Java tutorial
import java.awt.Image; import java.awt.image.ColorModel; import java.awt.image.IndexColorModel; import java.awt.image.PixelGrabber; import java.io.IOException; import java.io.OutputStream; /** GifEncoder - writes out an image as a GIF. * * Transparency handling and variable bit size courtesy of Jack Palevich. * * Copyright (C) 1996 by Jef Poskanzer <jef@acme.com>. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. 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. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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. * * Visit the ACME Labs Java page for up-to-date versions of this and other * fine Java utilities: http://www.acme.com/java/ */ public class GifEncoder { private boolean interlace = false; private int width, height; private byte[] pixels; private byte[] r, g, b; // the color look-up table private int pixelIndex; private int numPixels; private int transparentPixel = -1; // hpm /** * Constructs a new GifEncoder. * @param width The image width. * @param height The image height. * @param pixels The pixel data. * @param r The red look-up table. * @param g The green look-up table. * @param b The blue look-up table. */ public GifEncoder(int width, int height, byte[] pixels, byte[] r, byte[] g, byte[] b) { this.width = width; this.height = height; this.pixels = pixels; this.r = r; this.g = g; this.b = b; interlace = false; pixelIndex = 0; numPixels = width * height; } /** Constructs a new GifEncoder using an 8-bit AWT Image. The image is assumed to be fully loaded. */ public GifEncoder(Image img) { width = img.getWidth(null); height = img.getHeight(null); pixels = new byte[width * height]; PixelGrabber pg = new PixelGrabber(img, 0, 0, width, height, false); try { pg.grabPixels(); } catch (InterruptedException e) { System.err.println(e); } ColorModel cm = pg.getColorModel(); if (cm instanceof IndexColorModel) { pixels = (byte[]) (pg.getPixels()); // hpm IndexColorModel icm = (IndexColorModel) cm; setTransparentPixel(icm.getTransparentPixel()); } else throw new IllegalArgumentException("IMAGE_ERROR"); IndexColorModel m = (IndexColorModel) cm; int mapSize = m.getMapSize(); r = new byte[mapSize]; g = new byte[mapSize]; b = new byte[mapSize]; m.getReds(r); m.getGreens(g); m.getBlues(b); interlace = false; pixelIndex = 0; numPixels = width * height; } /** Saves the image as a GIF file. */ public void write(OutputStream out) throws IOException { // Figure out how many bits to use. int numColors = r.length; int BitsPerPixel; if (numColors <= 2) BitsPerPixel = 1; else if (numColors <= 4) BitsPerPixel = 2; else if (numColors <= 16) BitsPerPixel = 4; else BitsPerPixel = 8; int ColorMapSize = 1 << BitsPerPixel; byte[] reds = new byte[ColorMapSize]; byte[] grns = new byte[ColorMapSize]; byte[] blus = new byte[ColorMapSize]; for (int i = 0; i < numColors; i++) { reds[i] = r[i]; grns[i] = g[i]; blus[i] = b[i]; } // hpm GIFEncode(out, width, height, interlace, (byte) 0, getTransparentPixel(), BitsPerPixel, reds, grns, blus); } // hpm public void setTransparentPixel(int pixel) { transparentPixel = pixel; } // hpm public int getTransparentPixel() { return transparentPixel; } static void writeString(OutputStream out, String str) throws IOException { byte[] buf = str.getBytes(); out.write(buf); } // Adapted from ppmtogif, which is based on GIFENCOD by David // Rowley <mgardi@watdscu.waterloo.edu>. Lempel-Zim compression // based on "compress". int Width, Height; boolean Interlace; void GIFEncode(OutputStream outs, int Width, int Height, boolean Interlace, byte Background, int Transparent, int BitsPerPixel, byte[] Red, byte[] Green, byte[] Blue) throws IOException { byte B; int LeftOfs, TopOfs; int ColorMapSize; int InitCodeSize; int i; this.Width = Width; this.Height = Height; this.Interlace = Interlace; ColorMapSize = 1 << BitsPerPixel; LeftOfs = TopOfs = 0; // The initial code size if (BitsPerPixel <= 1) InitCodeSize = 2; else InitCodeSize = BitsPerPixel; // Write the Magic header writeString(outs, "GIF89a"); // Write out the screen width and height Putword(Width, outs); Putword(Height, outs); // Indicate that there is a global colour map B = (byte) 0x80; // Yes, there is a color map // OR in the resolution B |= (byte) ((8 - 1) << 4); // Not sorted // OR in the Bits per Pixel B |= (byte) ((BitsPerPixel - 1)); // Write it out Putbyte(B, outs); // Write out the Background colour Putbyte(Background, outs); // Pixel aspect ratio - 1:1. //Putbyte( (byte) 49, outs ); // Java's GIF reader currently has a bug, if the aspect ratio byte is // not zero it throws an ImageFormatException. It doesn't know that // 49 means a 1:1 aspect ratio. Well, whatever, zero works with all // the other decoders I've tried so it probably doesn't hurt. Putbyte((byte) 0, outs); // Write out the Global Colour Map for (i = 0; i < ColorMapSize; ++i) { Putbyte(Red[i], outs); Putbyte(Green[i], outs); Putbyte(Blue[i], outs); } // Write out extension for transparent colour index, if necessary. if (Transparent != -1) { Putbyte((byte) '!', outs); Putbyte((byte) 0xf9, outs); Putbyte((byte) 4, outs); Putbyte((byte) 1, outs); Putbyte((byte) 0, outs); Putbyte((byte) 0, outs); Putbyte((byte) Transparent, outs); Putbyte((byte) 0, outs); } // Write an Image separator Putbyte((byte) ',', outs); // Write the Image header Putword(LeftOfs, outs); Putword(TopOfs, outs); Putword(Width, outs); Putword(Height, outs); // Write out whether or not the image is interlaced if (Interlace) Putbyte((byte) 0x40, outs); else Putbyte((byte) 0x00, outs); // Write out the initial code size Putbyte((byte) InitCodeSize, outs); // Go and actually compress the data compress(InitCodeSize + 1, outs); // Write out a Zero-length packet (to end the series) Putbyte((byte) 0, outs); // Write the GIF file terminator Putbyte((byte) ';', outs); } static final int EOF = -1; // Return the next pixel from the image int GIFNextPixel() throws IOException { if (pixelIndex == numPixels) return EOF; else return ((byte[]) pixels)[pixelIndex++] & 0xff; } // Write out a word to the GIF file void Putword(int w, OutputStream outs) throws IOException { Putbyte((byte) (w & 0xff), outs); Putbyte((byte) ((w >> 8) & 0xff), outs); } // Write out a byte to the GIF file void Putbyte(byte b, OutputStream outs) throws IOException { outs.write(b); } // GIFCOMPR.C - GIF Image compression routines // // Lempel-Ziv compression based on 'compress'. GIF modifications by // David Rowley (mgardi@watdcsu.waterloo.edu) // General DEFINEs static final int BITS = 12; static final int HSIZE = 5003; // 80% occupancy // GIF Image compression - modified 'compress' // // Based on: compress.c - File compression ala IEEE Computer, June 1984. // // By Authors: Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas) // Jim McKie (decvax!mcvax!jim) // Steve Davies (decvax!vax135!petsd!peora!srd) // Ken Turkowski (decvax!decwrl!turtlevax!ken) // James A. Woods (decvax!ihnp4!ames!jaw) // Joe Orost (decvax!vax135!petsd!joe) int n_bits; // number of bits/code int maxbits = BITS; // user settable max # bits/code int maxcode; // maximum code, given n_bits int maxmaxcode = 1 << BITS; // should NEVER generate this code final int MAXCODE(int n_bits) { return (1 << n_bits) - 1; } int[] htab = new int[HSIZE]; int[] codetab = new int[HSIZE]; int hsize = HSIZE; // for dynamic table sizing int free_ent = 0; // first unused entry // block compression parameters -- after all codes are used up, // and compression rate changes, start over. boolean clear_flg = false; // Algorithm: use open addressing double hashing (no chaining) on the // prefix code / next character combination. We do a variant of Knuth's // algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime // secondary probe. Here, the modular division first probe is gives way // to a faster exclusive-or manipulation. Also do block compression with // an adaptive reset, whereby the code table is cleared when the compression // ratio decreases, but after the table fills. The variable-length output // codes are re-sized at this point, and a special CLEAR code is generated // for the decompressor. Late addition: construct the table according to // file size for noticeable speed improvement on small files. Please direct // questions about this implementation to ames!jaw. int g_init_bits; int ClearCode; int EOFCode; void compress(int init_bits, OutputStream outs) throws IOException { int fcode; int i /* = 0 */; int c; int ent; int disp; int hsize_reg; int hshift; // Set up the globals: g_init_bits - initial number of bits g_init_bits = init_bits; // Set up the necessary values clear_flg = false; n_bits = g_init_bits; maxcode = MAXCODE(n_bits); ClearCode = 1 << (init_bits - 1); EOFCode = ClearCode + 1; free_ent = ClearCode + 2; char_init(); ent = GIFNextPixel(); hshift = 0; for (fcode = hsize; fcode < 65536; fcode *= 2) ++hshift; hshift = 8 - hshift; // set hash code range bound hsize_reg = hsize; cl_hash(hsize_reg); // clear hash table output(ClearCode, outs); outer_loop: while ((c = GIFNextPixel()) != EOF) { fcode = (c << maxbits) + ent; i = (c << hshift) ^ ent; // xor hashing if (htab[i] == fcode) { ent = codetab[i]; continue; } else if (htab[i] >= 0) // non-empty slot { disp = hsize_reg - i; // secondary hash (after G. Knott) if (i == 0) disp = 1; do { if ((i -= disp) < 0) i += hsize_reg; if (htab[i] == fcode) { ent = codetab[i]; continue outer_loop; } } while (htab[i] >= 0); } output(ent, outs); ent = c; if (free_ent < maxmaxcode) { codetab[i] = free_ent++; // code -> hashtable htab[i] = fcode; } else cl_block(outs); } // Put out the final code. output(ent, outs); output(EOFCode, outs); } // output // // Output the given code. // Inputs: // code: A n_bits-bit integer. If == -1, then EOF. This assumes // that n_bits =< wordsize - 1. // Outputs: // Outputs code to the file. // Assumptions: // Chars are 8 bits long. // Algorithm: // Maintain a BITS character long buffer (so that 8 codes will // fit in it exactly). Use the VAX insv instruction to insert each // code in turn. When the buffer fills up empty it and start over. int cur_accum = 0; int cur_bits = 0; int masks[] = { 0x0000, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF, 0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF }; void output(int code, OutputStream outs) throws IOException { cur_accum &= masks[cur_bits]; if (cur_bits > 0) cur_accum |= (code << cur_bits); else cur_accum = code; cur_bits += n_bits; while (cur_bits >= 8) { char_out((byte) (cur_accum & 0xff), outs); cur_accum >>= 8; cur_bits -= 8; } // If the next entry is going to be too big for the code size, // then increase it, if possible. if (free_ent > maxcode || clear_flg) { if (clear_flg) { maxcode = MAXCODE(n_bits = g_init_bits); clear_flg = false; } else { ++n_bits; if (n_bits == maxbits) maxcode = maxmaxcode; else maxcode = MAXCODE(n_bits); } } if (code == EOFCode) { // At EOF, write the rest of the buffer. while (cur_bits > 0) { char_out((byte) (cur_accum & 0xff), outs); cur_accum >>= 8; cur_bits -= 8; } flush_char(outs); } } // Clear out the hash table // table clear for block compress void cl_block(OutputStream outs) throws IOException { cl_hash(hsize); free_ent = ClearCode + 2; clear_flg = true; output(ClearCode, outs); } // reset code table void cl_hash(int hsize) { for (int i = 0; i < hsize; ++i) htab[i] = -1; } // GIF Specific routines // Number of characters so far in this 'packet' int a_count; // Set up the 'byte output' routine void char_init() { a_count = 0; } // Define the storage for the packet accumulator byte[] accum = new byte[256]; // Add a character to the end of the current packet, and if it is 254 // characters, flush the packet to disk. void char_out(byte c, OutputStream outs) throws IOException { accum[a_count++] = c; if (a_count >= 254) flush_char(outs); } // Flush the packet to disk, and reset the accumulator void flush_char(OutputStream outs) throws IOException { if (a_count > 0) { outs.write(a_count); outs.write(accum, 0, a_count); a_count = 0; } } } class GifEncoderHashitem { public int rgb; public int count; public int index; public boolean isTransparent; public GifEncoderHashitem(int rgb, int count, int index, boolean isTransparent) { this.rgb = rgb; this.count = count; this.index = index; this.isTransparent = isTransparent; } }