This is an edge case: I’m working on a WooCommerce project where I’m importing tens of thousands of product images from a supplier. The problem is, all the images have a 1 pixel black border and they look terrible when they’re displayed on the site. I have no idea why the supplier thought this was a good idea, but there you go.
To workaround the issue, I decided to attempt to hide the image border using the CSS3 box-shadow property. First, I wrapped the img element inside a div element. I then applied an inset box-shadow property to the div element, before adjusting the z-index of the img element to make it sit below the div. See the demo below.