Source: cropper.js

/**
 * Cropper Component<BR>
 * <BR><BR><img src=/tk/lib/components/w/img/cropper.png width=30% style="border:1px lime dashed;padding:20px">
 * <BR><BR><a href="/tk/lib/components/w/html/cropper.html">DEMO</a>
 */
class Cropper extends HTMLElement {
    constructor() {
        wc.group("Cropper.constructor")
	
        super();

        wc.groupEnd();
    };
    
    /**
     * Set observable values here. When Changed, attributeChangedCallback is invoked
     * @observedAttributes
     */
    static get observedAttributes() {
        wc.group("Cropper.observedAttributes");

	this.observables = [];

        wc.groupEnd();
        return this.observables;
    };

    /**
     * Initial Markup
     * @private
     * @_template
     */
    _template() {
        wc.group("Cropper.template");
	
	if (this.properties.filechoose == "true") {var fc = "block";} else {var fc = "none";}
	if (this.properties.filesave   == "true") {var fs = "block";} else {var fs = "none";}

	var temp = `
<div class="wc-cropper-wrapper">
    <div id="${this.id}-editor">
	<input type="file" id="cropper-file-chooser" class="cropit-image-input" style="display:none">
	<div class="cropit-preview"></div>

	<div style=padding-top:20px!important;>
	    <input type="range" class="cropit-image-zoom-input">
	</div>

	<div style=padding-top:20px!important>
	    <button id="wc-cropper-export" class="wc-cropper-export btn btn-primary btn-lg btn-block" style="display:${fs}">SAVE IMAGE</button>
	</div>

	<!-- conditional file chooser -->
        <button id="${this.id}-choose-btn" class="wc-chooser-btn btn btn-outline-success btn-block" style="display:${fc}">CHOOSE FILE</button>
    </div>
</div>`
        wc.groupEnd();
        return temp;
    };

    /**
     * Called when this is attached to DOM
     * @connectedCallback. 
     */
    connectedCallback() {
        wc.group("Cropper.connectedCallback")
	
	let self = this;

	// GET PROPERTIES AND INTERESTING ELEMENTS
	this._initialize();

	// ADD COMPONENT MARKTOP
	this.innerHTML = this._template()

	setTimeout(function(){
	    self.editor = $("#" + self.id + "-editor");

	    //$("[type=file]").css("margin-left","-2000px")

	    $("#" + self.id + "-choose-btn").css("margin-bottom","-25px").on("click", function() {
		$("[type=file]").click()
	    });

            let crop = self.editor.cropit({
		minZoom: "fit",
		maxZoom: self.properties.maxzoom,
		freeMove: true,
		smallImage: "reject",
		exportZoom: self.properties.savesize,
		imageBackground: true,
		imageState: {src: `${self.properties.img}`},
		onFileChange: function(e) {
		    wc.log("onFileChange:", e);
		},
		onFileReaderError: function(e) {
		    wc.log("onFileReaderError:", e);

		    wc.publish("wc-cropper", {
			time: new Date().getTime(),
			action: "error",
			id: self.id,
			eid: 2100,
			msg: e.message
		    });
		},
		onImageLoading: function(e) {
		    // CROPIT HARD RESET 
		    $('.cropit-preview').removeClass('cropit-image-loaded');
		    $('.cropit-preview-background').attr('src','');
		    $('.cropit-preview-image').attr('src','');
		    $('.cropit-preview-image').removeAttr('style');
		    $('.cropit-preview-image').attr('style','transform-origin: left top 0px; will-change: transform;');
		    $('input.cropit-image-input').val('');
		    $('.cropit-image-zoom-input').val('0');

		    wc.log("onImageLoading:", e);
		},
		onImageLoaded: function(e) {
		    wc.log("onImageLoaded:", e);

		    wc.publish("wc-cropper", {
			time: new Date().getTime(),
			action: "file",
			id: self.id
		    });
		},
		onImageError: function(e) {
		    wc.log("onImageError:", e);

		    if (e.code != 0) {
			wc.publish("wc-cropper", {
			    time: new Date().getTime(),
			    action: "error",
			    id: self.id,
			    eid: 2000,
			    msg: e.message
			});
		    }
		},
		onZoomEnabled: function(e) {
		    wc.log("onZoomEnabled:", e);
		},
		onZoomDisabled: function(e) {
		    wc.log("onZoomDisabled:", e);
		    //self.editor.cropit('reenable');
		},
		onZoomChange: function(e) {
		    wc.log("onZoomChange:", e);
		},
		onZoomOffset: function(e) {
		    wc.log("onZoomOffset:", e);
		},
            });

            $('.wc-cropper-export').click(function() {
		var imageData = self.editor.cropit('export');

		if (0) {
		    var tab = window.open('about:blank', '_blank');
		    tab.document.write("<img src=" + imageData + ">"); // where 'html' is a variable containing your HTML
		    tab.document.close(); // to finish loading the page
		} else {
		    wc.publish("wc-cropper", {
			time: new Date().getTime(),
			action: "save",
			id: this.id,
			img: imageData
		    });
		}
            });
	}, 0);

	// REPOSITION WHEN A MODAL IS SHOWN
	$('.modal').on('show.bs.modal', this._reposition);

	// ADD STATS AND OTHER FINAL STUFF
	this._finalize();

        wc.groupEnd();
    };

    /**
     * Centers the dialog
     * @private
     * @_reposition
     */
    _reposition() {
	wc.group("Cropper._reposition");

        var modal = $(this), dialog = modal.find('.modal-dialog');
        modal.css('display', 'block');
        
        // Dividing by two centers the modal exactly, but dividing by three 
        // or four works better for larger screens.
        dialog.css("margin-top", Math.max(0, ($(window).height() - dialog.height()) / 2));

	wc.groupEnd();
    }

    /**
     * Called with .setAttribute(...) function call
     * @attributeChangedCallback
     */
    attributeChangedCallback(attr, oldval, newval) {
        wc.group("Cropper.attributeChangedCallback:", attr, oldval, newval);

	this.properties = this.properties || [];

	let obs = Cropper.observedAttributes;

	for (let i = 0; i < obs.length; i++) {
	    if (newval) {
		this.properties[obs[i]] = newval;
	    }
	}
	
	// YOUR CODE FOR CHANGES GO HERE (MAYBE NULL FIRST TIME THROUGH)
	try {
	    switch(attr) 
	    {
		case "header":
		break;
		
		default:
		break;
	    }
	} catch(e) {
	    wc.warn(e.name + ' > ' + e.message);
	}

        wc.groupEnd();
    };

    /**
     * Stores DOM elements of interest for future use
     * @private
     * @_fetchElements
     */
    _fetchElements() {
	wc.group("Cropper._fetchElements");
	
	this.dom = this.dom || [];
	this.dom.content = this.innerHTML;

	wc.groupEnd();
    };

    /**
     * Component attributes are _fetched and defaults are set if undefined
     * @private
     * @_fetchAttributes
     */
    _fetchAttributes() {
	wc.group("Cropper._fetchAttributes");
	
	this.properties = {
	    cname      : "Cropper",
	    author     : "Mel M. Heravi",
	    version    : "1.0",
	    filechoose : "false",
	    filesave   : "false"
	};
	
	// SAVE WIDGET SPECIFIC PROPERTIES
	this.propertiesW = [];
	
	// SAVE ALL OTHER PROPERTIES
	let attrs = wc.getAttributes(this)
	
 	for (var key in attrs) {
	    let attr = this.getAttribute(key) || this.properties.key;
	    this.properties[key]  = this.getAttribute(key);
	    this.propertiesW[key] = this.getAttribute(key);
	    wc.log(key + ": " + attrs[key]);
	}

	// SET ALL INITIAL ATTRIBUTES
 	for (var key in this.properties) {
	    switch(key) 
	    {
		case "header":
		break;
		
		default:
		break;
	    }
	}

	wc.log("ATTRIBUTES: ", this.properties);

	wc.groupEnd();
    };

    /**
     * configure the instance object and artifacts
     * @configure
     */
    configure(aname) {
	wc.group("Cropper.configure:", aname);

	// IF JSON VARIABLE (aname) IS PROVIDED
	if (aname) {
	    this._process(aname);
	} else {
	    let self = this;

	    $.getJSON(this.properties.cfg, function(data) {
		self._process(data);
	    }).fail(function(jqXHR, textStatus, errorThrown) {
		alert("ERROR: INCOMING TEXT " + jqXHR.responseText);
	    });
	}

	wc.groupEnd();
    };

    /**
     * _process the instance object and artifacts
     * @private
     * @_process
     */
    _process(data) {
	wc.group("Cropper._process:", data);
	
	// DO WHATEVER WITH THE DATA
	
	wc.groupEnd();
    };

    /**
     * Initialize component
     * @private
     * @_initialize
     */
    _initialize() {
	wc.group("Cropper._initialize:", this.id);

	// FETCH ALL INTERESTING ELEMENTS
	this._fetchElements();

	// FETCH ALL ATTRIBUTES
	this._fetchAttributes();
	
	wc.groupEnd();
    };

    /**
     * Save data for analytics and final wrap up
     * @private
     * @_finalize
     */
    _finalize() {
	wc.group("Cropper._finalize:", this.id);

	this.classList.add("wc");

	// ADD ANALYTICS HERE
	wc.setStats(this, this.properties.cname, this.properties.version);
	
	// SHOW IT NOW (NO FLICKERS) 
	this.style.visibility = "visible";

	wc.groupEnd();
    };

    /**
     * Invoked When component is removed. Usually with a .remove() function call
     * @disconnectedCallback
     */
    disconnectedCallback() {
        wc.group("Cropper.disconnectedCallback")

	// FREE MEMORY AND CLEANUP

        wc.groupEnd();
    };

    /**
     * PUBLIC METHOD TO SAVE THE IMAGES
     * @save
     */
    save() {
        wc.group("Cropper.save")

	$('.wc-cropper-export').click();

        wc.groupEnd();
    }
}

window.customElements.define('wc-cropper', Cropper);