Java tutorial
/* * * This file is part of the iText (R) project. Copyright (c) 1998-2019 iText Group NV * Authors: Bruno Lowagie, Paulo Soares, et al. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU Affero General Public License version 3 * as published by the Free Software Foundation with the addition of the * following permission added to Section 15 as permitted in Section 7(a): * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT * OF THIRD PARTY RIGHTS * * This program 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 Affero General Public License for more details. * You should have received a copy of the GNU Affero General Public License * along with this program; if not, see http://www.gnu.org/licenses or write to * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, * Boston, MA, 02110-1301 USA, or download the license from the following URL: * http://itextpdf.com/terms-of-use/ * * The interactive user interfaces in modified source and object code versions * of this program must display Appropriate Legal Notices, as required under * Section 5 of the GNU Affero General Public License. * * In accordance with Section 7(b) of the GNU Affero General Public License, * a covered work must retain the producer line in every PDF that is created * or manipulated using iText. * * You can be released from the requirements of the license by purchasing * a commercial license. Buying such a license is mandatory as soon as you * develop commercial activities involving the iText software without * disclosing the source code of your own applications. * These activities include: offering paid services to customers as an ASP, * serving PDFs on the fly in a web application, shipping iText with a closed * source product. * * For more information, please contact iText Software Corp. at this * address: sales@itextpdf.com */ package com.itextpdf.text.pdf.codec; import com.itextpdf.text.DocWriter; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.OutputStream; import java.util.zip.DeflaterOutputStream; /** * Writes a PNG image. * * @author Paulo Soares * @since 5.0.3 */ public class PngWriter { private static final byte[] PNG_SIGNTURE = { (byte) 137, 80, 78, 71, 13, 10, 26, 10 }; private static final byte[] IHDR = DocWriter.getISOBytes("IHDR"); private static final byte[] PLTE = DocWriter.getISOBytes("PLTE"); private static final byte[] IDAT = DocWriter.getISOBytes("IDAT"); private static final byte[] IEND = DocWriter.getISOBytes("IEND"); private static final byte[] iCCP = DocWriter.getISOBytes("iCCP"); private static int[] crc_table; private OutputStream outp; public PngWriter(OutputStream outp) throws IOException { this.outp = outp; outp.write(PNG_SIGNTURE); } public void writeHeader(int width, int height, int bitDepth, int colorType) throws IOException { ByteArrayOutputStream ms = new ByteArrayOutputStream(); outputInt(width, ms); outputInt(height, ms); ms.write(bitDepth); ms.write(colorType); ms.write(0); ms.write(0); ms.write(0); writeChunk(IHDR, ms.toByteArray()); } public void writeEnd() throws IOException { writeChunk(IEND, new byte[0]); } public void writeData(byte[] data, final int stride) throws IOException { ByteArrayOutputStream stream = new ByteArrayOutputStream(); DeflaterOutputStream zip = new DeflaterOutputStream(stream); int k; for (k = 0; k < data.length - stride; k += stride) { zip.write(0); zip.write(data, k, stride); } int remaining = data.length - k; if (remaining > 0) { zip.write(0); zip.write(data, k, remaining); } zip.close(); writeChunk(IDAT, stream.toByteArray()); } public void writePalette(byte[] data) throws IOException { writeChunk(PLTE, data); } public void writeIccProfile(byte[] data) throws IOException { ByteArrayOutputStream stream = new ByteArrayOutputStream(); stream.write((byte) 'I'); stream.write((byte) 'C'); stream.write((byte) 'C'); stream.write(0); stream.write(0); DeflaterOutputStream zip = new DeflaterOutputStream(stream); zip.write(data); zip.close(); writeChunk(iCCP, stream.toByteArray()); } private static void make_crc_table() { if (crc_table != null) return; int[] crc2 = new int[256]; for (int n = 0; n < 256; n++) { int c = n; for (int k = 0; k < 8; k++) { if ((c & 1) != 0) c = 0xedb88320 ^ (c >>> 1); else c = c >>> 1; } crc2[n] = c; } crc_table = crc2; } private static int update_crc(int crc, byte[] buf, int offset, int len) { int c = crc; if (crc_table == null) make_crc_table(); for (int n = 0; n < len; n++) { c = crc_table[(c ^ buf[n + offset]) & 0xff] ^ (c >>> 8); } return c; } private static int crc(byte[] buf, int offset, int len) { return update_crc(0xffffffff, buf, offset, len) ^ 0xffffffff; } private static int crc(byte[] buf) { return update_crc(0xffffffff, buf, 0, buf.length) ^ 0xffffffff; } public void outputInt(int n) throws IOException { outputInt(n, outp); } public static void outputInt(int n, OutputStream s) throws IOException { s.write((byte) (n >> 24)); s.write((byte) (n >> 16)); s.write((byte) (n >> 8)); s.write((byte) n); } public void writeChunk(byte[] chunkType, byte[] data) throws IOException { outputInt(data.length); outp.write(chunkType, 0, 4); outp.write(data); int c = update_crc(0xffffffff, chunkType, 0, chunkType.length); c = update_crc(c, data, 0, data.length) ^ 0xffffffff; outputInt(c); } }