#region Java Info
/**
* Class GifDecoder - Decodes a GIF file into one or more frames.
* <br><pre>
* Example:
* GifDecoder d = new GifDecoder();
* d.read("sample.gif");
* int n = d.getFrameCount();
* for (int i = 0; i < n; i++) {
* BufferedImage frame = d.getFrame(i); // frame i
* int t = d.getDelay(i); // display duration of frame in milliseconds
* // do something with frame
* }
* </pre>
* No copyright asserted on the source code of this class. May be used for
* any purpose, however, refer to the Unisys LZW patent for any additional
* restrictions. Please forward any corrections to kweiner@fmsware.com.
*
* @author Kevin Weiner, FM Software; LZW decoder adapted from John Cristy's ImageMagick.
* @version 1.03 November 2003
*
*/
#endregion
using System;
using System.Collections;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
namespace Aga.Controls
{
public class GifFrame
{
private Image _image;
public Image Image
{
get { return _image; }
}
private int _delay;
public int Delay
{
get { return _delay; }
}
public GifFrame(Image im, int del)
{
_image = im;
_delay = del;
}
}
public class GifDecoder
{
public const int StatusOK = 0;//File read status: No errors.
public const int StatusFormatError = 1; //File read status: Error decoding file (may be partially decoded)
public const int StatusOpenError = 2; //Unable to open source.
private Stream inStream;
private int status;
private int width; // full image width
private int height; // full image height
private bool gctFlag; // global color table used
private int gctSize; // size of global color table
private int loopCount = 1; // iterations; 0 = repeat forever
private int[] gct; // global color table
private int[] lct; // local color table
private int[] act; // active color table
private int bgIndex; // background color index
private int bgColor; // background color
private int lastBgColor; // previous bg color
private int pixelAspect; // pixel aspect ratio
private bool lctFlag; // local color table flag
private bool interlace; // interlace flag
private int lctSize; // local color table size
private int ix, iy, iw, ih; // current image rectangle
private Rectangle lastRect; // last image rect
private Image image; // current frame
private Bitmap bitmap;
private Image lastImage; // previous frame
private byte[] block = new byte[256]; // current data block
private int blockSize = 0; // block size
// last graphic control extension info
private int dispose = 0;
// 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prev
private int lastDispose = 0;
private bool transparency = false; // use transparent color
private int delay = 0; // delay in milliseconds
private int transIndex; // transparent color index
private const int MaxStackSize = 4096;
// max decoder pixel stack size
// LZW decoder working arrays
private short[] prefix;
private byte[] suffix;
private byte[] pixelStack;
private byte[] pixels;
private ArrayList frames; // frames read from current file
private int frameCount;
private bool _makeTransparent;
/**
* Gets the number of frames read from file.
* @return frame count
*/
public int FrameCount
{
get
{
return frameCount;
}
}
/**
* Gets the first (or only) image read.
*
* @return BufferedImage containing first frame, or null if none.
*/
public Image Image
{
get
{
return GetFrame(0).Image;
}
}
/**
* Gets the "Netscape" iteration count, if any.
* A count of 0 means repeat indefinitiely.
*
* @return iteration count if one was specified, else 1.
*/
public int LoopCount
{
get
{
return loopCount;
}
}
public GifDecoder(Stream stream, bool makeTransparent)
{
_makeTransparent = makeTransparent;
if (Read(stream) != 0)
throw new InvalidOperationException();
}
/**
* Creates new frame image from current data (and previous
* frames as specified by their disposition codes).
*/
private int[] GetPixels(Bitmap bitmap)
{
int [] pixels = new int [ 3 * image.Width * image.Height ];
int count = 0;
for (int th = 0; th < image.Height; th++)
{
for (int tw = 0; tw < image.Width; tw++)
{
Color color = bitmap.GetPixel(tw, th);
pixels[count] = color.R;
count++;
pixels[count] = color.G;
count++;
pixels[count] = color.B;
count++;
}
}
return pixels;
}
private void SetPixels(int[] pixels)
{
int count = 0;
for (int th = 0; th < image.Height; th++)
{
for (int tw = 0; tw < image.Width; tw++)
{
Color color = Color.FromArgb( pixels[count++] );
bitmap.SetPixel( tw, th, color );
}
}
if (_makeTransparent)
bitmap.MakeTransparent(bitmap.GetPixel(0, 0));
}
private void SetPixels()
{
// expose destination image's pixels as int array
// int[] dest =
// (( int ) image.getRaster().getDataBuffer()).getData();
int[] dest = GetPixels( bitmap );
// fill in starting image contents based on last image's dispose code
if (lastDispose > 0)
{
if (lastDispose == 3)
{
// use image before last
int n = frameCount - 2;
if (n > 0)
{
lastImage = GetFrame(n - 1).Image;
}
else
{
lastImage = null;
}
}
if (lastImage != null)
{
// int[] prev =
// ((DataBufferInt) lastImage.getRaster().getDataBuffer()).getData();
int[] prev = GetPixels( new Bitmap( lastImage ) );
Array.Copy(prev, 0, dest, 0, width * height);
// copy pixels
if (lastDispose == 2)
{
// fill last image rect area with background color
Graphics g = Graphics.FromImage( image );
Color c = Color.Empty;
if (transparency)
{
c = Color.FromArgb( 0, 0, 0, 0 ); // assume background is transparent
}
else
{
c = Color.FromArgb( lastBgColor ) ;
// c = new Color(lastBgColor); // use given background color
}
Brush brush = new SolidBrush( c );
g.FillRectangle( brush, lastRect );
brush.Dispose();
g.Dispose();
}
}
}
// copy each source line to the appropriate place in the destination
int pass = 1;
int inc = 8;
int iline = 0;
for (int i = 0; i < ih; i++)
{
int line = 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)
{
int k = line * width;
int dx = k + ix; // start of line in dest
int dlim = dx + iw; // end of dest line
if ((k + width) < dlim)
{
dlim = k + width; // past dest edge
}
int sx = i * iw; // start of line in source
while (dx < dlim)
{
// map color and insert in destination
int index = ((int) pixels[sx++]) & 0xff;
int c = act[index];
if (c != 0)
{
dest[dx] = c;
}
dx++;
}
}
}
SetPixels( dest );
}
/**
* Gets the image contents of frame n.
*
* @return BufferedImage representation of frame.
*/
public GifFrame GetFrame(int n)
{
if ((n >= 0) && (n < frameCount))
return (GifFrame)frames[n];
else
throw new ArgumentOutOfRangeException();
}
/**
* Gets image size.
*
* @return GIF image dimensions
*/
public Size FrameSize
{
get
{
return new Size(width, height);
}
}
/**
* Reads GIF image from stream
*
* @param BufferedInputStream containing GIF file.
* @return read status code (0 = no errors)
*/
private int Read( Stream inStream )
{
Init();
if ( inStream != null)
{
this.inStream = inStream;
ReadHeader();
if (!Error())
{
ReadContents();
if (frameCount < 0)
{
status = StatusFormatError;
}
}
inStream.Close();
}
else
{
status = StatusOpenError;
}
return status;
}
/**
* Decodes LZW image data into pixel array.
* Adapted from John Cristy's ImageMagick.
*/
private void DecodeImageData()
{
int NullCode = -1;
int npix = iw * ih;
int available,
clear,
code_mask,
code_size,
end_of_information,
in_code,
old_code,
bits,
code,
count,
i,
datum,
data_size,
first,
top,
bi,
pi;
if ((pixels == null) || (pixels.Length < npix))
{
pixels = new byte[npix]; // allocate new pixel array
}
if (prefix == null) prefix = new short[MaxStackSize];
if (suffix == null) suffix = new byte[MaxStackSize];
if (pixelStack == null) pixelStack = new byte[MaxStackSize + 1];
// Initialize GIF data stream decoder.
data_size = Read();
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[code] = 0;
suffix[code] = (byte) 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[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[top++] = suffix[code];
old_code = code;
first = code;
continue;
}
in_code = code;
if (code == available)
{
pixelStack[top++] = (byte) first;
code = old_code;
}
while (code > clear)
{
pixelStack[top++] = suffix[code];
code = prefix[code];
}
first = ((int) suffix[code]) & 0xff;
// Add a new string to the string table,
if (available >= MaxStackSize)
break;
pixelStack[top++] = (byte) first;
prefix[available] = (short) old_code;
suffix[available] = (byte) 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[pi++] = pixelStack[top];
i++;
}
for (i = pi; i < npix; i++)
{
pixels[i] = 0; // clear missing pixels
}
}
/**
* Returns true if an error was encountered during reading/decoding
*/
private bool Error()
{
return status != StatusOK;
}
/**
* Initializes or re-initializes reader
*/
private void Init()
{
status = StatusOK;
frameCount = 0;
frames = new ArrayList();
gct = null;
lct = null;
}
/**
* Reads a single byte from the input stream.
*/
private int Read()
{
int curByte = 0;
try
{
curByte = inStream.ReadByte();
}
catch (IOException)
{
status = StatusFormatError;
}
return curByte;
}
/**
* Reads next variable length block from input.
*
* @return number of bytes stored in "buffer"
*/
private int ReadBlock()
{
blockSize = Read();
int n = 0;
if (blockSize > 0)
{
try
{
int count = 0;
while (n < blockSize)
{
count = inStream.Read(block, n, blockSize - n);
if (count == -1)
break;
n += count;
}
}
catch (IOException)
{
}
if (n < blockSize)
{
status = StatusFormatError;
}
}
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 int[] ReadColorTable(int ncolors)
{
int nbytes = 3 * ncolors;
int[] tab = null;
byte[] c = new byte[nbytes];
int n = 0;
try
{
n = inStream.Read(c, 0, c.Length );
}
catch (IOException)
{
}
if (n < nbytes)
{
status = StatusFormatError;
}
else
{
tab = new int[256]; // max size to avoid bounds checks
int i = 0;
int j = 0;
while (i < ncolors)
{
int r = ((int) c[j++]) & 0xff;
int g = ((int) c[j++]) & 0xff;
int b = ((int) c[j++]) & 0xff;
tab[i++] = ( int ) ( 0xff000000 | (r << 16) | (g << 8) | b );
}
}
return tab;
}
/**
* Main file parser. Reads GIF content blocks.
*/
private void ReadContents()
{
// read GIF file content blocks
bool done = false;
while (!(done || Error()))
{
int code = Read();
switch (code)
{
case 0x2C : // image separator
ReadImage();
break;
case 0x21 : // extension
code = Read();
switch (code)
{
case 0xf9 : // graphics control extension
ReadGraphicControlExt();
break;
case 0xff : // application extension
ReadBlock();
String app = "";
for (int i = 0; i < 11; i++)
{
app += (char) block[i];
}
if (app.Equals("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 = StatusFormatError;
break;
}
}
}
/**
* Reads Graphics Control Extension values
*/
private void ReadGraphicControlExt()
{
Read(); // block size
int packed = Read(); // 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 = Read(); // transparent color index
Read(); // block terminator
}
/**
* Reads GIF file header information.
*/
private void ReadHeader()
{
String id = "";
for (int i = 0; i < 6; i++)
{
id += (char) Read();
}
if (!id.StartsWith("GIF"))
{
status = StatusFormatError;
return;
}
ReadLSD();
if (gctFlag && !Error())
{
gct = ReadColorTable(gctSize);
bgColor = gct[bgIndex];
}
}
/**
* Reads next frame image
*/
private void ReadImage()
{
ix = ReadShort(); // (sub)image position & size
iy = ReadShort();
iw = ReadShort();
ih = ReadShort();
int packed = Read();
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;
}
int save = 0;
if (transparency)
{
save = act[transIndex];
act[transIndex] = 0; // set transparent color if specified
}
if (act == null)
{
status = StatusFormatError; // no color table defined
}
if (Error()) return;
DecodeImageData(); // decode pixel data
Skip();
if (Error()) return;
frameCount++;
// create new image to receive frame data
// image =
// new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB_PRE);
bitmap = new Bitmap( width, height );
image = bitmap;
SetPixels(); // transfer pixel data to image
frames.Add(new GifFrame(bitmap, delay)); // add image to frame list
if (transparency)
{
act[transIndex] = save;
}
ResetFrame();
}
/**
* Reads Logical Screen Descriptor
*/
private void ReadLSD()
{
// logical screen size
width = ReadShort();
height = ReadShort();
// packed fields
int packed = Read();
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 = Read(); // background color index
pixelAspect = Read(); // pixel aspect ratio
}
/**
* Reads Netscape extenstion to obtain iteration count
*/
private void ReadNetscapeExt()
{
do
{
ReadBlock();
if (block[0] == 1)
{
// loop count sub-block
int b1 = ((int) block[1]) & 0xff;
int b2 = ((int) block[2]) & 0xff;
loopCount = (b2 << 8) | b1;
}
} while ((blockSize > 0) && !Error());
}
/**
* Reads next 16-bit value, LSB first
*/
private int ReadShort()
{
// read 16-bit value, LSB first
return Read() | (Read() << 8);
}
/**
* Resets frame state for reading next image.
*/
private void ResetFrame()
{
lastDispose = dispose;
lastRect = new Rectangle(ix, iy, iw, ih);
lastImage = image;
lastBgColor = bgColor;
// int dispose = 0;
lct = null;
}
/**
* Skips variable length blocks up to and including
* next zero length block.
*/
private void Skip()
{
do
{
ReadBlock();
} while ((blockSize > 0) && !Error());
}
}
}
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