function replace_unsplash_urls() {
    var width = 1500;
    var height = 600;

    var links = document.querySelectorAll('#gridMulti a');
    for(var i = 0; i < links.length; i++) {
        var item = links.item(i);
        var url = links.item(i).style.getPropertyValue('background-image');
        if (url) {
            url = url.slice(4, -1);
            url = url.replace(/(w=).*?(&)/,'$1' + width + '$2');
            url = url.replace(/(h=).*?(&)/,'$1' + height + '$2');
            item.href = url;
        }
    }
}
replace_unsplash_urls();