    /**
     * @class Ext.chart.Label
     *
     * Labels is a mixin to the Series class. Labels methods are implemented
     * in each of the Series (Pie, Bar, etc) for label creation and placement.
     *
     * The methods implemented by the Series are:
     *
     * - **`onCreateLabel(storeItem, item, i, display)`** Called each time a new label is created.
     *   The arguments of the method are:
     *   - *`storeItem`* The element of the store that is related to the label sprite.
     *   - *`item`* The item related to the label sprite. An item is an object containing the position of the shape
     *     used to describe the visualization and also pointing to the actual shape (circle, rectangle, path, etc).
     *   - *`i`* The index of the element created (i.e the first created label, second created label, etc)
     *   - *`display`* The display type. May be <b>false</b> if the label is hidden
     *
     *  - **`onPlaceLabel(label, storeItem, item, i, display, animate)`** Called for updating the position of the label.
     *    The arguments of the method are:
     *    - *`label`* The sprite label.</li>
     *    - *`storeItem`* The element of the store that is related to the label sprite</li>
     *    - *`item`* The item related to the label sprite. An item is an object containing the position of the shape
     *      used to describe the visualization and also pointing to the actual shape (circle, rectangle, path, etc).
     *    - *`i`* The index of the element to be updated (i.e. whether it is the first, second, third from the labelGroup)
     *    - *`display`* The display type. May be <b>false</b> if the label is hidden.
     *    - *`animate`* A boolean value to set or unset animations for the labels.
     */
    Ext.define('Ext.chart.Label', {

        /* Begin Definitions */

        requires: ['Ext.draw.Color'],

        /* End Definitions */

        /**
         * @cfg {Object} label
         * Object with the following properties:
         *
         * - **display** : String
         *
         *   Specifies the presence and position of labels for each pie slice. Either "rotate", "middle", "insideStart",
         *   "insideEnd", "outside", "over", "under", or "none" to prevent label rendering.
         *   Default value: 'none'.
         *
         * - **color** : String
         *
         *   The color of the label text.
         *   Default value: '#000' (black).
         *
         * - **contrast** : Boolean
         *
         *   True to render the label in contrasting color with the backround.
         *   Default value: false.
         *
         * - **field** : String
         *
         *   The name of the field to be displayed in the label.
         *   Default value: 'name'.
         *
         * - **minMargin** : Number
         *
         *   Specifies the minimum distance from a label to the origin of the visualization.
         *   This parameter is useful when using PieSeries width variable pie slice lengths.
         *   Default value: 50.
         *
         * - **font** : String
         *
         *   The font used for the labels.
         *   Default value: "11px Helvetica, sans-serif".
         *
         * - **orientation** : String
         *
         *   Either "horizontal" or "vertical".
         *   Dafault value: "horizontal".
         *
         * - **renderer** : Function
         *
         *   Optional function for formatting the label into a displayable value.
         *   Default value: function(v) { return v; }
         */

        // @private a regex to parse url type colors.
        colorStringRe: /url\s*\(\s*#([^\/)]+)\s*\)/,

        // @private the mixin constructor. Used internally by Series.
        constructor: function(config) {
            var me = this;
            me.label = Ext.applyIf(me.label || {},
            {
                display: "none",
                color: "#000",
                field: "name",
                minMargin: 50,
                font: "11px Helvetica, sans-serif",
                orientation: "horizontal",
                renderer: function(v) {
                    return v;
                }
            });

            if (me.label.display !== 'none') {
                me.labelsGroup = me.chart.surface.getGroup(me.seriesId + '-labels');
            }
        },

        // @private a method to render all labels in the labelGroup
        renderLabels: function() {
            var me = this,
                chart = me.chart,
                gradients = chart.gradients,
                items = me.items,
                animate = chart.animate,
                config = me.label,
                display = config.display,
                color = config.color,
                field = [].concat(config.field),
                group = me.labelsGroup,
                groupLength = (group || 0) && group.length,
                store = me.chart.getChartStore(),
                len = store.getCount(),
                itemLength = (items || 0) && items.length,
                ratio = itemLength / len,
                gradientsCount = (gradients || 0) && gradients.length,
                Color = Ext.draw.Color,
                hides = [],
                gradient, i, count, groupIndex, index, j, k, colorStopTotal, colorStopIndex, colorStop, item, label,
                storeItem, sprite, spriteColor, spriteBrightness, labelColor, colorString;

            if (display == 'none') {
                return;
            }
            // no items displayed, hide all labels
            if(itemLength == 0){
                while(groupLength--) {
                    hides.push(groupLength);
                }
            } else {
                for (i = 0, count = 0, groupIndex = 0; i < len; i++) {
                    index = 0;
                    for (j = 0; j < ratio; j++) {
                        item = items[count];
                        label = group.getAt(groupIndex);
                        storeItem = store.getAt(i);
                        //check the excludes
                        while(this.__excludes && this.__excludes[index]) {
                            index++;
                        }

                        if (!item && label) {
                            label.hide(true);
                            groupIndex++;
                        }

                        if (item && field[j]) {
                            if (!label) {
                                label = me.onCreateLabel(storeItem, item, i, display, j, index);
                            }
                            me.onPlaceLabel(label, storeItem, item, i, display, animate, j, index);
                            groupIndex++;

                            //set contrast
                            if (config.contrast && item.sprite) {
                                sprite = item.sprite;
                                //set the color string to the color to be set.
                                if (sprite._endStyle) {
                                    colorString = sprite._endStyle.fill;
                                }
                                else if (sprite._to) {
                                    colorString = sprite._to.fill;
                                }
                                else {
                                    colorString = sprite.attr.fill;
                                }
                                colorString = colorString || sprite.attr.fill;

                                spriteColor = Color.fromString(colorString);
                                //color wasn't parsed property maybe because it's a gradient id
                                if (colorString && !spriteColor) {
                                    colorString = colorString.match(me.colorStringRe)[1];
                                    for (k = 0; k < gradientsCount; k++) {
                                        gradient = gradients[k];
                                        if (gradient.id == colorString) {
                                            //avg color stops
                                            colorStop = 0; colorStopTotal = 0;
                                            for (colorStopIndex in gradient.stops) {
                                                colorStop++;
                                                colorStopTotal += Color.fromString(gradient.stops[colorStopIndex].color).getGrayscale();
                                            }
                                            spriteBrightness = (colorStopTotal / colorStop) / 255;
                                            break;
                                        }
                                    }
                                }
                                else {
                                    spriteBrightness = spriteColor.getGrayscale() / 255;
                                }
                                if (label.isOutside) {
                                    spriteBrightness = 1;
                                }
                                labelColor = Color.fromString(label.attr.color || label.attr.fill).getHSL();
                                labelColor[2] = spriteBrightness > 0.5 ? 0.2 : 0.8;
                                label.setAttributes({
                                    fill: String(Color.fromHSL.apply({}, labelColor))
                                }, true);
                            }

                        }
                        count++;
                        index++;
                    }
                }
                groupLength = group.length;

                while(groupLength > groupIndex){
                    hides.push(groupIndex);
                    groupIndex++;
               }
            }
            me.hideLabels(hides);
        },

        hideLabels: function(hides){
            var labelsGroup = this.labelsGroup,
                hlen = !!hides && hides.length;

            if (!labelsGroup) {
                return;
            }

            if (hlen === false) {
                hlen = labelsGroup.getCount();
                while (hlen--) {
                  labelsGroup.getAt(hlen).hide(true);
                }
            } else {
                while(hlen--) {
                    labelsGroup.getAt(hides[hlen]).hide(true);
                }
            }
        }
    });