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/* DecodeRLE4.java --

   Copyright (C)  2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2, or (at your option)

any later version.

GNU Classpath is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

package gnu.javax.imageio.bmp;

import java.io.IOException;

import javax.imageio.stream.ImageInputStream;

import java.awt.image.BufferedImage;

import java.awt.image.IndexColorModel;

import java.awt.image.Raster;

import java.awt.image.WritableRaster;

import java.awt.image.DataBuffer;

import java.awt.image.DataBufferByte;

import java.awt.image.MultiPixelPackedSampleModel;

import java.awt.image.SampleModel;

import java.awt.Dimension;

public class DecodeRLE4 extends BMPDecoder {

    public DecodeRLE4(BMPFileHeader fh, BMPInfoHeader ih){

        super(fh, ih);

    }

    /**

     * RLE control codes

     */

    private static final byte ESCAPE = (byte)0;

    private static final byte EOL = (byte)0; // end of line

    private static final byte EOB = (byte)1; // end of bitmap

    private static final byte DELTA = (byte)2; // delta

    public BufferedImage decode(ImageInputStream in) throws IOException, BMPException {

        IndexColorModel palette = readPalette(in);

        skipToImage(in);

        Dimension d = infoHeader.getSize();

        int h = (int)d.getHeight();

        int w = (int)d.getWidth();

        byte[] data = uncompress(w, h, in);

        SampleModel sm = new MultiPixelPackedSampleModel(DataBuffer.TYPE_BYTE,

                                                         w, h, 4);

        DataBuffer db = new DataBufferByte(data, w*h, 0);

        WritableRaster raster = Raster.createWritableRaster(sm, db, null);

        return new BufferedImage(palette, raster, false, null);

    }

    private byte[] uncompress(int w, int h, ImageInputStream in)

        throws BMPException, IOException {

        byte[] cmd = new byte[2];

        byte[] data = new byte[w*h>>1];

        int offIn = 0;

        int x=0,y=0;

        // width in bytes

        w += (w&1);

        w = w >> 1;

        try {

            while(((x>>1) + y*w) < w*h){

                if(in.read(cmd) != 2)

                    throw new IOException("Error reading compressed data.");

                if(cmd[0] == ESCAPE){

                    switch(cmd[1]){

                    case EOB: // end of bitmap

                        return data;

                    case EOL: // end of line

                        x = 0;

                        y++;

                        break;

                    case DELTA: // delta

                        if(in.read(cmd) != 2)

                            throw new IOException("Error reading compressed data.");

                        int dx = cmd[0] & (0xFF);

                        int dy = cmd[1] & (0xFF);

                        x += dx;

                        y += dy;

                        break;

                    default:

                        // decode a literal run

                        int length = cmd[1] & (0xFF);

                        // size of run, which is word aligned.

                        int bytesize = length;

                        bytesize += (bytesize & 1);

                        bytesize >>= 1;

                        bytesize += (bytesize & 1);

                        byte[] run = new byte[bytesize];

                        if(in.read(run) != bytesize)

                            throw new IOException("Error reading compressed data.");

                        if((x&1) == 0){

                            length += (length&1);

                            length >>= 1;

                            System.arraycopy(run, 0, data, ((x>>1) + w*(h-y-1)),

                                             length);

                        } else {

                            for(int i=0;i<length;i++){

                                if((i&1) == 0) // copy high to low

                                    data[((x+i)>>1) + w*(h-y-1)]

                                        |= ((run[i>>1]&0xF0) >> 4);

                                else  // copy low to high

                                    data[((x+i)>>1) + w*(h-y-1)]

                                        |= ((run[i>>1]&0x0F) << 4);

                            }

                        }

                        x += cmd[1] & (0xFF);

                        break;

                    }

                } else {

                    // decode a byte run

                    int length = cmd[0] & (0xFF);

                    if((x&1) == 0){

                        length += (length&1);

                        length >>= 1;

                        for(int i=0;i<length;i++)

                            data[(h-y-1)*w + i + (x >> 1)] = cmd[1];

                    } else {

                        for(int i=0;i<length;i++){

                            if((i&1) == 0) // copy high to low

                                data[((x+i)>>1) + w*(h-y-1)]

                                    |= ((cmd[1]&0xF0) >> 4);

                            else  // copy low to high

                                data[((x+i)>>1) + w*(h-y-1)]

                                    |= ((cmd[1]&0x0F) << 4);

                        }

                    }

                    x += cmd[0] & (0xFF);

                }

            }

            return data;

        } catch(ArrayIndexOutOfBoundsException e){

            throw new BMPException("Invalid RLE data.");

        }

    }

}