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Store the modified pixel data in the bitmap
Listing 6 copies the modified pixel data from the ByteArray object back into the bitmap, overwriting the pixel data previously stored in the bitmap.
//Put the modified pixels back into the bitmapData
// object.rawBytes.position = 0;//this is critical
bitmapData.setPixels(new Rectangle(0,0,bitmapData.width,bitmapData.height),
rawBytes);} //end processChromaKey method//--------------------------------------------------//} //end class
} //end package I explained all of the code in Listing 6 in the earlier lesson titled Fundamentals of Image Pixel Processing.
The end of the class
Listing 6 also signals the end of the method, the end of the class, the end of the package, and the end of the program.
I encourage you to run this program from the web. Then copy the code from Listing 7 and Listing 8. Use that code to create a newproject. Compile and run the project. Experiment with the code, making changes, and observing the results of your changes. Make certain that you can explain whyyour changes behave as they do.
I will publish a list containing links to ActionScript resources as a separate document. Search for ActionScript Resources in theConnexions search box.
Complete listings for the program discussed in this lesson are provided in Listing 7 and Listing 8 below.
Listing/*Project ChromaKey01
This project scans all of the pixels in an image toidentify those pixels with a color of pure magenta. The
alpha value for those pixels is set to zero to make themtransparent.
*********************************************************/package CustomClasses{
import flash.display.Bitmap;import flash.display.BitmapData;
import flash.geom.Rectangle;import flash.utils.ByteArray;
import mx.containers.Canvas;import mx.controls.Image;
import mx.events.FlexEvent;//====================================================//public class Driver extends Canvas {
private var origImage:Image = new Image();public function Driver(){//constructor//Make this Canvas visible with a yellow background.
setStyle("backgroundColor",0xFFFF00);setStyle("backgroundAlpha",1.0);
//Load the origImage and embed it in the swf file.//Note the slash that is required by FlashDevelop.
[Embed("/dancer.png")]var img:Class;
origImage.load(img);//Register a CREATION_COMPLETE listener
this.addEventListener(FlexEvent.CREATION_COMPLETE,completeHandler);
} //end constructor//--------------------------------------------------//
//This handler method is executed when the Canvas has// been fully created.
private function completeHandler(event:mx.events.FlexEvent):void{
//Get and save a reference to a Bitmap object// containing the contents of the origImage file.
var origBitMap:Bitmap = Bitmap(origImage.content);//Set the width and height of the Canvas object// based on the size of the origBitMap bitmap. Make
// ten pixels wider and twice as high as the// bitmap.
this.width = origBitMap.width + 10;this.height = 2*origBitMap.height;
//Add the original image to the Canvas object at// the default location of 0,0.
this.addChild(origImage);//Clone the origBitMap to create a// duplicate.
var dupBitMap:Bitmap = new Bitmap(origBitMap.bitmapData.clone());//Put the dupBitMap in a new Image object and
// place it on the canvas below the original image.dupBitMap.x = 0;
dupBitMap.y = origBitMap.height;var newImage:Image = new Image();newImage.addChild(dupBitMap);
this.addChild(newImage);//Set the alpha value for all pixels in the new// image with a color of pure magenta to zero.
processChromaKey(dupBitMap);} //end completeHandler
//--------------------------------------------------////This method identifies all of the pixels in the// incoming bitmap with a pure magenta color and sets
// the alpha bytes for those pixels to a value of// zero.
private function processChromaKey(bitmap:Bitmap):void{//Get the BitmapData object.
var bitmapData:BitmapData = bitmap.bitmapData;//Populate a one-dimensional byte array of pixel
// data from the bitmapData object. Note that the// pixel data format is ARGB.
var rawBytes:ByteArray = new ByteArray();rawBytes = bitmapData.getPixels(new Rectangle(
0,0,bitmapData.width,bitmapData.height));//Declare working variables. Note that there is// no requirement to deal with the green color
// value in this case of testing for magenta.var cnt:uint;
var red:uint;var green:uint;
var blue:uint;for (cnt = 0; cnt<rawBytes.length; cnt += 4) {
//alpha is in rawBytes[cnt]red = rawBytes[cnt + 1];green = rawBytes[cnt + 2];blue = rawBytes[cnt + 3];if ((red == 255)&&(green == 0 )&&(blue == 255)) {//The color is pure magenta. Set the value
// of the alpha byte to zero.rawBytes[cnt] = 0;}//end if
}//end for loop//Put the modified pixels back into the bitmapData// object.
rawBytes.position = 0;//this is criticalbitmapData.setPixels(new Rectangle(
0,0,bitmapData.width,bitmapData.height),rawBytes);} //end processChromaKey method
//--------------------------------------------------//} //end class
} //end package
<?xml version="1.0" encoding="utf-8"?><!--
Project ChromaKey01This project scans all of the pixels in an image to
identify those pixels with a color of pure magenta. Thealpha value for those pixels is set to zero to make them
transparent.--><mx:Application
xmlns:mx="http://www.adobe.com/2006/mxml"xmlns:cc="CustomClasses.*"><cc:Driver/></mx:Application> This section contains a variety of miscellaneous materials.
-end-
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