/*
 * @(#)GIFEncoder.java    0.90 4/21/96 Adam Doppelt
 */
import java.io.*;
import java.awt.*;
import java.awt.image.*;
public class GIFEncoder {
    short width_, height_;
    int numColors_;
    byte pixels_[], colors_[];
    
    ScreenDescriptor sd_;
    ImageDescriptor id_;
    public GIFEncoder(Image image) throws AWTException {
        width_ = (short)image.getWidth(null);
        height_ = (short)image.getHeight(null);
        int values[] = new int[width_ * height_];
        PixelGrabber grabber = new PixelGrabber(
            image, 0, 0, width_, height_, values, 0, width_);
		
        try {
            if(grabber.grabPixels() != true)
                throw new AWTException("Grabber returned false: " +
                                       grabber.status());
        }
        catch (InterruptedException e) { ; }
        

        byte r[][] = new byte[width_][height_];
        byte g[][] = new byte[width_][height_];
        byte b[][] = new byte[width_][height_];
        int index = 0;
        for (int y = 0; y < height_; ++y)
            for (int x = 0; x < width_; ++x) {
                r[x][y] = (byte)((values[index] >> 16) & 0xFF);
                g[x][y] = (byte)((values[index] >> 8) & 0xFF);
                b[x][y] = (byte)((values[index]) & 0xFF);  
                ++index;
            }
        ToIndexedColor(r, g, b);
    }

    public GIFEncoder(byte r[][], byte g[][], byte b[][]) throws AWTException {
        width_ = (short)(r.length);
        height_ = (short)(r[0].length);

        ToIndexedColor(r, g, b);
    }
    public void Write(OutputStream output) throws IOException {
        BitUtils.WriteString(output, "GIF87a");
        
        ScreenDescriptor sd = new ScreenDescriptor(width_, height_,
                                                   numColors_);
        sd.Write(output);

        output.write(colors_, 0, colors_.length);

        ImageDescriptor id = new ImageDescriptor(width_, height_, ',');
        id.Write(output);

        byte codesize = BitUtils.BitsNeeded(numColors_);
        if (codesize == 1)
            ++codesize;
        output.write(codesize);

        LZWCompressor.LZWCompress(output, codesize, pixels_);
        output.write(0);

        id = new ImageDescriptor((byte)0, (byte)0, ';');
        id.Write(output);
        output.flush();
    }

    void ToIndexedColor(byte r[][], byte g[][],
                        byte b[][]) throws AWTException {
        pixels_ = new byte[width_ * height_];
        colors_ = new byte[256 * 3];
        int colornum = 0;
        for (int x = 0; x < width_; ++x) {
            for (int y = 0; y < height_; ++y) {
                int search;
                for (search = 0; search < colornum; ++search)
                    if (colors_[search * 3]     == r[x][y] &&
                        colors_[search * 3 + 1] == g[x][y] &&
                        colors_[search * 3 + 2] == b[x][y])
                        break;
                
                if (search > 255)
                    throw new AWTException("Too many colors.");

                pixels_[y * width_ + x] = (byte)search;
                
                if (search == colornum) {
                    colors_[search * 3]     = r[x][y];
                    colors_[search * 3 + 1] = g[x][y];
                    colors_[search * 3 + 2] = b[x][y];
                    ++colornum;
                }
            }
        }
        numColors_ = 1 << BitUtils.BitsNeeded(colornum);
        byte copy[] = new byte[numColors_ * 3];
        System.arraycopy(colors_, 0, copy, 0, numColors_ * 3);
        colors_ = copy;
    }
    
}

class BitFile {
    OutputStream output_;
    byte buffer_[];
    int index_, bitsLeft_;

    public BitFile(OutputStream output) {
        output_ = output;
        buffer_ = new byte[256];
        index_ = 0;
        bitsLeft_ = 8;
    }

    public void Flush() throws IOException {
        int numBytes = index_ + (bitsLeft_ == 8 ? 0 : 1);
        if (numBytes > 0) {
            output_.write(numBytes);
            output_.write(buffer_, 0, numBytes);
            buffer_[0] = 0;
            index_ = 0;
            bitsLeft_ = 8;
        }
    }

    public void WriteBits(int bits, int numbits) throws IOException {
        int bitsWritten = 0;
        int numBytes = 255;
        do {
            if ((index_ == 254 && bitsLeft_ == 0) || index_ > 254) {
                output_.write(numBytes);
                output_.write(buffer_, 0, numBytes);

                buffer_[0] = 0;
                index_ = 0;
                bitsLeft_ = 8;
            }

            if (numbits <= bitsLeft_) {
                buffer_[index_] |= (bits & ((1 << numbits) - 1)) <<
                    (8 - bitsLeft_);
                bitsWritten += numbits;
                bitsLeft_ -= numbits;
                numbits = 0;
            }
            else {
                buffer_[index_] |= (bits & ((1 << bitsLeft_) - 1)) <<
                    (8 - bitsLeft_);
                bitsWritten += bitsLeft_;
                bits >>= bitsLeft_;
                numbits -= bitsLeft_;
                buffer_[++index_] = 0;
                bitsLeft_ = 8;
            }
        } while (numbits != 0);
    }
}

class LZWStringTable {
    private final static int RES_CODES = 2;
    private final static short HASH_FREE = (short)0xFFFF;
    private final static short NEXT_FIRST = (short)0xFFFF;
    private final static int MAXBITS = 12;
    private final static int MAXSTR = (1 << MAXBITS);
    private final static short HASHSIZE = 9973;
    private final static short HASHSTEP = 2039;

    byte strChr_[];
    short strNxt_[];
    short strHsh_[];
    short numStrings_;

    public LZWStringTable() {
        strChr_ = new byte[MAXSTR];
        strNxt_ = new short[MAXSTR];
        strHsh_ = new short[HASHSIZE];    
    }

    public int AddCharString(short index, byte b) {
        int hshidx;

        if (numStrings_ >= MAXSTR)
            return 0xFFFF;
        
        hshidx = Hash(index, b);
        while (strHsh_[hshidx] != HASH_FREE)
            hshidx = (hshidx + HASHSTEP) % HASHSIZE;
        
        strHsh_[hshidx] = numStrings_;
        strChr_[numStrings_] = b;
        strNxt_[numStrings_] = (index != HASH_FREE) ? index : NEXT_FIRST;

        return numStrings_++;
    }
    
    public short FindCharString(short index, byte b) {
        int hshidx, nxtidx;

        if (index == HASH_FREE)
            return b;

        hshidx = Hash(index, b);
        while ((nxtidx = strHsh_[hshidx]) != HASH_FREE) {
            if (strNxt_[nxtidx] == index && strChr_[nxtidx] == b)
                return (short)nxtidx;
            hshidx = (hshidx + HASHSTEP) % HASHSIZE;
        }

        return (short)0xFFFF;
    }

    public void ClearTable(int codesize) {
        numStrings_ = 0;
        
        for (int q = 0; q < HASHSIZE; q++) {
            strHsh_[q] = HASH_FREE;
        }

        int w = (1 << codesize) + RES_CODES;
        for (int q = 0; q < w; q++)
            AddCharString((short)0xFFFF, (byte)q);
    }
    
    static public int Hash(short index, byte lastbyte) {
        return ((int)((short)(lastbyte << 8) ^ index) & 0xFFFF) % HASHSIZE;
    }
}

class LZWCompressor {

    public static void LZWCompress(OutputStream output, int codesize,
                                   byte toCompress[]) throws IOException {
        byte c;
        short index;
        int clearcode, endofinfo, numbits, limit, errcode;
        short prefix = (short)0xFFFF;

        BitFile bitFile = new BitFile(output);
        LZWStringTable strings = new LZWStringTable();

        clearcode = 1 << codesize;
        endofinfo = clearcode + 1;
    
        numbits = codesize + 1;
        limit = (1 << numbits) - 1;
        
        strings.ClearTable(codesize);
        bitFile.WriteBits(clearcode, numbits);

        for (int loop = 0; loop < toCompress.length; ++loop) {
            c = toCompress[loop];
            if ((index = strings.FindCharString(prefix, c)) != -1)
                prefix = index;
            else {
                bitFile.WriteBits(prefix, numbits);
                if (strings.AddCharString(prefix, c) > limit) {
                    if (++numbits > 12) {
                        bitFile.WriteBits(clearcode, numbits - 1);
                        strings.ClearTable(codesize);
                        numbits = codesize + 1;
                    }
                    limit = (1 << numbits) - 1;
                }
                
                prefix = (short)((short)c & 0xFF);
            }
        }
        
        if (prefix != -1)
            bitFile.WriteBits(prefix, numbits);
        
        bitFile.WriteBits(endofinfo, numbits);
        bitFile.Flush();
    }
}

class ScreenDescriptor {
    public short localScreenWidth_, localScreenHeight_;
    private byte byte_;
    public byte backgroundColorIndex_, pixelAspectRatio_;

    public ScreenDescriptor(short width, short height, int numColors) {
        localScreenWidth_ = width;
        localScreenHeight_ = height;
        SetGlobalColorTableSize((byte)(BitUtils.BitsNeeded(numColors) - 1));
        SetGlobalColorTableFlag((byte)1);
        SetSortFlag((byte)0);
        SetColorResolution((byte)7);
        backgroundColorIndex_ = 0;
        pixelAspectRatio_ = 0;
    }

    public void Write(OutputStream output) throws IOException {
        BitUtils.WriteWord(output, localScreenWidth_);
        BitUtils.WriteWord(output, localScreenHeight_);

        output.write(byte_);
        output.write(backgroundColorIndex_);
        output.write(pixelAspectRatio_);
    }

    public void SetGlobalColorTableSize(byte num) {
        byte_ |= (num & 7);
    }

    public void SetSortFlag(byte num) {
        byte_ |= (num & 1) << 3;
    }

    public void SetColorResolution(byte num) {
        byte_ |= (num & 7) << 4;
    }
    
    public void SetGlobalColorTableFlag(byte num) {
        byte_ |= (num & 1) << 7;
    }
}

class ImageDescriptor {
    public byte separator_;
    public short leftPosition_, topPosition_, width_, height_;
    private byte byte_;

    public ImageDescriptor(short width, short height, char separator) {
        separator_ = (byte)separator;
        leftPosition_ = 0;
        topPosition_ = 0;
        width_ = width;
        height_ = height;
        SetLocalColorTableSize((byte)0);
        SetReserved((byte)0);
        SetSortFlag((byte)0);
        SetInterlaceFlag((byte)0);
        SetLocalColorTableFlag((byte)0);
    }
    
    public void Write(OutputStream output) throws IOException {
        output.write(separator_);
        BitUtils.WriteWord(output, leftPosition_);
        BitUtils.WriteWord(output, topPosition_);
        BitUtils.WriteWord(output, width_);
        BitUtils.WriteWord(output, height_);            
        output.write(byte_);
    }

    public void SetLocalColorTableSize(byte num) {
        byte_ |= (num & 7);
    }

    public void SetReserved(byte num) {
        byte_ |= (num & 3) << 3;
    }

    public void SetSortFlag(byte num) {
        byte_ |= (num & 1) << 5;
    }
    
    public void SetInterlaceFlag(byte num) {
        byte_ |= (num & 1) << 6;
    }

    public void SetLocalColorTableFlag(byte num) {
        byte_ |= (num & 1) << 7;
    }
}

class BitUtils {
    public static byte BitsNeeded(int n) {
        byte ret = 1;

        if (n-- == 0)
            return 0;

        while ((n >>= 1) != 0)
            ++ret;
        
        return ret;
    }    

    public static void WriteWord(OutputStream output,
                                 short w) throws IOException {
        output.write(w & 0xFF);
        output.write((w >> 8) & 0xFF);
    }
    
    static void WriteString(OutputStream output,
                            String string) throws IOException {
        for (int loop = 0; loop < string.length(); ++loop)
            output.write((byte)(string.charAt(loop)));
    }
}