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niandeng
@@ -0,0 +1,868 @@
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/**
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* This class lets you decode animated GIF files, and show animated GIF's in the Flash player
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* Base Class : http://www.java2s.com/Code/Java/2D-Graphics-GUI/GiffileEncoder.htm
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* @author Kevin Weiner (original Java version - kweiner@fmsware.com)
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* @author Thibault Imbert (AS3 version - bytearray.org)
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* @version 0.1 AS3 implementation
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*/
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package org.bytearray.gif.decoder
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{
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import flash.display.Bitmap;
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import flash.display.BitmapData;
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import flash.geom.Rectangle;
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import flash.utils.ByteArray;
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import org.bytearray.gif.errors.FileTypeError;
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import org.bytearray.gif.frames.GIFFrame;
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public class GIFDecoder
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{
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/**
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* File read status: No errors.
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*/
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private static var STATUS_OK:int = 0;
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/**
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* File read status: Error decoding file (may be partially decoded)
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*/
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private static var STATUS_FORMAT_ERROR:int = 1;
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/**
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* File read status: Unable to open source.
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*/
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private static var STATUS_OPEN_ERROR:int = 2;
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private static var frameRect:Rectangle = new Rectangle;
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private var inStream:ByteArray;
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private var status:int;
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// full image width
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private var width:int;
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// full image height
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private var height:int;
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// global color table used
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private var gctFlag:Boolean;
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// size of global color table
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private var gctSize:int;
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// iterations; 0 = repeat forever
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private var loopCount:int = 1;
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// global color table
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private var gct:Array;
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// local color table
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private var lct:Array;
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// active color table
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private var act:Array;
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// background color index
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private var bgIndex:int;
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// background color
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private var bgColor:int;
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// previous bg color
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private var lastBgColor:int;
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// pixel aspect ratio
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private var pixelAspect:int;
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private var lctFlag:Boolean // local color table flag
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// interlace flag
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private var interlace:Boolean;
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// local color table size
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private var lctSize:int;
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private var ix:int;
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private var iy:int;
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private var iw:int;
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// current image rectangle
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private var ih:int;
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// last image rect
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private var lastRect:Rectangle;
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// current frame
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private var image:BitmapData;
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private var bitmap:BitmapData;
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// previous frame
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private var lastImage:BitmapData;
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// current data block
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private var block:ByteArray;
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// block size
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private var blockSize:int = 0;
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// last graphic control extension info
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private var dispose:int= 0;
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// 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prev
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private var lastDispose:int = 0;
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// use transparent color
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private var transparency:Boolean = false;
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// delay in milliseconds
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private var delay:int = 0;
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// transparent color index
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private var transIndex:int;
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// max decoder pixel stack size
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private static var MaxStackSize:int = 4096;
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// LZW decoder working arrays
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private var prefix:Array
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private var suffix:Array;
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private var pixelStack:Array;
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private var pixels:Array;
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// frames read from current file
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private var frames:Array
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private var frameCount:int
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public function GIFDecoder ( )
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{
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block = new ByteArray;
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}
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public function get disposeValue():int
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{
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return dispose;
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}
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/**
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* Gets display duration for specified frame.
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*
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* @param n int index of frame
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* @return delay in milliseconds
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*/
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public function getDelay(n:int):int
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{
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delay = -1;
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if ((n >= 0) && (n < frameCount))
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{
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delay = frames[n].delay;
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}
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return delay;
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}
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/**
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* Gets the number of frames read from file.
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* @return frame count
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*/
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public function getFrameCount():int
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{
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return frameCount;
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}
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/**
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* Gets the first (or only) image read.
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*
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* @return BitmapData containing first frame, or null if none.
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*/
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public function getImage():GIFFrame
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{
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return getFrame(0);
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}
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/**
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* Gets the "Netscape" iteration count, if any.
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* A count of 0 means repeat indefinitiely.
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*
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* @return iteration count if one was specified, else 1.
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*/
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public function getLoopCount():int
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{
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return loopCount;
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}
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/**
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* Creates new frame image from current data (and previous
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* frames as specified by their disposition codes).
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*/
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private function getPixels( bitmap:BitmapData ):Array
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{
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var pixels:Array = new Array ( 4 * image.width * image.height );
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var count:int = 0;
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var lngWidth:int = image.width;
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var lngHeight:int = image.height;
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var color:int;
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for (var th:int = 0; th < lngHeight; th++)
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{
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for (var tw:int = 0; tw < lngWidth; tw++)
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{
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color = bitmap.getPixel (th, tw);
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pixels[count++] = (color & 0xFF0000) >> 16;
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pixels[count++] = (color & 0x00FF00) >> 8;
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pixels[count++] = (color & 0x0000FF);
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}
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}
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return pixels;
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}
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private function setPixels( pixels:Array ):void
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{
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var count:int = 0;
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var color:int;
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pixels.position = 0;
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var lngWidth:int = image.width;
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var lngHeight:int = image.height;
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bitmap.lock();
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for (var th:int = 0; th < lngHeight; th++)
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{
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for (var tw:int = 0; tw < lngWidth; tw++)
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{
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color = pixels[int(count++)];
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bitmap.setPixel32 ( tw, th, color );
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}
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}
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bitmap.unlock();
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}
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private function transferPixels():void
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{
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// expose destination image's pixels as int array
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var dest:Array = getPixels( bitmap );
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// fill in starting image contents based on last image's dispose code
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if (lastDispose > 0)
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{
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if (lastDispose == 3)
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{
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// use image before last
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var n:int = frameCount - 2;
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lastImage = n > 0 ? getFrame(n - 1).bitmapData : null;
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}
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if (lastImage != null)
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{
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var prev:Array = getPixels( lastImage );
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dest = prev.slice();
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// copy pixels
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if (lastDispose == 2)
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{
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// fill last image rect area with background color
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var c:Number;
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// assume background is transparent
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c = transparency ? 0x00000000 : lastBgColor;
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// use given background color
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image.fillRect( lastRect, c );
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}
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}
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}
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// copy each source line to the appropriate place in the destination
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var pass:int = 1;
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var inc:int = 8;
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var iline:int = 0;
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for (var i:int = 0; i < ih; i++)
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{
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var line:int = i;
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if (interlace)
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{
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if (iline >= ih)
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{
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pass++;
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switch (pass)
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{
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case 2 :
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iline = 4;
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break;
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case 3 :
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iline = 2;
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inc = 4;
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break;
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case 4 :
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iline = 1;
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inc = 2;
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break;
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}
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}
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line = iline;
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iline += inc;
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}
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line += iy;
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if (line < height)
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{
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var k:int = line * width;
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var dx:int = k + ix; // start of line in dest
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var dlim:int = dx + iw; // end of dest line
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if ((k + width) < dlim)
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{
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dlim = k + width; // past dest edge
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}
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var sx:int = i * iw; // start of line in source
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var index:int;
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var tmp:int;
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while (dx < dlim)
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{
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// map color and insert in destination
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index = (pixels[sx++]) & 0xff;
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tmp = act[index];
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if (tmp != 0)
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{
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dest[dx] = tmp;
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}
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dx++;
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}
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}
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}
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setPixels( dest );
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}
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/**
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* Gets the image contents of frame n.
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*
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* @return BufferedImage representation of frame, or null if n is invalid.
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*/
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public function getFrame(n:int):GIFFrame
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{
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var im:GIFFrame = null;
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if ((n >= 0) && (n < frameCount))
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{
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im =frames[n];
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} else throw new RangeError ("Wrong frame number passed");
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return im;
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}
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/**
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* Gets image size.
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*
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* @return GIF image dimensions
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*/
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public function getFrameSize():Rectangle
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{
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var rect:Rectangle = GIFDecoder.frameRect;
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rect.x = rect.y = 0; rect.width = width; rect.height = height;
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return rect;
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}
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/**
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* Reads GIF image from stream
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*
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* @param BufferedInputStream containing GIF file.
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* @return read status code (0 = no errors)
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*/
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public function read( inStream:ByteArray ):int
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{
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init();
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if ( inStream != null)
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{
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this.inStream = inStream;
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readHeader();
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if (!hasError())
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{
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readContents();
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if (frameCount < 0) status = STATUS_FORMAT_ERROR;
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}
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}
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else
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{
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status = STATUS_OPEN_ERROR;
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}
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return status;
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}
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/**
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* Decodes LZW image data into pixel array.
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* Adapted from John Cristy's ImageMagick.
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*/
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private function decodeImageData():void
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{
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var NullCode:int = -1;
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var npix:int = iw * ih;
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var available:int;
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var clear:int;
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var code_mask:int;
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var code_size:int;
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var end_of_information:int;
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var in_code:int;
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var old_code:int;
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var bits:int;
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var code:int;
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var count:int;
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var i:int;
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var datum:int;
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var data_size:int;
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var first:int;
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var top:int;
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var bi:int;
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var pi:int;
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if ((pixels == null) || (pixels.length < npix))
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{
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pixels = new Array ( npix ); // allocate new pixel array
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}
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if (prefix == null) prefix = new Array ( MaxStackSize );
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if (suffix == null) suffix = new Array ( MaxStackSize );
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if (pixelStack == null) pixelStack = new Array ( MaxStackSize + 1 );
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// Initialize GIF data stream decoder.
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data_size = readSingleByte();
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clear = 1 << data_size;
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end_of_information = clear + 1;
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available = clear + 2;
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old_code = NullCode;
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code_size = data_size + 1;
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code_mask = (1 << code_size) - 1;
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for (code = 0; code < clear; code++)
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{
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prefix[int(code)] = 0;
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suffix[int(code)] = code;
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}
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// Decode GIF pixel stream.
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datum = bits = count = first = top = pi = bi = 0;
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for (i = 0; i < npix;)
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{
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if (top == 0)
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{
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if (bits < code_size)
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{
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// Load bytes until there are enough bits for a code.
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if (count == 0)
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{
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// Read a new data block.
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count = readBlock();
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if (count <= 0)
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break;
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bi = 0;
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}
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datum += (int((block[int(bi)])) & 0xff) << bits;
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bits += 8;
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bi++;
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count--;
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continue;
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}
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// Get the next code.
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code = datum & code_mask;
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datum >>= code_size;
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bits -= code_size;
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// Interpret the code
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if ((code > available) || (code == end_of_information))
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break;
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if (code == clear)
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{
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// Reset decoder.
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code_size = data_size + 1;
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code_mask = (1 << code_size) - 1;
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available = clear + 2;
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old_code = NullCode;
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continue;
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}
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if (old_code == NullCode)
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{
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pixelStack[int(top++)] = suffix[int(code)];
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old_code = code;
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first = code;
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continue;
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}
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in_code = code;
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if (code == available)
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{
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pixelStack[int(top++)] = first;
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code = old_code;
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}
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while (code > clear)
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{
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pixelStack[int(top++)] = suffix[int(code)];
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code = prefix[int(code)];
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}
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first = (suffix[int(code)]) & 0xff;
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// Add a new string to the string table,
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if (available >= MaxStackSize) break;
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pixelStack[int(top++)] = first;
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prefix[int(available)] = old_code;
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suffix[int(available)] = first;
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available++;
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if (((available & code_mask) == 0)
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&& (available < MaxStackSize))
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{
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code_size++;
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code_mask += available;
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}
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old_code = in_code;
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}
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// Pop a pixel off the pixel stack.
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top--;
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pixels[int(pi++)] = pixelStack[int(top)];
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i++;
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}
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||||
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for (i = pi; i < npix; i++)
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||||
{
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pixels[int(i)] = 0; // clear missing pixels
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||||
}
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||||
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||||
}
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||||
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||||
/**
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* Returns true if an error was encountered during reading/decoding
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||||
*/
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||||
private function hasError():Boolean
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||||
{
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return status != STATUS_OK;
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}
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||||
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||||
/**
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* Initializes or re-initializes reader
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||||
*/
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private function init():void
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||||
{
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status = STATUS_OK;
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frameCount = 0;
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||||
frames = new Array;
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||||
gct = null;
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lct = null;
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}
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||||
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/**
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* Reads a single byte from the input stream.
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*/
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||||
private function readSingleByte():int
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||||
{
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var curByte:int = 0;
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try
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||||
{
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||||
curByte = inStream.readUnsignedByte();
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||||
}
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||||
catch (e:Error)
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||||
{
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||||
status = STATUS_FORMAT_ERROR;
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||||
}
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||||
return curByte;
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||||
}
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||||
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||||
/**
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||||
* Reads next variable length block from input.
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||||
*
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||||
* @return number of bytes stored in "buffer"
|
||||
*/
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||||
private function readBlock():int
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||||
{
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||||
blockSize = readSingleByte();
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||||
var n:int = 0;
|
||||
if (blockSize > 0)
|
||||
{
|
||||
try
|
||||
{
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||||
var count:int = 0;
|
||||
while (n < blockSize)
|
||||
{
|
||||
|
||||
inStream.readBytes(block, n, blockSize - n);
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||||
if ( (blockSize - n) == -1)
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||||
break;
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||||
n += (blockSize - n);
|
||||
}
|
||||
}
|
||||
catch (e:Error)
|
||||
{
|
||||
}
|
||||
|
||||
if (n < blockSize)
|
||||
{
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||||
status = STATUS_FORMAT_ERROR;
|
||||
}
|
||||
}
|
||||
return n;
|
||||
}
|
||||
|
||||
/**
|
||||
* Reads color table as 256 RGB integer values
|
||||
*
|
||||
* @param ncolors int number of colors to read
|
||||
* @return int array containing 256 colors (packed ARGB with full alpha)
|
||||
*/
|
||||
private function readColorTable(ncolors:int):Array
|
||||
{
|
||||
var nbytes:int = 3 * ncolors;
|
||||
var tab:Array = null;
|
||||
var c:ByteArray = new ByteArray;
|
||||
var n:int = 0;
|
||||
try
|
||||
{
|
||||
inStream.readBytes(c, 0, nbytes );
|
||||
n = nbytes;
|
||||
}
|
||||
catch (e:Error)
|
||||
{
|
||||
}
|
||||
if (n < nbytes)
|
||||
{
|
||||
status = STATUS_FORMAT_ERROR;
|
||||
}
|
||||
else
|
||||
{
|
||||
tab = new Array(256); // max size to avoid bounds checks
|
||||
var i:int = 0;
|
||||
var j:int = 0;
|
||||
while (i < ncolors)
|
||||
{
|
||||
var r:int = (c[j++]) & 0xff;
|
||||
var g:int = (c[j++]) & 0xff;
|
||||
var b:int = (c[j++]) & 0xff;
|
||||
tab[i++] = ( 0xff000000 | (r << 16) | (g << 8) | b );
|
||||
}
|
||||
}
|
||||
return tab;
|
||||
}
|
||||
|
||||
/**
|
||||
* Main file parser. Reads GIF content blocks.
|
||||
*/
|
||||
private function readContents():void
|
||||
{
|
||||
// read GIF file content blocks
|
||||
var done:Boolean = false;
|
||||
|
||||
while (!(done || hasError()))
|
||||
{
|
||||
|
||||
var code:int = readSingleByte();
|
||||
|
||||
switch (code)
|
||||
{
|
||||
|
||||
case 0x2C : // image separator
|
||||
readImage();
|
||||
break;
|
||||
|
||||
case 0x21 : // extension
|
||||
code = readSingleByte();
|
||||
switch (code)
|
||||
{
|
||||
case 0xf9 : // graphics control extension
|
||||
readGraphicControlExt();
|
||||
break;
|
||||
|
||||
case 0xff : // application extension
|
||||
readBlock();
|
||||
var app:String = "";
|
||||
for (var i:int = 0; i < 11; i++)
|
||||
{
|
||||
app += block[int(i)];
|
||||
}
|
||||
if (app == "NETSCAPE2.0")
|
||||
{
|
||||
readNetscapeExt();
|
||||
}
|
||||
else
|
||||
skip(); // don't care
|
||||
break;
|
||||
|
||||
default : // uninteresting extension
|
||||
skip();
|
||||
break;
|
||||
}
|
||||
break;
|
||||
|
||||
case 0x3b : // terminator
|
||||
done = true;
|
||||
break;
|
||||
|
||||
case 0x00 : // bad byte, but keep going and see what happens
|
||||
break;
|
||||
|
||||
default :
|
||||
status = STATUS_FORMAT_ERROR;
|
||||
break;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Reads Graphics Control Extension values
|
||||
*/
|
||||
private function readGraphicControlExt():void
|
||||
{
|
||||
readSingleByte(); // block size
|
||||
var packed:int = readSingleByte(); // packed fields
|
||||
dispose = (packed & 0x1c) >> 2; // disposal method
|
||||
if (dispose == 0)
|
||||
{
|
||||
dispose = 1; // elect to keep old image if discretionary
|
||||
}
|
||||
transparency = (packed & 1) != 0;
|
||||
delay = readShort() * 10; // delay in milliseconds
|
||||
transIndex = readSingleByte(); // transparent color index
|
||||
readSingleByte(); // block terminator
|
||||
}
|
||||
|
||||
/**
|
||||
* Reads GIF file header information.
|
||||
*/
|
||||
private function readHeader():void
|
||||
{
|
||||
var id:String = "";
|
||||
for (var i:int = 0; i < 6; i++)
|
||||
{
|
||||
id += String.fromCharCode (readSingleByte());
|
||||
|
||||
}
|
||||
if (!( id.indexOf("GIF") == 0 ) )
|
||||
{
|
||||
status = STATUS_FORMAT_ERROR;
|
||||
throw new FileTypeError ( "Invalid file type" );
|
||||
return;
|
||||
}
|
||||
readLSD();
|
||||
if (gctFlag && !hasError())
|
||||
{
|
||||
gct = readColorTable(gctSize);
|
||||
bgColor = gct[bgIndex];
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Reads next frame image
|
||||
*/
|
||||
private function readImage():void
|
||||
{
|
||||
ix = readShort(); // (sub)image position & size
|
||||
iy = readShort();
|
||||
iw = readShort();
|
||||
ih = readShort();
|
||||
|
||||
var packed:int = readSingleByte();
|
||||
lctFlag = (packed & 0x80) != 0; // 1 - local color table flag
|
||||
interlace = (packed & 0x40) != 0; // 2 - interlace flag
|
||||
// 3 - sort flag
|
||||
// 4-5 - reserved
|
||||
lctSize = 2 << (packed & 7); // 6-8 - local color table size
|
||||
|
||||
if (lctFlag)
|
||||
{
|
||||
lct = readColorTable(lctSize); // read table
|
||||
act = lct; // make local table active
|
||||
}
|
||||
else
|
||||
{
|
||||
act = gct; // make global table active
|
||||
if (bgIndex == transIndex)
|
||||
bgColor = 0;
|
||||
}
|
||||
var save:int = 0;
|
||||
if (transparency)
|
||||
{
|
||||
save = act[transIndex];
|
||||
act[transIndex] = 0; // set transparent color if specified
|
||||
}
|
||||
|
||||
if (act == null)
|
||||
{
|
||||
status = STATUS_FORMAT_ERROR; // no color table defined
|
||||
}
|
||||
|
||||
if (hasError()) return;
|
||||
|
||||
decodeImageData(); // decode pixel data
|
||||
skip();
|
||||
if (hasError()) return;
|
||||
|
||||
frameCount++;
|
||||
// create new image to receive frame data
|
||||
|
||||
bitmap = new BitmapData ( width, height );
|
||||
|
||||
image = bitmap;
|
||||
|
||||
transferPixels(); // transfer pixel data to image
|
||||
|
||||
frames.push ( new GIFFrame (bitmap, delay) ); // add image to frame list
|
||||
|
||||
if (transparency) act[transIndex] = save;
|
||||
|
||||
resetFrame();
|
||||
|
||||
}
|
||||
|
||||
/**
|
||||
* Reads Logical Screen Descriptor
|
||||
*/
|
||||
private function readLSD():void
|
||||
{
|
||||
|
||||
// logical screen size
|
||||
width = readShort();
|
||||
height = readShort();
|
||||
|
||||
// packed fields
|
||||
var packed:int = readSingleByte();
|
||||
|
||||
gctFlag = (packed & 0x80) != 0; // 1 : global color table flag
|
||||
// 2-4 : color resolution
|
||||
// 5 : gct sort flag
|
||||
gctSize = 2 << (packed & 7); // 6-8 : gct size
|
||||
bgIndex = readSingleByte(); // background color index
|
||||
pixelAspect = readSingleByte(); // pixel aspect ratio
|
||||
|
||||
}
|
||||
|
||||
/**
|
||||
* Reads Netscape extenstion to obtain iteration count
|
||||
*/
|
||||
private function readNetscapeExt():void
|
||||
{
|
||||
do
|
||||
{
|
||||
readBlock();
|
||||
if (block[0] == 1)
|
||||
{
|
||||
// loop count sub-block
|
||||
var b1:int = (block[1]) & 0xff;
|
||||
var b2:int = (block[2]) & 0xff;
|
||||
loopCount = (b2 << 8) | b1;
|
||||
}
|
||||
} while ((blockSize > 0) && !hasError());
|
||||
}
|
||||
|
||||
/**
|
||||
* Reads next 16-bit value, LSB first
|
||||
*/
|
||||
private function readShort():int
|
||||
{
|
||||
// read 16-bit value, LSB first
|
||||
return readSingleByte() | (readSingleByte() << 8);
|
||||
}
|
||||
|
||||
/**
|
||||
* Resets frame state for reading next image.
|
||||
*/
|
||||
private function resetFrame():void
|
||||
{
|
||||
lastDispose = dispose;
|
||||
lastRect = new Rectangle(ix, iy, iw, ih);
|
||||
lastImage = image;
|
||||
lastBgColor = bgColor;
|
||||
// int dispose = 0;
|
||||
var transparency:Boolean = false;
|
||||
var delay:int = 0;
|
||||
lct = null;
|
||||
}
|
||||
|
||||
/**
|
||||
* Skips variable length blocks up to and including
|
||||
* next zero length block.
|
||||
*/
|
||||
private function skip():void
|
||||
{
|
||||
do
|
||||
{
|
||||
readBlock();
|
||||
|
||||
} while ((blockSize > 0) && !hasError());
|
||||
}
|
||||
}
|
||||
|
||||
}
|
||||
Reference in New Issue
Block a user