1 package   
 2 {  
 3          import  flash.geom. * ;  
 4          import  flash.display. * ;  
 5          import  flash.utils. * ;  
 6          public   class  PNGEncoder  
 7         {  
 8   
 9              public   static  function encode(img:BitmapData):ByteArray {  
10                  //  Create output byte array   
11                  var png:ByteArray  =   new  ByteArray();  
12                  //  Write PNG signature   
13                  png.writeUnsignedInt( 0x89504e47 );  
14                 png.writeUnsignedInt( 0x0D0A1A0A );  
15                  //  Build IHDR chunk   
16                  var IHDR:ByteArray  =   new  ByteArray();  
17                 IHDR.writeInt(img.width);  
18                 IHDR.writeInt(img.height);  
19                 IHDR.writeUnsignedInt( 0x08060000 );  //  32bit RGBA   
20                  IHDR.writeByte( 0 );  
21                 writeChunk(png, 0x49484452 ,IHDR);  
22                  //  Build IDAT chunk   
23                  var IDAT:ByteArray =   new  ByteArray();  
24                  for (var i: int = 0 ;i  <  img.height;i ++ ) {  
25                      //  no filter   
26                      IDAT.writeByte( 0 );  
27                     var p:uint;  
28                      if  (  ! img.transparent ) {  
29                          for (var j: int = 0 ;j  <  img.width;j ++ ) {  
30                             p  =  img.getPixel(j,i);  
31                             IDAT.writeUnsignedInt(  
32                                 uint(((p & 0xFFFFFF )  <<   8 ) | 0xFF ));  
33                         }  
34                     }  else  {  
35                          for (var k: int = 0 ;k  <  img.width;k ++ ) {  
36                             p  =  img.getPixel32(k,i);  
37                             IDAT.writeUnsignedInt(  
38                                 uint(((p & 0xFFFFFF )  <<   8 ) | (p  >>>  
 24 )));  
39                         }  
40                     }  
41                 }  
42                 IDAT.compress();  
43                 writeChunk(png, 0x49444154 ,IDAT);  
44                  //  Build IEND chunk   
45                  writeChunk(png, 0x49454E44 , null );  
46                  //  return PNG   
47                   return  png;  
48             }  
49   
50              private   static  var crcTable:Array;  
51              private   static  var crcTableComputed:Boolean  =   false ;  
52   
53              private   static  function writeChunk(png:ByteArray,  
54                     type:uint, data:ByteArray) {  
55                  if  ( ! crcTableComputed) {  
56                     crcTableComputed  =   true ;  
57                     crcTable  =  [];  
58                      for  (var n:uint  =   0 ; n  <   256 ; n ++ ) {  
59                         var c_1:uint  =  n;  
60                          for  (var k:uint  =   0 ; k  <   8 ; k ++ ) {  
61                              if  (c_1  &   1 ) {  
62                                 c_1  =  uint(uint( 0xedb88320 )  ^   
63                                     uint(c_1  >>>   1 ));  
64                             }  else  {  
65                                 c_1  =  uint(c_1  >>>   1 );  
66                             }  
67                         }  
68                         crcTable[n]  =  c_1;  
69                     }  
70                 }  
71                 var len:uint  =   0 ;  
72                  if  (data  !=   null ) {  
73                     len  =  data.length;  
74                 }  
75                 png.writeUnsignedInt(len);  
76                 var p:uint  =  png.position;  
77                 png.writeUnsignedInt(type);  
78                  if  ( data  !=   null  ) {  
79                     png.writeBytes(data);  
80                 }  
81                 var e:uint  =  png.position;  
82                 ppng.position  =  p;  
83                 var c:uint  =   0xffffffff ;  
84                  for  (var i: int   =   0 ; i  <  (e - p); i ++ ) {  
85                     c  =  uint(crcTable[  
86                         (c  ^  png.readUnsignedByte())  &   
87                         uint( 0xff )]  ^  uint(c  >>>   8 ));  
88                 }  
89                 c  =  uint(c ^ uint( 0xffffffff ));  
90                 png.position  =  e;  
91                 png.writeUnsignedInt(c);  
92             }  
93         }  

var myBitmapData:BitmapData = new BitmapData(480, 360,true,0x00);  
myBitmapData.draw(_base);