server/core/js/placeholder.js

/**
 * ownCloud
 *
 * @author John Molakvoæ
 * @copyright 2016-2018 John Molakvoæ <skjnldsv@protonmail.com>
 * @author Morris Jobke
 * @copyright 2013 Morris Jobke <morris.jobke@gmail.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU AFFERO GENERAL PUBLIC LICENSE for more details.
 *
 * You should have received a copy of the GNU Affero General Public
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

/*
 * Adds a background color to the element called on and adds the first character
 * of the passed in string. This string is also the seed for the generation of
 * the background color.
 *
 * You have following HTML:
 *
 * <div id="albumart"></div>
 *
 * And call this from Javascript:
 *
 * $('#albumart').imageplaceholder('The Album Title');
 *
 * Which will result in:
 *
 * <div id="albumart" style="background-color: rgb(121, 90, 171); ... ">T</div>
 *
 * You may also call it like this, to have a different background, than the seed:
 *
 * $('#albumart').imageplaceholder('The Album Title', 'Album Title');
 *
 * Resulting in:
 *
 * <div id="albumart" style="background-color: rgb(121, 90, 171); ... ">A</div>
 *
 */

 /*
 * Alternatively, you can use the prototype function to convert your string to rgb colors:
 *
 * "a6741a86aded5611a8e46ce16f2ad646".toRgb()
 *
 * Will return the rgb parameters within the following object:
 *
 * Color {r: 208, g: 158, b: 109}
 *
 */

(function ($) {

	String.prototype.toRgb = function() {
		// Normalize hash		
		var hash = this.toLowerCase();

		// Already a md5 hash?
		if( hash.match(/^([0-9a-f]{4}-?){8}$/) === null ) {
			hash = md5(hash);
		}

		hash = hash.replace(/[^0-9a-f]/g, '');

		function Color(r,g,b) {
			this.r = r;
			this.g = g;
			this.b = b;
		}

		function stepCalc(steps, ends) {
			var step = new Array(3);
			step[0] = (ends[1].r - ends[0].r) / steps;
			step[1] = (ends[1].g - ends[0].g) / steps;
			step[2] = (ends[1].b - ends[0].b) / steps;
			return step;
		}

		function mixPalette(steps, color1, color2) {
			var count = steps + 1;
			var palette = new Array();
			palette.push(color1);
			var step = stepCalc(steps, [color1, color2])
			for (i = 1; i < steps; i++) {
				var r = parseInt(color1.r + (step[0] * i));
				var g = parseInt(color1.g + (step[1] * i));
				var b = parseInt(color1.b + (step[2] * i));
					palette.push(new Color(r,g,b));
			}
			return palette;
		}

		var red = new Color(182, 70, 157);
		var yellow = new Color(221, 203, 85);
		var blue = new Color(0, 130, 201); // Nextcloud blue
		// Number of steps to go from a color to another
		// 3 colors * 6 will result in 18 generated colors
		var steps = 6;

		var palette1 = mixPalette(steps, red, yellow);
		var palette2 = mixPalette(steps, yellow, blue);
		var palette3 = mixPalette(steps, blue, red);

		var finalPalette = palette1.concat(palette2).concat(palette3);

		// Convert a string to an integer evenly
		function hashToInt(hash, maximum) {
			var finalInt = 0;
			var result = Array();

			// Splitting evenly the string
			for (var i=0; i<hash.length; i++) {
				// chars in md5 goes up to f, hex:16
				result.push(parseInt(hash.charAt(i), 16) % 16);
			}
			// Adds up all results
			for (var j in result) {
				finalInt += result[j];
			}
			// chars in md5 goes up to f, hex:16
			// make sure we're always using int in our operation
			return parseInt(parseInt(finalInt) % maximum);
		}
		return finalPalette[hashToInt(hash, steps * 3 )];
	};

	$.fn.imageplaceholder = function(seed, text, size) {
		text = text || seed;

		// Compute the hash
		var rgb = seed.toRgb();
		this.css('background-color', 'rgb('+rgb.r+', '+rgb.g+', '+rgb.b+')');

		// Placeholders are square
		var height = this.height() || size || 32;
		this.height(height);
		this.width(height);

		// CSS rules
		this.css('color', '#fff');
		this.css('font-weight', 'normal');
		this.css('text-align', 'center');

		// calculate the height
		this.css('line-height', height + 'px');
		this.css('font-size', (height * 0.55) + 'px');

		if(seed !== null && seed.length) {
			this.html(text[0].toUpperCase());
		}
	};

	$.fn.clearimageplaceholder = function() {
		this.css('background-color', '');
		this.css('color', '');
		this.css('font-weight', '');
		this.css('text-align', '');
		this.css('line-height', '');
		this.css('font-size', '');
		this.html('');
		this.removeClass('icon-loading');
		this.removeClass('icon-loading-small');
	};
}(jQuery));