开发基于FLARToolKit的增强现实（AR）基础教程（三）

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Creating An AR Detector(创建一个AR检测器)

当尝试了其他的一些关于FLARToolKit的例子后很容易忘记它是如何工作的。当我一行一行地分析代码才发现了它是如何构建的。我经常努力地去创建简单的，独立的类，并且可以轻松地重用和扩展。这就是我将FLARToolKit的构建密封到我们自己的叫做ARDetector类中的原因。让我们一同来创建这个类。

/**
* Original Author: Jesse Freeman
* Class File: ARDetector.as
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*
* Licensed under The MIT License
* Redistributions of files must retain the above copyright notice.
*
* Revisions
* 1.0 Initial version April 29, 2009
*
*/
package com.insideria.flar{
import flash.display.BitmapData;
import flash.events.Event;
import flash.events.EventDispatcher;
import flash.events.IEventDispatcher;
import flash.events.IOErrorEvent;
import flash.events.SecurityErrorEvent;
import flash.net.URLLoader;
import flash.net.URLLoaderDataFormat;
import flash.net.URLRequest;
import org.libspark.flartoolkit.core.FLARCode;
import org.libspark.flartoolkit.core.param.FLARParam;
import org.libspark.flartoolkit.core.raster.rgb.FLARRgbRaster_BitmapData;
import org.libspark.flartoolkit.core.transmat.FLARTransMatResult;
import org.libspark.flartoolkit.detector.FLARSingleMarkerDetector;
/**
* The ARDetector is a manager for the FLARToolKit and helps facilitate
* the setup, configuration, and detection of markers while using the
* FLARToolKit's underlining core classes.
*
* This class is a modification of an example on
* http://saqoosha.net/en/flartoolkit/start-up-guide
*
*
* @author Jesse Freeman
*
*/
public class ARDetector extends EventDispatcher{
protected var cameraURL:String;
protected var markerURL:String;
protected var codeWidth:int;
protected var _flarParam:FLARParam;
protected var code:FLARCode;
protected var raster:FLARRgbRaster_BitmapData;
protected var detector:FLARSingleMarkerDetector;
public var width:int;
public var height:int;
public var markerWidth:Number = 16;
public var markerHeight:Number = 16;
/**
*
* This is the ARDetector consturctor. By default we set the width and
* height to 320 x 240 to match our video source.
*
* @param canvasWidth set to 320 by default
* @param canvasHeight set to 240 by default
* @param codeWidth set to 80 by default. This represents the width of the marker.
*
*/
public function ARDetector(canvasWidth:int = 320, canvasHeight:int = 240, codeWidth:int = 80) {
width = canvasWidth;
height = canvasHeight;
this.codeWidth = codeWidth;
}
/**
* This will return an instance of the FLARParam.
*
*/
public function get flarParam():FLARParam
{
return _flarParam;
}
/**
* This sets the BitmapData src to be monitored for patterns.
*
*/
public function set src(target:BitmapData):void
{
// setup ARToolkit
raster = new FLARRgbRaster_BitmapData(target);
detector = new FLARSingleMarkerDetector(_flarParam, code, codeWidth);
}
/**
* @private
*
* Loads in the camera.dat file. This file contains information about
* the webcam.
*
* @param url path to camera.dat file.
*
*/
protected function loadCameraFile(url:String):void
{
var camLoader:URLLoader = new URLLoader();
camLoader.dataFormat = URLLoaderDataFormat.BINARY;
camLoader.addEventListener(Event.COMPLETE, onCameraFileLoad, false, 0, true);
addErrorListeners(camLoader);
camLoader.load(new URLRequest(url));
}
/**
* @private
*
* Triggered on a successful camera.dat file load. Once a complete
* event is received we remove the listeners, create a new FLARParam,
* and set it's screen size. Finally we load the marker.
*
* @param event
*
*/
protected function onCameraFileLoad(event:Event):void
{
event.stopImmediatePropagation();
var target:URLLoader = event.target as URLLoader;
target.removeEventListener(Event.COMPLETE, onCameraFileLoad);
removeErrorListeners(target);
_flarParam = new FLARParam();
_flarParam.loadARParam(target.data);
_flarParam.changeScreenSize(width, height);
loadMarkerFile(markerURL);
}
/**
* @private
*
* This loads the marker.pat file. The marker represents the image we
* look for from the src BitmapData.
*
*/
protected function loadMarkerFile(url:String):void
{
var patLoader:URLLoader = new URLLoader();
patLoader.dataFormat = URLLoaderDataFormat.TEXT;
patLoader.addEventListener(Event.COMPLETE, onMarkerFileLoad, false, 0, true);
addErrorListeners(patLoader);
patLoader.load(new URLRequest(url) );
}
/**
* @private
*
* Triggered when a marker.pat file is loaded. We remove the listeners
* create a new 16x16 FLARCode instance, and pass in the pattern. This
* represents the resolution of your marker. By default 16x16 works for
* lower detailed patterns. After this the ARDetector is configured and
* dispatches a Complete event.
*
* @param event
*
*/
protected function onMarkerFileLoad(event:Event):void
{
event.stopImmediatePropagation();
var target:URLLoader = event.target as URLLoader;
target.removeEventListener(Event.COMPLETE, onCameraFileLoad);
removeErrorListeners(target);
code = new FLARCode(markerWidth, markerHeight);
code.loadARPatt(target.data);
dispatchEvent(new Event(Event.COMPLETE, true, true) );
}
/**
* @private
*
* Adds error event listeners and re-dispatches them once received.
*
*/
protected function addErrorListeners(target:IEventDispatcher):void
{
target.addEventListener(IOErrorEvent.IO_ERROR, dispatchEvent);
target.addEventListener(SecurityErrorEvent.SECURITY_ERROR, dispatchEvent);
}
/**
* @private
*
* Removes error event listeners.
*
*/
protected function removeErrorListeners(target:IEventDispatcher):void
{
target.removeEventListener(IOErrorEvent.IO_ERROR, dispatchEvent);
target.removeEventListener(SecurityErrorEvent.SECURITY_ERROR, dispatchEvent);
}
/**
* In order to set up the FLARDetector we will need two things: the
* camera.dat and the marker.pat files. The camera.dat
*
* @param cameraURL this is the path to the camera.dat file.
* @param markerURL this is the path to the marker.pat file.
*
*/
public function setup(cameraURL:String, markerURL:String):void {
this.cameraURL = cameraURL;
this.markerURL = markerURL;
loadCameraFile(cameraURL);
}
/**
*
* This calculates the transformation Matrix to match the found
* marker's coordinates.
*
* @param resultMat - a type of matrix that can be used to store values
* of the detected marker's orientation.
*
*/
public function calculateTransformMatrix(resultMat:FLARTransMatResult):void
{
detector.getTransformMatrix(resultMat);
}
/**
*
* This validates if we have found a marker from the set src (raster).
* It returns a true/false based on the supplied values. You must supply
* a source for this to work correctly.
*
* @param threshold The threshold value to be used for detecting the marker.
* @param confidence This is how confident the detector is that it found
* a marker.
*
*/
public function detectMarker(threshold:int = 90, confidence:Number = .5):Boolean
{
return (detector.detectMarkerLite(raster,threshold) && detector.getConfidence() > confidence)
}
}
}

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转自：http://miyaonanhai.blogbus.com/logs/70836798.html