#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) 
				{
					uint r = ((uint) c[j++]) & 0xff;
					uint g = ((uint) c[j++]) & 0xff;
					uint b = ((uint) 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());
		}
	}
}
