actionscript 截图功能实现

由于截图访问的是外部 rtmp直播流所以调用BitmapData.draw时控制台报以下错误：

　　SecurityError: Error #2123: 安全沙箱冲突:BitmapData.draw: XXX 不能访问 rtmp://XXXXX。未被授权访问任何策略文件。

解决方法是：

　　我们的视频服务器是用Crtmpserver，网上的解决办法大多是FMS的；

在转码服务器的 BaseOutNetRTMPStream::SignalAttachedToInStream() 方法中添加以下 + 号的代码：

in void BaseOutNetRTMPStream::SignalAttachedToInStream(), I added the
following code after stream begin to allow Video samples:

+        //XXX. notify |RtmpSampleAccess
+ /*
+        message = StreamMessageFactory::GetNotifyRtmpSampleAccess(
+                        _pChannelVideo->id, _rtmpStreamId, absoluteTimestamp, false, true,
true);
+        TRACK_MESSAGE("Message:\n%s", STR(message.ToString()));
+        if (!_pRTMPProtocol->SendMessage(message)) {
+                FATAL("Unable to send message");
+                _pRTMPProtocol->EnqueueForDelete();
+                return false;
+        }
+ */
+

修改以下代码:
//10. notify |RtmpSampleAccess
message = StreamMessageFactory::GetNotifyRtmpSampleAccess(
_pChannelAudio->id, _rtmpStreamId, 0, true, true, true);
TRACK_MESSAGE("Message:\n%s", STR(message.ToString()));
if (!_pRTMPProtocol->SendMessage(message)) {
FATAL("Unable to send message");
_pRTMPProtocol->EnqueueForDelete();
return;
}

在actionscript中的截图实现过程为：

var imager:BitmapData = new BitmapData(mvideo.width,mvideo.height);
                    ExternalInterface.call("errorFun","1");    
                    imager.draw(mvideo.video);
                    var bs:ByteArray = new ByteArray();
                    imager.encode(new Rectangle(0,0,mvideo.width,mvideo.height), new flash.display.JPEGEncoderOptions(), bs);
                    var base64Code:String = Base64.encode(bs);
                    ExternalInterface.call("setImage",base64Code);

Base64的源码为：

/* Base64 library for ActionScript 3.0.  
*  
* Copyright (C) 2007 Ma Bingyao <andot@ujn.edu.cn>  
* Version: 1.1  
* LastModified: Oct 26, 2007  
* This library is free.  You can redistribute it and/or modify it.  
*/    
/*  
* interfaces:  
* import org.phprpc.util.Base64;  
* import flash.utils.ByteArray;  
* var data:ByteArray = new ByteArray();  
* data.writeUTFBytes("Hello PHPRPC");  
* var b64:String = Base64.encode(data);  
* trace(b64);  
* trace(Base64.decode(b64));  
*/    
package com.zonekey.player{
        import flash.utils.ByteArray;    
        public class Base64 {  
                private static  const encodeChars:Array =     
                    ['A','B','C','D','E','F','G','H',    
                        'I','J','K','L','M','N','O','P',    
                        'Q','R','S','T','U','V','W','X',    
                        'Y','Z','a','b','c','d','e','f',    
                        'g','h','i','j','k','l','m','n',    
                        'o','p','q','r','s','t','u','v',    
                        'w','x','y','z','0','1','2','3',    
                        '4','5','6','7','8','9','+','/'];    
                private static  const decodeChars:Array =     
                    [-1, -1, -1, -1, -1, -1, -1, -1,    
                        -1, -1, -1, -1, -1, -1, -1, -1,    
                        -1, -1, -1, -1, -1, -1, -1, -1,    
                        -1, -1, -1, -1, -1, -1, -1, -1,    
                        -1, -1, -1, -1, -1, -1, -1, -1,    
                        -1, -1, -1, 62, -1, -1, -1, 63,    
                        52, 53, 54, 55, 56, 57, 58, 59,    
                        60, 61, -1, -1, -1, -1, -1, -1,    
                        -1,  0,  1,  2,  3,  4,  5,  6,    
                         7,  8,  9, 10, 11, 12, 13, 14,    
                        15, 16, 17, 18, 19, 20, 21, 22,    
                        23, 24, 25, -1, -1, -1, -1, -1,    
                        -1, 26, 27, 28, 29, 30, 31, 32,    
                        33, 34, 35, 36, 37, 38, 39, 40,    
                        41, 42, 43, 44, 45, 46, 47, 48,    
                        49, 50, 51, -1, -1, -1, -1, -1];    
                
                public static function encode(data:ByteArray):String {
                        var out:Array = [];    
                        var i:int = 0;    
                        var j:int = 0;    
                        var r:int = data.length % 3;    
                        var len:int = data.length-r;    
                        var c:int;    
                        while (i < len) {    
                                c = data[i++] << 16 | data[i++] << 8 | data[i++];    
                                out[j++] = encodeChars[c >> 18] + encodeChars[c >> 12 & 0x3f] + encodeChars[c >> 6 & 0x3f] + encodeChars[c & 0x3f];    
                            }    
                        if (r == 1) {    
                                c = data[i++];    
                                out[j++] = encodeChars[c >> 2] + encodeChars[(c & 0x03) << 4] + "==";    
                            }    
                        else if (r == 2) {    
                                c = data[i++] << 8 | data[i++];    
                                out[j++] = encodeChars[c >> 10] + encodeChars[c >> 4 & 0x3f] + encodeChars[(c & 0x0f) << 2] + "=";    
                            }    
                        return out.join('');    
                }
                
                public static function decode(str:String):ByteArray {
                    var c1:int;
                    var c2:int;    
                    var c3:int;    
                    var c4:int;    
                    var i:int;    
                    var len:int;    
                    var out:ByteArray;    
                    len = str.length;    
                    i = 0;
                    out = new ByteArray();
                    while (i < len) {  
                        do {
                            c1 = decodeChars[str.charCodeAt(i++) & 0xff];    
                        } while (i < len && c1 == -1);    
                        if (c1 == -1) {    
                            break;    
                        }    
                        // c2        
                        do {    
                            c2 = decodeChars[str.charCodeAt(i++) & 0xff];    
                        } while (i < len && c2 == -1);    
                        if (c2 == -1) {    
                            break;    
                        }    
                        out.writeByte((c1 << 2) | ((c2 & 0x30) >> 4));    
                        // c3    
                        do {    
                            c3 = str.charCodeAt(i++) & 0xff;    
                            if (c3 == 61) {    
                                return out;    
                            }    
                            c3 = decodeChars[c3];    
                        } while (i < len && c3 == -1);    
                        if (c3 == -1) {    
                            break;    
                        }    
                        out.writeByte(((c2 & 0x0f) << 4) | ((c3 & 0x3c) >> 2));    
                        // c4    
                        do {
                            c4 = str.charCodeAt(i++) & 0xff;    
                            if (c4 == 61) {    
                                return out;    
                            }    
                            c4 = decodeChars[c4];    
                        } while (i < len && c4 == -1);    
                        if (c4 == -1) {    
                            break;    
                        }    
                        out.writeByte(((c3 & 0x03) << 6) | c4);    
                    }
                    return out;
                }
            }    
    }

至此，actionscript的截图并将图片的base64码传递给javascript的功能就实现了。