Java PNGDecoder
资料：Java PNGDecoder
/*
* Copyright (c) 2008-2010, Matthias Mann
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Matthias Mann nor the names of its contributors may
* be used to endorse or promote products derived from this software
* without specific prior written permission.
* * Redistributions in source or binary form must keep the original package
* and class name.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package de.matthiasmann.twl.utils;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.zip.CRC32;
import java.util.zip.DataFormatException;
import java.util.zip.Inflater;
/**
* A PNGDecoder. The slick PNG decoder is based on this class :)
*
* @author Matthias Mann
*/
public class PNGDecoder {
public enum Format {
ALPHA(1, true),
LUMINANCE(1, false),
LUMINANCE_ALPHA(2, true),
RGB(3, false),
RGBA(4, true),
BGRA(4, true),
ABGR(4, true);
final int numComponents;
final boolean hasAlpha;
private Format(int numComponents, boolean hasAlpha) {
this.numComponents = numComponents;
this.hasAlpha = hasAlpha;
}
public int getNumComponents() {
return numComponents;
}
public boolean isHasAlpha() {
return hasAlpha;
}
}
private static final byte[] SIGNATURE = {(byte)137, 80, 78, 71, 13, 10, 26, 10};
private static final int IHDR = 0x49484452;
private static final int PLTE = 0x504C5445;
private static final int tRNS = 0x74524E53;
private static final int IDAT = 0x49444154;
private static final int IEND = 0x49454E44;
private static final byte COLOR_GREYSCALE = 0;
private static final byte COLOR_TRUECOLOR = 2;
private static final byte COLOR_INDEXED = 3;
private static final byte COLOR_GREYALPHA = 4;
private static final byte COLOR_TRUEALPHA = 6;
private final InputStream input;
private final CRC32 crc;
private final byte[] buffer;
private int chunkLength;
private int chunkType;
private int chunkRemaining;
private int width;
private int height;
private int bitdepth;
private int colorType;
private int bytesPerPixel;
private byte[] palette;
private byte[] paletteA;
private byte[] transPixel;
public PNGDecoder(InputStream input) throws IOException {
this.input = input;
this.crc = new CRC32();
this.buffer = new byte[4096];
readFully(buffer, 0, SIGNATURE.length);
if(!checkSignature(buffer)) {
throw new IOException("Not a valid PNG file");
}
openChunk(IHDR);
readIHDR();
closeChunk();
searchIDAT: for(;;) {
openChunk();
switch (chunkType) {
case IDAT:
break searchIDAT;
case PLTE:
readPLTE();
break;
case tRNS:
readtRNS();
break;
}
closeChunk();
}
if(colorType == COLOR_INDEXED && palette == null) {
throw new IOException("Missing PLTE chunk");
}
}
public int getHeight() {
return height;
}
public int getWidth() {
return width;
}
/**
* Checks if the image has a real alpha channel.
* This method does not check for the presence of a tRNS chunk.
*
* @return true if the image has an alpha channel
* @see #hasAlpha()
*/
public boolean hasAlphaChannel() {
return colorType == COLOR_TRUEALPHA || colorType == COLOR_GREYALPHA;
}
/**
* Checks if the image has transparency information either from
* an alpha channel or from a tRNS chunk.
*
* @return true if the image has transparency
* @see #hasAlphaChannel()
* @see #overwriteTRNS(byte, byte, byte)
*/
public boolean hasAlpha() {
return hasAlphaChannel() ||
paletteA != null || transPixel != null;
}
public boolean isRGB() {
return colorType == COLOR_TRUEALPHA ||
colorType == COLOR_TRUECOLOR ||
colorType == COLOR_INDEXED;
}
/**
* Overwrites the tRNS chunk entry to make a selected color transparent.
* This can only be invoked when the image has no alpha channel.
* Calling this method causes {@link #hasAlpha()} to return true.
*
* @param r the red component of the color to make transparent
* @param g the green component of the color to make transparent
* @param b the blue component of the color to make transparent
* @throws UnsupportedOperationException if the tRNS chunk data can't be set
* @see #hasAlphaChannel()
*/
public void overwriteTRNS(byte r, byte g, byte b) {
if(hasAlphaChannel()) {
throw new UnsupportedOperationException("image has an alpha channel");
}
byte[] pal = this.palette;
if(pal == null) {
transPixel = new byte[] { 0, r, 0, g, 0, b };
} else {
paletteA = new byte[pal.length/3];
for(int i=0,j=0 ; i> 1)] & 255;
switch(n-i) {
default: dst[i+1] = (byte)(val & 15);
case 1: dst[i ] = (byte)(val >> 4);
}
}
}
private void expand2(byte[] src, byte[] dst) {
for(int i=1,n=dst.length ; i> 2)] & 255;
switch(n-i) {
default: dst[i+3] = (byte)((val ) & 3);
case 3: dst[i+2] = (byte)((val >> 2) & 3);
case 2: dst[i+1] = (byte)((val >> 4) & 3);
case 1: dst[i ] = (byte)((val >> 6) );
}
}
}
private void expand1(byte[] src, byte[] dst) {
for(int i=1,n=dst.length ; i> 3)] & 255;
switch(n-i) {
default: dst[i+7] = (byte)((val ) & 1);
case 7: dst[i+6] = (byte)((val >> 1) & 1);
case 6: dst[i+5] = (byte)((val >> 2) & 1);
case 5: dst[i+4] = (byte)((val >> 3) & 1);
case 4: dst[i+3] = (byte)((val >> 4) & 1);
case 3: dst[i+2] = (byte)((val >> 5) & 1);
case 2: dst[i+1] = (byte)((val >> 6) & 1);
case 1: dst[i ] = (byte)((val >> 7) );
}
}
}
private void unfilter(byte[] curLine, byte[] prevLine) throws IOException {
switch (curLine[0]) {
case 0: // none
break;
case 1:
unfilterSub(curLine);
break;
case 2:
unfilterUp(curLine, prevLine);
break;
case 3:
unfilterAverage(curLine, prevLine);
break;
case 4:
unfilterPaeth(curLine, prevLine);
break;
default:
throw new IOException("invalide filter type in scanline: " + curLine[0]);
}
}
private void unfilterSub(byte[] curLine) {
final int bpp = this.bytesPerPixel;
for(int i=bpp+1,n=curLine.length ; i>> 1);
}
for(int n=curLine.length ; i>> 1);
}
}
private void unfilterPaeth(byte[] curLine, byte[] prevLine) {
final int bpp = this.bytesPerPixel;
int i;
for(i=1 ; i<=bpp ; ++i) {
curLine[i] += prevLine[i];
}
for(int n=curLine.length ; i 256 || (chunkLength % 3) != 0) {
throw new IOException("PLTE chunk has wrong length");
}
palette = new byte[paletteEntries*3];
readChunk(palette, 0, palette.length);
}
private void readtRNS() throws IOException {
switch (colorType) {
case COLOR_GREYSCALE:
checkChunkLength(2);
transPixel = new byte[2];
readChunk(transPixel, 0, 2);
break;
case COLOR_TRUECOLOR:
checkChunkLength(6);
transPixel = new byte[6];
readChunk(transPixel, 0, 6);
break;
case COLOR_INDEXED:
if(palette == null) {
throw new IOException("tRNS chunk without PLTE chunk");
}
paletteA = new byte[palette.length/3];
Arrays.fill(paletteA, (byte)0xFF);
readChunk(paletteA, 0, paletteA.length);
break;
default:
// just ignore it
}
}
private void closeChunk() throws IOException {
if(chunkRemaining > 0) {
// just skip the rest and the CRC
skip(chunkRemaining + 4);
} else {
readFully(buffer, 0, 4);
int expectedCrc = readInt(buffer, 0);
int computedCrc = (int)crc.getValue();
if(computedCrc != expectedCrc) {
throw new IOException("Invalid CRC");
}
}
chunkRemaining = 0;
chunkLength = 0;
chunkType = 0;
}
private void openChunk() throws IOException {
readFully(buffer, 0, 8);
chunkLength = readInt(buffer, 0);
chunkType = readInt(buffer, 4);
chunkRemaining = chunkLength;
crc.reset();
crc.update(buffer, 4, 4); // only chunkType
}
private void openChunk(int expected) throws IOException {
openChunk();
if(chunkType != expected) {
throw new IOException("Expected chunk: " + Integer.toHexString(expected));
}
}
private void checkChunkLength(int expected) throws IOException {
if(chunkLength != expected) {
throw new IOException("Chunk has wrong size");
}
}
private int readChunk(byte[] buffer, int offset, int length) throws IOException {
if(length > chunkRemaining) {
length = chunkRemaining;
}
readFully(buffer, offset, length);
crc.update(buffer, offset, length);
chunkRemaining -= length;
return length;
}
private void refillInflater(Inflater inflater) throws IOException {
while(chunkRemaining == 0) {
closeChunk();
openChunk(IDAT);
}
int read = readChunk(buffer, 0, buffer.length);
inflater.setInput(buffer, 0, read);
}
private void readChunkUnzip(Inflater inflater, byte[] buffer, int offset, int length) throws IOException {
assert(buffer != this.buffer);
try {
do {
int read = inflater.inflate(buffer, offset, length);
if(read <= 0) {
if(inflater.finished()) {
throw new EOFException();
}
if(inflater.needsInput()) {
refillInflater(inflater);
} else {
throw new IOException("Can't inflate " + length + " bytes");
}
} else {
offset += read;
length -= read;
}
} while(length > 0);
} catch (DataFormatException ex) {
throw (IOException)(new IOException("inflate error").initCause(ex));
}
}
private void readFully(byte[] buffer, int offset, int length) throws IOException {
do {
int read = input.read(buffer, offset, length);
if(read < 0) {
throw new EOFException();
}
offset += read;
length -= read;
} while(length > 0);
}
private int readInt(byte[] buffer, int offset) {
return
((buffer[offset ] ) << 24) |
((buffer[offset+1] & 255) << 16) |
((buffer[offset+2] & 255) << 8) |
((buffer[offset+3] & 255) );
}
private void skip(long amount) throws IOException {
while(amount > 0) {
long skipped = input.skip(amount);
if(skipped < 0) {
throw new EOFException();
}
amount -= skipped;
}
}
private static boolean checkSignature(byte[] buffer) {
for(int i=0 ; i