+
−package ar.com.hjg.pngj.chunks;
+
−
+
−// see http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html
+
−// http://www.w3.org/TR/PNG/#5Chunk-naming-conventions
+
−// http://www.w3.org/TR/PNG/#table53
+
−import java.io.ByteArrayInputStream;
+
−import java.io.ByteArrayOutputStream;
+
−import java.io.IOException;
+
−import java.io.InputStream;
+
−import java.io.OutputStream;
+
−import java.io.UnsupportedEncodingException;
+
−import java.util.ArrayList;
+
−import java.util.Iterator;
+
−import java.util.List;
+
−import java.util.zip.DeflaterOutputStream;
+
−import java.util.zip.InflaterInputStream;
+
−
+
−import ar.com.hjg.pngj.PngHelperInternal;
+
−import ar.com.hjg.pngj.PngjException;
+
−
+
−/**
+
− * Helper methods and constants related to Chunk processing.
+
− * <p>
+
− * This should only be of interest to developers doing special chunk processing or extending the ChunkFactory
+
− */
+
−public class ChunkHelper {
+
−  ChunkHelper() {}
+
−
+
−  public static final String IHDR = "IHDR";
+
−  public static final String PLTE = "PLTE";
+
−  public static final String IDAT = "IDAT";
+
−  public static final String IEND = "IEND";
+
−  public static final String cHRM = "cHRM";
+
−  public static final String gAMA = "gAMA";
+
−  public static final String iCCP = "iCCP";
+
−  public static final String sBIT = "sBIT";
+
−  public static final String sRGB = "sRGB";
+
−  public static final String bKGD = "bKGD";
+
−  public static final String hIST = "hIST";
+
−  public static final String tRNS = "tRNS";
+
−  public static final String pHYs = "pHYs";
+
−  public static final String sPLT = "sPLT";
+
−  public static final String tIME = "tIME";
+
−  public static final String iTXt = "iTXt";
+
−  public static final String tEXt = "tEXt";
+
−  public static final String zTXt = "zTXt";
+
−
+
−  public static final byte[] b_IHDR = toBytes(IHDR);
+
−  public static final byte[] b_PLTE = toBytes(PLTE);
+
−  public static final byte[] b_IDAT = toBytes(IDAT);
+
−  public static final byte[] b_IEND = toBytes(IEND);
+
−
+
−  /*
+
−   * static auxiliary buffer. any method that uses this should synchronize against this
+
−   */
+
−  private static byte[] tmpbuffer = new byte[4096];
+
−
+
−  /**
+
−   * Converts to bytes using Latin1 (ISO-8859-1)
+
−   */
+
−  public static byte[] toBytes(String x) {
+
−    try {
+
−      return x.getBytes(PngHelperInternal.charsetLatin1name);
+
−    } catch (UnsupportedEncodingException e) {
+
−      throw new PngBadCharsetException(e);
+
−    }
+
−  }
+
−
+
−  /**
+
−   * Converts to String using Latin1 (ISO-8859-1)
+
−   */
+
−  public static String toString(byte[] x) {
+
−    try {
+
−      return new String(x, PngHelperInternal.charsetLatin1name);
+
−    } catch (UnsupportedEncodingException e) {
+
−      throw new PngBadCharsetException(e);
+
−    }
+
−  }
+
−
+
−  /**
+
−   * Converts to String using Latin1 (ISO-8859-1)
+
−   */
+
−  public static String toString(byte[] x, int offset, int len) {
+
−    try {
+
−      return new String(x, offset, len, PngHelperInternal.charsetLatin1name);
+
−    } catch (UnsupportedEncodingException e) {
+
−      throw new PngBadCharsetException(e);
+
−    }
+
−  }
+
−
+
−  /**
+
−   * Converts to bytes using UTF-8
+
−   */
+
−  public static byte[] toBytesUTF8(String x) {
+
−    try {
+
−      return x.getBytes(PngHelperInternal.charsetUTF8name);
+
−    } catch (UnsupportedEncodingException e) {
+
−      throw new PngBadCharsetException(e);
+
−    }
+
−  }
+
−
+
−  /**
+
−   * Converts to string using UTF-8
+
−   */
+
−  public static String toStringUTF8(byte[] x) {
+
−    try {
+
−      return new String(x, PngHelperInternal.charsetUTF8name);
+
−    } catch (UnsupportedEncodingException e) {
+
−      throw new PngBadCharsetException(e);
+
−    }
+
−  }
+
−
+
−  /**
+
−   * Converts to string using UTF-8
+
−   */
+
−  public static String toStringUTF8(byte[] x, int offset, int len) {
+
−    try {
+
−      return new String(x, offset, len, PngHelperInternal.charsetUTF8name);
+
−    } catch (UnsupportedEncodingException e) {
+
−      throw new PngBadCharsetException(e);
+
−    }
+
−  }
+
−
+
−  /**
+
−   * critical chunk : first letter is uppercase
+
−   */
+
−  public static boolean isCritical(String id) {
+
−    return (Character.isUpperCase(id.charAt(0)));
+
−  }
+
−
+
−  /**
+
−   * public chunk: second letter is uppercase
+
−   */
+
−  public static boolean isPublic(String id) { //
+
−    return (Character.isUpperCase(id.charAt(1)));
+
−  }
+
−
+
−  /**
+
−   * Safe to copy chunk: fourth letter is lower case
+
−   */
+
−  public static boolean isSafeToCopy(String id) {
+
−    return (!Character.isUpperCase(id.charAt(3)));
+
−  }
+
−
+
−  /**
+
−   * "Unknown" just means that our chunk factory (even when it has been augmented by client code) did not recognize its
+
−   * id
+
−   */
+
−  public static boolean isUnknown(PngChunk c) {
+
−    return c instanceof PngChunkUNKNOWN;
+
−  }
+
−
+
−  /**
+
−   * Finds position of null byte in array
+
−   * 
+
−   * @param b
+
−   * @return -1 if not found
+
−   */
+
−  public static int posNullByte(byte[] b) {
+
−    for (int i = 0; i < b.length; i++)
+
−      if (b[i] == 0)
+
−        return i;
+
−    return -1;
+
−  }
+
−
+
−  /**
+
−   * Decides if a chunk should be loaded, according to a ChunkLoadBehaviour
+
−   * 
+
−   * @param id
+
−   * @param behav
+
−   * @return true/false
+
−   */
+
−  public static boolean shouldLoad(String id, ChunkLoadBehaviour behav) {
+
−    if (isCritical(id))
+
−      return true;
+
−    switch (behav) {
+
−      case LOAD_CHUNK_ALWAYS:
+
−        return true;
+
−      case LOAD_CHUNK_IF_SAFE:
+
−        return isSafeToCopy(id);
+
−      case LOAD_CHUNK_NEVER:
+
−        return false;
+
−    }
+
−    return false; // should not reach here
+
−  }
+
−
+
−  public final static byte[] compressBytes(byte[] ori, boolean compress) {
+
−    return compressBytes(ori, 0, ori.length, compress);
+
−  }
+
−
+
−  public static byte[] compressBytes(byte[] ori, int offset, int len, boolean compress) {
+
−    try {
+
−      ByteArrayInputStream inb = new ByteArrayInputStream(ori, offset, len);
+
−      InputStream in = compress ? inb : new InflaterInputStream(inb);
+
−      ByteArrayOutputStream outb = new ByteArrayOutputStream();
+
−      OutputStream out = compress ? new DeflaterOutputStream(outb) : outb;
+
−      shovelInToOut(in, out);
+
−      in.close();
+
−      out.close();
+
−      return outb.toByteArray();
+
−    } catch (Exception e) {
+
−      throw new PngjException(e);
+
−    }
+
−  }
+
−
+
−  /**
+
−   * Shovels all data from an input stream to an output stream.
+
−   */
+
−  private static void shovelInToOut(InputStream in, OutputStream out) throws IOException {
+
−    synchronized (tmpbuffer) {
+
−      int len;
+
−      while ((len = in.read(tmpbuffer)) > 0) {
+
−        out.write(tmpbuffer, 0, len);
+
−      }
+
−    }
+
−  }
+
−
+
−  /**
+
−   * Returns only the chunks that "match" the predicate
+
−   * 
+
−   * See also trimList()
+
−   */
+
−  public static List<PngChunk> filterList(List<PngChunk> target, ChunkPredicate predicateKeep) {
+
−    List<PngChunk> result = new ArrayList<PngChunk>();
+
−    for (PngChunk element : target) {
+
−      if (predicateKeep.match(element)) {
+
−        result.add(element);
+
−      }
+
−    }
+
−    return result;
+
−  }
+
−
+
−  /**
+
−   * Remove (in place) the chunks that "match" the predicate
+
−   * 
+
−   * See also filterList
+
−   */
+
−  public static int trimList(List<PngChunk> target, ChunkPredicate predicateRemove) {
+
−    Iterator<PngChunk> it = target.iterator();
+
−    int cont = 0;
+
−    while (it.hasNext()) {
+
−      PngChunk c = it.next();
+
−      if (predicateRemove.match(c)) {
+
−        it.remove();
+
−        cont++;
+
−      }
+
−    }
+
−    return cont;
+
−  }
+
−
+
−  /**
+
−   * Adhoc criteria: two ancillary chunks are "equivalent" ("practically same type") if they have same id and (perhaps,
+
−   * if multiple are allowed) if the match also in some "internal key" (eg: key for string values, palette for sPLT,
+
−   * etc)
+
−   * 
+
−   * When we use this method, we implicitly assume that we don't allow/expect two "equivalent" chunks in a single PNG
+
−   * 
+
−   * Notice that the use of this is optional, and that the PNG standard actually allows text chunks that have same key
+
−   * 
+
−   * @return true if "equivalent"
+
−   */
+
−  public static final boolean equivalent(PngChunk c1, PngChunk c2) {
+
−    if (c1 == c2)
+
−      return true;
+
−    if (c1 == null || c2 == null || !c1.id.equals(c2.id))
+
−      return false;
+
−    if (c1.crit)
+
−      return false;
+
−    // same id
+
−    if (c1.getClass() != c2.getClass())
+
−      return false; // should not happen
+
−    if (!c2.allowsMultiple())
+
−      return true;
+
−    if (c1 instanceof PngChunkTextVar) {
+
−      return ((PngChunkTextVar) c1).getKey().equals(((PngChunkTextVar) c2).getKey());
+
−    }
+
−    if (c1 instanceof PngChunkSPLT) {
+
−      return ((PngChunkSPLT) c1).getPalName().equals(((PngChunkSPLT) c2).getPalName());
+
−    }
+
−    // unknown chunks that allow multiple? consider they don't match
+
−    return false;
+
−  }
+
−
+
−  public static boolean isText(PngChunk c) {
+
−    return c instanceof PngChunkTextVar;
+
−  }
+
−
+
−}