001    package com.keypoint;
002    
003    import java.awt.Image;
004    import java.awt.image.ImageObserver;
005    import java.awt.image.PixelGrabber;
006    import java.io.ByteArrayOutputStream;
007    import java.io.IOException;
008    import java.util.zip.CRC32;
009    import java.util.zip.Deflater;
010    import 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    
054    public 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    }