com.keypoint.PngEncoder Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of jcommon Show documentation
Show all versions of jcommon Show documentation
JCommon is a free general purpose Java class library that is used in several projects at www.jfree.org, including JFreeChart and JFreeReport.
package com.keypoint;
import java.awt.Image;
import java.awt.image.ImageObserver;
import java.awt.image.PixelGrabber;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.zip.CRC32;
import java.util.zip.Deflater;
import java.util.zip.DeflaterOutputStream;
/**
* PngEncoder takes a Java Image object and creates a byte string which can be
* saved as a PNG file. The Image is presumed to use the DirectColorModel.
*
* Thanks to Jay Denny at KeyPoint Software
* http://www.keypoint.com/
* who let me develop this code on company time.
*
* You may contact me with (probably very-much-needed) improvements,
* comments, and bug fixes at:
*
*
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
* USA. A copy of the GNU LGPL may be found at
* http://www.gnu.org/copyleft/lesser.html
*
* @author J. David Eisenberg
* @version 1.5, 19 Oct 2003
*
* CHANGES:
* --------
* 19-Nov-2002 : CODING STYLE CHANGES ONLY (by David Gilbert for Object
* Refinery Limited);
* 19-Sep-2003 : Fix for platforms using EBCDIC (contributed by Paulo Soares);
* 19-Oct-2003 : Change private fields to protected fields so that
* PngEncoderB can inherit them (JDE)
* Fixed bug with calculation of nRows
*/
public class PngEncoder {
/** Constant specifying that alpha channel should be encoded. */
public static final boolean ENCODE_ALPHA = true;
/** Constant specifying that alpha channel should not be encoded. */
public static final boolean NO_ALPHA = false;
/** Constants for filter (NONE). */
public static final int FILTER_NONE = 0;
/** Constants for filter (SUB). */
public static final int FILTER_SUB = 1;
/** Constants for filter (UP). */
public static final int FILTER_UP = 2;
/** Constants for filter (LAST). */
public static final int FILTER_LAST = 2;
/** IHDR tag. */
protected static final byte[] IHDR = {73, 72, 68, 82};
/** IDAT tag. */
protected static final byte[] IDAT = {73, 68, 65, 84};
/** IEND tag. */
protected static final byte[] IEND = {73, 69, 78, 68};
protected static final byte[] PHYS = {(byte)'p', (byte)'H', (byte)'Y', (byte)'s'};
/** The png bytes. */
protected byte[] pngBytes;
/** The prior row. */
protected byte[] priorRow;
/** The left bytes. */
protected byte[] leftBytes;
/** The image. */
protected Image image;
/** The width. */
protected int width;
/** The height. */
protected int height;
/** The byte position. */
protected int bytePos;
/** The maximum position. */
protected int maxPos;
/** CRC. */
protected CRC32 crc = new CRC32();
/** The CRC value. */
protected long crcValue;
/** Encode alpha? */
protected boolean encodeAlpha;
/** The filter type. */
protected int filter;
/** The bytes-per-pixel. */
protected int bytesPerPixel;
/** The physical pixel dimension : number of pixels per inch on the X axis. */
private int xDpi = 0;
/** The physical pixel dimension : number of pixels per inch on the Y axis. */
private int yDpi = 0;
/** Used for conversion of DPI to Pixels per Meter. */
static private float INCH_IN_METER_UNIT = 0.0254f;
/**
* The compression level (1 = best speed, 9 = best compression,
* 0 = no compression).
*/
protected int compressionLevel;
/**
* Class constructor.
*/
public PngEncoder() {
this(null, false, FILTER_NONE, 0);
}
/**
* Class constructor specifying Image to encode, with no alpha channel
* encoding.
*
* @param image A Java Image object which uses the DirectColorModel
* @see java.awt.Image
*/
public PngEncoder(Image image) {
this(image, false, FILTER_NONE, 0);
}
/**
* Class constructor specifying Image to encode, and whether to encode
* alpha.
*
* @param image A Java Image object which uses the DirectColorModel
* @param encodeAlpha Encode the alpha channel? false=no; true=yes
* @see java.awt.Image
*/
public PngEncoder(Image image, boolean encodeAlpha) {
this(image, encodeAlpha, FILTER_NONE, 0);
}
/**
* Class constructor specifying Image to encode, whether to encode alpha,
* and filter to use.
*
* @param image A Java Image object which uses the DirectColorModel
* @param encodeAlpha Encode the alpha channel? false=no; true=yes
* @param whichFilter 0=none, 1=sub, 2=up
* @see java.awt.Image
*/
public PngEncoder(Image image, boolean encodeAlpha, int whichFilter) {
this(image, encodeAlpha, whichFilter, 0);
}
/**
* Class constructor specifying Image source to encode, whether to encode
* alpha, filter to use, and compression level.
*
* @param image A Java Image object
* @param encodeAlpha Encode the alpha channel? false=no; true=yes
* @param whichFilter 0=none, 1=sub, 2=up
* @param compLevel 0..9 (1 = best speed, 9 = best compression, 0 = no
* compression)
* @see java.awt.Image
*/
public PngEncoder(Image image, boolean encodeAlpha, int whichFilter,
int compLevel) {
this.image = image;
this.encodeAlpha = encodeAlpha;
setFilter(whichFilter);
if (compLevel >= 0 && compLevel <= 9) {
this.compressionLevel = compLevel;
}
}
/**
* Set the image to be encoded.
*
* @param image A Java Image object which uses the DirectColorModel
* @see java.awt.Image
* @see java.awt.image.DirectColorModel
*/
public void setImage(Image image) {
this.image = image;
this.pngBytes = null;
}
/**
* Returns the image to be encoded.
*/
public Image getImage() {
return image;
}
/**
* Creates an array of bytes that is the PNG equivalent of the current
* image, specifying whether to encode alpha or not.
*
* @param encodeAlpha boolean false=no alpha, true=encode alpha
* @return an array of bytes, or null if there was a problem
*/
public byte[] pngEncode(boolean encodeAlpha) {
byte[] pngIdBytes = {-119, 80, 78, 71, 13, 10, 26, 10};
if (this.image == null) {
return null;
}
this.width = this.image.getWidth(null);
this.height = this.image.getHeight(null);
/*
* start with an array that is big enough to hold all the pixels
* (plus filter bytes), and an extra 200 bytes for header info
*/
this.pngBytes = new byte[((this.width + 1) * this.height * 3) + 200];
/*
* keep track of largest byte written to the array
*/
this.maxPos = 0;
this.bytePos = writeBytes(pngIdBytes, 0);
//hdrPos = bytePos;
writeHeader();
writeResolution();
//dataPos = bytePos;
if (writeImageData()) {
writeEnd();
this.pngBytes = resizeByteArray(this.pngBytes, this.maxPos);
}
else {
this.pngBytes = null;
}
return this.pngBytes;
}
/**
* Creates an array of bytes that is the PNG equivalent of the current
* image. Alpha encoding is determined by its setting in the constructor.
*
* @return an array of bytes, or null if there was a problem
*/
public byte[] pngEncode() {
return pngEncode(this.encodeAlpha);
}
/**
* Set the alpha encoding on or off.
*
* @param encodeAlpha false=no, true=yes
*/
public void setEncodeAlpha(boolean encodeAlpha) {
this.encodeAlpha = encodeAlpha;
}
/**
* Retrieve alpha encoding status.
*
* @return boolean false=no, true=yes
*/
public boolean getEncodeAlpha() {
return this.encodeAlpha;
}
/**
* Set the filter to use.
*
* @param whichFilter from constant list
*/
public void setFilter(int whichFilter) {
this.filter = FILTER_NONE;
if (whichFilter <= FILTER_LAST) {
this.filter = whichFilter;
}
}
/**
* Retrieve filtering scheme.
*
* @return int (see constant list)
*/
public int getFilter() {
return this.filter;
}
/**
* Set the compression level to use.
*
* @param level the compression level (1 = best speed, 9 = best compression,
* 0 = no compression)
*/
public void setCompressionLevel(int level) {
if (level >= 0 && level <= 9) {
this.compressionLevel = level;
}
}
/**
* Retrieve compression level.
*
* @return int (1 = best speed, 9 = best compression, 0 = no compression)
*/
public int getCompressionLevel() {
return this.compressionLevel;
}
/**
* Increase or decrease the length of a byte array.
*
* @param array The original array.
* @param newLength The length you wish the new array to have.
* @return Array of newly desired length. If shorter than the
* original, the trailing elements are truncated.
*/
protected byte[] resizeByteArray(byte[] array, int newLength) {
byte[] newArray = new byte[newLength];
int oldLength = array.length;
System.arraycopy(array, 0, newArray, 0, Math.min(oldLength, newLength));
return newArray;
}
/**
* Write an array of bytes into the pngBytes array.
* Note: This routine has the side effect of updating
* maxPos, the largest element written in the array.
* The array is resized by 1000 bytes or the length
* of the data to be written, whichever is larger.
*
* @param data The data to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeBytes(byte[] data, int offset) {
this.maxPos = Math.max(this.maxPos, offset + data.length);
if (data.length + offset > this.pngBytes.length) {
this.pngBytes = resizeByteArray(this.pngBytes, this.pngBytes.length
+ Math.max(1000, data.length));
}
System.arraycopy(data, 0, this.pngBytes, offset, data.length);
return offset + data.length;
}
/**
* Write an array of bytes into the pngBytes array, specifying number of
* bytes to write. Note: This routine has the side effect of updating
* maxPos, the largest element written in the array.
* The array is resized by 1000 bytes or the length
* of the data to be written, whichever is larger.
*
* @param data The data to be written into pngBytes.
* @param nBytes The number of bytes to be written.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeBytes(byte[] data, int nBytes, int offset) {
this.maxPos = Math.max(this.maxPos, offset + nBytes);
if (nBytes + offset > this.pngBytes.length) {
this.pngBytes = resizeByteArray(this.pngBytes, this.pngBytes.length
+ Math.max(1000, nBytes));
}
System.arraycopy(data, 0, this.pngBytes, offset, nBytes);
return offset + nBytes;
}
/**
* Write a two-byte integer into the pngBytes array at a given position.
*
* @param n The integer to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeInt2(int n, int offset) {
byte[] temp = {(byte) ((n >> 8) & 0xff), (byte) (n & 0xff)};
return writeBytes(temp, offset);
}
/**
* Write a four-byte integer into the pngBytes array at a given position.
*
* @param n The integer to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeInt4(int n, int offset) {
byte[] temp = {(byte) ((n >> 24) & 0xff),
(byte) ((n >> 16) & 0xff),
(byte) ((n >> 8) & 0xff),
(byte) (n & 0xff)};
return writeBytes(temp, offset);
}
/**
* Write a single byte into the pngBytes array at a given position.
*
* @param b The integer to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeByte(int b, int offset) {
byte[] temp = {(byte) b};
return writeBytes(temp, offset);
}
/**
* Write a PNG "IHDR" chunk into the pngBytes array.
*/
protected void writeHeader() {
int startPos = this.bytePos = writeInt4(13, this.bytePos);
this.bytePos = writeBytes(IHDR, this.bytePos);
this.width = this.image.getWidth(null);
this.height = this.image.getHeight(null);
this.bytePos = writeInt4(this.width, this.bytePos);
this.bytePos = writeInt4(this.height, this.bytePos);
this.bytePos = writeByte(8, this.bytePos); // bit depth
this.bytePos = writeByte((this.encodeAlpha) ? 6 : 2, this.bytePos);
// direct model
this.bytePos = writeByte(0, this.bytePos); // compression method
this.bytePos = writeByte(0, this.bytePos); // filter method
this.bytePos = writeByte(0, this.bytePos); // no interlace
this.crc.reset();
this.crc.update(this.pngBytes, startPos, this.bytePos - startPos);
this.crcValue = this.crc.getValue();
this.bytePos = writeInt4((int) this.crcValue, this.bytePos);
}
/**
* Perform "sub" filtering on the given row.
* Uses temporary array leftBytes to store the original values
* of the previous pixels. The array is 16 bytes long, which
* will easily hold two-byte samples plus two-byte alpha.
*
* @param pixels The array holding the scan lines being built
* @param startPos Starting position within pixels of bytes to be filtered.
* @param width Width of a scanline in pixels.
*/
protected void filterSub(byte[] pixels, int startPos, int width) {
int offset = this.bytesPerPixel;
int actualStart = startPos + offset;
int nBytes = width * this.bytesPerPixel;
int leftInsert = offset;
int leftExtract = 0;
for (int i = actualStart; i < startPos + nBytes; i++) {
this.leftBytes[leftInsert] = pixels[i];
pixels[i] = (byte) ((pixels[i] - this.leftBytes[leftExtract])
% 256);
leftInsert = (leftInsert + 1) % 0x0f;
leftExtract = (leftExtract + 1) % 0x0f;
}
}
/**
* Perform "up" filtering on the given row.
* Side effect: refills the prior row with current row
*
* @param pixels The array holding the scan lines being built
* @param startPos Starting position within pixels of bytes to be filtered.
* @param width Width of a scanline in pixels.
*/
protected void filterUp(byte[] pixels, int startPos, int width) {
final int nBytes = width * this.bytesPerPixel;
for (int i = 0; i < nBytes; i++) {
final byte currentByte = pixels[startPos + i];
pixels[startPos + i] = (byte) ((pixels[startPos + i]
- this.priorRow[i]) % 256);
this.priorRow[i] = currentByte;
}
}
/**
* Write the image data into the pngBytes array.
* This will write one or more PNG "IDAT" chunks. In order
* to conserve memory, this method grabs as many rows as will
* fit into 32K bytes, or the whole image; whichever is less.
*
*
* @return true if no errors; false if error grabbing pixels
*/
protected boolean writeImageData() {
int rowsLeft = this.height; // number of rows remaining to write
int startRow = 0; // starting row to process this time through
int nRows; // how many rows to grab at a time
byte[] scanLines; // the scan lines to be compressed
int scanPos; // where we are in the scan lines
int startPos; // where this line's actual pixels start (used
// for filtering)
byte[] compressedLines; // the resultant compressed lines
int nCompressed; // how big is the compressed area?
//int depth; // color depth ( handle only 8 or 32 )
PixelGrabber pg;
this.bytesPerPixel = (this.encodeAlpha) ? 4 : 3;
Deflater scrunch = new Deflater(this.compressionLevel);
ByteArrayOutputStream outBytes = new ByteArrayOutputStream(1024);
DeflaterOutputStream compBytes = new DeflaterOutputStream(outBytes,
scrunch);
try {
while (rowsLeft > 0) {
nRows = Math.min(32767 / (this.width
* (this.bytesPerPixel + 1)), rowsLeft);
nRows = Math.max(nRows, 1);
int[] pixels = new int[this.width * nRows];
pg = new PixelGrabber(this.image, 0, startRow,
this.width, nRows, pixels, 0, this.width);
try {
pg.grabPixels();
}
catch (Exception e) {
System.err.println("interrupted waiting for pixels!");
return false;
}
if ((pg.getStatus() & ImageObserver.ABORT) != 0) {
System.err.println("image fetch aborted or errored");
return false;
}
/*
* Create a data chunk. scanLines adds "nRows" for
* the filter bytes.
*/
scanLines = new byte[this.width * nRows * this.bytesPerPixel
+ nRows];
if (this.filter == FILTER_SUB) {
this.leftBytes = new byte[16];
}
if (this.filter == FILTER_UP) {
this.priorRow = new byte[this.width * this.bytesPerPixel];
}
scanPos = 0;
startPos = 1;
for (int i = 0; i < this.width * nRows; i++) {
if (i % this.width == 0) {
scanLines[scanPos++] = (byte) this.filter;
startPos = scanPos;
}
scanLines[scanPos++] = (byte) ((pixels[i] >> 16) & 0xff);
scanLines[scanPos++] = (byte) ((pixels[i] >> 8) & 0xff);
scanLines[scanPos++] = (byte) ((pixels[i]) & 0xff);
if (this.encodeAlpha) {
scanLines[scanPos++] = (byte) ((pixels[i] >> 24)
& 0xff);
}
if ((i % this.width == this.width - 1)
&& (this.filter != FILTER_NONE)) {
if (this.filter == FILTER_SUB) {
filterSub(scanLines, startPos, this.width);
}
if (this.filter == FILTER_UP) {
filterUp(scanLines, startPos, this.width);
}
}
}
/*
* Write these lines to the output area
*/
compBytes.write(scanLines, 0, scanPos);
startRow += nRows;
rowsLeft -= nRows;
}
compBytes.close();
/*
* Write the compressed bytes
*/
compressedLines = outBytes.toByteArray();
nCompressed = compressedLines.length;
this.crc.reset();
this.bytePos = writeInt4(nCompressed, this.bytePos);
this.bytePos = writeBytes(IDAT, this.bytePos);
this.crc.update(IDAT);
this.bytePos = writeBytes(compressedLines, nCompressed,
this.bytePos);
this.crc.update(compressedLines, 0, nCompressed);
this.crcValue = this.crc.getValue();
this.bytePos = writeInt4((int) this.crcValue, this.bytePos);
scrunch.finish();
return true;
}
catch (IOException e) {
System.err.println(e.toString());
return false;
}
}
/**
* Write a PNG "IEND" chunk into the pngBytes array.
*/
protected void writeEnd() {
this.bytePos = writeInt4(0, this.bytePos);
this.bytePos = writeBytes(IEND, this.bytePos);
this.crc.reset();
this.crc.update(IEND);
this.crcValue = this.crc.getValue();
this.bytePos = writeInt4((int) this.crcValue, this.bytePos);
}
/**
* Set the DPI for the X axis.
*
* @param xDpi The number of dots per inch
*/
public void setXDpi(int xDpi) {
this.xDpi = Math.round(xDpi / INCH_IN_METER_UNIT);
}
/**
* Get the DPI for the X axis.
*
* @return The number of dots per inch
*/
public int getXDpi() {
return Math.round(xDpi * INCH_IN_METER_UNIT);
}
/**
* Set the DPI for the Y axis.
*
* @param yDpi The number of dots per inch
*/
public void setYDpi(int yDpi) {
this.yDpi = Math.round(yDpi / INCH_IN_METER_UNIT);
}
/**
* Get the DPI for the Y axis.
*
* @return The number of dots per inch
*/
public int getYDpi() {
return Math.round(yDpi * INCH_IN_METER_UNIT);
}
/**
* Set the DPI resolution.
*
* @param xDpi The number of dots per inch for the X axis.
* @param yDpi The number of dots per inch for the Y axis.
*/
public void setDpi(int xDpi, int yDpi) {
this.xDpi = Math.round(xDpi / INCH_IN_METER_UNIT);
this.yDpi = Math.round(yDpi / INCH_IN_METER_UNIT);
}
/**
* Write a PNG "pHYs" chunk into the pngBytes array.
*/
protected void writeResolution() {
if (xDpi > 0 && yDpi > 0) {
final int startPos = bytePos = writeInt4(9, bytePos);
bytePos = writeBytes(PHYS, bytePos);
bytePos = writeInt4(xDpi, bytePos);
bytePos = writeInt4(yDpi, bytePos);
bytePos = writeByte(1, bytePos); // unit is the meter.
crc.reset();
crc.update(pngBytes, startPos, bytePos - startPos);
crcValue = crc.getValue();
bytePos = writeInt4((int) crcValue, bytePos);
}
}
}