001package com.keypoint;
002
003import java.awt.Image;
004import java.awt.image.ImageObserver;
005import java.awt.image.PixelGrabber;
006import java.io.ByteArrayOutputStream;
007import java.io.IOException;
008import java.util.zip.CRC32;
009import java.util.zip.Deflater;
010import java.util.zip.DeflaterOutputStream;
011
012/**
013 * PngEncoder takes a Java Image object and creates a byte string which can be 
014 * saved as a PNG file.  The Image is presumed to use the DirectColorModel.
015 *
016 * <p>Thanks to Jay Denny at KeyPoint Software
017 *    http://www.keypoint.com/
018 * who let me develop this code on company time.</p>
019 *
020 * <p>You may contact me with (probably very-much-needed) improvements,
021 * comments, and bug fixes at:</p>
022 *
023 *   <p><code>david@catcode.com</code></p>
024 *
025 * <p>This library is free software; you can redistribute it and/or
026 * modify it under the terms of the GNU Lesser General Public
027 * License as published by the Free Software Foundation; either
028 * version 2.1 of the License, or (at your option) any later version.</p>
029 *
030 * <p>This library is distributed in the hope that it will be useful,
031 * but WITHOUT ANY WARRANTY; without even the implied warranty of
032 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
033 * Lesser General Public License for more details.</p>
034 *
035 * <p>You should have received a copy of the GNU Lesser General Public
036 * License along with this library; if not, write to the Free Software
037 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
038 * USA. A copy of the GNU LGPL may be found at
039 * <code>http://www.gnu.org/copyleft/lesser.html</code></p>
040 *
041 * @author J. David Eisenberg
042 * @version 1.5, 19 Oct 2003
043 *
044 * CHANGES:
045 * --------
046 * 19-Nov-2002 : CODING STYLE CHANGES ONLY (by David Gilbert for Object 
047 *               Refinery Limited);
048 * 19-Sep-2003 : Fix for platforms using EBCDIC (contributed by Paulo Soares);
049 * 19-Oct-2003 : Change private fields to protected fields so that
050 *               PngEncoderB can inherit them (JDE)
051 *               Fixed bug with calculation of nRows
052 */
053
054public class PngEncoder {
055
056    /** Constant specifying that alpha channel should be encoded. */
057    public static final boolean ENCODE_ALPHA = true;
058
059    /** Constant specifying that alpha channel should not be encoded. */
060    public static final boolean NO_ALPHA = false;
061
062    /** Constants for filter (NONE). */
063    public static final int FILTER_NONE = 0;
064
065    /** Constants for filter (SUB). */
066    public static final int FILTER_SUB = 1;
067
068    /** Constants for filter (UP). */
069    public static final int FILTER_UP = 2;
070
071    /** Constants for filter (LAST). */
072    public static final int FILTER_LAST = 2;
073    
074    /** IHDR tag. */
075    protected static final byte[] IHDR = {73, 72, 68, 82};
076    
077    /** IDAT tag. */
078    protected static final byte[] IDAT = {73, 68, 65, 84};
079    
080    /** IEND tag. */
081    protected static final byte[] IEND = {73, 69, 78, 68};
082
083    protected static final byte[] PHYS = {(byte)'p', (byte)'H', (byte)'Y', (byte)'s'};
084
085    /** The png bytes. */
086    protected byte[] pngBytes;
087
088    /** The prior row. */
089    protected byte[] priorRow;
090
091    /** The left bytes. */
092    protected byte[] leftBytes;
093
094    /** The image. */
095    protected Image image;
096
097    /** The width. */
098    protected int width;
099
100    /** The height. */
101    protected int height;
102
103    /** The byte position. */
104    protected int bytePos;
105
106    /** The maximum position. */
107    protected int maxPos;
108
109    /** CRC. */
110    protected CRC32 crc = new CRC32();
111
112    /** The CRC value. */
113    protected long crcValue;
114
115    /** Encode alpha? */
116    protected boolean encodeAlpha;
117
118    /** The filter type. */
119    protected int filter;
120
121    /** The bytes-per-pixel. */
122    protected int bytesPerPixel;
123
124    /** The physical pixel dimension : number of pixels per inch on the X axis. */
125    private int xDpi = 0;
126
127    /** The physical pixel dimension : number of pixels per inch on the Y axis. */
128    private int yDpi = 0;
129
130    /** Used for conversion of DPI to Pixels per Meter. */
131    static private float INCH_IN_METER_UNIT = 0.0254f;
132
133    /** 
134     * The compression level (1 = best speed, 9 = best compression, 
135     * 0 = no compression). 
136     */
137    protected int compressionLevel;
138
139    /**
140     * Class constructor.
141     */
142    public PngEncoder() {
143        this(null, false, FILTER_NONE, 0);
144    }
145
146    /**
147     * Class constructor specifying Image to encode, with no alpha channel 
148     * encoding.
149     *
150     * @param image A Java Image object which uses the DirectColorModel
151     * @see java.awt.Image
152     */
153    public PngEncoder(Image image) {
154        this(image, false, FILTER_NONE, 0);
155    }
156
157    /**
158     * Class constructor specifying Image to encode, and whether to encode 
159     * alpha.
160     *
161     * @param image A Java Image object which uses the DirectColorModel
162     * @param encodeAlpha Encode the alpha channel? false=no; true=yes
163     * @see java.awt.Image
164     */
165    public PngEncoder(Image image, boolean encodeAlpha) {
166        this(image, encodeAlpha, FILTER_NONE, 0);
167    }
168
169    /**
170     * Class constructor specifying Image to encode, whether to encode alpha, 
171     * and filter to use.
172     *
173     * @param image A Java Image object which uses the DirectColorModel
174     * @param encodeAlpha Encode the alpha channel? false=no; true=yes
175     * @param whichFilter 0=none, 1=sub, 2=up
176     * @see java.awt.Image
177     */
178    public PngEncoder(Image image, boolean encodeAlpha, int whichFilter) {
179        this(image, encodeAlpha, whichFilter, 0);
180    }
181
182
183    /**
184     * Class constructor specifying Image source to encode, whether to encode 
185     * alpha, filter to use, and compression level.
186     *
187     * @param image A Java Image object
188     * @param encodeAlpha Encode the alpha channel? false=no; true=yes
189     * @param whichFilter 0=none, 1=sub, 2=up
190     * @param compLevel 0..9 (1 = best speed, 9 = best compression, 0 = no 
191     *        compression)
192     * @see java.awt.Image
193     */
194    public PngEncoder(Image image, boolean encodeAlpha, int whichFilter, 
195            int compLevel) {
196        this.image = image;
197        this.encodeAlpha = encodeAlpha;
198        setFilter(whichFilter);
199        if (compLevel >= 0 && compLevel <= 9) {
200            this.compressionLevel = compLevel;
201        }
202    }
203
204    /**
205     * Set the image to be encoded.
206     *
207     * @param image A Java Image object which uses the DirectColorModel
208     * @see java.awt.Image
209     * @see java.awt.image.DirectColorModel
210     */
211    public void setImage(Image image) {
212        this.image = image;
213        this.pngBytes = null;
214    }
215
216    /**
217     * Returns the image to be encoded.
218     */
219    public Image getImage() {
220      return image;
221    }
222
223  /**
224     * Creates an array of bytes that is the PNG equivalent of the current 
225     * image, specifying whether to encode alpha or not.
226     *
227     * @param encodeAlpha boolean false=no alpha, true=encode alpha
228     * @return an array of bytes, or null if there was a problem
229     */
230    public byte[] pngEncode(boolean encodeAlpha) {
231        byte[]  pngIdBytes = {-119, 80, 78, 71, 13, 10, 26, 10};
232
233        if (this.image == null) {
234            return null;
235        }
236        this.width = this.image.getWidth(null);
237        this.height = this.image.getHeight(null);
238
239        /*
240         * start with an array that is big enough to hold all the pixels
241         * (plus filter bytes), and an extra 200 bytes for header info
242         */
243        this.pngBytes = new byte[((this.width + 1) * this.height * 3) + 200];
244
245        /*
246         * keep track of largest byte written to the array
247         */
248        this.maxPos = 0;
249
250        this.bytePos = writeBytes(pngIdBytes, 0);
251        //hdrPos = bytePos;
252        writeHeader();
253        writeResolution();
254        //dataPos = bytePos;
255        if (writeImageData()) {
256            writeEnd();
257            this.pngBytes = resizeByteArray(this.pngBytes, this.maxPos);
258        }
259        else {
260            this.pngBytes = null;
261        }
262        return this.pngBytes;
263    }
264
265    /**
266     * Creates an array of bytes that is the PNG equivalent of the current 
267     * image.  Alpha encoding is determined by its setting in the constructor.
268     *
269     * @return an array of bytes, or null if there was a problem
270     */
271    public byte[] pngEncode() {
272        return pngEncode(this.encodeAlpha);
273    }
274
275    /**
276     * Set the alpha encoding on or off.
277     *
278     * @param encodeAlpha  false=no, true=yes
279     */
280    public void setEncodeAlpha(boolean encodeAlpha) {
281        this.encodeAlpha = encodeAlpha;
282    }
283
284    /**
285     * Retrieve alpha encoding status.
286     *
287     * @return boolean false=no, true=yes
288     */
289    public boolean getEncodeAlpha() {
290        return this.encodeAlpha;
291    }
292
293    /**
294     * Set the filter to use.
295     *
296     * @param whichFilter from constant list
297     */
298    public void setFilter(int whichFilter) {
299        this.filter = FILTER_NONE;
300        if (whichFilter <= FILTER_LAST) {
301            this.filter = whichFilter;
302        }
303    }
304
305    /**
306     * Retrieve filtering scheme.
307     *
308     * @return int (see constant list)
309     */
310    public int getFilter() {
311        return this.filter;
312    }
313
314    /**
315     * Set the compression level to use.
316     *
317     * @param level the compression level (1 = best speed, 9 = best compression,
318     *        0 = no compression)
319     */
320    public void setCompressionLevel(int level) {
321        if (level >= 0 && level <= 9) {
322            this.compressionLevel = level;
323        }
324    }
325
326    /**
327     * Retrieve compression level.
328     *
329     * @return int (1 = best speed, 9 = best compression, 0 = no compression)
330     */
331    public int getCompressionLevel() {
332        return this.compressionLevel;
333    }
334
335    /**
336     * Increase or decrease the length of a byte array.
337     *
338     * @param array The original array.
339     * @param newLength The length you wish the new array to have.
340     * @return Array of newly desired length. If shorter than the
341     *         original, the trailing elements are truncated.
342     */
343    protected byte[] resizeByteArray(byte[] array, int newLength) {
344        byte[]  newArray = new byte[newLength];
345        int     oldLength = array.length;
346
347        System.arraycopy(array, 0, newArray, 0, Math.min(oldLength, newLength));
348        return newArray;
349    }
350
351    /**
352     * Write an array of bytes into the pngBytes array.
353     * Note: This routine has the side effect of updating
354     * maxPos, the largest element written in the array.
355     * The array is resized by 1000 bytes or the length
356     * of the data to be written, whichever is larger.
357     *
358     * @param data The data to be written into pngBytes.
359     * @param offset The starting point to write to.
360     * @return The next place to be written to in the pngBytes array.
361     */
362    protected int writeBytes(byte[] data, int offset) {
363        this.maxPos = Math.max(this.maxPos, offset + data.length);
364        if (data.length + offset > this.pngBytes.length) {
365            this.pngBytes = resizeByteArray(this.pngBytes, this.pngBytes.length
366                    + Math.max(1000, data.length));
367        }
368        System.arraycopy(data, 0, this.pngBytes, offset, data.length);
369        return offset + data.length;
370    }
371
372    /**
373     * Write an array of bytes into the pngBytes array, specifying number of 
374     * bytes to write. Note: This routine has the side effect of updating
375     * maxPos, the largest element written in the array.
376     * The array is resized by 1000 bytes or the length
377     * of the data to be written, whichever is larger.
378     *
379     * @param data The data to be written into pngBytes.
380     * @param nBytes The number of bytes to be written.
381     * @param offset The starting point to write to.
382     * @return The next place to be written to in the pngBytes array.
383     */
384    protected int writeBytes(byte[] data, int nBytes, int offset) {
385        this.maxPos = Math.max(this.maxPos, offset + nBytes);
386        if (nBytes + offset > this.pngBytes.length) {
387            this.pngBytes = resizeByteArray(this.pngBytes, this.pngBytes.length
388                    + Math.max(1000, nBytes));
389        }
390        System.arraycopy(data, 0, this.pngBytes, offset, nBytes);
391        return offset + nBytes;
392    }
393
394    /**
395     * Write a two-byte integer into the pngBytes array at a given position.
396     *
397     * @param n The integer to be written into pngBytes.
398     * @param offset The starting point to write to.
399     * @return The next place to be written to in the pngBytes array.
400     */
401    protected int writeInt2(int n, int offset) {
402        byte[] temp = {(byte) ((n >> 8) & 0xff), (byte) (n & 0xff)};
403        return writeBytes(temp, offset);
404    }
405
406    /**
407     * Write a four-byte integer into the pngBytes array at a given position.
408     *
409     * @param n The integer to be written into pngBytes.
410     * @param offset The starting point to write to.
411     * @return The next place to be written to in the pngBytes array.
412     */
413    protected int writeInt4(int n, int offset) {
414        byte[] temp = {(byte) ((n >> 24) & 0xff),
415                       (byte) ((n >> 16) & 0xff),
416                       (byte) ((n >> 8) & 0xff),
417                       (byte) (n & 0xff)};
418        return writeBytes(temp, offset);
419    }
420
421    /**
422     * Write a single byte into the pngBytes array at a given position.
423     *
424     * @param b The integer to be written into pngBytes.
425     * @param offset The starting point to write to.
426     * @return The next place to be written to in the pngBytes array.
427     */
428    protected int writeByte(int b, int offset) {
429        byte[] temp = {(byte) b};
430        return writeBytes(temp, offset);
431    }
432
433    /**
434     * Write a PNG "IHDR" chunk into the pngBytes array.
435     */
436    protected void writeHeader() {
437
438        int startPos = this.bytePos = writeInt4(13, this.bytePos);
439        this.bytePos = writeBytes(IHDR, this.bytePos);
440        this.width = this.image.getWidth(null);
441        this.height = this.image.getHeight(null);
442        this.bytePos = writeInt4(this.width, this.bytePos);
443        this.bytePos = writeInt4(this.height, this.bytePos);
444        this.bytePos = writeByte(8, this.bytePos); // bit depth
445        this.bytePos = writeByte((this.encodeAlpha) ? 6 : 2, this.bytePos); 
446            // direct model
447        this.bytePos = writeByte(0, this.bytePos); // compression method
448        this.bytePos = writeByte(0, this.bytePos); // filter method
449        this.bytePos = writeByte(0, this.bytePos); // no interlace
450        this.crc.reset();
451        this.crc.update(this.pngBytes, startPos, this.bytePos - startPos);
452        this.crcValue = this.crc.getValue();
453        this.bytePos = writeInt4((int) this.crcValue, this.bytePos);
454    }
455
456    /**
457     * Perform "sub" filtering on the given row.
458     * Uses temporary array leftBytes to store the original values
459     * of the previous pixels.  The array is 16 bytes long, which
460     * will easily hold two-byte samples plus two-byte alpha.
461     *
462     * @param pixels The array holding the scan lines being built
463     * @param startPos Starting position within pixels of bytes to be filtered.
464     * @param width Width of a scanline in pixels.
465     */
466    protected void filterSub(byte[] pixels, int startPos, int width) {
467        int offset = this.bytesPerPixel;
468        int actualStart = startPos + offset;
469        int nBytes = width * this.bytesPerPixel;
470        int leftInsert = offset;
471        int leftExtract = 0;
472
473        for (int i = actualStart; i < startPos + nBytes; i++) {
474            this.leftBytes[leftInsert] =  pixels[i];
475            pixels[i] = (byte) ((pixels[i] - this.leftBytes[leftExtract])
476                     % 256);
477            leftInsert = (leftInsert + 1) % 0x0f;
478            leftExtract = (leftExtract + 1) % 0x0f;
479        }
480    }
481
482    /**
483     * Perform "up" filtering on the given row.
484     * Side effect: refills the prior row with current row
485     *
486     * @param pixels The array holding the scan lines being built
487     * @param startPos Starting position within pixels of bytes to be filtered.
488     * @param width Width of a scanline in pixels.
489     */
490    protected void filterUp(byte[] pixels, int startPos, int width) {
491
492        final int nBytes = width * this.bytesPerPixel;
493
494        for (int i = 0; i < nBytes; i++) {
495            final byte currentByte = pixels[startPos + i];
496            pixels[startPos + i] = (byte) ((pixels[startPos  + i] 
497                    - this.priorRow[i]) % 256);
498            this.priorRow[i] = currentByte;
499        }
500    }
501
502    /**
503     * Write the image data into the pngBytes array.
504     * This will write one or more PNG "IDAT" chunks. In order
505     * to conserve memory, this method grabs as many rows as will
506     * fit into 32K bytes, or the whole image; whichever is less.
507     *
508     *
509     * @return true if no errors; false if error grabbing pixels
510     */
511    protected boolean writeImageData() {
512        int rowsLeft = this.height;  // number of rows remaining to write
513        int startRow = 0;       // starting row to process this time through
514        int nRows;              // how many rows to grab at a time
515
516        byte[] scanLines;       // the scan lines to be compressed
517        int scanPos;            // where we are in the scan lines
518        int startPos;           // where this line's actual pixels start (used
519                                // for filtering)
520
521        byte[] compressedLines; // the resultant compressed lines
522        int nCompressed;        // how big is the compressed area?
523
524        //int depth;              // color depth ( handle only 8 or 32 )
525
526        PixelGrabber pg;
527
528        this.bytesPerPixel = (this.encodeAlpha) ? 4 : 3;
529
530        Deflater scrunch = new Deflater(this.compressionLevel);
531        ByteArrayOutputStream outBytes = new ByteArrayOutputStream(1024);
532
533        DeflaterOutputStream compBytes = new DeflaterOutputStream(outBytes, 
534                scrunch);
535        try {
536            while (rowsLeft > 0) {
537                nRows = Math.min(32767 / (this.width 
538                        * (this.bytesPerPixel + 1)), rowsLeft);
539                nRows = Math.max(nRows, 1);
540
541                int[] pixels = new int[this.width * nRows];
542
543                pg = new PixelGrabber(this.image, 0, startRow,
544                        this.width, nRows, pixels, 0, this.width);
545                try {
546                    pg.grabPixels();
547                }
548                catch (Exception e) {
549                    System.err.println("interrupted waiting for pixels!");
550                    return false;
551                }
552                if ((pg.getStatus() & ImageObserver.ABORT) != 0) {
553                    System.err.println("image fetch aborted or errored");
554                    return false;
555                }
556
557                /*
558                 * Create a data chunk. scanLines adds "nRows" for
559                 * the filter bytes.
560                 */
561                scanLines = new byte[this.width * nRows * this.bytesPerPixel 
562                                     + nRows];
563
564                if (this.filter == FILTER_SUB) {
565                    this.leftBytes = new byte[16];
566                }
567                if (this.filter == FILTER_UP) {
568                    this.priorRow = new byte[this.width * this.bytesPerPixel];
569                }
570
571                scanPos = 0;
572                startPos = 1;
573                for (int i = 0; i < this.width * nRows; i++) {
574                    if (i % this.width == 0) {
575                        scanLines[scanPos++] = (byte) this.filter;
576                        startPos = scanPos;
577                    }
578                    scanLines[scanPos++] = (byte) ((pixels[i] >> 16) & 0xff);
579                    scanLines[scanPos++] = (byte) ((pixels[i] >>  8) & 0xff);
580                    scanLines[scanPos++] = (byte) ((pixels[i]) & 0xff);
581                    if (this.encodeAlpha) {
582                        scanLines[scanPos++] = (byte) ((pixels[i] >> 24) 
583                                & 0xff);
584                    }
585                    if ((i % this.width == this.width - 1) 
586                            && (this.filter != FILTER_NONE)) {
587                        if (this.filter == FILTER_SUB) {
588                            filterSub(scanLines, startPos, this.width);
589                        }
590                        if (this.filter == FILTER_UP) {
591                            filterUp(scanLines, startPos, this.width);
592                        }
593                    }
594                }
595
596                /*
597                 * Write these lines to the output area
598                 */
599                compBytes.write(scanLines, 0, scanPos);
600
601                startRow += nRows;
602                rowsLeft -= nRows;
603            }
604            compBytes.close();
605
606            /*
607             * Write the compressed bytes
608             */
609            compressedLines = outBytes.toByteArray();
610            nCompressed = compressedLines.length;
611
612            this.crc.reset();
613            this.bytePos = writeInt4(nCompressed, this.bytePos);
614            this.bytePos = writeBytes(IDAT, this.bytePos);
615            this.crc.update(IDAT);
616            this.bytePos = writeBytes(compressedLines, nCompressed, 
617                    this.bytePos);
618            this.crc.update(compressedLines, 0, nCompressed);
619
620            this.crcValue = this.crc.getValue();
621            this.bytePos = writeInt4((int) this.crcValue, this.bytePos);
622            scrunch.finish();
623            return true;
624        }
625        catch (IOException e) {
626            System.err.println(e.toString());
627            return false;
628        }
629    }
630
631    /**
632     * Write a PNG "IEND" chunk into the pngBytes array.
633     */
634    protected void writeEnd() {
635        this.bytePos = writeInt4(0, this.bytePos);
636        this.bytePos = writeBytes(IEND, this.bytePos);
637        this.crc.reset();
638        this.crc.update(IEND);
639        this.crcValue = this.crc.getValue();
640        this.bytePos = writeInt4((int) this.crcValue, this.bytePos);
641    }
642
643
644    /**
645     * Set the DPI for the X axis.
646     *
647     * @param xDpi  The number of dots per inch
648     */
649    public void setXDpi(int xDpi) {
650        this.xDpi = Math.round(xDpi / INCH_IN_METER_UNIT);
651
652    }
653
654    /**
655     * Get the DPI for the X axis.
656     *
657     * @return The number of dots per inch
658     */
659    public int getXDpi() {
660        return Math.round(xDpi * INCH_IN_METER_UNIT);
661    }
662
663    /**
664     * Set the DPI for the Y axis.
665     *
666     * @param yDpi  The number of dots per inch
667     */
668    public void setYDpi(int yDpi) {
669        this.yDpi = Math.round(yDpi / INCH_IN_METER_UNIT);
670    }
671
672    /**
673     * Get the DPI for the Y axis.
674     *
675     * @return The number of dots per inch
676     */
677    public int getYDpi() {
678        return Math.round(yDpi * INCH_IN_METER_UNIT);
679    }
680
681    /**
682     * Set the DPI resolution.
683     *
684     * @param xDpi  The number of dots per inch for the X axis.
685     * @param yDpi  The number of dots per inch for the Y axis.
686     */
687    public void setDpi(int xDpi, int yDpi) {
688        this.xDpi = Math.round(xDpi / INCH_IN_METER_UNIT);
689        this.yDpi = Math.round(yDpi / INCH_IN_METER_UNIT);
690    }
691
692    /**
693     * Write a PNG "pHYs" chunk into the pngBytes array.
694     */
695    protected void writeResolution() {
696        if (xDpi > 0 && yDpi > 0) {
697
698            final int startPos = bytePos = writeInt4(9, bytePos);
699            bytePos = writeBytes(PHYS, bytePos);
700            bytePos = writeInt4(xDpi, bytePos);
701            bytePos = writeInt4(yDpi, bytePos);
702            bytePos = writeByte(1, bytePos); // unit is the meter.
703
704            crc.reset();
705            crc.update(pngBytes, startPos, bytePos - startPos);
706            crcValue = crc.getValue();
707            bytePos = writeInt4((int) crcValue, bytePos);
708        }
709    }
710}