Rotating images using the Matrix class

Somebody recently asked on a forum how you could rotate images using the Matrix class. I quickly built this super-simple little example which shows how to use the <mx:Rotate /> effect as well as the Matrix class’s rotate() method.

Full code after the jump.

If you’re new to transforms and matrices, check out Senocular.com’s excellent article, “Understanding the Transform Matrix in Flash 8“.

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2007/09/14/rotating-images-using-the-matrix-class/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="horizontal"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:String id="deg">&#0176;</mx:String>

    <mx:Script>
        <![CDATA[
            import mx.core.UIComponent;

            private function img1_effectEnd():void {
                /* Set the appropriate Label text. */
                lbl1.text = "img1.rotation = " + img1.rotation.toString() + deg;
            }

            private function img2_creationComplete():void {
                /* "Copy" the existing matrix. */
                var m1:Matrix = img2.transform.matrix;
                /* Rotate the matrix 45 degrees (note that we have to
                   convert from degrees to radians since the rotate()
                   method expects radians. */
                m1.rotate(degreesToRadians(45));
                /* Concatenate the original matrix onto the rotated
                   matrix so we don't lose the original X and Y
                   coordinates and any other effects. */
                m1.concat(img2.transform.matrix);
                /* "Copy" the new matrix over the existing matrix. */
                img2.transform.matrix = m1;
                /* Set the appropriate Label text. */
                lbl2.text = "img2.rotation = " + img2.rotation.toString() + deg;
            }

            private function img_rollOver(cTarget:UIComponent):void {
                cTarget.toolTip = cTarget.name + ".rotation = " + cTarget.rotation.toString();
            }

            private function radiansToDegrees(radians:Number):Number {
                var degrees:Number = radians * (180 / Math.PI);
                return degrees;
            }

            private function degreesToRadians(degrees:Number):Number {
                var radians:Number = degrees * (Math.PI / 180);
                return radians;
            }
        ]]>
    </mx:Script>

    <mx:Rotate id="rotate" angleFrom="0" angleTo="45" duration="1" />

    <mx:ApplicationControlBar dock="true">
        <mx:Label id="lbl1" />
        <mx:Spacer width="50" />
        <mx:Label id="lbl2" />
    </mx:ApplicationControlBar>

    <mx:Image id="img1"
            source="http://www.helpexamples.com/flash/images/logo.png"
            creationCompleteEffect="{rotate}"
            effectEnd="img1_effectEnd();"
            rollOver="img_rollOver(UIComponent(event.currentTarget));" />

    <mx:Spacer width="50" />

    <mx:Image id="img2"
            source="http://www.helpexamples.com/flash/images/logo.png"
            creationComplete="img2_creationComplete();"
            rollOver="img_rollOver(UIComponent(event.currentTarget));" />

</mx:Application>

View source is enabled in the following example.

And just for giggles, here is a similar example which lets you rotate the image using a couple of Button controls. Note that the rotation is done around the center point of the image by calling the Matrix class’s translate() method to move the image before and after the rotation.

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2007/09/14/rotating-images-using-the-matrix-class/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            private function button_click(evt:Event):void {
                var direction:int;
                switch (evt.currentTarget) {
                    case degreesUp:
                        direction = +1;
                        break;
                    case degreesDown:
                        direction = -1;
                        break;
                }

                var radians:Number = degreesToRadians(direction);
                var offsetWidth:Number = img.width / 2;
                var offsetHeight:Number = img.height / 2;
                var tempMatrix:Matrix = img.transform.matrix;
                tempMatrix.translate(-offsetWidth, -offsetHeight);
                tempMatrix.rotate(radians);
                tempMatrix.translate(+offsetWidth, +offsetHeight);

                img.transform.matrix = tempMatrix;

                rotateDeg = img.rotation;
            }

            private function radiansToDegrees(radians:Number):Number {
                var degrees:Number = radians * (180 / Math.PI);
                return degrees;
            }

            private function degreesToRadians(degrees:Number):Number {
                var radians:Number = degrees * (Math.PI / 180);
                return radians;
            }
        ]]>
    </mx:Script>

    <mx:Number id="rotateDeg">0</mx:Number>
    <mx:NumberFormatter id="numberFormatter" precision="0" />
    <mx:String id="deg">{String.fromCharCode(176)}</mx:String>

    <mx:ApplicationControlBar dock="true">
        <mx:Label text="rotation:" />
        <mx:Button id="degreesUp"
                label="+"
                autoRepeat="true"
                click="button_click(event);"
                buttonDown="button_click(event);" />
        <mx:Button id="degreesDown"
                label="-"
                autoRepeat="true"
                click="button_click(event);"
                buttonDown="button_click(event);" />
        <mx:Spacer width="50" />
        <mx:Label id="lbl"
                text="{numberFormatter.format(rotateDeg)}{deg}" />
    </mx:ApplicationControlBar>

    <mx:VBox>
        <mx:Image id="img"
                source="http://www.helpexamples.com/flash/images/logo.png" />
    </mx:VBox>

</mx:Application>

View source is enabled in the following example.

Tagged as: concat(), transform, translate()