Java example source code file (PNGImageReader.java)
The PNGImageReader.java Java example source code
/*
* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package com.sun.imageio.plugins.png;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.color.ColorSpace;
import java.awt.image.BufferedImage;
import java.awt.image.DataBuffer;
import java.awt.image.DataBufferByte;
import java.awt.image.DataBufferUShort;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;
import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.EOFException;
import java.io.InputStream;
import java.io.IOException;
import java.io.SequenceInputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.zip.Inflater;
import java.util.zip.InflaterInputStream;
import javax.imageio.IIOException;
import javax.imageio.ImageReader;
import javax.imageio.ImageReadParam;
import javax.imageio.ImageTypeSpecifier;
import javax.imageio.metadata.IIOMetadata;
import javax.imageio.spi.ImageReaderSpi;
import javax.imageio.stream.ImageInputStream;
import com.sun.imageio.plugins.common.InputStreamAdapter;
import com.sun.imageio.plugins.common.ReaderUtil;
import com.sun.imageio.plugins.common.SubImageInputStream;
import java.io.ByteArrayOutputStream;
import sun.awt.image.ByteInterleavedRaster;
class PNGImageDataEnumeration implements Enumeration<InputStream> {
boolean firstTime = true;
ImageInputStream stream;
int length;
public PNGImageDataEnumeration(ImageInputStream stream)
throws IOException {
this.stream = stream;
this.length = stream.readInt();
int type = stream.readInt(); // skip chunk type
}
public InputStream nextElement() {
try {
firstTime = false;
ImageInputStream iis = new SubImageInputStream(stream, length);
return new InputStreamAdapter(iis);
} catch (IOException e) {
return null;
}
}
public boolean hasMoreElements() {
if (firstTime) {
return true;
}
try {
int crc = stream.readInt();
this.length = stream.readInt();
int type = stream.readInt();
if (type == PNGImageReader.IDAT_TYPE) {
return true;
} else {
return false;
}
} catch (IOException e) {
return false;
}
}
}
public class PNGImageReader extends ImageReader {
/*
* Note: The following chunk type constants are autogenerated. Each
* one is derived from the ASCII values of its 4-character name. For
* example, IHDR_TYPE is calculated as follows:
* ('I' << 24) | ('H' << 16) | ('D' << 8) | 'R'
*/
// Critical chunks
static final int IHDR_TYPE = 0x49484452;
static final int PLTE_TYPE = 0x504c5445;
static final int IDAT_TYPE = 0x49444154;
static final int IEND_TYPE = 0x49454e44;
// Ancillary chunks
static final int bKGD_TYPE = 0x624b4744;
static final int cHRM_TYPE = 0x6348524d;
static final int gAMA_TYPE = 0x67414d41;
static final int hIST_TYPE = 0x68495354;
static final int iCCP_TYPE = 0x69434350;
static final int iTXt_TYPE = 0x69545874;
static final int pHYs_TYPE = 0x70485973;
static final int sBIT_TYPE = 0x73424954;
static final int sPLT_TYPE = 0x73504c54;
static final int sRGB_TYPE = 0x73524742;
static final int tEXt_TYPE = 0x74455874;
static final int tIME_TYPE = 0x74494d45;
static final int tRNS_TYPE = 0x74524e53;
static final int zTXt_TYPE = 0x7a545874;
static final int PNG_COLOR_GRAY = 0;
static final int PNG_COLOR_RGB = 2;
static final int PNG_COLOR_PALETTE = 3;
static final int PNG_COLOR_GRAY_ALPHA = 4;
static final int PNG_COLOR_RGB_ALPHA = 6;
// The number of bands by PNG color type
static final int[] inputBandsForColorType = {
1, // gray
-1, // unused
3, // rgb
1, // palette
2, // gray + alpha
-1, // unused
4 // rgb + alpha
};
static final int PNG_FILTER_NONE = 0;
static final int PNG_FILTER_SUB = 1;
static final int PNG_FILTER_UP = 2;
static final int PNG_FILTER_AVERAGE = 3;
static final int PNG_FILTER_PAETH = 4;
static final int[] adam7XOffset = { 0, 4, 0, 2, 0, 1, 0 };
static final int[] adam7YOffset = { 0, 0, 4, 0, 2, 0, 1 };
static final int[] adam7XSubsampling = { 8, 8, 4, 4, 2, 2, 1, 1 };
static final int[] adam7YSubsampling = { 8, 8, 8, 4, 4, 2, 2, 1 };
private static final boolean debug = true;
ImageInputStream stream = null;
boolean gotHeader = false;
boolean gotMetadata = false;
ImageReadParam lastParam = null;
long imageStartPosition = -1L;
Rectangle sourceRegion = null;
int sourceXSubsampling = -1;
int sourceYSubsampling = -1;
int sourceMinProgressivePass = 0;
int sourceMaxProgressivePass = 6;
int[] sourceBands = null;
int[] destinationBands = null;
Point destinationOffset = new Point(0, 0);
PNGMetadata metadata = new PNGMetadata();
DataInputStream pixelStream = null;
BufferedImage theImage = null;
// The number of source pixels processed
int pixelsDone = 0;
// The total number of pixels in the source image
int totalPixels;
public PNGImageReader(ImageReaderSpi originatingProvider) {
super(originatingProvider);
}
public void setInput(Object input,
boolean seekForwardOnly,
boolean ignoreMetadata) {
super.setInput(input, seekForwardOnly, ignoreMetadata);
this.stream = (ImageInputStream)input; // Always works
// Clear all values based on the previous stream contents
resetStreamSettings();
}
private String readNullTerminatedString(String charset, int maxLen) throws IOException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
int b;
int count = 0;
while ((maxLen > count++) && ((b = stream.read()) != 0)) {
if (b == -1) throw new EOFException();
baos.write(b);
}
return new String(baos.toByteArray(), charset);
}
private void readHeader() throws IIOException {
if (gotHeader) {
return;
}
if (stream == null) {
throw new IllegalStateException("Input source not set!");
}
try {
byte[] signature = new byte[8];
stream.readFully(signature);
if (signature[0] != (byte)137 ||
signature[1] != (byte)80 ||
signature[2] != (byte)78 ||
signature[3] != (byte)71 ||
signature[4] != (byte)13 ||
signature[5] != (byte)10 ||
signature[6] != (byte)26 ||
signature[7] != (byte)10) {
throw new IIOException("Bad PNG signature!");
}
int IHDR_length = stream.readInt();
if (IHDR_length != 13) {
throw new IIOException("Bad length for IHDR chunk!");
}
int IHDR_type = stream.readInt();
if (IHDR_type != IHDR_TYPE) {
throw new IIOException("Bad type for IHDR chunk!");
}
this.metadata = new PNGMetadata();
int width = stream.readInt();
int height = stream.readInt();
// Re-use signature array to bulk-read these unsigned byte values
stream.readFully(signature, 0, 5);
int bitDepth = signature[0] & 0xff;
int colorType = signature[1] & 0xff;
int compressionMethod = signature[2] & 0xff;
int filterMethod = signature[3] & 0xff;
int interlaceMethod = signature[4] & 0xff;
// Skip IHDR CRC
stream.skipBytes(4);
stream.flushBefore(stream.getStreamPosition());
if (width == 0) {
throw new IIOException("Image width == 0!");
}
if (height == 0) {
throw new IIOException("Image height == 0!");
}
if (bitDepth != 1 && bitDepth != 2 && bitDepth != 4 &&
bitDepth != 8 && bitDepth != 16) {
throw new IIOException("Bit depth must be 1, 2, 4, 8, or 16!");
}
if (colorType != 0 && colorType != 2 && colorType != 3 &&
colorType != 4 && colorType != 6) {
throw new IIOException("Color type must be 0, 2, 3, 4, or 6!");
}
if (colorType == PNG_COLOR_PALETTE && bitDepth == 16) {
throw new IIOException("Bad color type/bit depth combination!");
}
if ((colorType == PNG_COLOR_RGB ||
colorType == PNG_COLOR_RGB_ALPHA ||
colorType == PNG_COLOR_GRAY_ALPHA) &&
(bitDepth != 8 && bitDepth != 16)) {
throw new IIOException("Bad color type/bit depth combination!");
}
if (compressionMethod != 0) {
throw new IIOException("Unknown compression method (not 0)!");
}
if (filterMethod != 0) {
throw new IIOException("Unknown filter method (not 0)!");
}
if (interlaceMethod != 0 && interlaceMethod != 1) {
throw new IIOException("Unknown interlace method (not 0 or 1)!");
}
metadata.IHDR_present = true;
metadata.IHDR_width = width;
metadata.IHDR_height = height;
metadata.IHDR_bitDepth = bitDepth;
metadata.IHDR_colorType = colorType;
metadata.IHDR_compressionMethod = compressionMethod;
metadata.IHDR_filterMethod = filterMethod;
metadata.IHDR_interlaceMethod = interlaceMethod;
gotHeader = true;
} catch (IOException e) {
throw new IIOException("I/O error reading PNG header!", e);
}
}
private void parse_PLTE_chunk(int chunkLength) throws IOException {
if (metadata.PLTE_present) {
processWarningOccurred(
"A PNG image may not contain more than one PLTE chunk.\n" +
"The chunk wil be ignored.");
return;
} else if (metadata.IHDR_colorType == PNG_COLOR_GRAY ||
metadata.IHDR_colorType == PNG_COLOR_GRAY_ALPHA) {
processWarningOccurred(
"A PNG gray or gray alpha image cannot have a PLTE chunk.\n" +
"The chunk wil be ignored.");
return;
}
byte[] palette = new byte[chunkLength];
stream.readFully(palette);
int numEntries = chunkLength/3;
if (metadata.IHDR_colorType == PNG_COLOR_PALETTE) {
int maxEntries = 1 << metadata.IHDR_bitDepth;
if (numEntries > maxEntries) {
processWarningOccurred(
"PLTE chunk contains too many entries for bit depth, ignoring extras.");
numEntries = maxEntries;
}
numEntries = Math.min(numEntries, maxEntries);
}
// Round array sizes up to 2^2^n
int paletteEntries;
if (numEntries > 16) {
paletteEntries = 256;
} else if (numEntries > 4) {
paletteEntries = 16;
} else if (numEntries > 2) {
paletteEntries = 4;
} else {
paletteEntries = 2;
}
metadata.PLTE_present = true;
metadata.PLTE_red = new byte[paletteEntries];
metadata.PLTE_green = new byte[paletteEntries];
metadata.PLTE_blue = new byte[paletteEntries];
int index = 0;
for (int i = 0; i < numEntries; i++) {
metadata.PLTE_red[i] = palette[index++];
metadata.PLTE_green[i] = palette[index++];
metadata.PLTE_blue[i] = palette[index++];
}
}
private void parse_bKGD_chunk() throws IOException {
if (metadata.IHDR_colorType == PNG_COLOR_PALETTE) {
metadata.bKGD_colorType = PNG_COLOR_PALETTE;
metadata.bKGD_index = stream.readUnsignedByte();
} else if (metadata.IHDR_colorType == PNG_COLOR_GRAY ||
metadata.IHDR_colorType == PNG_COLOR_GRAY_ALPHA) {
metadata.bKGD_colorType = PNG_COLOR_GRAY;
metadata.bKGD_gray = stream.readUnsignedShort();
} else { // RGB or RGB_ALPHA
metadata.bKGD_colorType = PNG_COLOR_RGB;
metadata.bKGD_red = stream.readUnsignedShort();
metadata.bKGD_green = stream.readUnsignedShort();
metadata.bKGD_blue = stream.readUnsignedShort();
}
metadata.bKGD_present = true;
}
private void parse_cHRM_chunk() throws IOException {
metadata.cHRM_whitePointX = stream.readInt();
metadata.cHRM_whitePointY = stream.readInt();
metadata.cHRM_redX = stream.readInt();
metadata.cHRM_redY = stream.readInt();
metadata.cHRM_greenX = stream.readInt();
metadata.cHRM_greenY = stream.readInt();
metadata.cHRM_blueX = stream.readInt();
metadata.cHRM_blueY = stream.readInt();
metadata.cHRM_present = true;
}
private void parse_gAMA_chunk() throws IOException {
int gamma = stream.readInt();
metadata.gAMA_gamma = gamma;
metadata.gAMA_present = true;
}
private void parse_hIST_chunk(int chunkLength) throws IOException,
IIOException
{
if (!metadata.PLTE_present) {
throw new IIOException("hIST chunk without prior PLTE chunk!");
}
/* According to PNG specification length of
* hIST chunk is specified in bytes and
* hIST chunk consists of 2 byte elements
* (so we expect length is even).
*/
metadata.hIST_histogram = new char[chunkLength/2];
stream.readFully(metadata.hIST_histogram,
0, metadata.hIST_histogram.length);
metadata.hIST_present = true;
}
private void parse_iCCP_chunk(int chunkLength) throws IOException {
String keyword = readNullTerminatedString("ISO-8859-1", 80);
metadata.iCCP_profileName = keyword;
metadata.iCCP_compressionMethod = stream.readUnsignedByte();
byte[] compressedProfile =
new byte[chunkLength - keyword.length() - 2];
stream.readFully(compressedProfile);
metadata.iCCP_compressedProfile = compressedProfile;
metadata.iCCP_present = true;
}
private void parse_iTXt_chunk(int chunkLength) throws IOException {
long chunkStart = stream.getStreamPosition();
String keyword = readNullTerminatedString("ISO-8859-1", 80);
metadata.iTXt_keyword.add(keyword);
int compressionFlag = stream.readUnsignedByte();
metadata.iTXt_compressionFlag.add(Boolean.valueOf(compressionFlag == 1));
int compressionMethod = stream.readUnsignedByte();
metadata.iTXt_compressionMethod.add(Integer.valueOf(compressionMethod));
String languageTag = readNullTerminatedString("UTF8", 80);
metadata.iTXt_languageTag.add(languageTag);
long pos = stream.getStreamPosition();
int maxLen = (int)(chunkStart + chunkLength - pos);
String translatedKeyword =
readNullTerminatedString("UTF8", maxLen);
metadata.iTXt_translatedKeyword.add(translatedKeyword);
String text;
pos = stream.getStreamPosition();
byte[] b = new byte[(int)(chunkStart + chunkLength - pos)];
stream.readFully(b);
if (compressionFlag == 1) { // Decompress the text
text = new String(inflate(b), "UTF8");
} else {
text = new String(b, "UTF8");
}
metadata.iTXt_text.add(text);
}
private void parse_pHYs_chunk() throws IOException {
metadata.pHYs_pixelsPerUnitXAxis = stream.readInt();
metadata.pHYs_pixelsPerUnitYAxis = stream.readInt();
metadata.pHYs_unitSpecifier = stream.readUnsignedByte();
metadata.pHYs_present = true;
}
private void parse_sBIT_chunk() throws IOException {
int colorType = metadata.IHDR_colorType;
if (colorType == PNG_COLOR_GRAY ||
colorType == PNG_COLOR_GRAY_ALPHA) {
metadata.sBIT_grayBits = stream.readUnsignedByte();
} else if (colorType == PNG_COLOR_RGB ||
colorType == PNG_COLOR_PALETTE ||
colorType == PNG_COLOR_RGB_ALPHA) {
metadata.sBIT_redBits = stream.readUnsignedByte();
metadata.sBIT_greenBits = stream.readUnsignedByte();
metadata.sBIT_blueBits = stream.readUnsignedByte();
}
if (colorType == PNG_COLOR_GRAY_ALPHA ||
colorType == PNG_COLOR_RGB_ALPHA) {
metadata.sBIT_alphaBits = stream.readUnsignedByte();
}
metadata.sBIT_colorType = colorType;
metadata.sBIT_present = true;
}
private void parse_sPLT_chunk(int chunkLength)
throws IOException, IIOException {
metadata.sPLT_paletteName = readNullTerminatedString("ISO-8859-1", 80);
chunkLength -= metadata.sPLT_paletteName.length() + 1;
int sampleDepth = stream.readUnsignedByte();
metadata.sPLT_sampleDepth = sampleDepth;
int numEntries = chunkLength/(4*(sampleDepth/8) + 2);
metadata.sPLT_red = new int[numEntries];
metadata.sPLT_green = new int[numEntries];
metadata.sPLT_blue = new int[numEntries];
metadata.sPLT_alpha = new int[numEntries];
metadata.sPLT_frequency = new int[numEntries];
if (sampleDepth == 8) {
for (int i = 0; i < numEntries; i++) {
metadata.sPLT_red[i] = stream.readUnsignedByte();
metadata.sPLT_green[i] = stream.readUnsignedByte();
metadata.sPLT_blue[i] = stream.readUnsignedByte();
metadata.sPLT_alpha[i] = stream.readUnsignedByte();
metadata.sPLT_frequency[i] = stream.readUnsignedShort();
}
} else if (sampleDepth == 16) {
for (int i = 0; i < numEntries; i++) {
metadata.sPLT_red[i] = stream.readUnsignedShort();
metadata.sPLT_green[i] = stream.readUnsignedShort();
metadata.sPLT_blue[i] = stream.readUnsignedShort();
metadata.sPLT_alpha[i] = stream.readUnsignedShort();
metadata.sPLT_frequency[i] = stream.readUnsignedShort();
}
} else {
throw new IIOException("sPLT sample depth not 8 or 16!");
}
metadata.sPLT_present = true;
}
private void parse_sRGB_chunk() throws IOException {
metadata.sRGB_renderingIntent = stream.readUnsignedByte();
metadata.sRGB_present = true;
}
private void parse_tEXt_chunk(int chunkLength) throws IOException {
String keyword = readNullTerminatedString("ISO-8859-1", 80);
metadata.tEXt_keyword.add(keyword);
byte[] b = new byte[chunkLength - keyword.length() - 1];
stream.readFully(b);
metadata.tEXt_text.add(new String(b, "ISO-8859-1"));
}
private void parse_tIME_chunk() throws IOException {
metadata.tIME_year = stream.readUnsignedShort();
metadata.tIME_month = stream.readUnsignedByte();
metadata.tIME_day = stream.readUnsignedByte();
metadata.tIME_hour = stream.readUnsignedByte();
metadata.tIME_minute = stream.readUnsignedByte();
metadata.tIME_second = stream.readUnsignedByte();
metadata.tIME_present = true;
}
private void parse_tRNS_chunk(int chunkLength) throws IOException {
int colorType = metadata.IHDR_colorType;
if (colorType == PNG_COLOR_PALETTE) {
if (!metadata.PLTE_present) {
processWarningOccurred(
"tRNS chunk without prior PLTE chunk, ignoring it.");
return;
}
// Alpha table may have fewer entries than RGB palette
int maxEntries = metadata.PLTE_red.length;
int numEntries = chunkLength;
if (numEntries > maxEntries) {
processWarningOccurred(
"tRNS chunk has more entries than prior PLTE chunk, ignoring extras.");
numEntries = maxEntries;
}
metadata.tRNS_alpha = new byte[numEntries];
metadata.tRNS_colorType = PNG_COLOR_PALETTE;
stream.read(metadata.tRNS_alpha, 0, numEntries);
stream.skipBytes(chunkLength - numEntries);
} else if (colorType == PNG_COLOR_GRAY) {
if (chunkLength != 2) {
processWarningOccurred(
"tRNS chunk for gray image must have length 2, ignoring chunk.");
stream.skipBytes(chunkLength);
return;
}
metadata.tRNS_gray = stream.readUnsignedShort();
metadata.tRNS_colorType = PNG_COLOR_GRAY;
} else if (colorType == PNG_COLOR_RGB) {
if (chunkLength != 6) {
processWarningOccurred(
"tRNS chunk for RGB image must have length 6, ignoring chunk.");
stream.skipBytes(chunkLength);
return;
}
metadata.tRNS_red = stream.readUnsignedShort();
metadata.tRNS_green = stream.readUnsignedShort();
metadata.tRNS_blue = stream.readUnsignedShort();
metadata.tRNS_colorType = PNG_COLOR_RGB;
} else {
processWarningOccurred(
"Gray+Alpha and RGBS images may not have a tRNS chunk, ignoring it.");
return;
}
metadata.tRNS_present = true;
}
private static byte[] inflate(byte[] b) throws IOException {
InputStream bais = new ByteArrayInputStream(b);
InputStream iis = new InflaterInputStream(bais);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
int c;
try {
while ((c = iis.read()) != -1) {
baos.write(c);
}
} finally {
iis.close();
}
return baos.toByteArray();
}
private void parse_zTXt_chunk(int chunkLength) throws IOException {
String keyword = readNullTerminatedString("ISO-8859-1", 80);
metadata.zTXt_keyword.add(keyword);
int method = stream.readUnsignedByte();
metadata.zTXt_compressionMethod.add(new Integer(method));
byte[] b = new byte[chunkLength - keyword.length() - 2];
stream.readFully(b);
metadata.zTXt_text.add(new String(inflate(b), "ISO-8859-1"));
}
private void readMetadata() throws IIOException {
if (gotMetadata) {
return;
}
readHeader();
/*
* Optimization: We can skip the remaining metadata if the
* ignoreMetadata flag is set, and only if this is not a palette
* image (in that case, we need to read the metadata to get the
* tRNS chunk, which is needed for the getImageTypes() method).
*/
int colorType = metadata.IHDR_colorType;
if (ignoreMetadata && colorType != PNG_COLOR_PALETTE) {
try {
while (true) {
int chunkLength = stream.readInt();
int chunkType = stream.readInt();
if (chunkType == IDAT_TYPE) {
// We've reached the image data
stream.skipBytes(-8);
imageStartPosition = stream.getStreamPosition();
break;
} else {
// Skip the chunk plus the 4 CRC bytes that follow
stream.skipBytes(chunkLength + 4);
}
}
} catch (IOException e) {
throw new IIOException("Error skipping PNG metadata", e);
}
gotMetadata = true;
return;
}
try {
loop: while (true) {
int chunkLength = stream.readInt();
int chunkType = stream.readInt();
int chunkCRC;
// verify the chunk length
if (chunkLength < 0) {
throw new IIOException("Invalid chunk lenght " + chunkLength);
};
try {
stream.mark();
stream.seek(stream.getStreamPosition() + chunkLength);
chunkCRC = stream.readInt();
stream.reset();
} catch (IOException e) {
throw new IIOException("Invalid chunk length " + chunkLength);
}
switch (chunkType) {
case IDAT_TYPE:
// If chunk type is 'IDAT', we've reached the image data.
stream.skipBytes(-8);
imageStartPosition = stream.getStreamPosition();
break loop;
case PLTE_TYPE:
parse_PLTE_chunk(chunkLength);
break;
case bKGD_TYPE:
parse_bKGD_chunk();
break;
case cHRM_TYPE:
parse_cHRM_chunk();
break;
case gAMA_TYPE:
parse_gAMA_chunk();
break;
case hIST_TYPE:
parse_hIST_chunk(chunkLength);
break;
case iCCP_TYPE:
parse_iCCP_chunk(chunkLength);
break;
case iTXt_TYPE:
parse_iTXt_chunk(chunkLength);
break;
case pHYs_TYPE:
parse_pHYs_chunk();
break;
case sBIT_TYPE:
parse_sBIT_chunk();
break;
case sPLT_TYPE:
parse_sPLT_chunk(chunkLength);
break;
case sRGB_TYPE:
parse_sRGB_chunk();
break;
case tEXt_TYPE:
parse_tEXt_chunk(chunkLength);
break;
case tIME_TYPE:
parse_tIME_chunk();
break;
case tRNS_TYPE:
parse_tRNS_chunk(chunkLength);
break;
case zTXt_TYPE:
parse_zTXt_chunk(chunkLength);
break;
default:
// Read an unknown chunk
byte[] b = new byte[chunkLength];
stream.readFully(b);
StringBuilder chunkName = new StringBuilder(4);
chunkName.append((char)(chunkType >>> 24));
chunkName.append((char)((chunkType >> 16) & 0xff));
chunkName.append((char)((chunkType >> 8) & 0xff));
chunkName.append((char)(chunkType & 0xff));
int ancillaryBit = chunkType >>> 28;
if (ancillaryBit == 0) {
processWarningOccurred(
"Encountered unknown chunk with critical bit set!");
}
metadata.unknownChunkType.add(chunkName.toString());
metadata.unknownChunkData.add(b);
break;
}
// double check whether all chunk data were consumed
if (chunkCRC != stream.readInt()) {
throw new IIOException("Failed to read a chunk of type " +
chunkType);
}
stream.flushBefore(stream.getStreamPosition());
}
} catch (IOException e) {
throw new IIOException("Error reading PNG metadata", e);
}
gotMetadata = true;
}
// Data filtering methods
private static void decodeSubFilter(byte[] curr, int coff, int count,
int bpp) {
for (int i = bpp; i < count; i++) {
int val;
val = curr[i + coff] & 0xff;
val += curr[i + coff - bpp] & 0xff;
curr[i + coff] = (byte)val;
}
}
private static void decodeUpFilter(byte[] curr, int coff,
byte[] prev, int poff,
int count) {
for (int i = 0; i < count; i++) {
int raw = curr[i + coff] & 0xff;
int prior = prev[i + poff] & 0xff;
curr[i + coff] = (byte)(raw + prior);
}
}
private static void decodeAverageFilter(byte[] curr, int coff,
byte[] prev, int poff,
int count, int bpp) {
int raw, priorPixel, priorRow;
for (int i = 0; i < bpp; i++) {
raw = curr[i + coff] & 0xff;
priorRow = prev[i + poff] & 0xff;
curr[i + coff] = (byte)(raw + priorRow/2);
}
for (int i = bpp; i < count; i++) {
raw = curr[i + coff] & 0xff;
priorPixel = curr[i + coff - bpp] & 0xff;
priorRow = prev[i + poff] & 0xff;
curr[i + coff] = (byte)(raw + (priorPixel + priorRow)/2);
}
}
private static int paethPredictor(int a, int b, int c) {
int p = a + b - c;
int pa = Math.abs(p - a);
int pb = Math.abs(p - b);
int pc = Math.abs(p - c);
if ((pa <= pb) && (pa <= pc)) {
return a;
} else if (pb <= pc) {
return b;
} else {
return c;
}
}
private static void decodePaethFilter(byte[] curr, int coff,
byte[] prev, int poff,
int count, int bpp) {
int raw, priorPixel, priorRow, priorRowPixel;
for (int i = 0; i < bpp; i++) {
raw = curr[i + coff] & 0xff;
priorRow = prev[i + poff] & 0xff;
curr[i + coff] = (byte)(raw + priorRow);
}
for (int i = bpp; i < count; i++) {
raw = curr[i + coff] & 0xff;
priorPixel = curr[i + coff - bpp] & 0xff;
priorRow = prev[i + poff] & 0xff;
priorRowPixel = prev[i + poff - bpp] & 0xff;
curr[i + coff] = (byte)(raw + paethPredictor(priorPixel,
priorRow,
priorRowPixel));
}
}
private static final int[][] bandOffsets = {
null,
{ 0 }, // G
{ 0, 1 }, // GA in GA order
{ 0, 1, 2 }, // RGB in RGB order
{ 0, 1, 2, 3 } // RGBA in RGBA order
};
private WritableRaster createRaster(int width, int height, int bands,
int scanlineStride,
int bitDepth) {
DataBuffer dataBuffer;
WritableRaster ras = null;
Point origin = new Point(0, 0);
if ((bitDepth < 8) && (bands == 1)) {
dataBuffer = new DataBufferByte(height*scanlineStride);
ras = Raster.createPackedRaster(dataBuffer,
width, height,
bitDepth,
origin);
} else if (bitDepth <= 8) {
dataBuffer = new DataBufferByte(height*scanlineStride);
ras = Raster.createInterleavedRaster(dataBuffer,
width, height,
scanlineStride,
bands,
bandOffsets[bands],
origin);
} else {
dataBuffer = new DataBufferUShort(height*scanlineStride);
ras = Raster.createInterleavedRaster(dataBuffer,
width, height,
scanlineStride,
bands,
bandOffsets[bands],
origin);
}
return ras;
}
private void skipPass(int passWidth, int passHeight)
throws IOException, IIOException {
if ((passWidth == 0) || (passHeight == 0)) {
return;
}
int inputBands = inputBandsForColorType[metadata.IHDR_colorType];
int bytesPerRow = (inputBands*passWidth*metadata.IHDR_bitDepth + 7)/8;
// Read the image row-by-row
for (int srcY = 0; srcY < passHeight; srcY++) {
// Skip filter byte and the remaining row bytes
pixelStream.skipBytes(1 + bytesPerRow);
// If read has been aborted, just return
// processReadAborted will be called later
if (abortRequested()) {
return;
}
}
}
private void updateImageProgress(int newPixels) {
pixelsDone += newPixels;
processImageProgress(100.0F*pixelsDone/totalPixels);
}
private void decodePass(int passNum,
int xStart, int yStart,
int xStep, int yStep,
int passWidth, int passHeight) throws IOException {
if ((passWidth == 0) || (passHeight == 0)) {
return;
}
WritableRaster imRas = theImage.getWritableTile(0, 0);
int dstMinX = imRas.getMinX();
int dstMaxX = dstMinX + imRas.getWidth() - 1;
int dstMinY = imRas.getMinY();
int dstMaxY = dstMinY + imRas.getHeight() - 1;
// Determine which pixels will be updated in this pass
int[] vals =
ReaderUtil.computeUpdatedPixels(sourceRegion,
destinationOffset,
dstMinX, dstMinY,
dstMaxX, dstMaxY,
sourceXSubsampling,
sourceYSubsampling,
xStart, yStart,
passWidth, passHeight,
xStep, yStep);
int updateMinX = vals[0];
int updateMinY = vals[1];
int updateWidth = vals[2];
int updateXStep = vals[4];
int updateYStep = vals[5];
int bitDepth = metadata.IHDR_bitDepth;
int inputBands = inputBandsForColorType[metadata.IHDR_colorType];
int bytesPerPixel = (bitDepth == 16) ? 2 : 1;
bytesPerPixel *= inputBands;
int bytesPerRow = (inputBands*passWidth*bitDepth + 7)/8;
int eltsPerRow = (bitDepth == 16) ? bytesPerRow/2 : bytesPerRow;
// If no pixels need updating, just skip the input data
if (updateWidth == 0) {
for (int srcY = 0; srcY < passHeight; srcY++) {
// Update count of pixels read
updateImageProgress(passWidth);
// Skip filter byte and the remaining row bytes
pixelStream.skipBytes(1 + bytesPerRow);
}
return;
}
// Backwards map from destination pixels
// (dstX = updateMinX + k*updateXStep)
// to source pixels (sourceX), and then
// to offset and skip in passRow (srcX and srcXStep)
int sourceX =
(updateMinX - destinationOffset.x)*sourceXSubsampling +
sourceRegion.x;
int srcX = (sourceX - xStart)/xStep;
// Compute the step factor in the source
int srcXStep = updateXStep*sourceXSubsampling/xStep;
byte[] byteData = null;
short[] shortData = null;
byte[] curr = new byte[bytesPerRow];
byte[] prior = new byte[bytesPerRow];
// Create a 1-row tall Raster to hold the data
WritableRaster passRow = createRaster(passWidth, 1, inputBands,
eltsPerRow,
bitDepth);
// Create an array suitable for holding one pixel
int[] ps = passRow.getPixel(0, 0, (int[])null);
DataBuffer dataBuffer = passRow.getDataBuffer();
int type = dataBuffer.getDataType();
if (type == DataBuffer.TYPE_BYTE) {
byteData = ((DataBufferByte)dataBuffer).getData();
} else {
shortData = ((DataBufferUShort)dataBuffer).getData();
}
processPassStarted(theImage,
passNum,
sourceMinProgressivePass,
sourceMaxProgressivePass,
updateMinX, updateMinY,
updateXStep, updateYStep,
destinationBands);
// Handle source and destination bands
if (sourceBands != null) {
passRow = passRow.createWritableChild(0, 0,
passRow.getWidth(), 1,
0, 0,
sourceBands);
}
if (destinationBands != null) {
imRas = imRas.createWritableChild(0, 0,
imRas.getWidth(),
imRas.getHeight(),
0, 0,
destinationBands);
}
// Determine if all of the relevant output bands have the
// same bit depth as the source data
boolean adjustBitDepths = false;
int[] outputSampleSize = imRas.getSampleModel().getSampleSize();
int numBands = outputSampleSize.length;
for (int b = 0; b < numBands; b++) {
if (outputSampleSize[b] != bitDepth) {
adjustBitDepths = true;
break;
}
}
// If the bit depths differ, create a lookup table per band to perform
// the conversion
int[][] scale = null;
if (adjustBitDepths) {
int maxInSample = (1 << bitDepth) - 1;
int halfMaxInSample = maxInSample/2;
scale = new int[numBands][];
for (int b = 0; b < numBands; b++) {
int maxOutSample = (1 << outputSampleSize[b]) - 1;
scale[b] = new int[maxInSample + 1];
for (int s = 0; s <= maxInSample; s++) {
scale[b][s] =
(s*maxOutSample + halfMaxInSample)/maxInSample;
}
}
}
// Limit passRow to relevant area for the case where we
// will can setRect to copy a contiguous span
boolean useSetRect = srcXStep == 1 &&
updateXStep == 1 &&
!adjustBitDepths &&
(imRas instanceof ByteInterleavedRaster);
if (useSetRect) {
passRow = passRow.createWritableChild(srcX, 0,
updateWidth, 1,
0, 0,
null);
}
// Decode the (sub)image row-by-row
for (int srcY = 0; srcY < passHeight; srcY++) {
// Update count of pixels read
updateImageProgress(passWidth);
// Read the filter type byte and a row of data
int filter = pixelStream.read();
try {
// Swap curr and prior
byte[] tmp = prior;
prior = curr;
curr = tmp;
pixelStream.readFully(curr, 0, bytesPerRow);
} catch (java.util.zip.ZipException ze) {
// TODO - throw a more meaningful exception
throw ze;
}
switch (filter) {
case PNG_FILTER_NONE:
break;
case PNG_FILTER_SUB:
decodeSubFilter(curr, 0, bytesPerRow, bytesPerPixel);
break;
case PNG_FILTER_UP:
decodeUpFilter(curr, 0, prior, 0, bytesPerRow);
break;
case PNG_FILTER_AVERAGE:
decodeAverageFilter(curr, 0, prior, 0, bytesPerRow,
bytesPerPixel);
break;
case PNG_FILTER_PAETH:
decodePaethFilter(curr, 0, prior, 0, bytesPerRow,
bytesPerPixel);
break;
default:
throw new IIOException("Unknown row filter type (= " +
filter + ")!");
}
// Copy data into passRow byte by byte
if (bitDepth < 16) {
System.arraycopy(curr, 0, byteData, 0, bytesPerRow);
} else {
int idx = 0;
for (int j = 0; j < eltsPerRow; j++) {
shortData[j] =
(short)((curr[idx] << 8) | (curr[idx + 1] & 0xff));
idx += 2;
}
}
// True Y position in source
int sourceY = srcY*yStep + yStart;
if ((sourceY >= sourceRegion.y) &&
(sourceY < sourceRegion.y + sourceRegion.height) &&
(((sourceY - sourceRegion.y) %
sourceYSubsampling) == 0)) {
int dstY = destinationOffset.y +
(sourceY - sourceRegion.y)/sourceYSubsampling;
if (dstY < dstMinY) {
continue;
}
if (dstY > dstMaxY) {
break;
}
if (useSetRect) {
imRas.setRect(updateMinX, dstY, passRow);
} else {
int newSrcX = srcX;
for (int dstX = updateMinX;
dstX < updateMinX + updateWidth;
dstX += updateXStep) {
passRow.getPixel(newSrcX, 0, ps);
if (adjustBitDepths) {
for (int b = 0; b < numBands; b++) {
ps[b] = scale[b][ps[b]];
}
}
imRas.setPixel(dstX, dstY, ps);
newSrcX += srcXStep;
}
}
processImageUpdate(theImage,
updateMinX, dstY,
updateWidth, 1,
updateXStep, updateYStep,
destinationBands);
// If read has been aborted, just return
// processReadAborted will be called later
if (abortRequested()) {
return;
}
}
}
processPassComplete(theImage);
}
private void decodeImage()
throws IOException, IIOException {
int width = metadata.IHDR_width;
int height = metadata.IHDR_height;
this.pixelsDone = 0;
this.totalPixels = width*height;
clearAbortRequest();
if (metadata.IHDR_interlaceMethod == 0) {
decodePass(0, 0, 0, 1, 1, width, height);
} else {
for (int i = 0; i <= sourceMaxProgressivePass; i++) {
int XOffset = adam7XOffset[i];
int YOffset = adam7YOffset[i];
int XSubsampling = adam7XSubsampling[i];
int YSubsampling = adam7YSubsampling[i];
int xbump = adam7XSubsampling[i + 1] - 1;
int ybump = adam7YSubsampling[i + 1] - 1;
if (i >= sourceMinProgressivePass) {
decodePass(i,
XOffset,
YOffset,
XSubsampling,
YSubsampling,
(width + xbump)/XSubsampling,
(height + ybump)/YSubsampling);
} else {
skipPass((width + xbump)/XSubsampling,
(height + ybump)/YSubsampling);
}
// If read has been aborted, just return
// processReadAborted will be called later
if (abortRequested()) {
return;
}
}
}
}
private void readImage(ImageReadParam param) throws IIOException {
readMetadata();
int width = metadata.IHDR_width;
int height = metadata.IHDR_height;
// Init default values
sourceXSubsampling = 1;
sourceYSubsampling = 1;
sourceMinProgressivePass = 0;
sourceMaxProgressivePass = 6;
sourceBands = null;
destinationBands = null;
destinationOffset = new Point(0, 0);
// If an ImageReadParam is available, get values from it
if (param != null) {
sourceXSubsampling = param.getSourceXSubsampling();
sourceYSubsampling = param.getSourceYSubsampling();
sourceMinProgressivePass =
Math.max(param.getSourceMinProgressivePass(), 0);
sourceMaxProgressivePass =
Math.min(param.getSourceMaxProgressivePass(), 6);
sourceBands = param.getSourceBands();
destinationBands = param.getDestinationBands();
destinationOffset = param.getDestinationOffset();
}
Inflater inf = null;
try {
stream.seek(imageStartPosition);
Enumeration<InputStream> e = new PNGImageDataEnumeration(stream);
InputStream is = new SequenceInputStream(e);
/* InflaterInputStream uses an Inflater instance which consumes
* native (non-GC visible) resources. This is normally implicitly
* freed when the stream is closed. However since the
* InflaterInputStream wraps a client-supplied input stream,
* we cannot close it.
* But the app may depend on GC finalization to close the stream.
* Therefore to ensure timely freeing of native resources we
* explicitly create the Inflater instance and free its resources
* when we are done with the InflaterInputStream by calling
* inf.end();
*/
inf = new Inflater();
is = new InflaterInputStream(is, inf);
is = new BufferedInputStream(is);
this.pixelStream = new DataInputStream(is);
/*
* NB: the PNG spec declares that valid range for width
* and height is [1, 2^31-1], so here we may fail to allocate
* a buffer for destination image due to memory limitation.
*
* However, the recovery strategy for this case should be
* defined on the level of application, so we will not
* try to estimate the required amount of the memory and/or
* handle OOM in any way.
*/
theImage = getDestination(param,
getImageTypes(0),
width,
height);
Rectangle destRegion = new Rectangle(0, 0, 0, 0);
sourceRegion = new Rectangle(0, 0, 0, 0);
computeRegions(param, width, height,
theImage,
sourceRegion, destRegion);
destinationOffset.setLocation(destRegion.getLocation());
// At this point the header has been read and we know
// how many bands are in the image, so perform checking
// of the read param.
int colorType = metadata.IHDR_colorType;
checkReadParamBandSettings(param,
inputBandsForColorType[colorType],
theImage.getSampleModel().getNumBands());
processImageStarted(0);
decodeImage();
if (abortRequested()) {
processReadAborted();
} else {
processImageComplete();
}
} catch (IOException e) {
throw new IIOException("Error reading PNG image data", e);
} finally {
if (inf != null) {
inf.end();
}
}
}
public int getNumImages(boolean allowSearch) throws IIOException {
if (stream == null) {
throw new IllegalStateException("No input source set!");
}
if (seekForwardOnly && allowSearch) {
throw new IllegalStateException
("seekForwardOnly and allowSearch can't both be true!");
}
return 1;
}
public int getWidth(int imageIndex) throws IIOException {
if (imageIndex != 0) {
throw new IndexOutOfBoundsException("imageIndex != 0!");
}
readHeader();
return metadata.IHDR_width;
}
public int getHeight(int imageIndex) throws IIOException {
if (imageIndex != 0) {
throw new IndexOutOfBoundsException("imageIndex != 0!");
}
readHeader();
return metadata.IHDR_height;
}
public Iterator<ImageTypeSpecifier> getImageTypes(int imageIndex)
throws IIOException
{
if (imageIndex != 0) {
throw new IndexOutOfBoundsException("imageIndex != 0!");
}
readHeader();
ArrayList<ImageTypeSpecifier> l =
new ArrayList<ImageTypeSpecifier>(1);
ColorSpace rgb;
ColorSpace gray;
int[] bandOffsets;
int bitDepth = metadata.IHDR_bitDepth;
int colorType = metadata.IHDR_colorType;
int dataType;
if (bitDepth <= 8) {
dataType = DataBuffer.TYPE_BYTE;
} else {
dataType = DataBuffer.TYPE_USHORT;
}
switch (colorType) {
case PNG_COLOR_GRAY:
// Packed grayscale
l.add(ImageTypeSpecifier.createGrayscale(bitDepth,
dataType,
false));
break;
case PNG_COLOR_RGB:
if (bitDepth == 8) {
// some standard types of buffered images
// which can be used as destination
l.add(ImageTypeSpecifier.createFromBufferedImageType(
BufferedImage.TYPE_3BYTE_BGR));
l.add(ImageTypeSpecifier.createFromBufferedImageType(
BufferedImage.TYPE_INT_RGB));
l.add(ImageTypeSpecifier.createFromBufferedImageType(
BufferedImage.TYPE_INT_BGR));
}
// Component R, G, B
rgb = ColorSpace.getInstance(ColorSpace.CS_sRGB);
bandOffsets = new int[3];
bandOffsets[0] = 0;
bandOffsets[1] = 1;
bandOffsets[2] = 2;
l.add(ImageTypeSpecifier.createInterleaved(rgb,
bandOffsets,
dataType,
false,
false));
break;
case PNG_COLOR_PALETTE:
readMetadata(); // Need tRNS chunk
/*
* The PLTE chunk spec says:
*
* The number of palette entries must not exceed the range that
* can be represented in the image bit depth (for example, 2^4 = 16
* for a bit depth of 4). It is permissible to have fewer entries
* than the bit depth would allow. In that case, any out-of-range
* pixel value found in the image data is an error.
*
* http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html#C.PLTE
*
* Consequently, the case when the palette length is smaller than
* 2^bitDepth is legal in the view of PNG spec.
*
* However the spec of createIndexed() method demands the exact
* equality of the palette lengh and number of possible palette
* entries (2^bitDepth).
*
* {@link javax.imageio.ImageTypeSpecifier.html#createIndexed}
*
* In order to avoid this contradiction we need to extend the
* palette arrays to the limit defined by the bitDepth.
*/
int plength = 1 << bitDepth;
byte[] red = metadata.PLTE_red;
byte[] green = metadata.PLTE_green;
byte[] blue = metadata.PLTE_blue;
if (metadata.PLTE_red.length < plength) {
red = Arrays.copyOf(metadata.PLTE_red, plength);
Arrays.fill(red, metadata.PLTE_red.length, plength,
metadata.PLTE_red[metadata.PLTE_red.length - 1]);
green = Arrays.copyOf(metadata.PLTE_green, plength);
Arrays.fill(green, metadata.PLTE_green.length, plength,
metadata.PLTE_green[metadata.PLTE_green.length - 1]);
blue = Arrays.copyOf(metadata.PLTE_blue, plength);
Arrays.fill(blue, metadata.PLTE_blue.length, plength,
metadata.PLTE_blue[metadata.PLTE_blue.length - 1]);
}
// Alpha from tRNS chunk may have fewer entries than
// the RGB LUTs from the PLTE chunk; if so, pad with
// 255.
byte[] alpha = null;
if (metadata.tRNS_present && (metadata.tRNS_alpha != null)) {
if (metadata.tRNS_alpha.length == red.length) {
alpha = metadata.tRNS_alpha;
} else {
alpha = Arrays.copyOf(metadata.tRNS_alpha, red.length);
Arrays.fill(alpha,
metadata.tRNS_alpha.length,
red.length, (byte)255);
}
}
l.add(ImageTypeSpecifier.createIndexed(red, green,
blue, alpha,
bitDepth,
DataBuffer.TYPE_BYTE));
break;
case PNG_COLOR_GRAY_ALPHA:
// Component G, A
gray = ColorSpace.getInstance(ColorSpace.CS_GRAY);
bandOffsets = new int[2];
bandOffsets[0] = 0;
bandOffsets[1] = 1;
l.add(ImageTypeSpecifier.createInterleaved(gray,
bandOffsets,
dataType,
true,
false));
break;
case PNG_COLOR_RGB_ALPHA:
if (bitDepth == 8) {
// some standard types of buffered images
// wich can be used as destination
l.add(ImageTypeSpecifier.createFromBufferedImageType(
BufferedImage.TYPE_4BYTE_ABGR));
l.add(ImageTypeSpecifier.createFromBufferedImageType(
BufferedImage.TYPE_INT_ARGB));
}
// Component R, G, B, A (non-premultiplied)
rgb = ColorSpace.getInstance(ColorSpace.CS_sRGB);
bandOffsets = new int[4];
bandOffsets[0] = 0;
bandOffsets[1] = 1;
bandOffsets[2] = 2;
bandOffsets[3] = 3;
l.add(ImageTypeSpecifier.createInterleaved(rgb,
bandOffsets,
dataType,
true,
false));
break;
default:
break;
}
return l.iterator();
}
/*
* Super class implementation uses first element
* of image types list as raw image type.
*
* Also, super implementation uses first element of this list
* as default destination type image read param does not specify
* anything other.
*
* However, in case of RGB and RGBA color types, raw image type
* produces buffered image of custom type. It causes some
* performance degradation of subsequent rendering operations.
*
* To resolve this contradiction we put standard image types
* at the first positions of image types list (to produce standard
* images by default) and put raw image type (which is custom)
* at the last position of this list.
*
* After this changes we should override getRawImageType()
* to return last element of image types list.
*/
public ImageTypeSpecifier getRawImageType(int imageIndex)
throws IOException {
Iterator<ImageTypeSpecifier> types = getImageTypes(imageIndex);
ImageTypeSpecifier raw = null;
do {
raw = types.next();
} while (types.hasNext());
return raw;
}
public ImageReadParam getDefaultReadParam() {
return new ImageReadParam();
}
public IIOMetadata getStreamMetadata()
throws IIOException {
return null;
}
public IIOMetadata getImageMetadata(int imageIndex) throws IIOException {
if (imageIndex != 0) {
throw new IndexOutOfBoundsException("imageIndex != 0!");
}
readMetadata();
return metadata;
}
public BufferedImage read(int imageIndex, ImageReadParam param)
throws IIOException {
if (imageIndex != 0) {
throw new IndexOutOfBoundsException("imageIndex != 0!");
}
readImage(param);
return theImage;
}
public void reset() {
super.reset();
resetStreamSettings();
}
private void resetStreamSettings() {
gotHeader = false;
gotMetadata = false;
metadata = null;
pixelStream = null;
}
}
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