Files
moeplayer/source/org/bytearray/gif/decoder/GIFDecoder.as
T
2020-09-17 18:40:01 +08:00

868 lines
19 KiB
ActionScript

/**
* This class lets you decode animated GIF files, and show animated GIF's in the Flash player
* Base Class : http://www.java2s.com/Code/Java/2D-Graphics-GUI/GiffileEncoder.htm
* @author Kevin Weiner (original Java version - kweiner@fmsware.com)
* @author Thibault Imbert (AS3 version - bytearray.org)
* @version 0.1 AS3 implementation
*/
package org.bytearray.gif.decoder
{
import flash.display.Bitmap;
import flash.display.BitmapData;
import flash.geom.Rectangle;
import flash.utils.ByteArray;
import org.bytearray.gif.errors.FileTypeError;
import org.bytearray.gif.frames.GIFFrame;
public class GIFDecoder
{
/**
* File read status: No errors.
*/
private static var STATUS_OK:int = 0;
/**
* File read status: Error decoding file (may be partially decoded)
*/
private static var STATUS_FORMAT_ERROR:int = 1;
/**
* File read status: Unable to open source.
*/
private static var STATUS_OPEN_ERROR:int = 2;
private static var frameRect:Rectangle = new Rectangle;
private var inStream:ByteArray;
private var status:int;
// full image width
private var width:int;
// full image height
private var height:int;
// global color table used
private var gctFlag:Boolean;
// size of global color table
private var gctSize:int;
// iterations; 0 = repeat forever
private var loopCount:int = 1;
// global color table
private var gct:Array;
// local color table
private var lct:Array;
// active color table
private var act:Array;
// background color index
private var bgIndex:int;
// background color
private var bgColor:int;
// previous bg color
private var lastBgColor:int;
// pixel aspect ratio
private var pixelAspect:int;
private var lctFlag:Boolean // local color table flag
// interlace flag
private var interlace:Boolean;
// local color table size
private var lctSize:int;
private var ix:int;
private var iy:int;
private var iw:int;
// current image rectangle
private var ih:int;
// last image rect
private var lastRect:Rectangle;
// current frame
private var image:BitmapData;
private var bitmap:BitmapData;
// previous frame
private var lastImage:BitmapData;
// current data block
private var block:ByteArray;
// block size
private var blockSize:int = 0;
// last graphic control extension info
private var dispose:int= 0;
// 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prev
private var lastDispose:int = 0;
// use transparent color
private var transparency:Boolean = false;
// delay in milliseconds
private var delay:int = 0;
// transparent color index
private var transIndex:int;
// max decoder pixel stack size
private static var MaxStackSize:int = 4096;
// LZW decoder working arrays
private var prefix:Array
private var suffix:Array;
private var pixelStack:Array;
private var pixels:Array;
// frames read from current file
private var frames:Array
private var frameCount:int
public function GIFDecoder ( )
{
block = new ByteArray;
}
public function get disposeValue():int
{
return dispose;
}
/**
* Gets display duration for specified frame.
*
* @param n int index of frame
* @return delay in milliseconds
*/
public function getDelay(n:int):int
{
delay = -1;
if ((n >= 0) && (n < frameCount))
{
delay = frames[n].delay;
}
return delay;
}
/**
* Gets the number of frames read from file.
* @return frame count
*/
public function getFrameCount():int
{
return frameCount;
}
/**
* Gets the first (or only) image read.
*
* @return BitmapData containing first frame, or null if none.
*/
public function getImage():GIFFrame
{
return getFrame(0);
}
/**
* Gets the "Netscape" iteration count, if any.
* A count of 0 means repeat indefinitiely.
*
* @return iteration count if one was specified, else 1.
*/
public function getLoopCount():int
{
return loopCount;
}
/**
* Creates new frame image from current data (and previous
* frames as specified by their disposition codes).
*/
private function getPixels( bitmap:BitmapData ):Array
{
var pixels:Array = new Array ( 4 * image.width * image.height );
var count:int = 0;
var lngWidth:int = image.width;
var lngHeight:int = image.height;
var color:int;
for (var th:int = 0; th < lngHeight; th++)
{
for (var tw:int = 0; tw < lngWidth; tw++)
{
color = bitmap.getPixel (th, tw);
pixels[count++] = (color & 0xFF0000) >> 16;
pixels[count++] = (color & 0x00FF00) >> 8;
pixels[count++] = (color & 0x0000FF);
}
}
return pixels;
}
private function setPixels( pixels:Array ):void
{
var count:int = 0;
var color:int;
pixels.position = 0;
var lngWidth:int = image.width;
var lngHeight:int = image.height;
bitmap.lock();
for (var th:int = 0; th < lngHeight; th++)
{
for (var tw:int = 0; tw < lngWidth; tw++)
{
color = pixels[int(count++)];
bitmap.setPixel32 ( tw, th, color );
}
}
bitmap.unlock();
}
private function transferPixels():void
{
// expose destination image's pixels as int array
var dest:Array = getPixels( bitmap );
// fill in starting image contents based on last image's dispose code
if (lastDispose > 0)
{
if (lastDispose == 3)
{
// use image before last
var n:int = frameCount - 2;
lastImage = n > 0 ? getFrame(n - 1).bitmapData : null;
}
if (lastImage != null)
{
var prev:Array = getPixels( lastImage );
dest = prev.slice();
// copy pixels
if (lastDispose == 2)
{
// fill last image rect area with background color
var c:Number;
// assume background is transparent
c = transparency ? 0x00000000 : lastBgColor;
// use given background color
image.fillRect( lastRect, c );
}
}
}
// copy each source line to the appropriate place in the destination
var pass:int = 1;
var inc:int = 8;
var iline:int = 0;
for (var i:int = 0; i < ih; i++)
{
var line:int = i;
if (interlace)
{
if (iline >= ih)
{
pass++;
switch (pass)
{
case 2 :
iline = 4;
break;
case 3 :
iline = 2;
inc = 4;
break;
case 4 :
iline = 1;
inc = 2;
break;
}
}
line = iline;
iline += inc;
}
line += iy;
if (line < height)
{
var k:int = line * width;
var dx:int = k + ix; // start of line in dest
var dlim:int = dx + iw; // end of dest line
if ((k + width) < dlim)
{
dlim = k + width; // past dest edge
}
var sx:int = i * iw; // start of line in source
var index:int;
var tmp:int;
while (dx < dlim)
{
// map color and insert in destination
index = (pixels[sx++]) & 0xff;
tmp = act[index];
if (tmp != 0)
{
dest[dx] = tmp;
}
dx++;
}
}
}
setPixels( dest );
}
/**
* Gets the image contents of frame n.
*
* @return BufferedImage representation of frame, or null if n is invalid.
*/
public function getFrame(n:int):GIFFrame
{
var im:GIFFrame = null;
if ((n >= 0) && (n < frameCount))
{
im =frames[n];
} else throw new RangeError ("Wrong frame number passed");
return im;
}
/**
* Gets image size.
*
* @return GIF image dimensions
*/
public function getFrameSize():Rectangle
{
var rect:Rectangle = GIFDecoder.frameRect;
rect.x = rect.y = 0; rect.width = width; rect.height = height;
return rect;
}
/**
* Reads GIF image from stream
*
* @param BufferedInputStream containing GIF file.
* @return read status code (0 = no errors)
*/
public function read( inStream:ByteArray ):int
{
init();
if ( inStream != null)
{
this.inStream = inStream;
readHeader();
if (!hasError())
{
readContents();
if (frameCount < 0) status = STATUS_FORMAT_ERROR;
}
}
else
{
status = STATUS_OPEN_ERROR;
}
return status;
}
/**
* Decodes LZW image data into pixel array.
* Adapted from John Cristy's ImageMagick.
*/
private function decodeImageData():void
{
var NullCode:int = -1;
var npix:int = iw * ih;
var available:int;
var clear:int;
var code_mask:int;
var code_size:int;
var end_of_information:int;
var in_code:int;
var old_code:int;
var bits:int;
var code:int;
var count:int;
var i:int;
var datum:int;
var data_size:int;
var first:int;
var top:int;
var bi:int;
var pi:int;
if ((pixels == null) || (pixels.length < npix))
{
pixels = new Array ( npix ); // allocate new pixel array
}
if (prefix == null) prefix = new Array ( MaxStackSize );
if (suffix == null) suffix = new Array ( MaxStackSize );
if (pixelStack == null) pixelStack = new Array ( MaxStackSize + 1 );
// Initialize GIF data stream decoder.
data_size = readSingleByte();
clear = 1 << data_size;
end_of_information = clear + 1;
available = clear + 2;
old_code = NullCode;
code_size = data_size + 1;
code_mask = (1 << code_size) - 1;
for (code = 0; code < clear; code++)
{
prefix[int(code)] = 0;
suffix[int(code)] = code;
}
// Decode GIF pixel stream.
datum = bits = count = first = top = pi = bi = 0;
for (i = 0; i < npix;)
{
if (top == 0)
{
if (bits < code_size)
{
// Load bytes until there are enough bits for a code.
if (count == 0)
{
// Read a new data block.
count = readBlock();
if (count <= 0)
break;
bi = 0;
}
datum += (int((block[int(bi)])) & 0xff) << bits;
bits += 8;
bi++;
count--;
continue;
}
// Get the next code.
code = datum & code_mask;
datum >>= code_size;
bits -= code_size;
// Interpret the code
if ((code > available) || (code == end_of_information))
break;
if (code == clear)
{
// Reset decoder.
code_size = data_size + 1;
code_mask = (1 << code_size) - 1;
available = clear + 2;
old_code = NullCode;
continue;
}
if (old_code == NullCode)
{
pixelStack[int(top++)] = suffix[int(code)];
old_code = code;
first = code;
continue;
}
in_code = code;
if (code == available)
{
pixelStack[int(top++)] = first;
code = old_code;
}
while (code > clear)
{
pixelStack[int(top++)] = suffix[int(code)];
code = prefix[int(code)];
}
first = (suffix[int(code)]) & 0xff;
// Add a new string to the string table,
if (available >= MaxStackSize) break;
pixelStack[int(top++)] = first;
prefix[int(available)] = old_code;
suffix[int(available)] = first;
available++;
if (((available & code_mask) == 0)
&& (available < MaxStackSize))
{
code_size++;
code_mask += available;
}
old_code = in_code;
}
// Pop a pixel off the pixel stack.
top--;
pixels[int(pi++)] = pixelStack[int(top)];
i++;
}
for (i = pi; i < npix; i++)
{
pixels[int(i)] = 0; // clear missing pixels
}
}
/**
* Returns true if an error was encountered during reading/decoding
*/
private function hasError():Boolean
{
return status != STATUS_OK;
}
/**
* Initializes or re-initializes reader
*/
private function init():void
{
status = STATUS_OK;
frameCount = 0;
frames = new Array;
gct = null;
lct = null;
}
/**
* Reads a single byte from the input stream.
*/
private function readSingleByte():int
{
var curByte:int = 0;
try
{
curByte = inStream.readUnsignedByte();
}
catch (e:Error)
{
status = STATUS_FORMAT_ERROR;
}
return curByte;
}
/**
* Reads next variable length block from input.
*
* @return number of bytes stored in "buffer"
*/
private function readBlock():int
{
blockSize = readSingleByte();
var n:int = 0;
if (blockSize > 0)
{
try
{
var count:int = 0;
while (n < blockSize)
{
inStream.readBytes(block, n, blockSize - n);
if ( (blockSize - n) == -1)
break;
n += (blockSize - n);
}
}
catch (e:Error)
{
}
if (n < blockSize)
{
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());
}
}
}