I’ve noticed a hole in the ShopifyAPI.
You can set ‘alt’ tags on Product Images… yet you cannot filter Product Images depending on the ‘alt’ tag.
I see the ‘alt’ tag is saved as a Metafield of the Product Image, yet it does not exist when retrieving the Product Image Metafields.
Could Metafields please be also allowed for Product Images? Or allow Product Images to be filtered depending on the ‘alt’ tag.
Shopify Liquid can filter depending on the Product Images 'alt' tag.
N.B. I know 'alt' tags are really for SEO. But I cannot see any other way of adding properties to a Product Image.
Refering from: http://www.shopify.com/technology/3032322-new-feature-metafields