Ctrl+LeftClick to save image

ctrl-lclick-save-image.user.js

// ==UserScript==
// @name           Ctrl+LeftClick to save image
// @namespace      https://gist.github.com/justdanpo
// @version        0.1
// @description    Ctrl+LeftClick to save image
// @author         den_po
// @match          http://*/*
// @match          https://*/*
// @grant          none
// ==/UserScript==

(function() {

    function checkCommon(evt) {
        if (evt.target.tagName != "IMG")
            return false;
        if (evt.button != 0)
            return false;
        if (!evt.ctrlKey || evt.altKey || evt.shiftKey)
            return false;

        evt.preventDefault();
        evt.stopPropagation();
        return true;
    }

    window.addEventListener('mousedown', function(evt) {
        if (checkCommon(evt)) {
            var a = document.createElement('a');
            a.href = evt.target.src;
            a.setAttribute('download', '');
            a.dispatchEvent(new MouseEvent('click'));
        }
    }, true);

    window.addEventListener('click', function(evt) {
        checkCommon(evt);
    }, true);
})();