src/main/java/org/apache/commons/imaging/formats/xpm/XpmImageParser.java

/*
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 * 
 *       http://www.apache.org/licenses/LICENSE-2.0
 * 
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *  under the License.
 */

package org.apache.commons.imaging.formats.xpm;

import java.awt.Dimension;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.DataBuffer;
import java.awt.image.DirectColorModel;
import java.awt.image.IndexColorModel;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;
import java.util.UUID;

import org.apache.commons.imaging.ImageFormat;
import org.apache.commons.imaging.ImageFormats;
import org.apache.commons.imaging.ImageInfo;
import org.apache.commons.imaging.ImageParser;
import org.apache.commons.imaging.ImageReadException;
import org.apache.commons.imaging.ImageWriteException;
import org.apache.commons.imaging.common.BasicCParser;
import org.apache.commons.imaging.common.IImageMetadata;
import org.apache.commons.imaging.common.bytesource.ByteSource;
import org.apache.commons.imaging.palette.PaletteFactory;
import org.apache.commons.imaging.palette.SimplePalette;
import org.apache.commons.imaging.util.IoUtils;

public class XpmImageParser extends ImageParser {
    private static Map<String, Integer> colorNames = null;

    public XpmImageParser() {
    }

    private synchronized static void loadColorNames() throws ImageReadException {
        if (colorNames != null) {
            return;
        }

        try {
            final InputStream rgbTxtStream =
                    XpmImageParser.class.getResourceAsStream("rgb.txt");
            if (rgbTxtStream == null) {
                throw new ImageReadException("Couldn't find rgb.txt in our resources");
            }
            final Map<String, Integer> colors = new HashMap<String, Integer>();
            BufferedReader reader = null;
            boolean canThrow = false;
            try {
                reader = new BufferedReader(new InputStreamReader(rgbTxtStream,
                        "US-ASCII"));
                String line;
                while ((line = reader.readLine()) != null) {
                    if (line.startsWith("!")) {
                        continue;
                    }
                    try {
                        final int red = Integer.parseInt(line.substring(0, 3).trim());
                        final int green = Integer.parseInt(line.substring(4, 7).trim());
                        final int blue = Integer.parseInt(line.substring(8, 11).trim());
                        final String colorName = line.substring(11).trim();
                        colors.put(colorName, 0xff000000 | (red << 16)
                                | (green << 8) | blue);
                    } catch (final NumberFormatException nfe) {
                        throw new ImageReadException("Couldn't parse color in rgb.txt", nfe);
                    }
                }
                canThrow = true;
            } finally {
                IoUtils.closeQuietly(canThrow, reader);
            }
            colorNames = colors;
        } catch (final IOException ioException) {
            throw new ImageReadException("Could not parse rgb.txt", ioException);
        }
    }

    @Override
    public String getName() {
        return "Xpm-Custom";
    }

    @Override
    public String getDefaultExtension() {
        return DEFAULT_EXTENSION;
    }

    private static final String DEFAULT_EXTENSION = ".xpm";
    private static final String ACCEPTED_EXTENSIONS[] = { ".xpm", };

    @Override
    protected String[] getAcceptedExtensions() {
        return ACCEPTED_EXTENSIONS;
    }

    @Override
    protected ImageFormat[] getAcceptedTypes() {
        return new ImageFormat[] { ImageFormats.XPM, //
        };
    }

    @Override
    public boolean embedICCProfile(final File src, final File dst, final byte profile[]) {
        return false;
    }

    @Override
    public IImageMetadata getMetadata(final ByteSource byteSource, final Map<String,Object> params)
            throws ImageReadException, IOException {
        return null;
    }

    @Override
    public ImageInfo getImageInfo(final ByteSource byteSource, final Map<String,Object> params)
            throws ImageReadException, IOException {
        final XpmHeader xpmHeader = readXpmHeader(byteSource);
        boolean isTransparent = false;
        int colorType = ImageInfo.COLOR_TYPE_BW;
        for (final Entry<Object, PaletteEntry> entry : xpmHeader.palette
                .entrySet()) {
         final PaletteEntry paletteEntry = entry.getValue();
         if ((paletteEntry.getBestARGB() & 0xff000000) != 0xff000000) {
        isTransparent = true;
         }
         if (paletteEntry.haveColor) {
        colorType = ImageInfo.COLOR_TYPE_RGB;
         } else if (colorType != ImageInfo.COLOR_TYPE_RGB
            && (paletteEntry.haveGray || paletteEntry.haveGray4Level)) {
        colorType = ImageInfo.COLOR_TYPE_GRAYSCALE;
         }
      }
        return new ImageInfo("XPM version 3", xpmHeader.numCharsPerPixel * 8,
                new ArrayList<String>(), ImageFormats.XPM,
                "X PixMap", xpmHeader.height, "image/x-xpixmap", 1, 0, 0, 0, 0,
                xpmHeader.width, false, isTransparent, true, colorType,
                ImageInfo.COMPRESSION_ALGORITHM_NONE);
    }

    @Override
    public Dimension getImageSize(final ByteSource byteSource, final Map<String,Object> params)
            throws ImageReadException, IOException {
        final XpmHeader xpmHeader = readXpmHeader(byteSource);
        return new Dimension(xpmHeader.width, xpmHeader.height);
    }

    @Override
    public byte[] getICCProfileBytes(final ByteSource byteSource, final Map<String,Object> params)
            throws ImageReadException, IOException {
        return null;
    }

    private static class XpmHeader {
        int width;
        int height;
        int numColors;
        int numCharsPerPixel;
        int xHotSpot = -1;
        int yHotSpot = -1;
        boolean xpmExt;

        Map<Object, PaletteEntry> palette = new HashMap<Object, PaletteEntry>();

        public XpmHeader(final int width, final int height, final int numColors,
                final int numCharsPerPixel, final int xHotSpot, final int yHotSpot, final boolean xpmExt) {
            this.width = width;
            this.height = height;
            this.numColors = numColors;
            this.numCharsPerPixel = numCharsPerPixel;
            this.xHotSpot = xHotSpot;
            this.yHotSpot = yHotSpot;
            this.xpmExt = xpmExt;
        }

        public void dump(final PrintWriter pw) {
            pw.println("XpmHeader");
            pw.println("Width: " + width);
            pw.println("Height: " + height);
            pw.println("NumColors: " + numColors);
            pw.println("NumCharsPerPixel: " + numCharsPerPixel);
            if (xHotSpot != -1 && yHotSpot != -1) {
                pw.println("X hotspot: " + xHotSpot);
                pw.println("Y hotspot: " + yHotSpot);
            }
            pw.println("XpmExt: " + xpmExt);
        }
    }

    private static class PaletteEntry {
        int index;
        boolean haveColor = false;
        int colorArgb;
        boolean haveGray = false;
        int grayArgb;
        boolean haveGray4Level = false;
        int gray4LevelArgb;
        boolean haveMono = false;
        int monoArgb;

        int getBestARGB() {
            if (haveColor) {
                return colorArgb;
            } else if (haveGray) {
                return grayArgb;
            } else if (haveGray4Level) {
                return gray4LevelArgb;
            } else if (haveMono) {
                return monoArgb;
            } else {
                return 0x00000000;
            }
        }
    }

    private static class XpmParseResult {
        XpmHeader xpmHeader;
        BasicCParser cParser;
    }

    private XpmHeader readXpmHeader(final ByteSource byteSource)
            throws ImageReadException, IOException {
        final XpmParseResult result = parseXpmHeader(byteSource);
        return result.xpmHeader;
    }

    private XpmParseResult parseXpmHeader(final ByteSource byteSource)
            throws ImageReadException, IOException {
        InputStream is = null;
        boolean canThrow = false;
        try {
            is = byteSource.getInputStream();
            final StringBuilder firstComment = new StringBuilder();
            final ByteArrayOutputStream preprocessedFile = BasicCParser.preprocess(
                    is, firstComment, null);
            if (!firstComment.toString().trim().equals("XPM")) {
                throw new ImageReadException("Parsing XPM file failed, "
                        + "signature isn't '/* XPM */'");
            }

            final XpmParseResult xpmParseResult = new XpmParseResult();
            xpmParseResult.cParser = new BasicCParser(new ByteArrayInputStream(
                    preprocessedFile.toByteArray()));
            xpmParseResult.xpmHeader = parseXpmHeader(xpmParseResult.cParser);
            canThrow = true;
            return xpmParseResult;
        } finally {
            IoUtils.closeQuietly(canThrow, is);
        }
    }

    private boolean parseNextString(final BasicCParser cParser,
            final StringBuilder stringBuilder) throws IOException, ImageReadException {
        stringBuilder.setLength(0);
        String token = cParser.nextToken();
        if (token.charAt(0) != '"') {
            throw new ImageReadException("Parsing XPM file failed, "
                    + "no string found where expected");
        }
        BasicCParser.unescapeString(stringBuilder, token);
        for (token = cParser.nextToken(); token.charAt(0) == '"'; token = cParser
                .nextToken()) {
            BasicCParser.unescapeString(stringBuilder, token);
        }
        if (token.equals(",")) {
            return true;
        } else if (token.equals("}")) {
            return false;
        } else {
            throw new ImageReadException("Parsing XPM file failed, "
                    + "no ',' or '}' found where expected");
        }
    }

    private XpmHeader parseXpmValuesSection(final String row)
            throws ImageReadException {
        final String[] tokens = BasicCParser.tokenizeRow(row);
        if (tokens.length < 4 && tokens.length > 7) {
            throw new ImageReadException("Parsing XPM file failed, "
                    + "<Values> section has incorrect tokens");
        }
        try {
            final int width = Integer.parseInt(tokens[0]);
            final int height = Integer.parseInt(tokens[1]);
            final int numColors = Integer.parseInt(tokens[2]);
            final int numCharsPerPixel = Integer.parseInt(tokens[3]);
            int xHotSpot = -1;
            int yHotSpot = -1;
            boolean xpmExt = false;
            if (tokens.length >= 6) {
                xHotSpot = Integer.parseInt(tokens[4]);
                yHotSpot = Integer.parseInt(tokens[5]);
            }
            if (tokens.length == 5 || tokens.length == 7) {
                if (tokens[tokens.length - 1].equals("XPMEXT")) {
                    xpmExt = true;
                } else {
                    throw new ImageReadException("Parsing XPM file failed, "
                            + "can't parse <Values> section XPMEXT");
                }
            }
            return new XpmHeader(width, height, numColors, numCharsPerPixel,
                    xHotSpot, yHotSpot, xpmExt);
        } catch (final NumberFormatException nfe) {
            throw new ImageReadException("Parsing XPM file failed, "
                    + "error parsing <Values> section", nfe);
        }
    }

    private int parseColor(String color) throws ImageReadException {
        if (color.charAt(0) == '#') {
            color = color.substring(1);
            if (color.length() == 3) {
                final int red = Integer.parseInt(color.substring(0, 1), 16);
                final int green = Integer.parseInt(color.substring(1, 2), 16);
                final int blue = Integer.parseInt(color.substring(2, 3), 16);
                return 0xff000000 | (red << 20) | (green << 12) | (blue << 4);
            } else if (color.length() == 6) {
                return 0xff000000 | Integer.parseInt(color, 16);
            } else if (color.length() == 9) {
                final int red = Integer.parseInt(color.substring(0, 1), 16);
                final int green = Integer.parseInt(color.substring(3, 4), 16);
                final int blue = Integer.parseInt(color.substring(6, 7), 16);
                return 0xff000000 | (red << 16) | (green << 8) | blue;
            } else if (color.length() == 12) {
                final int red = Integer.parseInt(color.substring(0, 1), 16);
                final int green = Integer.parseInt(color.substring(4, 5), 16);
                final int blue = Integer.parseInt(color.substring(8, 9), 16);
                return 0xff000000 | (red << 16) | (green << 8) | blue;
            } else {
                return 0x00000000;
            }
        } else if (color.charAt(0) == '%') {
            throw new ImageReadException("HSV colors are not implemented "
                    + "even in the XPM specification!");
        } else if (color.equals("None")) {
            return 0x00000000;
        } else {
            loadColorNames();
            if (colorNames.containsKey(color)) {
                return (colorNames.get(color)).intValue();
            } else {
                return 0x00000000;
            }
        }
    }
    
    private void populatePaletteEntry(final PaletteEntry paletteEntry, final String key, final String color) throws ImageReadException {
        if (key.equals("m")) {
            paletteEntry.monoArgb = parseColor(color);
            paletteEntry.haveMono = true;
        } else if (key.equals("g4")) {
            paletteEntry.gray4LevelArgb = parseColor(color);
            paletteEntry.haveGray4Level = true;
        } else if (key.equals("g")) {
            paletteEntry.grayArgb = parseColor(color);
            paletteEntry.haveGray = true;
        } else if (key.equals("s")) {
            paletteEntry.colorArgb = parseColor(color);
            paletteEntry.haveColor = true;
        } else if (key.equals("c")) {
            paletteEntry.colorArgb = parseColor(color);
            paletteEntry.haveColor = true;
        }
    }

    private void parsePaletteEntries(final XpmHeader xpmHeader, final BasicCParser cParser)
            throws IOException, ImageReadException {
        final StringBuilder row = new StringBuilder();
        for (int i = 0; i < xpmHeader.numColors; i++) {
            row.setLength(0);
            final boolean hasMore = parseNextString(cParser, row);
            if (!hasMore) {
                throw new ImageReadException("Parsing XPM file failed, "
                        + "file ended while reading palette");
            }
            final String name = row.substring(0, xpmHeader.numCharsPerPixel);
            final String[] tokens = BasicCParser.tokenizeRow(
                    row.substring(xpmHeader.numCharsPerPixel));
            final PaletteEntry paletteEntry = new PaletteEntry();
            paletteEntry.index = i;
            int previousKeyIndex = Integer.MIN_VALUE;
            final StringBuilder colorBuffer = new StringBuilder();
            for (int j = 0; j < tokens.length; j++) {
                final String token = tokens[j];
                boolean isKey = false;
                if (previousKeyIndex < (j - 1) && 
                    token.equals("m") || token.equals("g4") ||
                    token.equals("g") || token.equals("c") ||
                    token.equals("s")) {
                    isKey = true;
                }
                if (isKey) {
                    if (previousKeyIndex >= 0) {
                        final String key = tokens[previousKeyIndex];
                        final String color = colorBuffer.toString();
                        colorBuffer.setLength(0);
                        populatePaletteEntry(paletteEntry, key, color);
                    }
                    previousKeyIndex = j;
                } else {
                    if (previousKeyIndex < 0) {
                        break;
                    }
                    if (colorBuffer.length() > 0) {
                        colorBuffer.append(' ');
                    }
                    colorBuffer.append(token);
                }
            }
            if (previousKeyIndex >= 0 && colorBuffer.length() > 0) {
                final String key = tokens[previousKeyIndex];
                final String color = colorBuffer.toString();
                colorBuffer.setLength(0);
                populatePaletteEntry(paletteEntry, key, color);
            }
            xpmHeader.palette.put(name, paletteEntry);
        }
    }

    private XpmHeader parseXpmHeader(final BasicCParser cParser)
            throws ImageReadException, IOException {
        String name;
        String token;
        token = cParser.nextToken();
        if (token == null || !token.equals("static")) {
            throw new ImageReadException(
                    "Parsing XPM file failed, no 'static' token");
        }
        token = cParser.nextToken();
        if (token == null || !token.equals("char")) {
            throw new ImageReadException(
                    "Parsing XPM file failed, no 'char' token");
        }
        token = cParser.nextToken();
        if (token == null || !token.equals("*")) {
            throw new ImageReadException(
                    "Parsing XPM file failed, no '*' token");
        }
        name = cParser.nextToken();
        if (name == null) {
            throw new ImageReadException(
                    "Parsing XPM file failed, no variable name");
        }
        if (name.charAt(0) != '_' && !Character.isLetter(name.charAt(0))) {
            throw new ImageReadException(
                    "Parsing XPM file failed, variable name "
                            + "doesn't start with letter or underscore");
        }
        for (int i = 0; i < name.length(); i++) {
            final char c = name.charAt(i);
            if (!Character.isLetterOrDigit(c) && c != '_') {
                throw new ImageReadException(
                        "Parsing XPM file failed, variable name "
                                + "contains non-letter non-digit non-underscore");
            }
        }
        token = cParser.nextToken();
        if (token == null || !token.equals("[")) {
            throw new ImageReadException(
                    "Parsing XPM file failed, no '[' token");
        }
        token = cParser.nextToken();
        if (token == null || !token.equals("]")) {
            throw new ImageReadException(
                    "Parsing XPM file failed, no ']' token");
        }
        token = cParser.nextToken();
        if (token == null || !token.equals("=")) {
            throw new ImageReadException(
                    "Parsing XPM file failed, no '=' token");
        }
        token = cParser.nextToken();
        if (token == null || !token.equals("{")) {
            throw new ImageReadException(
                    "Parsing XPM file failed, no '{' token");
        }

        final StringBuilder row = new StringBuilder();
        final boolean hasMore = parseNextString(cParser, row);
        if (!hasMore) {
            throw new ImageReadException("Parsing XPM file failed, "
                    + "file too short");
        }
        final XpmHeader xpmHeader = parseXpmValuesSection(row.toString());
        parsePaletteEntries(xpmHeader, cParser);
        return xpmHeader;
    }

    private BufferedImage readXpmImage(final XpmHeader xpmHeader, final BasicCParser cParser)
            throws ImageReadException, IOException {
        ColorModel colorModel;
        WritableRaster raster;
        int bpp;
        if (xpmHeader.palette.size() <= (1 << 8)) {
            final int[] palette = new int[xpmHeader.palette.size()];
            for (final Entry<Object, PaletteEntry> entry : xpmHeader.palette
                    .entrySet()) {
            final PaletteEntry paletteEntry = entry.getValue();
            palette[paletteEntry.index] = paletteEntry.getBestARGB();
         }
            colorModel = new IndexColorModel(8, xpmHeader.palette.size(),
                    palette, 0, true, -1, DataBuffer.TYPE_BYTE);
            raster = Raster.createInterleavedRaster(
                    DataBuffer.TYPE_BYTE, xpmHeader.width, xpmHeader.height, 1,
                    null);
            bpp = 8;
        } else if (xpmHeader.palette.size() <= (1 << 16)) {
            final int[] palette = new int[xpmHeader.palette.size()];
            for (final Entry<Object, PaletteEntry> entry : xpmHeader.palette
                    .entrySet()) {
            final PaletteEntry paletteEntry = entry.getValue();
            palette[paletteEntry.index] = paletteEntry.getBestARGB();
         }
            colorModel = new IndexColorModel(16, xpmHeader.palette.size(),
                    palette, 0, true, -1, DataBuffer.TYPE_USHORT);
            raster = Raster.createInterleavedRaster(
                    DataBuffer.TYPE_USHORT, xpmHeader.width, xpmHeader.height,
                    1, null);
            bpp = 16;
        } else {
            colorModel = new DirectColorModel(32, 0x00ff0000, 0x0000ff00,
                    0x000000ff, 0xff000000);
            raster = Raster.createPackedRaster(DataBuffer.TYPE_INT,
                    xpmHeader.width, xpmHeader.height, new int[] { 0x00ff0000,
                            0x0000ff00, 0x000000ff, 0xff000000 }, null);
            bpp = 32;
        }

        final BufferedImage image = new BufferedImage(colorModel, raster,
                colorModel.isAlphaPremultiplied(), new Properties());
        final DataBuffer dataBuffer = raster.getDataBuffer();
        final StringBuilder row = new StringBuilder();
        boolean hasMore = true;
        for (int y = 0; y < xpmHeader.height; y++) {
            row.setLength(0);
            hasMore = parseNextString(cParser, row);
            if (y < (xpmHeader.height - 1) && !hasMore) {
                throw new ImageReadException("Parsing XPM file failed, "
                        + "insufficient image rows in file");
            }
            final int rowOffset = y * xpmHeader.width;
            for (int x = 0; x < xpmHeader.width; x++) {
                final String index = row.substring(x * xpmHeader.numCharsPerPixel,
                        (x + 1) * xpmHeader.numCharsPerPixel);
                final PaletteEntry paletteEntry = xpmHeader.palette.get(index);
                if (paletteEntry == null) {
                    throw new ImageReadException(
                            "No palette entry was defined " + "for " + index);
                }
                if (bpp <= 16) {
                    dataBuffer.setElem(rowOffset + x, paletteEntry.index);
                } else {
                    dataBuffer.setElem(rowOffset + x,
                            paletteEntry.getBestARGB());
                }
            }
        }

        while (hasMore) {
            row.setLength(0);
            hasMore = parseNextString(cParser, row);
        }

        final String token = cParser.nextToken();
        if (!token.equals(";")) {
            throw new ImageReadException("Last token wasn't ';'");
        }

        return image;
    }

    @Override
    public boolean dumpImageFile(final PrintWriter pw, final ByteSource byteSource)
            throws ImageReadException, IOException {
        readXpmHeader(byteSource).dump(pw);
        return true;
    }

    @Override
    public final BufferedImage getBufferedImage(final ByteSource byteSource,
            final Map<String,Object> params) throws ImageReadException, IOException {
        final XpmParseResult result = parseXpmHeader(byteSource);
        return readXpmImage(result.xpmHeader, result.cParser);
    }

    private String randomName() {
        final UUID uuid = UUID.randomUUID();
        final StringBuilder stringBuilder = new StringBuilder("a");
        long bits = uuid.getMostSignificantBits();
        // Long.toHexString() breaks for very big numbers
        for (int i = 64 - 8; i >= 0; i -= 8) {
            stringBuilder.append(Integer.toHexString((int) ((bits >> i) & 0xff)));
        }
        bits = uuid.getLeastSignificantBits();
        for (int i = 64 - 8; i >= 0; i -= 8) {
            stringBuilder.append(Integer.toHexString((int) ((bits >> i) & 0xff)));
        }
        return stringBuilder.toString();
    }

    private String pixelsForIndex(int index, final int charsPerPixel) {
        final StringBuilder stringBuilder = new StringBuilder();
        int highestPower = 1;
        for (int i = 1; i < charsPerPixel; i++) {
            highestPower *= writePalette.length;
        }
        for (int i = 0; i < charsPerPixel; i++) {
            final int multiple = index / highestPower;
            index -= (multiple * highestPower);
            highestPower /= writePalette.length;
            stringBuilder.append(writePalette[multiple]);
        }
        return stringBuilder.toString();
    }

    private String toColor(final int color) {
        final String hex = Integer.toHexString(color);
        if (hex.length() < 6) {
            final char zeroes[] = new char[6 - hex.length()];
            Arrays.fill(zeroes, '0');
            return "#" + new String(zeroes) + hex;
        } else {
            return "#" + hex;
        }
    }

    @Override
    public void writeImage(final BufferedImage src, final OutputStream os, Map<String,Object> params)
            throws ImageWriteException, IOException {
        // make copy of params; we'll clear keys as we consume them.
        params = (params == null) ? new HashMap<String,Object>() : new HashMap<String,Object>(params);

        // clear format key.
        if (params.containsKey(PARAM_KEY_FORMAT)) {
            params.remove(PARAM_KEY_FORMAT);
        }

        if (params.size() > 0) {
            final Object firstKey = params.keySet().iterator().next();
            throw new ImageWriteException("Unknown parameter: " + firstKey);
        }

        final PaletteFactory paletteFactory = new PaletteFactory();
        boolean hasTransparency = false;
        if (paletteFactory.hasTransparency(src, 1)) {
            hasTransparency = true;
        }
        SimplePalette palette = null;
        int maxColors = writePalette.length;
        int charsPerPixel = 1;
        for (; palette == null;) {
            palette = paletteFactory.makeExactRgbPaletteSimple(src,
                    hasTransparency ? maxColors - 1 : maxColors);
            if (palette == null) {
                maxColors *= writePalette.length;
                charsPerPixel++;
            }
        }
        int colors = palette.length();
        if (hasTransparency) {
            ++colors;
        }

        String line = "/* XPM */\n";
        os.write(line.getBytes("US-ASCII"));
        line = "static char *" + randomName() + "[] = {\n";
        os.write(line.getBytes("US-ASCII"));
        line = "\"" + src.getWidth() + " " + src.getHeight() + " " + colors
                + " " + charsPerPixel + "\",\n";
        os.write(line.getBytes("US-ASCII"));

        for (int i = 0; i < colors; i++) {
            String color;
            if (i < palette.length()) {
                color = toColor(palette.getEntry(i));
            } else {
                color = "None";
            }
            line = "\"" + pixelsForIndex(i, charsPerPixel) + " c " + color
                    + "\",\n";
            os.write(line.getBytes("US-ASCII"));
        }

        String separator = "";
        for (int y = 0; y < src.getHeight(); y++) {
            os.write(separator.getBytes("US-ASCII"));
            separator = ",\n";
            line = "\"";
            os.write(line.getBytes("US-ASCII"));
            for (int x = 0; x < src.getWidth(); x++) {
                final int argb = src.getRGB(x, y);
                if ((argb & 0xff000000) == 0) {
                    line = pixelsForIndex(palette.length(), charsPerPixel);
                } else {
                    line = pixelsForIndex(
                            palette.getPaletteIndex(0xffffff & argb),
                            charsPerPixel);
                }
                os.write(line.getBytes("US-ASCII"));
            }
            line = "\"";
            os.write(line.getBytes("US-ASCII"));
        }

        line = "\n};\n";
        os.write(line.getBytes("US-ASCII"));
    }

    private static final char writePalette[] = { ' ', '.', 'X', 'o', 'O', '+',
            '@', '#', '$', '%', '&', '*', '=', '-', ';', ':', '>', ',', '<',
            '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', 'q', 'w', 'e',
            'r', 't', 'y', 'u', 'i', 'p', 'a', 's', 'd', 'f', 'g', 'h', 'j',
            'k', 'l', 'z', 'x', 'c', 'v', 'b', 'n', 'm', 'M', 'N', 'B', 'V',
            'C', 'Z', 'A', 'S', 'D', 'F', 'G', 'H', 'J', 'K', 'L', 'P', 'I',
            'U', 'Y', 'T', 'R', 'E', 'W', 'Q', '!', '~', '^', '/', '(', ')',
            '_', '`', '\'', ']', '[', '{', '}', '|', };

    /**
     * Extracts embedded XML metadata as XML string.
     * <p>
     * 
     * @param byteSource
     *            File containing image data.
     * @param params
     *            Map of optional parameters, defined in ImagingConstants.
     * @return Xmp Xml as String, if present. Otherwise, returns null.
     */
    @Override
    public String getXmpXml(final ByteSource byteSource, final Map<String,Object> params)
            throws ImageReadException, IOException {
        return null;
    }
}