#pragma warning disable 675 // Bitwise-or operator used on a sign-extended operand

#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());

		}

	}

}