514 lines
13 KiB
ActionScript
514 lines
13 KiB
ActionScript
/**
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* This class lets you encode animated GIF files
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* Base class : http://www.java2s.com/Code/Java/2D-Graphics-GUI/AnimatedGifEncoder.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.encoder
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{
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import flash.utils.ByteArray;
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import flash.display.BitmapData;
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import flash.display.Bitmap;
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import org.bytearray.gif.encoder.NeuQuant
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import flash.net.URLRequestHeader;
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import flash.net.URLRequestMethod;
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import flash.net.URLRequest;
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import flash.net.navigateToURL;
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public class GIFEncoder
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{
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private var width:int // image size
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private var height:int;
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private var transparent:* = null; // transparent color if given
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private var transIndex:int; // transparent index in color table
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private var repeat:int = -1; // no repeat
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private var delay:int = 0; // frame delay (hundredths)
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private var started:Boolean = false; // ready to output frames
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private var out:ByteArray;
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private var image:Bitmap; // current frame
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private var pixels:ByteArray; // BGR byte array from frame
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private var indexedPixels:ByteArray // converted frame indexed to palette
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private var colorDepth:int; // number of bit planes
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private var colorTab:ByteArray; // RGB palette
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private var usedEntry:Array = new Array; // active palette entries
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private var palSize:int = 7; // color table size (bits-1)
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private var dispose:int = -1; // disposal code (-1 = use default)
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private var closeStream:Boolean = false; // close stream when finished
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private var firstFrame:Boolean = true;
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private var sizeSet:Boolean = false; // if false, get size from first frame
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private var sample:int = 10; // default sample interval for quantizer
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/**
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* Sets the delay time between each frame, or changes it for subsequent frames
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* (applies to last frame added)
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* int delay time in milliseconds
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* @param ms
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*/
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public function setDelay(ms:int):void
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{
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delay = Math.round(ms / 10);
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}
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/**
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* Sets the GIF frame disposal code for the last added frame and any
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*
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* subsequent frames. Default is 0 if no transparent color has been set,
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* otherwise 2.
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* @param code
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* int disposal code.
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*/
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public function setDispose(code:int):void
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{
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if (code >= 0) dispose = code;
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}
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/**
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* Sets the number of times the set of GIF frames should be played. Default is
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* 1; 0 means play indefinitely. Must be invoked before the first image is
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* added.
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*
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* @param iter
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* int number of iterations.
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* @return
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*/
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public function setRepeat(iter:int):void
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{
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if (iter >= 0) repeat = iter;
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}
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/**
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* Sets the transparent color for the last added frame and any subsequent
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* frames. Since all colors are subject to modification in the quantization
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* process, the color in the final palette for each frame closest to the given
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* color becomes the transparent color for that frame. May be set to null to
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* indicate no transparent color.
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* @param
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* Color to be treated as transparent on display.
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*/
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public function setTransparent(c:Number):void
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{
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transparent = c;
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}
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/**
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* The addFrame method takes an incoming BitmapData object to create each frames
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* @param
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* BitmapData object to be treated as a GIF's frame
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*/
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public function addFrame(im:BitmapData):Boolean
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{
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if ((im == null) || !started || out == null)
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{
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throw new Error ("Please call start method before calling addFrame");
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return false;
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}
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var ok:Boolean = true;
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try {
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image = new Bitmap ( im );
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if (!sizeSet) setSize(image.width, image.height);
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getImagePixels(); // convert to correct format if necessary
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analyzePixels(); // build color table & map pixels
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if (firstFrame)
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{
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writeLSD(); // logical screen descriptior
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writePalette(); // global color table
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if (repeat >= 0)
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{
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// use NS app extension to indicate reps
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writeNetscapeExt();
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}
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}
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writeGraphicCtrlExt(); // write graphic control extension
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writeImageDesc(); // image descriptor
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if (!firstFrame) writePalette(); // local color table
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writePixels(); // encode and write pixel data
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firstFrame = false;
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} catch (e:Error) {
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ok = false;
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}
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return ok;
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}
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/**
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* Adds final trailer to the GIF stream, if you don't call the finish method
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* the GIF stream will not be valid.
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*/
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public function finish():Boolean
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{
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if (!started) return false;
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var ok:Boolean = true;
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started = false;
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try {
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out.writeByte(0x3b); // gif trailer
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} catch (e:Error) {
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ok = false;
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}
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return ok;
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}
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/**
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* Resets some members so that a new stream can be started.
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* This method is actually called by the start method
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*/
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private function reset ( ):void
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{
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// reset for subsequent use
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transIndex = 0;
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image = null;
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pixels = null;
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indexedPixels = null;
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colorTab = null;
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closeStream = false;
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firstFrame = true;
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}
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/**
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* * Sets frame rate in frames per second. Equivalent to
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* <code>setDelay(1000/fps)</code>.
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* @param fps
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* float frame rate (frames per second)
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*/
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public function setFrameRate(fps:Number):void
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{
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if (fps != 0xf) delay = Math.round(100/fps);
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}
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/**
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* Sets quality of color quantization (conversion of images to the maximum 256
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* colors allowed by the GIF specification). Lower values (minimum = 1)
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* produce better colors, but slow processing significantly. 10 is the
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* default, and produces good color mapping at reasonable speeds. Values
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* greater than 20 do not yield significant improvements in speed.
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* @param quality
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* int greater than 0.
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* @return
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*/
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public function setQuality(quality:int):void
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{
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if (quality < 1) quality = 1;
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sample = quality;
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}
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/**
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* Sets the GIF frame size. The default size is the size of the first frame
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* added if this method is not invoked.
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* @param w
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* int frame width.
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* @param h
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* int frame width.
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*/
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private function setSize(w:int, h:int):void
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{
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if (started && !firstFrame) return;
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width = w;
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height = h;
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if (width < 1)width = 320;
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if (height < 1)height = 240;
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sizeSet = true
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}
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/**
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* Initiates GIF file creation on the given stream.
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* @param os
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* OutputStream on which GIF images are written.
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* @return false if initial write failed.
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*
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*/
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public function start():Boolean
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{
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reset();
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var ok:Boolean = true;
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closeStream = false;
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out = new ByteArray;
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try {
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out.writeUTFBytes("GIF89a"); // header
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} catch (e:Error) {
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ok = false;
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}
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return started = ok;
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}
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/**
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* Analyzes image colors and creates color map.
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*/
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private function analyzePixels():void
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{
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var len:int = pixels.length;
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var nPix:int = len / 3;
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indexedPixels = new ByteArray;
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var nq:NeuQuant = new NeuQuant(pixels, len, sample);
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// initialize quantizer
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colorTab = nq.process(); // create reduced palette
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// map image pixels to new palette
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var k:int = 0;
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for (var j:int = 0; j < nPix; j++) {
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var index:int = nq.map(pixels[k++] & 0xff, pixels[k++] & 0xff, pixels[k++] & 0xff);
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usedEntry[index] = true;
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indexedPixels[j] = index;
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}
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pixels = null;
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colorDepth = 8;
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palSize = 7;
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// get closest match to transparent color if specified
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if (transparent != null) {
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transIndex = findClosest(transparent);
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}
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}
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/**
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* Returns index of palette color closest to c
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*
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*/
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private function findClosest(c:Number):int
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{
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if (colorTab == null) return -1;
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var r:int = (c & 0xFF0000) >> 16;
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var g:int = (c & 0x00FF00) >> 8;
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var b:int = (c & 0x0000FF);
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var minpos:int = 0;
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var dmin:int = 256 * 256 * 256;
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var len:int = colorTab.length;
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for (var i:int = 0; i < len;) {
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var dr:int = r - (colorTab[i++] & 0xff);
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var dg:int = g - (colorTab[i++] & 0xff);
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var db:int = b - (colorTab[i] & 0xff);
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var d:int = dr * dr + dg * dg + db * db;
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var index:int = i / 3;
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if (usedEntry[index] && (d < dmin)) {
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dmin = d;
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minpos = index;
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}
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i++;
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}
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return minpos;
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}
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/**
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* Extracts image pixels into byte array "pixels
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*/
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private function getImagePixels():void
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{
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var w:int = image.width;
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var h:int = image.height;
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pixels = new ByteArray;
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var count:int = 0;
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for ( var i:int = 0; i < h; i++ )
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{
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for (var j:int = 0; j < w; j++ )
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{
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var pixel:Number = image.bitmapData.getPixel( j, i );
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pixels[count] = (pixel & 0xFF0000) >> 16;
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count++;
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pixels[count] = (pixel & 0x00FF00) >> 8;
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count++;
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pixels[count] = (pixel & 0x0000FF);
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count++;
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}
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}
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}
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/**
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* Writes Graphic Control Extension
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*/
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private function writeGraphicCtrlExt():void
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{
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out.writeByte(0x21); // extension introducer
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out.writeByte(0xf9); // GCE label
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out.writeByte(4); // data block size
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var transp:int
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var disp:int;
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if (transparent == null) {
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transp = 0;
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disp = 0; // dispose = no action
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} else {
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transp = 1;
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disp = 2; // force clear if using transparent color
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}
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if (dispose >= 0) {
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disp = dispose & 7; // user override
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}
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disp <<= 2;
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// packed fields
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out.writeByte(0 | // 1:3 reserved
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disp | // 4:6 disposal
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0 | // 7 user input - 0 = none
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transp); // 8 transparency flag
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WriteShort(delay); // delay x 1/100 sec
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out.writeByte(transIndex); // transparent color index
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out.writeByte(0); // block terminator
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}
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/**
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* Writes Image Descriptor
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*/
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private function writeImageDesc():void
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{
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out.writeByte(0x2c); // image separator
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WriteShort(0); // image position x,y = 0,0
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WriteShort(0);
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WriteShort(width); // image size
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WriteShort(height);
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// packed fields
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if (firstFrame) {
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// no LCT - GCT is used for first (or only) frame
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out.writeByte(0);
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} else {
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// specify normal LCT
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out.writeByte(0x80 | // 1 local color table 1=yes
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0 | // 2 interlace - 0=no
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0 | // 3 sorted - 0=no
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0 | // 4-5 reserved
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palSize); // 6-8 size of color table
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}
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}
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/**
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* Writes Logical Screen Descriptor
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*/
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private function writeLSD():void
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{
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// logical screen size
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WriteShort(width);
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WriteShort(height);
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// packed fields
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out.writeByte((0x80 | // 1 : global color table flag = 1 (gct used)
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0x70 | // 2-4 : color resolution = 7
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0x00 | // 5 : gct sort flag = 0
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palSize)); // 6-8 : gct size
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out.writeByte(0); // background color index
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out.writeByte(0); // pixel aspect ratio - assume 1:1
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}
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/**
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* Writes Netscape application extension to define repeat count.
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*/
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private function writeNetscapeExt():void
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{
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out.writeByte(0x21); // extension introducer
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out.writeByte(0xff); // app extension label
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out.writeByte(11); // block size
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out.writeUTFBytes("NETSCAPE" + "2.0"); // app id + auth code
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out.writeByte(3); // sub-block size
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out.writeByte(1); // loop sub-block id
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WriteShort(repeat); // loop count (extra iterations, 0=repeat forever)
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out.writeByte(0); // block terminator
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}
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/**
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* Writes color table
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*/
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private function writePalette():void
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{
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out.writeBytes(colorTab, 0, colorTab.length);
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var n:int = (3 * 256) - colorTab.length;
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for (var i:int = 0; i < n; i++) out.writeByte(0);
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}
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private function WriteShort (pValue:int):void
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{
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out.writeByte( pValue & 0xFF );
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out.writeByte( (pValue >> 8) & 0xFF);
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}
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/**
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* Encodes and writes pixel data
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*/
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private function writePixels():void
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{
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var myencoder:LZWEncoder = new LZWEncoder(width, height, indexedPixels, colorDepth);
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myencoder.encode(out);
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}
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/**
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* retrieves the GIF stream
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*/
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public function get stream ( ):ByteArray
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{
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return out;
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}
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}
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} |