full-size image in the light box and that is not what I want. Does someone have a clue?