moel@345: #pragma warning disable 675 // Bitwise-or operator used on a sign-extended operand
moel@345:
moel@345: #region Java Info
moel@345: /**
moel@345: * Class GifDecoder - Decodes a GIF file into one or more frames.
moel@345: * <br><pre>
moel@345: * Example:
moel@345: * GifDecoder d = new GifDecoder();
moel@345: * d.read("sample.gif");
moel@345: * int n = d.getFrameCount();
moel@345: * for (int i = 0; i < n; i++) {
moel@345: * BufferedImage frame = d.getFrame(i); // frame i
moel@345: * int t = d.getDelay(i); // display duration of frame in milliseconds
moel@345: * // do something with frame
moel@345: * }
moel@345: * </pre>
moel@345: * No copyright asserted on the source code of this class. May be used for
moel@345: * any purpose, however, refer to the Unisys LZW patent for any additional
moel@345: * restrictions. Please forward any corrections to kweiner@fmsware.com.
moel@345: *
moel@345: * @author Kevin Weiner, FM Software; LZW decoder adapted from John Cristy's ImageMagick.
moel@345: * @version 1.03 November 2003
moel@345: *
moel@345: */
moel@345: #endregion
moel@345:
moel@345: using System;
moel@345: using System.Collections;
moel@345: using System.Drawing;
moel@345: using System.Drawing.Imaging;
moel@345: using System.IO;
moel@345:
moel@345: namespace Aga.Controls
moel@345: {
moel@345: public class GifFrame
moel@345: {
moel@345: private Image _image;
moel@345: public Image Image
moel@345: {
moel@345: get { return _image; }
moel@345: }
moel@345:
moel@345: private int _delay;
moel@345: public int Delay
moel@345: {
moel@345: get { return _delay; }
moel@345: }
moel@345:
moel@345: public GifFrame(Image im, int del)
moel@345: {
moel@345: _image = im;
moel@345: _delay = del;
moel@345: }
moel@345: }
moel@345:
moel@345: public class GifDecoder
moel@345: {
moel@345: public const int StatusOK = 0;//File read status: No errors.
moel@345: public const int StatusFormatError = 1; //File read status: Error decoding file (may be partially decoded)
moel@345: public const int StatusOpenError = 2; //Unable to open source.
moel@345:
moel@345: private Stream inStream;
moel@345: private int status;
moel@345:
moel@345: private int width; // full image width
moel@345: private int height; // full image height
moel@345: private bool gctFlag; // global color table used
moel@345: private int gctSize; // size of global color table
moel@345: private int loopCount = 1; // iterations; 0 = repeat forever
moel@345:
moel@345: private int[] gct; // global color table
moel@345: private int[] lct; // local color table
moel@345: private int[] act; // active color table
moel@345:
moel@345: private int bgIndex; // background color index
moel@345: private int bgColor; // background color
moel@345: private int lastBgColor; // previous bg color
moel@345: private int pixelAspect; // pixel aspect ratio
moel@345:
moel@345: private bool lctFlag; // local color table flag
moel@345: private bool interlace; // interlace flag
moel@345: private int lctSize; // local color table size
moel@345:
moel@345: private int ix, iy, iw, ih; // current image rectangle
moel@345: private Rectangle lastRect; // last image rect
moel@345: private Image image; // current frame
moel@345: private Bitmap bitmap;
moel@345: private Image lastImage; // previous frame
moel@345:
moel@345: private byte[] block = new byte[256]; // current data block
moel@345: private int blockSize = 0; // block size
moel@345:
moel@345: // last graphic control extension info
moel@345: private int dispose = 0;
moel@345: // 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prev
moel@345: private int lastDispose = 0;
moel@345: private bool transparency = false; // use transparent color
moel@345: private int delay = 0; // delay in milliseconds
moel@345: private int transIndex; // transparent color index
moel@345:
moel@345: private const int MaxStackSize = 4096;
moel@345: // max decoder pixel stack size
moel@345:
moel@345: // LZW decoder working arrays
moel@345: private short[] prefix;
moel@345: private byte[] suffix;
moel@345: private byte[] pixelStack;
moel@345: private byte[] pixels;
moel@345:
moel@345: private ArrayList frames; // frames read from current file
moel@345: private int frameCount;
moel@345: private bool _makeTransparent;
moel@345:
moel@345: /**
moel@345: * Gets the number of frames read from file.
moel@345: * @return frame count
moel@345: */
moel@345: public int FrameCount
moel@345: {
moel@345: get
moel@345: {
moel@345: return frameCount;
moel@345: }
moel@345: }
moel@345:
moel@345: /**
moel@345: * Gets the first (or only) image read.
moel@345: *
moel@345: * @return BufferedImage containing first frame, or null if none.
moel@345: */
moel@345: public Image Image
moel@345: {
moel@345: get
moel@345: {
moel@345: return GetFrame(0).Image;
moel@345: }
moel@345: }
moel@345:
moel@345: /**
moel@345: * Gets the "Netscape" iteration count, if any.
moel@345: * A count of 0 means repeat indefinitiely.
moel@345: *
moel@345: * @return iteration count if one was specified, else 1.
moel@345: */
moel@345: public int LoopCount
moel@345: {
moel@345: get
moel@345: {
moel@345: return loopCount;
moel@345: }
moel@345: }
moel@345:
moel@345: public GifDecoder(Stream stream, bool makeTransparent)
moel@345: {
moel@345: _makeTransparent = makeTransparent;
moel@345: if (Read(stream) != 0)
moel@345: throw new InvalidOperationException();
moel@345: }
moel@345:
moel@345: /**
moel@345: * Creates new frame image from current data (and previous
moel@345: * frames as specified by their disposition codes).
moel@345: */
moel@345: private int[] GetPixels(Bitmap bitmap)
moel@345: {
moel@345: int [] pixels = new int [ 3 * image.Width * image.Height ];
moel@345: int count = 0;
moel@345: for (int th = 0; th < image.Height; th++)
moel@345: {
moel@345: for (int tw = 0; tw < image.Width; tw++)
moel@345: {
moel@345: Color color = bitmap.GetPixel(tw, th);
moel@345: pixels[count] = color.R;
moel@345: count++;
moel@345: pixels[count] = color.G;
moel@345: count++;
moel@345: pixels[count] = color.B;
moel@345: count++;
moel@345: }
moel@345: }
moel@345: return pixels;
moel@345: }
moel@345:
moel@345: private void SetPixels(int[] pixels)
moel@345: {
moel@345: int count = 0;
moel@345: for (int th = 0; th < image.Height; th++)
moel@345: {
moel@345: for (int tw = 0; tw < image.Width; tw++)
moel@345: {
moel@345: Color color = Color.FromArgb( pixels[count++] );
moel@345: bitmap.SetPixel( tw, th, color );
moel@345: }
moel@345: }
moel@345: if (_makeTransparent)
moel@345: bitmap.MakeTransparent(bitmap.GetPixel(0, 0));
moel@345: }
moel@345:
moel@345: private void SetPixels()
moel@345: {
moel@345: // expose destination image's pixels as int array
moel@345: // int[] dest =
moel@345: // (( int ) image.getRaster().getDataBuffer()).getData();
moel@345: int[] dest = GetPixels( bitmap );
moel@345:
moel@345: // fill in starting image contents based on last image's dispose code
moel@345: if (lastDispose > 0)
moel@345: {
moel@345: if (lastDispose == 3)
moel@345: {
moel@345: // use image before last
moel@345: int n = frameCount - 2;
moel@345: if (n > 0)
moel@345: {
moel@345: lastImage = GetFrame(n - 1).Image;
moel@345: }
moel@345: else
moel@345: {
moel@345: lastImage = null;
moel@345: }
moel@345: }
moel@345:
moel@345: if (lastImage != null)
moel@345: {
moel@345: // int[] prev =
moel@345: // ((DataBufferInt) lastImage.getRaster().getDataBuffer()).getData();
moel@345: int[] prev = GetPixels( new Bitmap( lastImage ) );
moel@345: Array.Copy(prev, 0, dest, 0, width * height);
moel@345: // copy pixels
moel@345:
moel@345: if (lastDispose == 2)
moel@345: {
moel@345: // fill last image rect area with background color
moel@345: Graphics g = Graphics.FromImage( image );
moel@345: Color c = Color.Empty;
moel@345: if (transparency)
moel@345: {
moel@345: c = Color.FromArgb( 0, 0, 0, 0 ); // assume background is transparent
moel@345: }
moel@345: else
moel@345: {
moel@345: c = Color.FromArgb( lastBgColor ) ;
moel@345: // c = new Color(lastBgColor); // use given background color
moel@345: }
moel@345: Brush brush = new SolidBrush( c );
moel@345: g.FillRectangle( brush, lastRect );
moel@345: brush.Dispose();
moel@345: g.Dispose();
moel@345: }
moel@345: }
moel@345: }
moel@345:
moel@345: // copy each source line to the appropriate place in the destination
moel@345: int pass = 1;
moel@345: int inc = 8;
moel@345: int iline = 0;
moel@345: for (int i = 0; i < ih; i++)
moel@345: {
moel@345: int line = i;
moel@345: if (interlace)
moel@345: {
moel@345: if (iline >= ih)
moel@345: {
moel@345: pass++;
moel@345: switch (pass)
moel@345: {
moel@345: case 2 :
moel@345: iline = 4;
moel@345: break;
moel@345: case 3 :
moel@345: iline = 2;
moel@345: inc = 4;
moel@345: break;
moel@345: case 4 :
moel@345: iline = 1;
moel@345: inc = 2;
moel@345: break;
moel@345: }
moel@345: }
moel@345: line = iline;
moel@345: iline += inc;
moel@345: }
moel@345: line += iy;
moel@345: if (line < height)
moel@345: {
moel@345: int k = line * width;
moel@345: int dx = k + ix; // start of line in dest
moel@345: int dlim = dx + iw; // end of dest line
moel@345: if ((k + width) < dlim)
moel@345: {
moel@345: dlim = k + width; // past dest edge
moel@345: }
moel@345: int sx = i * iw; // start of line in source
moel@345: while (dx < dlim)
moel@345: {
moel@345: // map color and insert in destination
moel@345: int index = ((int) pixels[sx++]) & 0xff;
moel@345: int c = act[index];
moel@345: if (c != 0)
moel@345: {
moel@345: dest[dx] = c;
moel@345: }
moel@345: dx++;
moel@345: }
moel@345: }
moel@345: }
moel@345: SetPixels( dest );
moel@345: }
moel@345:
moel@345: /**
moel@345: * Gets the image contents of frame n.
moel@345: *
moel@345: * @return BufferedImage representation of frame.
moel@345: */
moel@345: public GifFrame GetFrame(int n)
moel@345: {
moel@345: if ((n >= 0) && (n < frameCount))
moel@345: return (GifFrame)frames[n];
moel@345: else
moel@345: throw new ArgumentOutOfRangeException();
moel@345: }
moel@345:
moel@345: /**
moel@345: * Gets image size.
moel@345: *
moel@345: * @return GIF image dimensions
moel@345: */
moel@345: public Size FrameSize
moel@345: {
moel@345: get
moel@345: {
moel@345: return new Size(width, height);
moel@345: }
moel@345: }
moel@345:
moel@345: /**
moel@345: * Reads GIF image from stream
moel@345: *
moel@345: * @param BufferedInputStream containing GIF file.
moel@345: * @return read status code (0 = no errors)
moel@345: */
moel@345: private int Read( Stream inStream )
moel@345: {
moel@345: Init();
moel@345: if ( inStream != null)
moel@345: {
moel@345: this.inStream = inStream;
moel@345: ReadHeader();
moel@345: if (!Error())
moel@345: {
moel@345: ReadContents();
moel@345: if (frameCount < 0)
moel@345: {
moel@345: status = StatusFormatError;
moel@345: }
moel@345: }
moel@345: inStream.Close();
moel@345: }
moel@345: else
moel@345: {
moel@345: status = StatusOpenError;
moel@345: }
moel@345: return status;
moel@345: }
moel@345:
moel@345:
moel@345: /**
moel@345: * Decodes LZW image data into pixel array.
moel@345: * Adapted from John Cristy's ImageMagick.
moel@345: */
moel@345: private void DecodeImageData()
moel@345: {
moel@345: int NullCode = -1;
moel@345: int npix = iw * ih;
moel@345: int available,
moel@345: clear,
moel@345: code_mask,
moel@345: code_size,
moel@345: end_of_information,
moel@345: in_code,
moel@345: old_code,
moel@345: bits,
moel@345: code,
moel@345: count,
moel@345: i,
moel@345: datum,
moel@345: data_size,
moel@345: first,
moel@345: top,
moel@345: bi,
moel@345: pi;
moel@345:
moel@345: if ((pixels == null) || (pixels.Length < npix))
moel@345: {
moel@345: pixels = new byte[npix]; // allocate new pixel array
moel@345: }
moel@345: if (prefix == null) prefix = new short[MaxStackSize];
moel@345: if (suffix == null) suffix = new byte[MaxStackSize];
moel@345: if (pixelStack == null) pixelStack = new byte[MaxStackSize + 1];
moel@345:
moel@345: // Initialize GIF data stream decoder.
moel@345:
moel@345: data_size = Read();
moel@345: clear = 1 << data_size;
moel@345: end_of_information = clear + 1;
moel@345: available = clear + 2;
moel@345: old_code = NullCode;
moel@345: code_size = data_size + 1;
moel@345: code_mask = (1 << code_size) - 1;
moel@345: for (code = 0; code < clear; code++)
moel@345: {
moel@345: prefix[code] = 0;
moel@345: suffix[code] = (byte) code;
moel@345: }
moel@345:
moel@345: // Decode GIF pixel stream.
moel@345:
moel@345: datum = bits = count = first = top = pi = bi = 0;
moel@345:
moel@345: for (i = 0; i < npix;)
moel@345: {
moel@345: if (top == 0)
moel@345: {
moel@345: if (bits < code_size)
moel@345: {
moel@345: // Load bytes until there are enough bits for a code.
moel@345: if (count == 0)
moel@345: {
moel@345: // Read a new data block.
moel@345: count = ReadBlock();
moel@345: if (count <= 0)
moel@345: break;
moel@345: bi = 0;
moel@345: }
moel@345: datum += (((int) block[bi]) & 0xff) << bits;
moel@345: bits += 8;
moel@345: bi++;
moel@345: count--;
moel@345: continue;
moel@345: }
moel@345:
moel@345: // Get the next code.
moel@345:
moel@345: code = datum & code_mask;
moel@345: datum >>= code_size;
moel@345: bits -= code_size;
moel@345:
moel@345: // Interpret the code
moel@345:
moel@345: if ((code > available) || (code == end_of_information))
moel@345: break;
moel@345: if (code == clear)
moel@345: {
moel@345: // Reset decoder.
moel@345: code_size = data_size + 1;
moel@345: code_mask = (1 << code_size) - 1;
moel@345: available = clear + 2;
moel@345: old_code = NullCode;
moel@345: continue;
moel@345: }
moel@345: if (old_code == NullCode)
moel@345: {
moel@345: pixelStack[top++] = suffix[code];
moel@345: old_code = code;
moel@345: first = code;
moel@345: continue;
moel@345: }
moel@345: in_code = code;
moel@345: if (code == available)
moel@345: {
moel@345: pixelStack[top++] = (byte) first;
moel@345: code = old_code;
moel@345: }
moel@345: while (code > clear)
moel@345: {
moel@345: pixelStack[top++] = suffix[code];
moel@345: code = prefix[code];
moel@345: }
moel@345: first = ((int) suffix[code]) & 0xff;
moel@345:
moel@345: // Add a new string to the string table,
moel@345:
moel@345: if (available >= MaxStackSize)
moel@345: break;
moel@345: pixelStack[top++] = (byte) first;
moel@345: prefix[available] = (short) old_code;
moel@345: suffix[available] = (byte) first;
moel@345: available++;
moel@345: if (((available & code_mask) == 0)
moel@345: && (available < MaxStackSize))
moel@345: {
moel@345: code_size++;
moel@345: code_mask += available;
moel@345: }
moel@345: old_code = in_code;
moel@345: }
moel@345:
moel@345: // Pop a pixel off the pixel stack.
moel@345:
moel@345: top--;
moel@345: pixels[pi++] = pixelStack[top];
moel@345: i++;
moel@345: }
moel@345:
moel@345: for (i = pi; i < npix; i++)
moel@345: {
moel@345: pixels[i] = 0; // clear missing pixels
moel@345: }
moel@345:
moel@345: }
moel@345:
moel@345: /**
moel@345: * Returns true if an error was encountered during reading/decoding
moel@345: */
moel@345: private bool Error()
moel@345: {
moel@345: return status != StatusOK;
moel@345: }
moel@345:
moel@345: /**
moel@345: * Initializes or re-initializes reader
moel@345: */
moel@345: private void Init()
moel@345: {
moel@345: status = StatusOK;
moel@345: frameCount = 0;
moel@345: frames = new ArrayList();
moel@345: gct = null;
moel@345: lct = null;
moel@345: }
moel@345:
moel@345: /**
moel@345: * Reads a single byte from the input stream.
moel@345: */
moel@345: private int Read()
moel@345: {
moel@345: int curByte = 0;
moel@345: try
moel@345: {
moel@345: curByte = inStream.ReadByte();
moel@345: }
moel@345: catch (IOException)
moel@345: {
moel@345: status = StatusFormatError;
moel@345: }
moel@345: return curByte;
moel@345: }
moel@345:
moel@345: /**
moel@345: * Reads next variable length block from input.
moel@345: *
moel@345: * @return number of bytes stored in "buffer"
moel@345: */
moel@345: private int ReadBlock()
moel@345: {
moel@345: blockSize = Read();
moel@345: int n = 0;
moel@345: if (blockSize > 0)
moel@345: {
moel@345: try
moel@345: {
moel@345: int count = 0;
moel@345: while (n < blockSize)
moel@345: {
moel@345: count = inStream.Read(block, n, blockSize - n);
moel@345: if (count == -1)
moel@345: break;
moel@345: n += count;
moel@345: }
moel@345: }
moel@345: catch (IOException)
moel@345: {
moel@345: }
moel@345:
moel@345: if (n < blockSize)
moel@345: {
moel@345: status = StatusFormatError;
moel@345: }
moel@345: }
moel@345: return n;
moel@345: }
moel@345:
moel@345: /**
moel@345: * Reads color table as 256 RGB integer values
moel@345: *
moel@345: * @param ncolors int number of colors to read
moel@345: * @return int array containing 256 colors (packed ARGB with full alpha)
moel@345: */
moel@345: private int[] ReadColorTable(int ncolors)
moel@345: {
moel@345: int nbytes = 3 * ncolors;
moel@345: int[] tab = null;
moel@345: byte[] c = new byte[nbytes];
moel@345: int n = 0;
moel@345: try
moel@345: {
moel@345: n = inStream.Read(c, 0, c.Length );
moel@345: }
moel@345: catch (IOException)
moel@345: {
moel@345: }
moel@345: if (n < nbytes)
moel@345: {
moel@345: status = StatusFormatError;
moel@345: }
moel@345: else
moel@345: {
moel@345: tab = new int[256]; // max size to avoid bounds checks
moel@345: int i = 0;
moel@345: int j = 0;
moel@345: while (i < ncolors)
moel@345: {
moel@345: int r = ((int) c[j++]) & 0xff;
moel@345: int g = ((int) c[j++]) & 0xff;
moel@345: int b = ((int) c[j++]) & 0xff;
moel@345: tab[i++] = ( int ) ( 0xff000000 | (r << 16) | (g << 8) | b );
moel@345: }
moel@345: }
moel@345: return tab;
moel@345: }
moel@345:
moel@345: /**
moel@345: * Main file parser. Reads GIF content blocks.
moel@345: */
moel@345: private void ReadContents()
moel@345: {
moel@345: // read GIF file content blocks
moel@345: bool done = false;
moel@345: while (!(done || Error()))
moel@345: {
moel@345: int code = Read();
moel@345: switch (code)
moel@345: {
moel@345:
moel@345: case 0x2C : // image separator
moel@345: ReadImage();
moel@345: break;
moel@345:
moel@345: case 0x21 : // extension
moel@345: code = Read();
moel@345: switch (code)
moel@345: {
moel@345: case 0xf9 : // graphics control extension
moel@345: ReadGraphicControlExt();
moel@345: break;
moel@345:
moel@345: case 0xff : // application extension
moel@345: ReadBlock();
moel@345: String app = "";
moel@345: for (int i = 0; i < 11; i++)
moel@345: {
moel@345: app += (char) block[i];
moel@345: }
moel@345: if (app.Equals("NETSCAPE2.0"))
moel@345: {
moel@345: ReadNetscapeExt();
moel@345: }
moel@345: else
moel@345: Skip(); // don't care
moel@345: break;
moel@345:
moel@345: default : // uninteresting extension
moel@345: Skip();
moel@345: break;
moel@345: }
moel@345: break;
moel@345:
moel@345: case 0x3b : // terminator
moel@345: done = true;
moel@345: break;
moel@345:
moel@345: case 0x00 : // bad byte, but keep going and see what happens
moel@345: break;
moel@345:
moel@345: default :
moel@345: status = StatusFormatError;
moel@345: break;
moel@345: }
moel@345: }
moel@345: }
moel@345:
moel@345: /**
moel@345: * Reads Graphics Control Extension values
moel@345: */
moel@345: private void ReadGraphicControlExt()
moel@345: {
moel@345: Read(); // block size
moel@345: int packed = Read(); // packed fields
moel@345: dispose = (packed & 0x1c) >> 2; // disposal method
moel@345: if (dispose == 0)
moel@345: {
moel@345: dispose = 1; // elect to keep old image if discretionary
moel@345: }
moel@345: transparency = (packed & 1) != 0;
moel@345: delay = ReadShort() * 10; // delay in milliseconds
moel@345: transIndex = Read(); // transparent color index
moel@345: Read(); // block terminator
moel@345: }
moel@345:
moel@345: /**
moel@345: * Reads GIF file header information.
moel@345: */
moel@345: private void ReadHeader()
moel@345: {
moel@345: String id = "";
moel@345: for (int i = 0; i < 6; i++)
moel@345: {
moel@345: id += (char) Read();
moel@345: }
moel@345: if (!id.StartsWith("GIF"))
moel@345: {
moel@345: status = StatusFormatError;
moel@345: return;
moel@345: }
moel@345:
moel@345: ReadLSD();
moel@345: if (gctFlag && !Error())
moel@345: {
moel@345: gct = ReadColorTable(gctSize);
moel@345: bgColor = gct[bgIndex];
moel@345: }
moel@345: }
moel@345:
moel@345: /**
moel@345: * Reads next frame image
moel@345: */
moel@345: private void ReadImage()
moel@345: {
moel@345: ix = ReadShort(); // (sub)image position & size
moel@345: iy = ReadShort();
moel@345: iw = ReadShort();
moel@345: ih = ReadShort();
moel@345:
moel@345: int packed = Read();
moel@345: lctFlag = (packed & 0x80) != 0; // 1 - local color table flag
moel@345: interlace = (packed & 0x40) != 0; // 2 - interlace flag
moel@345: // 3 - sort flag
moel@345: // 4-5 - reserved
moel@345: lctSize = 2 << (packed & 7); // 6-8 - local color table size
moel@345:
moel@345: if (lctFlag)
moel@345: {
moel@345: lct = ReadColorTable(lctSize); // read table
moel@345: act = lct; // make local table active
moel@345: }
moel@345: else
moel@345: {
moel@345: act = gct; // make global table active
moel@345: if (bgIndex == transIndex)
moel@345: bgColor = 0;
moel@345: }
moel@345: int save = 0;
moel@345: if (transparency)
moel@345: {
moel@345: save = act[transIndex];
moel@345: act[transIndex] = 0; // set transparent color if specified
moel@345: }
moel@345:
moel@345: if (act == null)
moel@345: {
moel@345: status = StatusFormatError; // no color table defined
moel@345: }
moel@345:
moel@345: if (Error()) return;
moel@345:
moel@345: DecodeImageData(); // decode pixel data
moel@345: Skip();
moel@345:
moel@345: if (Error()) return;
moel@345:
moel@345: frameCount++;
moel@345:
moel@345: // create new image to receive frame data
moel@345: // image =
moel@345: // new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB_PRE);
moel@345:
moel@345: bitmap = new Bitmap( width, height );
moel@345: image = bitmap;
moel@345: SetPixels(); // transfer pixel data to image
moel@345:
moel@345: frames.Add(new GifFrame(bitmap, delay)); // add image to frame list
moel@345:
moel@345: if (transparency)
moel@345: {
moel@345: act[transIndex] = save;
moel@345: }
moel@345: ResetFrame();
moel@345:
moel@345: }
moel@345:
moel@345: /**
moel@345: * Reads Logical Screen Descriptor
moel@345: */
moel@345: private void ReadLSD()
moel@345: {
moel@345:
moel@345: // logical screen size
moel@345: width = ReadShort();
moel@345: height = ReadShort();
moel@345:
moel@345: // packed fields
moel@345: int packed = Read();
moel@345: gctFlag = (packed & 0x80) != 0; // 1 : global color table flag
moel@345: // 2-4 : color resolution
moel@345: // 5 : gct sort flag
moel@345: gctSize = 2 << (packed & 7); // 6-8 : gct size
moel@345:
moel@345: bgIndex = Read(); // background color index
moel@345: pixelAspect = Read(); // pixel aspect ratio
moel@345: }
moel@345:
moel@345: /**
moel@345: * Reads Netscape extenstion to obtain iteration count
moel@345: */
moel@345: private void ReadNetscapeExt()
moel@345: {
moel@345: do
moel@345: {
moel@345: ReadBlock();
moel@345: if (block[0] == 1)
moel@345: {
moel@345: // loop count sub-block
moel@345: int b1 = ((int) block[1]) & 0xff;
moel@345: int b2 = ((int) block[2]) & 0xff;
moel@345: loopCount = (b2 << 8) | b1;
moel@345: }
moel@345: } while ((blockSize > 0) && !Error());
moel@345: }
moel@345:
moel@345: /**
moel@345: * Reads next 16-bit value, LSB first
moel@345: */
moel@345: private int ReadShort()
moel@345: {
moel@345: // read 16-bit value, LSB first
moel@345: return Read() | (Read() << 8);
moel@345: }
moel@345:
moel@345: /**
moel@345: * Resets frame state for reading next image.
moel@345: */
moel@345: private void ResetFrame()
moel@345: {
moel@345: lastDispose = dispose;
moel@345: lastRect = new Rectangle(ix, iy, iw, ih);
moel@345: lastImage = image;
moel@345: lastBgColor = bgColor;
moel@345: // int dispose = 0;
moel@345: lct = null;
moel@345: }
moel@345:
moel@345: /**
moel@345: * Skips variable length blocks up to and including
moel@345: * next zero length block.
moel@345: */
moel@345: private void Skip()
moel@345: {
moel@345: do
moel@345: {
moel@345: ReadBlock();
moel@345: } while ((blockSize > 0) && !Error());
moel@345: }
moel@345: }
moel@345: }