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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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/*-
 *      Reads GIF images from an InputStream and reports the
 *      image data to an InputStreamImageSource object.
 *
 * The algorithm is copyright of CompuServe.
 */
package sun.awt.image;

import java.util.Vector;
import java.util.Hashtable;
import java.io.InputStream;
import java.io.IOException;
import java.awt.image.*;

Gif Image converter
Author:Arthur van Hoff, Jim Graham
/** * Gif Image converter * * @author Arthur van Hoff * @author Jim Graham */
public class GifImageDecoder extends ImageDecoder { private static final boolean verbose = false; private static final int IMAGESEP = 0x2c; private static final int EXBLOCK = 0x21; private static final int EX_GRAPHICS_CONTROL= 0xf9; private static final int EX_COMMENT = 0xfe; private static final int EX_APPLICATION = 0xff; private static final int TERMINATOR = 0x3b; private static final int TRANSPARENCYMASK = 0x01; private static final int INTERLACEMASK = 0x40; private static final int COLORMAPMASK = 0x80; int num_global_colors; byte[] global_colormap; int trans_pixel = -1; IndexColorModel global_model; Hashtable props = new Hashtable(); byte[] saved_image; IndexColorModel saved_model; int global_width; int global_height; int global_bgpixel; GifFrame curframe; public GifImageDecoder(InputStreamImageSource src, InputStream is) { super(src, is); }
An error has occurred. Throw an exception.
/** * An error has occurred. Throw an exception. */
private static void error(String s1) throws ImageFormatException { throw new ImageFormatException(s1); }
Read a number of bytes into a buffer.
Returns:number of bytes that were not read due to EOF or error
/** * Read a number of bytes into a buffer. * @return number of bytes that were not read due to EOF or error */
private int readBytes(byte buf[], int off, int len) { while (len > 0) { try { int n = input.read(buf, off, len); if (n < 0) { break; } off += n; len -= n; } catch (IOException e) { break; } } return len; } private static final int ExtractByte(byte buf[], int off) { return (buf[off] & 0xFF); } private static final int ExtractWord(byte buf[], int off) { return (buf[off] & 0xFF) | ((buf[off + 1] & 0xFF) << 8); }
produce an image from the stream.
/** * produce an image from the stream. */
public void produceImage() throws IOException, ImageFormatException { try { readHeader(); int totalframes = 0; int frameno = 0; int nloops = -1; int disposal_method = 0; int delay = -1; boolean loopsRead = false; boolean isAnimation = false; while (!aborted) { int code; switch (code = input.read()) { case EXBLOCK: switch (code = input.read()) { case EX_GRAPHICS_CONTROL: { byte buf[] = new byte[6]; if (readBytes(buf, 0, 6) != 0) { return;//error("corrupt GIF file"); } if ((buf[0] != 4) || (buf[5] != 0)) { return;//error("corrupt GIF file (GCE size)"); } // Get the index of the transparent color delay = ExtractWord(buf, 2) * 10; if (delay > 0 && !isAnimation) { isAnimation = true; ImageFetcher.startingAnimation(); } disposal_method = (buf[1] >> 2) & 7; if ((buf[1] & TRANSPARENCYMASK) != 0) { trans_pixel = ExtractByte(buf, 4); } else { trans_pixel = -1; } break; } case EX_COMMENT: case EX_APPLICATION: default: boolean loop_tag = false; String comment = ""; while (true) { int n = input.read(); if (n <= 0) { break; } byte buf[] = new byte[n]; if (readBytes(buf, 0, n) != 0) { return;//error("corrupt GIF file"); } if (code == EX_COMMENT) { comment += new String(buf, 0); } else if (code == EX_APPLICATION) { if (loop_tag) { if (n == 3 && buf[0] == 1) { if (loopsRead) { ExtractWord(buf, 1); } else { nloops = ExtractWord(buf, 1); loopsRead = true; } } else { loop_tag = false; } } if ("NETSCAPE2.0".equals(new String(buf, 0))) { loop_tag = true; } } } if (code == EX_COMMENT) { props.put("comment", comment); } if (loop_tag && !isAnimation) { isAnimation = true; ImageFetcher.startingAnimation(); } break; case -1: return; //error("corrupt GIF file"); } break; case IMAGESEP: if (!isAnimation) { input.mark(0); // we don't need the mark buffer } try { if (!readImage(totalframes == 0, disposal_method, delay)) { return; } } catch (Exception e) { if (verbose) { e.printStackTrace(); } return; } frameno++; totalframes++; break; default: case -1: if (verbose) { if (code == -1) { System.err.println("Premature EOF in GIF file," + " frame " + frameno); } else { System.err.println("corrupt GIF file (parse) [" + code + "]."); } } if (frameno == 0) { return; } // NOBREAK case TERMINATOR: if (nloops == 0 || nloops-- >= 0) { try { if (curframe != null) { curframe.dispose(); curframe = null; } input.reset(); saved_image = null; saved_model = null; frameno = 0; break; } catch (IOException e) { return; // Unable to reset input buffer } } if (verbose && frameno != 1) { System.out.println("processing GIF terminator," + " frames: " + frameno + " total: " + totalframes); } imageComplete(ImageConsumer.STATICIMAGEDONE, true); return; } } } finally { close(); } }
Read Image header
/** * Read Image header */
private void readHeader() throws IOException, ImageFormatException { // Create a buffer byte buf[] = new byte[13]; // Read the header if (readBytes(buf, 0, 13) != 0) { throw new IOException(); } // Check header if ((buf[0] != 'G') || (buf[1] != 'I') || (buf[2] != 'F')) { error("not a GIF file."); } // Global width&height global_width = ExtractWord(buf, 6); global_height = ExtractWord(buf, 8); // colormap info int ch = ExtractByte(buf, 10); if ((ch & COLORMAPMASK) == 0) { // no global colormap so make up our own // If there is a local colormap, it will override what we // have here. If there is not a local colormap, the rules // for GIF89 say that we can use whatever colormap we want. // This means that we should probably put in a full 256 colormap // at some point. REMIND! num_global_colors = 2; global_bgpixel = 0; global_colormap = new byte[2*3]; global_colormap[0] = global_colormap[1] = global_colormap[2] = (byte)0; global_colormap[3] = global_colormap[4] = global_colormap[5] = (byte)255; } else { num_global_colors = 1 << ((ch & 0x7) + 1); global_bgpixel = ExtractByte(buf, 11); if (buf[12] != 0) { props.put("aspectratio", ""+((ExtractByte(buf, 12) + 15) / 64.0)); } // Read colors global_colormap = new byte[num_global_colors * 3]; if (readBytes(global_colormap, 0, num_global_colors * 3) != 0) { throw new IOException(); } } input.mark(Integer.MAX_VALUE); // set this mark in case this is an animated GIF }
The ImageConsumer hints flag for a non-interlaced GIF image.
/** * The ImageConsumer hints flag for a non-interlaced GIF image. */
private static final int normalflags = ImageConsumer.TOPDOWNLEFTRIGHT | ImageConsumer.COMPLETESCANLINES | ImageConsumer.SINGLEPASS | ImageConsumer.SINGLEFRAME;
The ImageConsumer hints flag for an interlaced GIF image.
/** * The ImageConsumer hints flag for an interlaced GIF image. */
private static final int interlaceflags = ImageConsumer.RANDOMPIXELORDER | ImageConsumer.COMPLETESCANLINES | ImageConsumer.SINGLEPASS | ImageConsumer.SINGLEFRAME; private short prefix[] = new short[4096]; private byte suffix[] = new byte[4096]; private byte outCode[] = new byte[4097]; private static native void initIDs(); static { /* ensure that the necessary native libraries are loaded */ NativeLibLoader.loadLibraries(); initIDs(); } private native boolean parseImage(int x, int y, int width, int height, boolean interlace, int initCodeSize, byte block[], byte rasline[], IndexColorModel model); private int sendPixels(int x, int y, int width, int height, byte rasline[], ColorModel model) { int rasbeg, rasend, x2; if (y < 0) { height += y; y = 0; } if (y + height > global_height) { height = global_height - y; } if (height <= 0) { return 1; } // rasline[0] == pixel at coordinate (x,y) // rasline[width] == pixel at coordinate (x+width, y) if (x < 0) { rasbeg = -x; width += x; // same as (width -= rasbeg) x2 = 0; // same as (x2 = x + rasbeg) } else { rasbeg = 0; // width -= 0; // same as (width -= rasbeg) x2 = x; // same as (x2 = x + rasbeg) } // rasline[rasbeg] == pixel at coordinate (x2,y) // rasline[width] == pixel at coordinate (x+width, y) // rasline[rasbeg + width] == pixel at coordinate (x2+width, y) if (x2 + width > global_width) { width = global_width - x2; } if (width <= 0) { return 1; } rasend = rasbeg + width; // rasline[rasbeg] == pixel at coordinate (x2,y) // rasline[rasend] == pixel at coordinate (x2+width, y) int off = y * global_width + x2; boolean save = (curframe.disposal_method == GifFrame.DISPOSAL_SAVE); if (trans_pixel >= 0 && !curframe.initialframe) { if (saved_image != null && model.equals(saved_model)) { for (int i = rasbeg; i < rasend; i++, off++) { byte pixel = rasline[i]; if ((pixel & 0xff) == trans_pixel) { rasline[i] = saved_image[off]; } else if (save) { saved_image[off] = pixel; } } } else { // We have to do this the hard way - only transmit // the non-transparent sections of the line... // Fix for 6301050: the interlacing is ignored in this case // in order to avoid artefacts in case of animated images. int runstart = -1; int count = 1; for (int i = rasbeg; i < rasend; i++, off++) { byte pixel = rasline[i]; if ((pixel & 0xff) == trans_pixel) { if (runstart >= 0) { count = setPixels(x + runstart, y, i - runstart, 1, model, rasline, runstart, 0); if (count == 0) { break; } } runstart = -1; } else { if (runstart < 0) { runstart = i; } if (save) { saved_image[off] = pixel; } } } if (runstart >= 0) { count = setPixels(x + runstart, y, rasend - runstart, 1, model, rasline, runstart, 0); } return count; } } else if (save) { System.arraycopy(rasline, rasbeg, saved_image, off, width); } int count = setPixels(x2, y, width, height, model, rasline, rasbeg, 0); return count; }
Read Image data
/** * Read Image data */
private boolean readImage(boolean first, int disposal_method, int delay) throws IOException { if (curframe != null && !curframe.dispose()) { abort(); return false; } long tm = 0; if (verbose) { tm = System.currentTimeMillis(); } // Allocate the buffer byte block[] = new byte[256 + 3]; // Read the image descriptor if (readBytes(block, 0, 10) != 0) { throw new IOException(); } int x = ExtractWord(block, 0); int y = ExtractWord(block, 2); int width = ExtractWord(block, 4); int height = ExtractWord(block, 6); /* * Majority of gif images have * same logical screen and frame dimensions. * Also, Photoshop and Mozilla seem to use the logical * screen dimension (from the global stream header) * if frame dimension is invalid. * * We use similar heuristic and trying to recover * frame width from logical screen dimension and * frame offset. */ if (width == 0 && global_width != 0) { width = global_width - x; } if (height == 0 && global_height != 0) { height = global_height - y; } boolean interlace = (block[8] & INTERLACEMASK) != 0; IndexColorModel model = global_model; if ((block[8] & COLORMAPMASK) != 0) { // We read one extra byte above so now when we must // transfer that byte as the first colormap byte // and manually read the code size when we are done int num_local_colors = 1 << ((block[8] & 0x7) + 1); // Read local colors byte[] local_colormap = new byte[num_local_colors * 3]; local_colormap[0] = block[9]; if (readBytes(local_colormap, 1, num_local_colors * 3 - 1) != 0) { throw new IOException(); } // Now read the "real" code size byte which follows // the local color table if (readBytes(block, 9, 1) != 0) { throw new IOException(); } if (trans_pixel >= num_local_colors) { // Fix for 4233748: extend colormap to contain transparent pixel num_local_colors = trans_pixel + 1; local_colormap = grow_colormap(local_colormap, num_local_colors); } model = new IndexColorModel(8, num_local_colors, local_colormap, 0, false, trans_pixel); } else if (model == null || trans_pixel != model.getTransparentPixel()) { if (trans_pixel >= num_global_colors) { // Fix for 4233748: extend colormap to contain transparent pixel num_global_colors = trans_pixel + 1; global_colormap = grow_colormap(global_colormap, num_global_colors); } model = new IndexColorModel(8, num_global_colors, global_colormap, 0, false, trans_pixel); global_model = model; } // Notify the consumers if (first) { if (global_width == 0) global_width = width; if (global_height == 0) global_height = height; setDimensions(global_width, global_height); setProperties(props); setColorModel(model); headerComplete(); } if (disposal_method == GifFrame.DISPOSAL_SAVE && saved_image == null) { saved_image = new byte[global_width * global_height]; /* * If height of current image is smaller than the global height, * fill the gap with transparent pixels. */ if ((height < global_height) && (model != null)) { byte tpix = (byte)model.getTransparentPixel(); if (tpix >= 0) { byte trans_rasline[] = new byte[global_width]; for (int i=0; i<global_width;i++) { trans_rasline[i] = tpix; } setPixels(0, 0, global_width, y, model, trans_rasline, 0, 0); setPixels(0, y+height, global_width, global_height-height-y, model, trans_rasline, 0, 0); } } } int hints = (interlace ? interlaceflags : normalflags); setHints(hints); curframe = new GifFrame(this, disposal_method, delay, (curframe == null), model, x, y, width, height); // allocate the raster data byte rasline[] = new byte[width]; if (verbose) { System.out.print("Reading a " + width + " by " + height + " " + (interlace ? "" : "non-") + "interlaced image..."); } int initCodeSize = ExtractByte(block, 9); if (initCodeSize >= 12) { if (verbose) { System.out.println("Invalid initial code size: " + initCodeSize); } return false; } boolean ret = parseImage(x, y, width, height, interlace, initCodeSize, block, rasline, model); if (!ret) { abort(); } if (verbose) { System.out.println("done in " + (System.currentTimeMillis() - tm) + "ms"); } return ret; } public static byte[] grow_colormap(byte[] colormap, int newlen) { byte[] newcm = new byte[newlen * 3]; System.arraycopy(colormap, 0, newcm, 0, colormap.length); return newcm; } } class GifFrame { private static final boolean verbose = false; private static IndexColorModel trans_model; static final int DISPOSAL_NONE = 0x00; static final int DISPOSAL_SAVE = 0x01; static final int DISPOSAL_BGCOLOR = 0x02; static final int DISPOSAL_PREVIOUS = 0x03; GifImageDecoder decoder; int disposal_method; int delay; IndexColorModel model; int x; int y; int width; int height; boolean initialframe; public GifFrame(GifImageDecoder id, int dm, int dl, boolean init, IndexColorModel cm, int x, int y, int w, int h) { this.decoder = id; this.disposal_method = dm; this.delay = dl; this.model = cm; this.initialframe = init; this.x = x; this.y = y; this.width = w; this.height = h; } private void setPixels(int x, int y, int w, int h, ColorModel cm, byte[] pix, int off, int scan) { decoder.setPixels(x, y, w, h, cm, pix, off, scan); } public boolean dispose() { if (decoder.imageComplete(ImageConsumer.SINGLEFRAMEDONE, false) == 0) { return false; } else { if (delay > 0) { try { if (verbose) { System.out.println("sleeping: "+delay); } Thread.sleep(delay); } catch (InterruptedException e) { return false; } } else { Thread.yield(); } if (verbose && disposal_method != 0) { System.out.println("disposal method: "+disposal_method); } int global_width = decoder.global_width; int global_height = decoder.global_height; if (x < 0) { width += x; x = 0; } if (x + width > global_width) { width = global_width - x; } if (width <= 0) { disposal_method = DISPOSAL_NONE; } else { if (y < 0) { height += y; y = 0; } if (y + height > global_height) { height = global_height - y; } if (height <= 0) { disposal_method = DISPOSAL_NONE; } } switch (disposal_method) { case DISPOSAL_PREVIOUS: byte[] saved_image = decoder.saved_image; IndexColorModel saved_model = decoder.saved_model; if (saved_image != null) { setPixels(x, y, width, height, saved_model, saved_image, y * global_width + x, global_width); } break; case DISPOSAL_BGCOLOR: byte tpix; if (model.getTransparentPixel() < 0) { model = trans_model; if (model == null) { model = new IndexColorModel(8, 1, new byte[4], 0, true); trans_model = model; } tpix = 0; } else { tpix = (byte) model.getTransparentPixel(); } byte[] rasline = new byte[width]; if (tpix != 0) { for (int i = 0; i < width; i++) { rasline[i] = tpix; } } // clear saved_image using transparent pixels // this will be used as the background in the next display if( decoder.saved_image != null ) { for( int i = 0; i < global_width * global_height; i ++ ) decoder.saved_image[i] = tpix; } setPixels(x, y, width, height, model, rasline, 0, 0); break; case DISPOSAL_SAVE: decoder.saved_model = model; break; } } return true; } }