import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;
public class GifDecoder {
/** File read status: No errors. */
public static final int STATUS_OK = 0;
/** File read status: Error decoding file (may be partially decoded) */
public static final int STATUS_FORMAT_ERROR = 1;
/** File read status: Unable to open source. */
public static final int STATUS_OPEN_ERROR = 2;
private BufferedInputStream in;
private int status;
private int width; // full image width
private int height; // full image height
private boolean gctFlag; // global color table used
private int gctSize; // size of global color table
private int loopCount = 1; // iterations; 0 = repeat forever
private int[] gct; // global color table
private int[] lct; // local color table
private int[] act; // active color table
private int bgIndex; // background color index
private int bgColor; // background color
private int lastBgColor; // previous bg color
@SuppressWarnings("unused")
private int pixelAspect; // pixel aspect ratio
private boolean lctFlag; // local color table flag
private boolean interlace; // interlace flag
private int lctSize; // local color table size
private int ix, iy, iw, ih; // current image rectangle
private Rectangle lastRect; // last image rect
private BufferedImage image; // current frame
private BufferedImage lastImage; // previous frame
private byte[] block = new byte[256]; // current data block
private int blockSize = 0; // block size
// last graphic control extension info
private int dispose = 0;
// 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prev
private int lastDispose = 0;
private boolean transparency = false; // use transparent color
private int delay = 0; // delay in milliseconds
private int transIndex; // transparent color index
private static final int MaxStackSize = 4096;
// max decoder pixel stack size
// LZW decoder working arrays
private short[] prefix;
private byte[] suffix;
private byte[] pixelStack;
private byte[] pixels;
private ArrayList<GifFrame> frames; // frames read from current file
private int frameCount;
static class GifFrame {
public GifFrame(BufferedImage im, int del) {
image = im;
delay = del;
}
public BufferedImage image;
public int delay;
}
/**
* Gets display duration for specified frame.
* @param n
* int index of frame
* @return delay in milliseconds
*/
public int getDelay(int n) {
//
delay = -1;
if ((n >= 0) && (n < frameCount)) {
delay = ((GifFrame) frames.get(n)).delay;
}
return delay;
}
/**
* Gets the number of frames read from file.
* @return frame count
*/
public int getFrameCount() {
return frameCount;
}
/**
* Gets the first (or only) image read.
* @return BufferedImage containing first frame, or null if none.
*/
public BufferedImage getImage() {
return getFrame(0);
}
/**
* Gets the "Netscape" iteration count, if any. A count of 0 means repeat
* indefinitiely.
* @return iteration count if one was specified, else 1.
*/
public int getLoopCount() {
return loopCount;
}
/**
* Creates new frame image from current data (and previous frames as
* specified by their disposition codes).
*/
protected void setPixels() {
// expose destination image's pixels as int array
int[] dest = ((DataBufferInt) image.getRaster().getDataBuffer())
.getData();
// fill in starting image contents based on last image's dispose code
if (lastDispose > 0) {
if (lastDispose == 3) {
// use image before last
int n = frameCount - 2;
if (n > 0) {
lastImage = getFrame(n - 1);
} else {
lastImage = null;
}
}
if (lastImage != null) {
int[] prev = ((DataBufferInt) lastImage.getRaster()
.getDataBuffer()).getData();
System.arraycopy(prev, 0, dest, 0, width * height);
// copy pixels
if (lastDispose == 2) {
// fill last image rect area with background color
Graphics2D g = image.createGraphics();
Color c = null;
if (transparency) {
c = new Color(0, 0, 0, 0); // assume background is
// transparent
} else {
c = new Color(lastBgColor); // use given background
// color
}
g.setColor(c);
g.setComposite(AlphaComposite.Src); // replace area
g.fill(lastRect);
g.dispose();
}
}
}
// copy each source line to the appropriate place in the destination
int pass = 1;
int inc = 8;
int iline = 0;
for (int i = 0; i < ih; i++) {
int line = i;
if (interlace) {
if (iline >= ih) {
pass++;
switch (pass) {
case 2:
iline = 4;
break;
case 3:
iline = 2;
inc = 4;
break;
case 4:
iline = 1;
inc = 2;
}
}
line = iline;
iline += inc;
}
line += iy;
if (line < height) {
int k = line * width;
int dx = k + ix; // start of line in dest
int dlim = dx + iw; // end of dest line
if ((k + width) < dlim) {
dlim = k + width; // past dest edge
}
int sx = i * iw; // start of line in source
while (dx < dlim) {
// map color and insert in destination
int index = ((int) pixels[sx++]) & 0xff;
int c = act[index];
if (c != 0) {
dest[dx] = c;
}
dx++;
}
}
}
} // setPixels()
/**
* Gets the image contents of frame n.
* @return BufferedImage representation of frame, or null if n is invalid.
*/
public BufferedImage getFrame(int n) {
BufferedImage im = null;
if ((n >= 0) && (n < frameCount)) {
im = ((GifFrame) frames.get(n)).image;
}
return im;
}
/**
* Gets image size.
* @return GIF image dimensions
*/
public Dimension getFrameSize() {
return new Dimension(width, height);
}
/**
* Reads GIF image from stream
* @param BufferedInputStream
* containing GIF file.
* @return read status code (0 = no errors)
*/
public int read(BufferedInputStream is) {
init();
if (is != null) {
in = is;
readHeader();
if (!err()) {
readContents();
if (frameCount < 0) {
status = STATUS_FORMAT_ERROR;
}
}
} else {
status = STATUS_OPEN_ERROR;
}
try {
is.close();
} catch (IOException e) {
}
return status;
}
/**
* Reads GIF image from stream
* @param InputStream
* containing GIF file.
* @return read status code (0 = no errors)
*/
public int read(InputStream is) {
init();
if (is != null) {
if (!(is instanceof BufferedInputStream))
is = new BufferedInputStream(is);
in = (BufferedInputStream) is;
readHeader();
if (!err()) {
readContents();
if (frameCount < 0) {
status = STATUS_FORMAT_ERROR;
}
}
} else {
status = STATUS_OPEN_ERROR;
}
try {
is.close();
} catch (IOException e) {
}
return status;
}
/**
* Reads GIF file from specified file/URL source (URL assumed if name
* contains ":/" or "file:")
* @param name
* String containing source
* @return read status code (0 = no errors)
*/
public int read(String name) {
status = STATUS_OK;
try {
name = name.trim().toLowerCase();
if ((name.indexOf("file:") >= 0) || (name.indexOf(":/") > 0)) {
URL url = new URL(name);
in = new BufferedInputStream(url.openStream());
} else {
in = new BufferedInputStream(new FileInputStream(name));
}
