1 files changed, 1001 insertions, 415 deletions
diff --git a/src/jogl/classes/jogamp/opengl/util/pngj/PngReader.java b/src/jogl/classes/jogamp/opengl/util/pngj/PngReader.java
index 7343893b6..0412beb8c 100644
--- a/src/jogl/classes/jogamp/opengl/util/pngj/PngReader.java
+++ b/src/jogl/classes/jogamp/opengl/util/pngj/PngReader.java
@@ -1,415 +1,1001 @@
-package jogamp.opengl.util.pngj;
-
-import java.io.InputStream;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.List;
-import java.util.zip.InflaterInputStream;
-
-import jogamp.opengl.util.pngj.PngIDatChunkInputStream.IdatChunkInfo;
-import jogamp.opengl.util.pngj.chunks.ChunkHelper;
-import jogamp.opengl.util.pngj.chunks.ChunkList;
-import jogamp.opengl.util.pngj.chunks.ChunkLoadBehaviour;
-import jogamp.opengl.util.pngj.chunks.ChunkRaw;
-import jogamp.opengl.util.pngj.chunks.PngChunk;
-import jogamp.opengl.util.pngj.chunks.PngChunkIHDR;
-import jogamp.opengl.util.pngj.chunks.PngMetadata;
-
-
-/**
- * Reads a PNG image, line by line
- */
-public class PngReader {
-	/**
-	 * Basic image info - final and inmutable.
-	 */
-	public final ImageInfo imgInfo;
-	protected final String filename; // not necesarily a file, can be a description - merely informative
-
-	private static int MAX_BYTES_CHUNKS_TO_LOAD = 640000;
-	private ChunkLoadBehaviour chunkLoadBehaviour = ChunkLoadBehaviour.LOAD_CHUNK_ALWAYS;
-
-	private final InputStream is;
-	private InflaterInputStream idatIstream;
-	private PngIDatChunkInputStream iIdatCstream;
-
-	protected int currentChunkGroup = -1;
-	protected int rowNum = -1; // current row number
-	private int offset = 0;
-	private int bytesChunksLoaded; // bytes loaded from anciallary chunks
-
-	protected ImageLine imgLine;
-
-	// line as bytes, counting from 1 (index 0 is reserved for filter type)
-	protected byte[] rowb = null;
-	protected byte[] rowbprev = null; // rowb previous
-	protected byte[] rowbfilter = null; // current line 'filtered': exactly as in uncompressed stream
-
-	/**
-	 * All chunks loaded. Criticals are included, except that all IDAT chunks appearance are replaced by a single
-	 * dummy-marker IDAT chunk. These might be copied to the PngWriter
-	 */
-	private final ChunkList chunksList;
-	private final PngMetadata metadata; // this a wrapper over chunks
-
-	/**
-	 * Constructs a PngReader from an InputStream.
-	 * <p>
-	 * See also <code>FileHelper.createPngReader(File f)</code> if available.
-	 * 
-	 * Reads only the signature and first chunk (IDHR)
-	 * 
-	 * @param filenameOrDescription
-	 *            : Optional, can be a filename or a description. Just for error/debug messages
-	 * 
-	 */
-	public PngReader(InputStream inputStream, String filenameOrDescription) {
-		this.filename = filenameOrDescription == null ? "" : filenameOrDescription;
-		this.is = inputStream;
-		this.chunksList = new ChunkList(null);
-		this.metadata = new PngMetadata(chunksList, true);
-		// reads header (magic bytes)
-		byte[] pngid = new byte[PngHelper.pngIdBytes.length];
-		PngHelper.readBytes(is, pngid, 0, pngid.length);
-		offset += pngid.length;
-		if (!Arrays.equals(pngid, PngHelper.pngIdBytes))
-			throw new PngjInputException("Bad PNG signature");
-		// reads first chunk
-		currentChunkGroup = ChunkList.CHUNK_GROUP_0_IDHR;
-		int clen = PngHelper.readInt4(is);
-		offset += 4;
-		if (clen != 13)
-			throw new RuntimeException("IDHR chunk len != 13 ?? " + clen);
-		byte[] chunkid = new byte[4];
-		PngHelper.readBytes(is, chunkid, 0, 4);
-		if (!Arrays.equals(chunkid, ChunkHelper.b_IHDR))
-			throw new PngjInputException("IHDR not found as first chunk??? [" + ChunkHelper.toString(chunkid) + "]");
-		offset += 4;
-		ChunkRaw chunk = new ChunkRaw(clen, chunkid, true);
-		String chunkids = ChunkHelper.toString(chunkid);
-		offset += chunk.readChunkData(is);
-		PngChunkIHDR ihdr = (PngChunkIHDR) addChunkToList(chunk);
-		boolean alpha = (ihdr.getColormodel() & 0x04) != 0;
-		boolean palette = (ihdr.getColormodel() & 0x01) != 0;
-		boolean grayscale = (ihdr.getColormodel() == 0 || ihdr.getColormodel() == 4);
-		imgInfo = new ImageInfo(ihdr.getCols(), ihdr.getRows(), ihdr.getBitspc(), alpha, grayscale, palette);
-		imgLine = new ImageLine(imgInfo);
-		if (ihdr.getInterlaced() != 0)
-			throw new PngjUnsupportedException("PNG interlaced not supported by this library");
-		if (ihdr.getFilmeth() != 0 || ihdr.getCompmeth() != 0)
-			throw new PngjInputException("compmethod o filtermethod unrecognized");
-		if (ihdr.getColormodel() < 0 || ihdr.getColormodel() > 6 || ihdr.getColormodel() == 1
-				|| ihdr.getColormodel() == 5)
-			throw new PngjInputException("Invalid colormodel " + ihdr.getColormodel());
-		if (ihdr.getBitspc() != 1 && ihdr.getBitspc() != 2 && ihdr.getBitspc() != 4 && ihdr.getBitspc() != 8
-				&& ihdr.getBitspc() != 16)
-			throw new PngjInputException("Invalid bit depth " + ihdr.getBitspc());
-		// allocation: one extra byte for filter type one pixel
-		rowbfilter = new byte[imgInfo.bytesPerRow + 1];
-		rowb = new byte[imgInfo.bytesPerRow + 1];
-		rowbprev = new byte[rowb.length];
-	}
-
-	private static class FoundChunkInfo {
-		public final String id;
-		public final int len;
-		public final int offset;
-		public final boolean loaded;
-
-		private FoundChunkInfo(String id, int len, int offset, boolean loaded) {
-			this.id = id;
-			this.len = len;
-			this.offset = offset;
-			this.loaded = loaded;
-		}
-
-		public String toString() {
-			return "chunk " + id + " len=" + len + " offset=" + offset + (this.loaded ? " " : " X ");
-		}
-	}
-
-	private PngChunk addChunkToList(ChunkRaw chunk) {
-		// this requires that the currentChunkGroup is ok
-		PngChunk chunkType = PngChunk.factory(chunk, imgInfo);
-		if (!chunkType.crit) {
-			bytesChunksLoaded += chunk.len;
-		}
-		if (bytesChunksLoaded > MAX_BYTES_CHUNKS_TO_LOAD) {
-			throw new PngjInputException("Chunk exceeded available space (" + MAX_BYTES_CHUNKS_TO_LOAD + ") chunk: "
-					+ chunk + " See PngReader.MAX_BYTES_CHUNKS_TO_LOAD\n");
-		}
-		chunksList.appendReadChunk(chunkType, currentChunkGroup);
-		return chunkType;
-	}
-
-	/**
-	 * Reads chunks before first IDAT. Position before: after IDHR (crc included) Position after: just after the first
-	 * IDAT chunk id
-	 * 
-	 * This can be called several times (tentatively), it does nothing if already run
-	 * 
-	 * (Note: when should this be called? in the constructor? hardly, because we loose the opportunity to call
-	 * setChunkLoadBehaviour() and perhaps other settings before reading the first row? but sometimes we want to access
-	 * some metadata (plte, phys) before. Because of this, this method can be called explicitly but is also called
-	 * implicititly in some methods (getMetatada(), getChunks())
-	 * 
-	 **/
-	public void readFirstChunks() {
-		if (!firstChunksNotYetRead())
-			return;
-		int clen = 0;
-		boolean found = false;
-		byte[] chunkid = new byte[4]; // it's important to reallocate in each iteration
-		currentChunkGroup = ChunkList.CHUNK_GROUP_1_AFTERIDHR;
-		while (!found) {
-			clen = PngHelper.readInt4(is);
-			offset += 4;
-			if (clen < 0)
-				break;
-			PngHelper.readBytes(is, chunkid, 0, 4);
-			offset += 4;
-			if (Arrays.equals(chunkid, ChunkHelper.b_IDAT)) {
-				found = true;
-				currentChunkGroup = ChunkList.CHUNK_GROUP_4_IDAT;
-				// add dummy idat chunk to list
-				ChunkRaw chunk = new ChunkRaw(0, chunkid, false);
-				addChunkToList(chunk);
-				break;
-			} else if (Arrays.equals(chunkid, ChunkHelper.b_IEND)) {
-				throw new PngjInputException("END chunk found before image data (IDAT) at offset=" + offset);
-			}
-			ChunkRaw chunk = new ChunkRaw(clen, chunkid, true);
-			String chunkids = ChunkHelper.toString(chunkid);
-			boolean loadchunk = ChunkHelper.shouldLoad(chunkids, chunkLoadBehaviour);
-			offset += chunk.readChunkData(is);
-			if (chunkids.equals(ChunkHelper.PLTE))
-				currentChunkGroup = ChunkList.CHUNK_GROUP_2_PLTE;
-			if (loadchunk)
-				addChunkToList(chunk);
-			if (chunkids.equals(ChunkHelper.PLTE))
-				currentChunkGroup = ChunkList.CHUNK_GROUP_3_AFTERPLTE;
-		}
-		int idatLen = found ? clen : -1;
-		if (idatLen < 0)
-			throw new PngjInputException("first idat chunk not found!");
-		iIdatCstream = new PngIDatChunkInputStream(is, idatLen, offset);
-		idatIstream = new InflaterInputStream(iIdatCstream);
-	}
-
-	/**
-	 * Reads (and processes) chunks after last IDAT.
-	 **/
-	private void readLastChunks() {
-		// PngHelper.logdebug("idat ended? " + iIdatCstream.isEnded());
-		currentChunkGroup = ChunkList.CHUNK_GROUP_5_AFTERIDAT;
-		if (!iIdatCstream.isEnded())
-			iIdatCstream.forceChunkEnd();
-		int clen = iIdatCstream.getLenLastChunk();
-		byte[] chunkid = iIdatCstream.getIdLastChunk();
-		boolean endfound = false;
-		boolean first = true;
-		boolean ignore = false;
-		while (!endfound) {
-			ignore = false;
-			if (!first) {
-				clen = PngHelper.readInt4(is);
-				offset += 4;
-				if (clen < 0)
-					throw new PngjInputException("bad len " + clen);
-				PngHelper.readBytes(is, chunkid, 0, 4);
-				offset += 4;
-			}
-			first = false;
-			if (Arrays.equals(chunkid, ChunkHelper.b_IDAT)) {
-				// PngHelper.logdebug("extra IDAT chunk len - ignoring : ");
-				ignore = true;
-			} else if (Arrays.equals(chunkid, ChunkHelper.b_IEND)) {
-				currentChunkGroup = ChunkList.CHUNK_GROUP_6_END;
-				endfound = true;
-			}
-			ChunkRaw chunk = new ChunkRaw(clen, chunkid, true);
-			String chunkids = ChunkHelper.toString(chunkid);
-			boolean loadchunk = ChunkHelper.shouldLoad(chunkids, chunkLoadBehaviour);
-			offset += chunk.readChunkData(is);
-			if (loadchunk && !ignore) {
-				addChunkToList(chunk);
-			}
-		}
-		if (!endfound)
-			throw new PngjInputException("end chunk not found - offset=" + offset);
-		// PngHelper.logdebug("end chunk found ok offset=" + offset);
-	}
-
-	/**
-	 * Calls <code>readRow(int[] buffer, int nrow)</code> using internal ImageLine as buffer. This doesn't allocate or
-	 * copy anything.
-	 * 
-	 * @return The ImageLine that also is available inside this object.
-	 */
-	public ImageLine readRow(int nrow) {
-		readRow(imgLine.scanline, nrow);
-		imgLine.filterUsed = FilterType.getByVal(rowbfilter[0]);
-		imgLine.setRown(nrow);
-		return imgLine;
-	}
-
-	/**
-	 * Reads a line and returns it as a int[] array.
-	 * 
-	 * You can pass (optionally) a prealocatted buffer.
-	 * 
-	 * @param buffer
-	 *            Prealocated buffer, or null.
-	 * @param nrow
-	 *            Row number (0 is top). This is mostly for checking, because this library reads rows in sequence.
-	 * 
-	 * @return The scanline in the same passwd buffer if it was allocated, a newly allocated one otherwise
-	 */
-	public int[] readRow(int[] buffer, int nrow) {
-		if (nrow < 0 || nrow >= imgInfo.rows)
-			throw new PngjInputException("invalid line");
-		if (nrow != rowNum + 1)
-			throw new PngjInputException("invalid line (expected: " + (rowNum + 1));
-		if (nrow == 0 && firstChunksNotYetRead())
-			readFirstChunks();
-		rowNum++;
-		if (buffer == null || buffer.length < imgInfo.samplesPerRowP)
-			buffer = new int[imgInfo.samplesPerRowP];
-		// swap
-		byte[] tmp = rowb;
-		rowb = rowbprev;
-		rowbprev = tmp;
-		// loads in rowbfilter "raw" bytes, with filter
-		PngHelper.readBytes(idatIstream, rowbfilter, 0, rowbfilter.length);
-		rowb[0] = 0;
-		unfilterRow();
-		rowb[0] = rowbfilter[0];
-		convertRowFromBytes(buffer);
-		return buffer;
-	}
-
-	/**
-	 * This should be called after having read the last line. It reads extra chunks after IDAT, if present.
-	 */
-	public void end() {
-		offset = (int) iIdatCstream.getOffset();
-		try {
-			idatIstream.close();
-		} catch (Exception e) {
-		}
-		readLastChunks();
-		try {
-			is.close();
-		} catch (Exception e) {
-			throw new PngjInputException("error closing input stream!", e);
-		}
-	}
-
-	private void convertRowFromBytes(int[] buffer) {
-		// http://www.libpng.org/pub/png/spec/1.2/PNG-DataRep.html
-		int i, j;
-		if (imgInfo.bitDepth <= 8) {
-			for (i = 0, j = 1; i < imgInfo.samplesPerRowP; i++) {
-				buffer[i] = (rowb[j++] & 0xFF);
-			}
-		} else { // 16 bitspc
-			for (i = 0, j = 1; i < imgInfo.samplesPerRowP; i++) {
-				buffer[i] = ((rowb[j++] & 0xFF) << 8) + (rowb[j++] & 0xFF);
-			}
-		}
-	}
-
-	private void unfilterRow() {
-		int ftn = rowbfilter[0];
-		FilterType ft = FilterType.getByVal(ftn);
-		if (ft == null)
-			throw new PngjInputException("Filter type " + ftn + " invalid");
-		switch (ft) {
-		case FILTER_NONE:
-			unfilterRowNone();
-			break;
-		case FILTER_SUB:
-			unfilterRowSub();
-			break;
-		case FILTER_UP:
-			unfilterRowUp();
-			break;
-		case FILTER_AVERAGE:
-			unfilterRowAverage();
-			break;
-		case FILTER_PAETH:
-			unfilterRowPaeth();
-			break;
-		default:
-			throw new PngjInputException("Filter type " + ftn + " not implemented");
-		}
-	}
-
-	private void unfilterRowNone() {
-		for (int i = 1; i <= imgInfo.bytesPerRow; i++) {
-			rowb[i] = (byte) (rowbfilter[i]);
-		}
-	}
-
-	private void unfilterRowSub() {
-		int i, j;
-		for (i = 1; i <= imgInfo.bytesPixel; i++) {
-			rowb[i] = (byte) (rowbfilter[i]);
-		}
-		for (j = 1, i = imgInfo.bytesPixel + 1; i <= imgInfo.bytesPerRow; i++, j++) {
-			rowb[i] = (byte) (rowbfilter[i] + rowb[j]);
-		}
-	}
-
-	private void unfilterRowUp() {
-		for (int i = 1; i <= imgInfo.bytesPerRow; i++) {
-			rowb[i] = (byte) (rowbfilter[i] + rowbprev[i]);
-		}
-	}
-
-	private void unfilterRowAverage() {
-		int i, j, x;
-		for (j = 1 - imgInfo.bytesPixel, i = 1; i <= imgInfo.bytesPerRow; i++, j++) {
-			x = j > 0 ? (rowb[j] & 0xff) : 0;
-			rowb[i] = (byte) (rowbfilter[i] + (x + (rowbprev[i] & 0xFF)) / 2);
-		}
-	}
-
-	private void unfilterRowPaeth() {
-		int i, j, x, y;
-		for (j = 1 - imgInfo.bytesPixel, i = 1; i <= imgInfo.bytesPerRow; i++, j++) {
-			x = j > 0 ? (rowb[j] & 0xFF) : 0;
-			y = j > 0 ? (rowbprev[j] & 0xFF) : 0;
-			rowb[i] = (byte) (rowbfilter[i] + FilterType.filterPaethPredictor(x, rowbprev[i] & 0xFF, y));
-		}
-	}
-
-	public ChunkLoadBehaviour getChunkLoadBehaviour() {
-		return chunkLoadBehaviour;
-	}
-
-	public void setChunkLoadBehaviour(ChunkLoadBehaviour chunkLoadBehaviour) {
-		this.chunkLoadBehaviour = chunkLoadBehaviour;
-	}
-
-	private boolean firstChunksNotYetRead() {
-		return currentChunkGroup < ChunkList.CHUNK_GROUP_1_AFTERIDHR;
-	}
-
-	public ChunkList getChunksList() {
-		if (firstChunksNotYetRead())
-			readFirstChunks();
-		return chunksList;
-	}
-
-	public PngMetadata getMetadata() {
-		if (firstChunksNotYetRead())
-			readFirstChunks();
-		return metadata;
-	}
-
-	public String toString() { // basic info
-		return "filename=" + filename + " " + imgInfo.toString();
-	}
-
-}
+package jogamp.opengl.util.pngj;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.zip.CRC32;
+import java.util.zip.Inflater;
+import java.util.zip.InflaterInputStream;
+
+import jogamp.opengl.util.pngj.ImageLine.SampleType;
+import jogamp.opengl.util.pngj.chunks.ChunkHelper;
+import jogamp.opengl.util.pngj.chunks.ChunkLoadBehaviour;
+import jogamp.opengl.util.pngj.chunks.ChunkRaw;
+import jogamp.opengl.util.pngj.chunks.ChunksList;
+import jogamp.opengl.util.pngj.chunks.PngChunk;
+import jogamp.opengl.util.pngj.chunks.PngChunkIDAT;
+import jogamp.opengl.util.pngj.chunks.PngChunkIHDR;
+import jogamp.opengl.util.pngj.chunks.PngChunkSkipped;
+import jogamp.opengl.util.pngj.chunks.PngMetadata;
+
+/**
+ * Reads a PNG image, line by line.
+ * <p>
+ * The reading sequence is as follows: <br>
+ * 1. At construction time, the header and IHDR chunk are read (basic image
+ * info) <br>
+ * 2. Afterwards you can set some additional global options. Eg.
+ * {@link #setUnpackedMode(boolean)}, {@link #setCrcCheckDisabled()}.<br>
+ * 3. Optional: If you call getMetadata() or getChunksLisk() before start
+ * reading the rows, all the chunks before IDAT are automatically loaded and
+ * available <br>
+ * 4a. The rows are read onen by one of the <tt>readRowXXX</tt> methods:
+ * {@link #readRowInt(int)}, {@link PngReader#readRowByte(int)}, etc, in order,
+ * from 0 to nrows-1 (you can skip or repeat rows, but not go backwards)<br>
+ * 4b. Alternatively, you can read all rows, or a subset, in a single call:
+ * {@link #readRowsInt()}, {@link #readRowsByte()} ,etc. In general this
+ * consumes more memory, but for interlaced images this is equally efficient,
+ * and more so if reading a small subset of rows.<br>
+ * 5. Read of the last row auyomatically loads the trailing chunks, and ends the
+ * reader.<br>
+ * 6. end() forcibly finishes/aborts the reading and closes the stream
+ */
+public class PngReader {
+
+	/**
+	 * Basic image info - final and inmutable.
+	 */
+	public final ImageInfo imgInfo;
+	/**
+	 * not necesarily a filename, can be a description - merely informative
+	 */
+	protected final String filename;
+	private ChunkLoadBehaviour chunkLoadBehaviour = ChunkLoadBehaviour.LOAD_CHUNK_ALWAYS; // see setter/getter
+	private boolean shouldCloseStream = true; // true: closes stream after ending - see setter/getter
+	// some performance/defensive limits
+	private long maxTotalBytesRead = 200 * 1024 * 1024; // 200MB
+	private int maxBytesMetadata = 5 * 1024 * 1024; // for ancillary chunks - see setter/getter
+	private int skipChunkMaxSize = 2 * 1024 * 1024; // chunks exceeding this size will be skipped (nor even CRC checked)
+	private String[] skipChunkIds = { "fdAT" }; // chunks with these ids will be skipped (nor even CRC checked)
+	private HashSet<String> skipChunkIdsSet; // lazily created from skipChunksById
+	protected final PngMetadata metadata; // this a wrapper over chunks
+	protected final ChunksList chunksList;
+	protected ImageLine imgLine;
+	// line as bytes, counting from 1 (index 0 is reserved for filter type)
+	protected final int buffersLen; // nominal length is imgInfo.bytesPerRow + 1 but it can be larger
+	protected byte[] rowb = null;
+	protected byte[] rowbprev = null; // rowb previous
+	protected byte[] rowbfilter = null; // current line 'filtered': exactly as in uncompressed stream
+	// only set for interlaced PNG
+	private final boolean interlaced;
+	private final PngDeinterlacer deinterlacer;
+	private boolean crcEnabled = true;
+	// this only influences the 1-2-4 bitdepth format
+	private boolean unpackedMode = false;
+	private Inflater inflater = null;	// can be reused among several objects. see reuseBuffersFrom()
+	/**
+	 * Current chunk group, (0-6) already read or reading
+	 * <p>
+	 * see {@link ChunksList}
+	 */
+	protected int currentChunkGroup = -1;
+	protected int rowNum = -1; // last read row number, starting from 0
+	private long offset = 0; // offset in InputStream = bytes read
+	private int bytesChunksLoaded; // bytes loaded from anciallary chunks
+	protected final InputStream inputStream;
+	protected InflaterInputStream idatIstream;
+	protected PngIDatChunkInputStream iIdatCstream;
+	protected CRC32 crctest; // If set to non null, it gets a CRC of the unfiltered bytes, to check for images equality
+
+	/**
+	 * Constructs a PngReader from an InputStream.
+	 * <p>
+	 * See also <code>FileHelper.createPngReader(File f)</code> if available.
+	 *
+	 * Reads only the signature and first chunk (IDHR)
+	 *
+	 * @param filenameOrDescription
+	 *            : Optional, can be a filename or a description. Just for
+	 *            error/debug messages
+	 *
+	 */
+	public PngReader(InputStream inputStream, String filenameOrDescription) {
+		this.filename = filenameOrDescription == null ? "" : filenameOrDescription;
+		this.inputStream = inputStream;
+		this.chunksList = new ChunksList(null);
+		this.metadata = new PngMetadata(chunksList);
+		// starts reading: signature
+		byte[] pngid = new byte[8];
+		PngHelperInternal.readBytes(inputStream, pngid, 0, pngid.length);
+		offset += pngid.length;
+		if (!Arrays.equals(pngid, PngHelperInternal.getPngIdSignature()))
+			throw new PngjInputException("Bad PNG signature");
+		// reads first chunk
+		currentChunkGroup = ChunksList.CHUNK_GROUP_0_IDHR;
+		int clen = PngHelperInternal.readInt4(inputStream);
+		offset += 4;
+		if (clen != 13)
+			throw new PngjInputException("IDHR chunk len != 13 ?? " + clen);
+		byte[] chunkid = new byte[4];
+		PngHelperInternal.readBytes(inputStream, chunkid, 0, 4);
+		if (!Arrays.equals(chunkid, ChunkHelper.b_IHDR))
+			throw new PngjInputException("IHDR not found as first chunk??? [" + ChunkHelper.toString(chunkid) + "]");
+		offset += 4;
+		PngChunkIHDR ihdr = (PngChunkIHDR) readChunk(chunkid, clen, false);
+		boolean alpha = (ihdr.getColormodel() & 0x04) != 0;
+		boolean palette = (ihdr.getColormodel() & 0x01) != 0;
+		boolean grayscale = (ihdr.getColormodel() == 0 || ihdr.getColormodel() == 4);
+		// creates ImgInfo and imgLine, and allocates buffers
+		imgInfo = new ImageInfo(ihdr.getCols(), ihdr.getRows(), ihdr.getBitspc(), alpha, grayscale, palette);
+		interlaced = ihdr.getInterlaced() == 1;
+		deinterlacer = interlaced ? new PngDeinterlacer(imgInfo) : null;
+		buffersLen = imgInfo.bytesPerRow + 1;
+		// some checks
+		if (ihdr.getFilmeth() != 0 || ihdr.getCompmeth() != 0 || (ihdr.getInterlaced() & 0xFFFE) != 0)
+			throw new PngjInputException("compression method o filter method or interlaced unrecognized ");
+		if (ihdr.getColormodel() < 0 || ihdr.getColormodel() > 6 || ihdr.getColormodel() == 1
+				|| ihdr.getColormodel() == 5)
+			throw new PngjInputException("Invalid colormodel " + ihdr.getColormodel());
+		if (ihdr.getBitspc() != 1 && ihdr.getBitspc() != 2 && ihdr.getBitspc() != 4 && ihdr.getBitspc() != 8
+				&& ihdr.getBitspc() != 16)
+			throw new PngjInputException("Invalid bit depth " + ihdr.getBitspc());
+	}
+
+	private boolean firstChunksNotYetRead() {
+		return currentChunkGroup < ChunksList.CHUNK_GROUP_1_AFTERIDHR;
+	}
+
+	private void allocateBuffers() { // only if needed
+		if (rowbfilter == null || rowbfilter.length < buffersLen) {
+			rowbfilter = new byte[buffersLen];
+			rowb = new byte[buffersLen];
+			rowbprev = new byte[buffersLen];
+		}
+	}
+
+	/**
+	 * Reads last Internally called after having read the last line. It reads
+	 * extra chunks after IDAT, if present.
+	 */
+	private void readLastAndClose() {
+		// offset = iIdatCstream.getOffset();
+		if (currentChunkGroup < ChunksList.CHUNK_GROUP_5_AFTERIDAT) {
+			try {
+				idatIstream.close();
+			} catch (Exception e) {
+			}
+			readLastChunks();
+		}
+		close();
+	}
+
+	private void close() {
+		if (currentChunkGroup < ChunksList.CHUNK_GROUP_6_END) { // this could only happen if forced close
+			try {
+				idatIstream.close();
+			} catch (Exception e) {
+			}
+			currentChunkGroup = ChunksList.CHUNK_GROUP_6_END;
+		}
+		if (shouldCloseStream) {
+			try {
+				inputStream.close();
+			} catch (Exception e) {
+				throw new PngjInputException("error closing input stream!", e);
+			}
+		}
+	}
+
+	// nbytes: NOT including the filter byte. leaves result in rowb
+	private void unfilterRow(int nbytes) {
+		int ftn = rowbfilter[0];
+		FilterType ft = FilterType.getByVal(ftn);
+		if (ft == null)
+			throw new PngjInputException("Filter type " + ftn + " invalid");
+		switch (ft) {
+		case FILTER_NONE:
+			unfilterRowNone(nbytes);
+			break;
+		case FILTER_SUB:
+			unfilterRowSub(nbytes);
+			break;
+		case FILTER_UP:
+			unfilterRowUp(nbytes);
+			break;
+		case FILTER_AVERAGE:
+			unfilterRowAverage(nbytes);
+			break;
+		case FILTER_PAETH:
+			unfilterRowPaeth(nbytes);
+			break;
+		default:
+			throw new PngjInputException("Filter type " + ftn + " not implemented");
+		}
+		if (crctest != null)
+			crctest.update(rowb, 1, buffersLen - 1);
+	}
+
+	private void unfilterRowAverage(final int nbytes) {
+		int i, j, x;
+		for (j = 1 - imgInfo.bytesPixel, i = 1; i <= nbytes; i++, j++) {
+			x = j > 0 ? (rowb[j] & 0xff) : 0;
+			rowb[i] = (byte) (rowbfilter[i] + (x + (rowbprev[i] & 0xFF)) / 2);
+		}
+	}
+
+	private void unfilterRowNone(final int nbytes) {
+		for (int i = 1; i <= nbytes; i++) {
+			rowb[i] = (byte) (rowbfilter[i]);
+		}
+	}
+
+	private void unfilterRowPaeth(final int nbytes) {
+		int i, j, x, y;
+		for (j = 1 - imgInfo.bytesPixel, i = 1; i <= nbytes; i++, j++) {
+			x = j > 0 ? (rowb[j] & 0xFF) : 0;
+			y = j > 0 ? (rowbprev[j] & 0xFF) : 0;
+			rowb[i] = (byte) (rowbfilter[i] + PngHelperInternal.filterPaethPredictor(x, rowbprev[i] & 0xFF, y));
+		}
+	}
+
+	private void unfilterRowSub(final int nbytes) {
+		int i, j;
+		for (i = 1; i <= imgInfo.bytesPixel; i++) {
+			rowb[i] = (byte) (rowbfilter[i]);
+		}
+		for (j = 1, i = imgInfo.bytesPixel + 1; i <= nbytes; i++, j++) {
+			rowb[i] = (byte) (rowbfilter[i] + rowb[j]);
+		}
+	}
+
+	private void unfilterRowUp(final int nbytes) {
+		for (int i = 1; i <= nbytes; i++) {
+			rowb[i] = (byte) (rowbfilter[i] + rowbprev[i]);
+		}
+	}
+
+	/**
+	 * Reads chunks before first IDAT. Normally this is called automatically
+	 * <p>
+	 * Position before: after IDHR (crc included) Position after: just after the
+	 * first IDAT chunk id
+	 * <P>
+	 * This can be called several times (tentatively), it does nothing if
+	 * already run
+	 * <p>
+	 * (Note: when should this be called? in the constructor? hardly, because we
+	 * loose the opportunity to call setChunkLoadBehaviour() and perhaps other
+	 * settings before reading the first row? but sometimes we want to access
+	 * some metadata (plte, phys) before. Because of this, this method can be
+	 * called explicitly but is also called implicititly in some methods
+	 * (getMetatada(), getChunksList())
+	 */
+	private final void readFirstChunks() {
+		if (!firstChunksNotYetRead())
+			return;
+		int clen = 0;
+		boolean found = false;
+		byte[] chunkid = new byte[4]; // it's important to reallocate in each iteration
+		currentChunkGroup = ChunksList.CHUNK_GROUP_1_AFTERIDHR;
+		while (!found) {
+			clen = PngHelperInternal.readInt4(inputStream);
+			offset += 4;
+			if (clen < 0)
+				break;
+			PngHelperInternal.readBytes(inputStream, chunkid, 0, 4);
+			offset += 4;
+			if (Arrays.equals(chunkid, ChunkHelper.b_IDAT)) {
+				found = true;
+				currentChunkGroup = ChunksList.CHUNK_GROUP_4_IDAT;
+				// add dummy idat chunk to list
+				chunksList.appendReadChunk(new PngChunkIDAT(imgInfo, clen, offset - 8), currentChunkGroup);
+				break;
+			} else if (Arrays.equals(chunkid, ChunkHelper.b_IEND)) {
+				throw new PngjInputException("END chunk found before image data (IDAT) at offset=" + offset);
+			}
+			if (Arrays.equals(chunkid, ChunkHelper.b_PLTE))
+				currentChunkGroup = ChunksList.CHUNK_GROUP_2_PLTE;
+			readChunk(chunkid, clen, false);
+			if (Arrays.equals(chunkid, ChunkHelper.b_PLTE))
+				currentChunkGroup = ChunksList.CHUNK_GROUP_3_AFTERPLTE;
+		}
+		int idatLen = found ? clen : -1;
+		if (idatLen < 0)
+			throw new PngjInputException("first idat chunk not found!");
+		iIdatCstream = new PngIDatChunkInputStream(inputStream, idatLen, offset);
+		if(inflater == null) {
+			inflater = new Inflater();
+		} else {
+		inflater.reset();
+		}
+		idatIstream = new InflaterInputStream(iIdatCstream, inflater);
+		if (!crcEnabled)
+			iIdatCstream.disableCrcCheck();
+	}
+
+	/**
+	 * Reads (and processes) chunks after last IDAT.
+	 **/
+	void readLastChunks() {
+		// PngHelper.logdebug("idat ended? " + iIdatCstream.isEnded());
+		currentChunkGroup = ChunksList.CHUNK_GROUP_5_AFTERIDAT;
+		if (!iIdatCstream.isEnded())
+			iIdatCstream.forceChunkEnd();
+		int clen = iIdatCstream.getLenLastChunk();
+		byte[] chunkid = iIdatCstream.getIdLastChunk();
+		boolean endfound = false;
+		boolean first = true;
+		boolean skip = false;
+		while (!endfound) {
+			skip = false;
+			if (!first) {
+				clen = PngHelperInternal.readInt4(inputStream);
+				offset += 4;
+				if (clen < 0)
+					throw new PngjInputException("bad chuck len " + clen);
+				PngHelperInternal.readBytes(inputStream, chunkid, 0, 4);
+				offset += 4;
+			}
+			first = false;
+			if (Arrays.equals(chunkid, ChunkHelper.b_IDAT)) {
+				skip = true; // extra dummy (empty?) idat chunk, it can happen, ignore it
+			} else if (Arrays.equals(chunkid, ChunkHelper.b_IEND)) {
+				currentChunkGroup = ChunksList.CHUNK_GROUP_6_END;
+				endfound = true;
+			}
+			readChunk(chunkid, clen, skip);
+		}
+		if (!endfound)
+			throw new PngjInputException("end chunk not found - offset=" + offset);
+		// PngHelper.logdebug("end chunk found ok offset=" + offset);
+	}
+
+	/**
+	 * Reads chunkd from input stream, adds to ChunksList, and returns it. If
+	 * it's skipped, a PngChunkSkipped object is created
+	 */
+	private PngChunk readChunk(byte[] chunkid, int clen, boolean skipforced) {
+		if (clen < 0)
+			throw new PngjInputException("invalid chunk lenght: " + clen);
+		// skipChunksByIdSet is created lazyly, if fist IHDR has already been read
+		if (skipChunkIdsSet == null && currentChunkGroup > ChunksList.CHUNK_GROUP_0_IDHR)
+			skipChunkIdsSet = new HashSet<String>(Arrays.asList(skipChunkIds));
+		String chunkidstr = ChunkHelper.toString(chunkid);
+		boolean critical = ChunkHelper.isCritical(chunkidstr);
+		PngChunk pngChunk = null;
+		boolean skip = skipforced;
+		if (maxTotalBytesRead > 0 && clen + offset > maxTotalBytesRead)
+			throw new PngjInputException("Maximum total bytes to read exceeeded: " + maxTotalBytesRead + " offset:"
+					+ offset + " clen=" + clen);
+		// an ancillary chunks can be skipped because of several reasons:
+		if (currentChunkGroup > ChunksList.CHUNK_GROUP_0_IDHR && !critical)
+			skip = skip || (skipChunkMaxSize > 0 && clen >= skipChunkMaxSize) || skipChunkIdsSet.contains(chunkidstr)
+					|| (maxBytesMetadata > 0 && clen > maxBytesMetadata - bytesChunksLoaded)
+					|| !ChunkHelper.shouldLoad(chunkidstr, chunkLoadBehaviour);
+		if (skip) {
+			PngHelperInternal.skipBytes(inputStream, clen);
+			PngHelperInternal.readInt4(inputStream); // skip - we dont call PngHelperInternal.skipBytes(inputStream,
+			// clen + 4) for risk of overflow
+			pngChunk = new PngChunkSkipped(chunkidstr, imgInfo, clen);
+		} else {
+			ChunkRaw chunk = new ChunkRaw(clen, chunkid, true);
+			chunk.readChunkData(inputStream, crcEnabled || critical);
+			pngChunk = PngChunk.factory(chunk, imgInfo);
+			if (!pngChunk.crit)
+				bytesChunksLoaded += chunk.len;
+		}
+		pngChunk.setOffset(offset - 8L);
+		chunksList.appendReadChunk(pngChunk, currentChunkGroup);
+		offset += clen + 4L;
+		return pngChunk;
+	}
+
+	/**
+	 * Logs/prints a warning.
+	 * <p>
+	 * The default behaviour is print to stderr, but it can be overriden.
+	 * <p>
+	 * This happens rarely - most errors are fatal.
+	 */
+	protected void logWarn(String warn) {
+		System.err.println(warn);
+	}
+
+	/**
+	 * @see #setChunkLoadBehaviour(ChunkLoadBehaviour)
+	 */
+	public ChunkLoadBehaviour getChunkLoadBehaviour() {
+		return chunkLoadBehaviour;
+	}
+
+	/**
+	 * Determines which ancillary chunks (metada) are to be loaded
+	 *
+	 * @param chunkLoadBehaviour
+	 *            {@link ChunkLoadBehaviour}
+	 */
+	public void setChunkLoadBehaviour(ChunkLoadBehaviour chunkLoadBehaviour) {
+		this.chunkLoadBehaviour = chunkLoadBehaviour;
+	}
+
+	/**
+	 * All loaded chunks (metada). If we have not yet end reading the image,
+	 * this will include only the chunks before the pixels data (IDAT)
+	 * <p>
+	 * Critical chunks are included, except that all IDAT chunks appearance are
+	 * replaced by a single dummy-marker IDAT chunk. These might be copied to
+	 * the PngWriter
+	 * <p>
+	 *
+	 * @see #getMetadata()
+	 */
+	public ChunksList getChunksList() {
+		if (firstChunksNotYetRead())
+			readFirstChunks();
+		return chunksList;
+	}
+
+	int getCurrentChunkGroup() {
+		return currentChunkGroup;
+	}
+
+	/**
+	 * High level wrapper over chunksList
+	 *
+	 * @see #getChunksList()
+	 */
+	public PngMetadata getMetadata() {
+		if (firstChunksNotYetRead())
+			readFirstChunks();
+		return metadata;
+	}
+
+	/**
+	 * If called for first time, calls readRowInt. Elsewhere, it calls the
+	 * appropiate readRowInt/readRowByte
+	 * <p>
+	 * In general, specifying the concrete readRowInt/readRowByte is preferrable
+	 *
+	 * @see #readRowInt(int) {@link #readRowByte(int)}
+	 */
+	public ImageLine readRow(int nrow) {
+		if (imgLine == null)
+			imgLine = new ImageLine(imgInfo, SampleType.INT, unpackedMode);
+		return imgLine.sampleType != SampleType.BYTE ? readRowInt(nrow) : readRowByte(nrow);
+	}
+
+	/**
+	 * Reads the row as INT, storing it in the {@link #imgLine} property and
+	 * returning it.
+	 *
+	 * The row must be greater or equal than the last read row.
+	 *
+	 * @param nrow
+	 *            Row number, from 0 to rows-1. Increasing order.
+	 * @return ImageLine object, also available as field. Data is in
+	 *         {@link ImageLine#scanline} (int) field.
+	 */
+	public ImageLine readRowInt(int nrow) {
+		if (imgLine == null)
+			imgLine = new ImageLine(imgInfo, SampleType.INT, unpackedMode);
+		if (imgLine.getRown() == nrow) // already read
+			return imgLine;
+		readRowInt(imgLine.scanline, nrow);
+		imgLine.setFilterUsed(FilterType.getByVal(rowbfilter[0]));
+		imgLine.setRown(nrow);
+		return imgLine;
+	}
+
+	/**
+	 * Reads the row as BYTES, storing it in the {@link #imgLine} property and
+	 * returning it.
+	 *
+	 * The row must be greater or equal than the last read row. This method
+	 * allows to pass the same row that was last read.
+	 *
+	 * @param nrow
+	 *            Row number, from 0 to rows-1. Increasing order.
+	 * @return ImageLine object, also available as field. Data is in
+	 *         {@link ImageLine#scanlineb} (byte) field.
+	 */
+	public ImageLine readRowByte(int nrow) {
+		if (imgLine == null)
+			imgLine = new ImageLine(imgInfo, SampleType.BYTE, unpackedMode);
+		if (imgLine.getRown() == nrow) // already read
+			return imgLine;
+		readRowByte(imgLine.scanlineb, nrow);
+		imgLine.setFilterUsed(FilterType.getByVal(rowbfilter[0]));
+		imgLine.setRown(nrow);
+		return imgLine;
+	}
+
+	/**
+	 * @see #readRowInt(int[], int)
+	 */
+	public final int[] readRow(int[] buffer, final int nrow) {
+		return readRowInt(buffer, nrow);
+	}
+
+	/**
+	 * Reads a line and returns it as a int[] array.
+	 * <p>
+	 * You can pass (optionally) a prealocatted buffer.
+	 * <p>
+	 * If the bitdepth is less than 8, the bytes are packed - unless
+	 * {@link #unpackedMode} is true.
+	 *
+	 * @param buffer
+	 *            Prealocated buffer, or null.
+	 * @param nrow
+	 *            Row number (0 is top). Most be strictly greater than the last
+	 *            read row.
+	 *
+	 * @return The scanline in the same passwd buffer if it was allocated, a
+	 *         newly allocated one otherwise
+	 */
+	public final int[] readRowInt(int[] buffer, final int nrow) {
+		if (buffer == null)
+			buffer = new int[unpackedMode ? imgInfo.samplesPerRow : imgInfo.samplesPerRowPacked];
+		if (!interlaced) {
+			if (nrow <= rowNum)
+				throw new PngjInputException("rows must be read in increasing order: " + nrow);
+			int bytesread = 0;
+			while (rowNum < nrow)
+				bytesread = readRowRaw(rowNum + 1); // read rows, perhaps skipping if necessary
+			decodeLastReadRowToInt(buffer, bytesread);
+		} else { // interlaced
+			if (deinterlacer.getImageInt() == null)
+				deinterlacer.setImageInt(readRowsInt().scanlines); // read all image and store it in deinterlacer
+			System.arraycopy(deinterlacer.getImageInt()[nrow], 0, buffer, 0, unpackedMode ? imgInfo.samplesPerRow
+					: imgInfo.samplesPerRowPacked);
+		}
+		return buffer;
+	}
+
+	/**
+	 * Reads a line and returns it as a byte[] array.
+	 * <p>
+	 * You can pass (optionally) a prealocatted buffer.
+	 * <p>
+	 * If the bitdepth is less than 8, the bytes are packed - unless
+	 * {@link #unpackedMode} is true. <br>
+	 * If the bitdepth is 16, the least significant byte is lost.
+	 * <p>
+	 *
+	 * @param buffer
+	 *            Prealocated buffer, or null.
+	 * @param nrow
+	 *            Row number (0 is top). Most be strictly greater than the last
+	 *            read row.
+	 *
+	 * @return The scanline in the same passwd buffer if it was allocated, a
+	 *         newly allocated one otherwise
+	 */
+	public final byte[] readRowByte(byte[] buffer, final int nrow) {
+		if (buffer == null)
+			buffer = new byte[unpackedMode ? imgInfo.samplesPerRow : imgInfo.samplesPerRowPacked];
+		if (!interlaced) {
+			if (nrow <= rowNum)
+				throw new PngjInputException("rows must be read in increasing order: " + nrow);
+			int bytesread = 0;
+			while (rowNum < nrow)
+				bytesread = readRowRaw(rowNum + 1); // read rows, perhaps skipping if necessary
+			decodeLastReadRowToByte(buffer, bytesread);
+		} else { // interlaced
+			if (deinterlacer.getImageByte() == null)
+				deinterlacer.setImageByte(readRowsByte().scanlinesb); // read all image and store it in deinterlacer
+			System.arraycopy(deinterlacer.getImageByte()[nrow], 0, buffer, 0, unpackedMode ? imgInfo.samplesPerRow
+					: imgInfo.samplesPerRowPacked);
+		}
+		return buffer;
+	}
+
+	/**
+	 * @param nrow
+	 * @deprecated Now {@link #readRow(int)} implements the same funcion. This
+	 *             method will be removed in future releases
+	 */
+	public ImageLine getRow(int nrow) {
+		return readRow(nrow);
+	}
+
+	private void decodeLastReadRowToInt(int[] buffer, int bytesRead) {
+		if (imgInfo.bitDepth <= 8)
+			for (int i = 0, j = 1; i < bytesRead; i++)
+				buffer[i] = (rowb[j++] & 0xFF); // http://www.libpng.org/pub/png/spec/1.2/PNG-DataRep.html
+		else
+			for (int i = 0, j = 1; j <= bytesRead; i++)
+				buffer[i] = ((rowb[j++] & 0xFF) << 8) + (rowb[j++] & 0xFF); // 16 bitspc
+		if (imgInfo.packed && unpackedMode)
+			ImageLine.unpackInplaceInt(imgInfo, buffer, buffer, false);
+	}
+
+	private void decodeLastReadRowToByte(byte[] buffer, int bytesRead) {
+		if (imgInfo.bitDepth <= 8)
+			System.arraycopy(rowb, 1, buffer, 0, bytesRead);
+		else
+			for (int i = 0, j = 1; j < bytesRead; i++, j += 2)
+				buffer[i] = rowb[j];// 16 bits in 1 byte: this discards the LSB!!!
+		if (imgInfo.packed && unpackedMode)
+			ImageLine.unpackInplaceByte(imgInfo, buffer, buffer, false);
+	}
+
+	/**
+	 * Reads a set of lines and returns it as a ImageLines object, which wraps
+	 * matrix. Internally it reads all lines, but decodes and stores only the
+	 * wanted ones. This starts and ends the reading, and cannot be combined
+	 * with other reading methods.
+	 * <p>
+	 * This it's more efficient (speed an memory) that doing calling
+	 * readRowInt() for each desired line only if the image is interlaced.
+	 * <p>
+	 * Notice that the columns in the matrix is not the pixel width of the
+	 * image, but rather pixels x channels
+	 *
+	 * @see #readRowInt(int) to read about the format of each row
+	 *
+	 * @param rowOffset
+	 *            Number of rows to be skipped
+	 * @param nRows
+	 *            Total number of rows to be read. -1: read all available
+	 * @param rowStep
+	 *            Row increment. If 1, we read consecutive lines; if 2, we read
+	 *            even/odd lines, etc
+	 * @return Set of lines as a ImageLines, which wraps a matrix
+	 */
+	public ImageLines readRowsInt(int rowOffset, int nRows, int rowStep) {
+		if (nRows < 0)
+			nRows = (imgInfo.rows - rowOffset) / rowStep;
+		if (rowStep < 1 || rowOffset < 0 || nRows * rowStep + rowOffset > imgInfo.rows)
+			throw new PngjInputException("bad args");
+		ImageLines imlines = new ImageLines(imgInfo, SampleType.INT, unpackedMode, rowOffset, nRows, rowStep);
+		if (!interlaced) {
+			for (int j = 0; j < imgInfo.rows; j++) {
+				int bytesread = readRowRaw(j); // read and perhaps discards
+				int mrow = imlines.imageRowToMatrixRowStrict(j);
+				if (mrow >= 0)
+					decodeLastReadRowToInt(imlines.scanlines[mrow], bytesread);
+			}
+		} else { // and now, for something completely different (interlaced)
+			int[] buf = new int[unpackedMode ? imgInfo.samplesPerRow : imgInfo.samplesPerRowPacked];
+			for (int p = 1; p <= 7; p++) {
+				deinterlacer.setPass(p);
+				for (int i = 0; i < deinterlacer.getRows(); i++) {
+					int bytesread = readRowRaw(i);
+					int j = deinterlacer.getCurrRowReal();
+					int mrow = imlines.imageRowToMatrixRowStrict(j);
+					if (mrow >= 0) {
+						decodeLastReadRowToInt(buf, bytesread);
+						deinterlacer.deinterlaceInt(buf, imlines.scanlines[mrow], !unpackedMode);
+					}
+				}
+			}
+		}
+		end();
+		return imlines;
+	}
+
+	/**
+	 * Same as readRowsInt(0, imgInfo.rows, 1)
+	 *
+	 * @see #readRowsInt(int, int, int)
+	 */
+	public ImageLines readRowsInt() {
+		return readRowsInt(0, imgInfo.rows, 1);
+	}
+
+	/**
+	 * Reads a set of lines and returns it as a ImageLines object, which wrapas
+	 * a byte[][] matrix. Internally it reads all lines, but decodes and stores
+	 * only the wanted ones. This starts and ends the reading, and cannot be
+	 * combined with other reading methods.
+	 * <p>
+	 * This it's more efficient (speed an memory) that doing calling
+	 * readRowByte() for each desired line only if the image is interlaced.
+	 * <p>
+	 * Notice that the columns in the matrix is not the pixel width of the
+	 * image, but rather pixels x channels
+	 *
+	 * @see #readRowByte(int) to read about the format of each row. Notice that
+	 *      if the bitdepth is 16 this will lose information
+	 *
+	 * @param rowOffset
+	 *            Number of rows to be skipped
+	 * @param nRows
+	 *            Total number of rows to be read. -1: read all available
+	 * @param rowStep
+	 *            Row increment. If 1, we read consecutive lines; if 2, we read
+	 *            even/odd lines, etc
+	 * @return Set of lines as a matrix
+	 */
+	public ImageLines readRowsByte(int rowOffset, int nRows, int rowStep) {
+		if (nRows < 0)
+			nRows = (imgInfo.rows - rowOffset) / rowStep;
+		if (rowStep < 1 || rowOffset < 0 || nRows * rowStep + rowOffset > imgInfo.rows)
+			throw new PngjInputException("bad args");
+		ImageLines imlines = new ImageLines(imgInfo, SampleType.BYTE, unpackedMode, rowOffset, nRows, rowStep);
+		if (!interlaced) {
+			for (int j = 0; j < imgInfo.rows; j++) {
+				int bytesread = readRowRaw(j); // read and perhaps discards
+				int mrow = imlines.imageRowToMatrixRowStrict(j);
+				if (mrow >= 0)
+					decodeLastReadRowToByte(imlines.scanlinesb[mrow], bytesread);
+			}
+		} else { // and now, for something completely different (interlaced)
+			byte[] buf = new byte[unpackedMode ? imgInfo.samplesPerRow : imgInfo.samplesPerRowPacked];
+			for (int p = 1; p <= 7; p++) {
+				deinterlacer.setPass(p);
+				for (int i = 0; i < deinterlacer.getRows(); i++) {
+					int bytesread = readRowRaw(i);
+					int j = deinterlacer.getCurrRowReal();
+					int mrow = imlines.imageRowToMatrixRowStrict(j);
+					if (mrow >= 0) {
+						decodeLastReadRowToByte(buf, bytesread);
+						deinterlacer.deinterlaceByte(buf, imlines.scanlinesb[mrow], !unpackedMode);
+					}
+				}
+			}
+		}
+		end();
+		return imlines;
+	}
+
+	/**
+	 * Same as readRowsByte(0, imgInfo.rows, 1)
+	 *
+	 * @see #readRowsByte(int, int, int)
+	 */
+	public ImageLines readRowsByte() {
+		return readRowsByte(0, imgInfo.rows, 1);
+	}
+
+	/*
+	 * For the interlaced case, nrow indicates the subsampled image - the pass must be set already.
+	 *
+	 * This must be called in strict order, both for interlaced or no interlaced.
+	 *
+	 * Updates rowNum.
+	 *
+	 * Leaves raw result in rowb
+	 *
+	 * Returns bytes actually read (not including the filter byte)
+	 */
+	private int readRowRaw(final int nrow) {
+		if (nrow == 0) {
+			if (firstChunksNotYetRead())
+				readFirstChunks();
+			allocateBuffers();
+			if (interlaced)
+				Arrays.fill(rowb, (byte) 0); // new subimage: reset filters: this is enough, see the swap that happens lines
+		}
+		// below
+		int bytesRead = imgInfo.bytesPerRow; // NOT including the filter byte
+		if (interlaced) {
+			if (nrow < 0 || nrow > deinterlacer.getRows() || (nrow != 0 && nrow != deinterlacer.getCurrRowSubimg() + 1))
+				throw new PngjInputException("invalid row in interlaced mode: " + nrow);
+			deinterlacer.setRow(nrow);
+			bytesRead = (imgInfo.bitspPixel * deinterlacer.getPixelsToRead() + 7) / 8;
+			if (bytesRead < 1)
+				throw new PngjExceptionInternal("wtf??");
+		} else { // check for non interlaced
+			if (nrow < 0 || nrow >= imgInfo.rows || nrow != rowNum + 1)
+				throw new PngjInputException("invalid row: " + nrow);
+		}
+		rowNum = nrow;
+		// swap buffers
+		byte[] tmp = rowb;
+		rowb = rowbprev;
+		rowbprev = tmp;
+		// loads in rowbfilter "raw" bytes, with filter
+		PngHelperInternal.readBytes(idatIstream, rowbfilter, 0, bytesRead + 1);
+		offset = iIdatCstream.getOffset();
+		if (offset < 0)
+			throw new PngjExceptionInternal("bad offset ??" + offset);
+		if (maxTotalBytesRead > 0 && offset >= maxTotalBytesRead)
+			throw new PngjInputException("Reading IDAT: Maximum total bytes to read exceeeded: " + maxTotalBytesRead
+					+ " offset:" + offset);
+		rowb[0] = 0;
+		unfilterRow(bytesRead);
+		rowb[0] = rowbfilter[0];
+		if ((rowNum == imgInfo.rows - 1 && !interlaced) || (interlaced && deinterlacer.isAtLastRow()))
+			readLastAndClose();
+		return bytesRead;
+	}
+
+	/**
+	 * Reads all the (remaining) file, skipping the pixels data. This is much
+	 * more efficient that calling readRow(), specially for big files (about 10
+	 * times faster!), because it doesn't even decompress the IDAT stream and
+	 * disables CRC check Use this if you are not interested in reading
+	 * pixels,only metadata.
+	 */
+	public void readSkippingAllRows() {
+		if (firstChunksNotYetRead())
+			readFirstChunks();
+		// we read directly from the compressed stream, we dont decompress nor chec CRC
+		iIdatCstream.disableCrcCheck();
+		allocateBuffers();
+		try {
+			int r;
+			do {
+				r = iIdatCstream.read(rowbfilter, 0, buffersLen);
+			} while (r >= 0);
+		} catch (IOException e) {
+			throw new PngjInputException("error in raw read of IDAT", e);
+		}
+		offset = iIdatCstream.getOffset();
+		if (offset < 0)
+			throw new PngjExceptionInternal("bad offset ??" + offset);
+		if (maxTotalBytesRead > 0 && offset >= maxTotalBytesRead)
+			throw new PngjInputException("Reading IDAT: Maximum total bytes to read exceeeded: " + maxTotalBytesRead
+					+ " offset:" + offset);
+		readLastAndClose();
+	}
+
+	/**
+	 * Set total maximum bytes to read (0: unlimited; default: 200MB). <br>
+	 * These are the bytes read (not loaded) in the input stream. If exceeded,
+	 * an exception will be thrown.
+	 */
+	public void setMaxTotalBytesRead(long maxTotalBytesToRead) {
+		this.maxTotalBytesRead = maxTotalBytesToRead;
+	}
+
+	/**
+	 * @return Total maximum bytes to read.
+	 */
+	public long getMaxTotalBytesRead() {
+		return maxTotalBytesRead;
+	}
+
+	/**
+	 * Set total maximum bytes to load from ancillary chunks (0: unlimited;
+	 * default: 5Mb).<br>
+	 * If exceeded, some chunks will be skipped
+	 */
+	public void setMaxBytesMetadata(int maxBytesChunksToLoad) {
+		this.maxBytesMetadata = maxBytesChunksToLoad;
+	}
+
+	/**
+	 * @return Total maximum bytes to load from ancillary ckunks.
+	 */
+	public int getMaxBytesMetadata() {
+		return maxBytesMetadata;
+	}
+
+	/**
+	 * Set maximum size in bytes for individual ancillary chunks (0: unlimited;
+	 * default: 2MB). <br>
+	 * Chunks exceeding this length will be skipped (the CRC will not be
+	 * checked) and the chunk will be saved as a PngChunkSkipped object. See
+	 * also setSkipChunkIds
+	 */
+	public void setSkipChunkMaxSize(int skipChunksBySize) {
+		this.skipChunkMaxSize = skipChunksBySize;
+	}
+
+	/**
+	 * @return maximum size in bytes for individual ancillary chunks.
+	 */
+	public int getSkipChunkMaxSize() {
+		return skipChunkMaxSize;
+	}
+
+	/**
+	 * Chunks ids to be skipped. <br>
+	 * These chunks will be skipped (the CRC will not be checked) and the chunk
+	 * will be saved as a PngChunkSkipped object. See also setSkipChunkMaxSize
+	 */
+	public void setSkipChunkIds(String[] skipChunksById) {
+		this.skipChunkIds = skipChunksById == null ? new String[] {} : skipChunksById;
+	}
+
+	/**
+	 * @return Chunk-IDs to be skipped.
+	 */
+	public String[] getSkipChunkIds() {
+		return skipChunkIds;
+	}
+
+	/**
+	 * if true, input stream will be closed after ending read
+	 * <p>
+	 * default=true
+	 */
+	public void setShouldCloseStream(boolean shouldCloseStream) {
+		this.shouldCloseStream = shouldCloseStream;
+	}
+
+	/**
+	 * Normally this does nothing, but it can be used to force a premature
+	 * closing. Its recommended practice to call it after reading the image
+	 * pixels.
+	 */
+	public void end() {
+		if (currentChunkGroup < ChunksList.CHUNK_GROUP_6_END)
+			close();
+	}
+
+	/**
+	 * Interlaced PNG is accepted -though not welcomed- now...
+	 */
+	public boolean isInterlaced() {
+		return interlaced;
+	}
+
+	/**
+	 * set/unset "unpackedMode"<br>
+	 * If false (default) packed types (bitdepth=1,2 or 4) will keep several
+	 * samples packed in one element (byte or int) <br>
+	 * If true, samples will be unpacked on reading, and each element in the
+	 * scanline will be sample. This implies more processing and memory, but
+	 * it's the most efficient option if you intend to read individual pixels. <br>
+	 * This option should only be set before start reading.
+	 *
+	 * @param unPackedMode
+	 */
+	public void setUnpackedMode(boolean unPackedMode) {
+		this.unpackedMode = unPackedMode;
+	}
+
+	/**
+	 * @see PngReader#setUnpackedMode(boolean)
+	 */
+	public boolean isUnpackedMode() {
+		return unpackedMode;
+	}
+
+	/**
+	 * Tries to reuse the allocated buffers from other already used PngReader
+	 * object. This will have no effect if the buffers are smaller than necessary.
+	 * It also reuses the inflater.
+	 *
+	 * @param other A PngReader that has already finished reading pixels. Can be null.
+	 */
+	public void reuseBuffersFrom(PngReader other) {
+		if(other==null) return;
+		if (other.currentChunkGroup < ChunksList.CHUNK_GROUP_5_AFTERIDAT)
+			throw new PngjInputException("PngReader to be reused have not yet ended reading pixels");
+		if (other.rowbfilter != null && other.rowbfilter.length >= buffersLen) {
+			rowbfilter = other.rowbfilter;
+			rowb = other.rowb;
+			rowbprev = other.rowbprev;
+		}
+		inflater = other.inflater;
+	}
+
+	/**
+	 * Disables the CRC integrity check in IDAT chunks and ancillary chunks,
+	 * this gives a slight increase in reading speed for big files
+	 */
+	public void setCrcCheckDisabled() {
+		crcEnabled = false;
+	}
+
+	/**
+	 * Just for testing. TO be called after ending reading, only if
+	 * initCrctest() was called before start
+	 *
+	 * @return CRC of the raw pixels values
+	 */
+	long getCrctestVal() {
+		return crctest.getValue();
+	}
+
+	/**
+	 * Inits CRC object and enables CRC calculation
+	 */
+	void initCrctest() {
+		this.crctest = new CRC32();
+	}
+
+	/**
+	 * Basic info, for debugging.
+	 */
+	@Override
+	public String toString() { // basic info
+		return "filename=" + filename + " " + imgInfo.toString();
+	}
+}