Displaying an icon on a toggle button in Flex 4

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/07/28/displaying-an-icon-on-a-toggle-button-in-flex-4/ -->
<s:Application name="Spark_ButtonBarButton_data_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark">
 
    <fx:Style>
        @namespace s "library://ns.adobe.com/flex/spark";
 
        s|ButtonBarButton.iconButton {
            skinClass: ClassReference("skins.CustomIconButtonSkin");
        }
    </fx:Style>
 
    <s:HGroup horizontalCenter="0" verticalCenter="0">
        <s:ButtonBarButton id="redBtn"
                label="Red"
                data="@Embed('assets/bullet_red.png')"
                styleName="iconButton" />
        <s:ButtonBarButton id="orangeBtn"
                label="Orange"
                data="@Embed('assets/bullet_orange.png')"
                styleName="iconButton" />
        <s:ButtonBarButton id="yelloyBtn"
                label="Yellow"
                data="@Embed('assets/bullet_yellow.png')"
                styleName="iconButton" />
        <s:ButtonBarButton id="greenBtn"
                label="Green"
                data="@Embed('assets/bullet_green.png')"
                styleName="iconButton" />
        <s:ButtonBarButton id="blueBtn"
                label="Blue"
                data="@Embed('assets/bullet_blue.png')"
                styleName="iconButton" />
    </s:HGroup>
 
</s:Application>

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/07/28/displaying-an-icon-on-a-toggle-button-in-flex-4/ -->
<s:SparkSkin name="CustomIconButtonSkin"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark" 
        minWidth="21" minHeight="21"
        alpha.disabledStates="0.5">
    <!-- states -->
    <s:states>
        <s:State name="up" />
        <s:State name="over" stateGroups="overStates" />
        <s:State name="down" stateGroups="downStates" />
        <s:State name="disabled" stateGroups="disabledStates" />
        <s:State name="upAndSelected" stateGroups="selectedStates, selectedUpStates" />
        <s:State name="overAndSelected" stateGroups="overStates, selectedStates" />
        <s:State name="downAndSelected" stateGroups="downStates, selectedStates" />
        <s:State name="disabledAndSelected" stateGroups="selectedUpStates, disabledStates, selectedStates" />
    </s:states>
 
    <!-- host component -->
    <fx:Metadata>
        <![CDATA[ 
            [HostComponent("spark.components.ButtonBarButton")]
        ]]>
    </fx:Metadata>
 
    <fx:Script>
        /* Define the skin elements that should not be colorized. 
        For toggle button, the graphics are colorized but the label is not. */
        static private const exclusions:Array = ["labelDisplay"];
 
        override public function get colorizeExclusions():Array {return exclusions;}
    </fx:Script>
 
    <!-- layer 1: shadow -->
    <s:Rect left="-1" right="-1" top="-1" bottom="-1"
            radiusX="2" radiusY="2">
        <s:fill>
            <s:LinearGradient rotation="90">
                <s:GradientEntry color="0x000000" 
                        color.downStates="0xFFFFFF"
                        alpha="0.01"
                        alpha.downStates="0" />
                <s:GradientEntry color="0x000000" 
                        color.downStates="0xFFFFFF" 
                        alpha="0.07"
                        alpha.downStates="0.5" />
            </s:LinearGradient>
        </s:fill>
    </s:Rect>
 
    <!-- layer 2: fill -->
    <s:Rect left="1" right="1" top="1" bottom="1" radiusX="2" radiusY="2">
        <s:fill>
            <s:LinearGradient rotation="90">
                <s:GradientEntry color="0xFFFFFF" 
                        color.selectedUpStates="0xBBBDBD"
                        color.overStates="0xBBBDBD" 
                        color.downStates="0xAAAAAA" 
                        alpha="0.85" 
                        alpha.overAndSelected="1" />
                <s:GradientEntry color="0xD8D8D8" 
                        color.selectedUpStates="0x9FA0A1"
                        color.over="0x9FA0A1" 
                        color.overAndSelected="0x8E8F90"
                        color.downStates="0x929496" 
                        alpha="0.85"
                        alpha.overAndSelected="1" />
            </s:LinearGradient>
        </s:fill>
    </s:Rect>
 
    <!-- layer 3: fill lowlight -->
    <s:Rect left="1" right="1" bottom="1" height="9"
            radiusX="2" radiusY="2">
        <s:fill>
            <s:LinearGradient rotation="90">
                <s:GradientEntry color="0x000000" alpha="0.0099" />
                <s:GradientEntry color="0x000000" alpha="0.0627" />
            </s:LinearGradient>
        </s:fill>
    </s:Rect>
 
    <!-- layer 4: fill highlight -->
    <s:Rect left="1" right="1" top="1" height="9"
            radiusX="2" radiusY="2">
        <s:fill>
            <s:SolidColor color="0xFFFFFF" 
                    alpha="0.33" 
                    alpha.selectedUpStates="0.22"
                    alpha.overStates="0.22" 
                    alpha.downStates="0.12" />
        </s:fill>
    </s:Rect>
 
    <!-- layer 5: highlight stroke (all states except down) -->
    <s:Rect left="1" right="1" top="1" bottom="1"
            radiusX="2" radiusY="2"
            excludeFrom="downStates">
        <s:stroke>
            <s:LinearGradientStroke rotation="90" weight="1">
                <s:GradientEntry color="0xFFFFFF"
                        alpha.overStates="0.22"
                        alpha.selectedUpStates="0.33" />
                <s:GradientEntry color="0xD8D8D8"
                        alpha.overStates="0.22"
                        alpha.selectedUpStates="0.33" />
            </s:LinearGradientStroke>
        </s:stroke>
    </s:Rect>
 
    <!-- layer 6: highlight stroke (down state only) -->
    <s:Rect left="1" top="1" bottom="1" width="1"
            includeIn="downStates, selectedUpStates, overAndSelected">
        <s:fill>
            <s:SolidColor color="0x000000" alpha="0.07" />
        </s:fill>
    </s:Rect>
    <s:Rect right="1" top="1" bottom="1" width="1"
            includeIn="downStates, selectedUpStates, overAndSelected">
        <s:fill>
            <s:SolidColor color="0x000000" alpha="0.07" />
        </s:fill>
    </s:Rect>
    <s:Rect left="2" top="1" right="2" height="1"
            includeIn="downStates, selectedUpStates, overAndSelected">
        <s:fill>
            <s:SolidColor color="0x000000" alpha="0.25" />
        </s:fill>
    </s:Rect>
    <s:Rect left="1" top="2" right="1" height="1"
            includeIn="downStates, selectedUpStates, overAndSelected">
        <s:fill>
            <s:SolidColor color="0x000000" alpha="0.09" />
        </s:fill>
    </s:Rect>
 
    <!-- layer 7: border - put on top of the fill so it doesn't disappear when scale is less than 1 -->
    <s:Rect left="0" right="0" top="0" bottom="0"
            width="69" height="20"
            radiusX="2" radiusY="2">
        <s:stroke>
            <s:LinearGradientStroke rotation="90" weight="1">
                <s:GradientEntry color="0x000000"
                        alpha="0.5625"
                        alpha.down="0.6375"
                        alpha.selectedStates="0.6375" />
                <s:GradientEntry color="0x000000" 
                        alpha="0.75"
                        alpha.down="0.85"
                        alpha.selectedStates="0.85" />
            </s:LinearGradientStroke>
        </s:stroke>
    </s:Rect>
 
    <s:HGroup horizontalCenter="0" verticalCenter="1"
            left="10" right="10" top="2" bottom="2"
            creationComplete="img.source = hostComponent.data;">
        <!-- layer 8: icon -->
        <s:BitmapImage id="img" />
 
        <!-- layer 9: text -->
        <s:SimpleText id="labelDisplay"
                textAlign="center"
                verticalAlign="middle"
                maxDisplayedLines="1"
                height="100%"/>
    </s:HGroup>
 
</s:SparkSkin>