| Method from com.lowagie.text.pdf.codec.GifImage Detail: |
|---|
 protected boolean decodeImageData() throws IOException {
int NullCode = -1;
int npix = iw * ih;
int available, clear, code_mask, code_size, end_of_information, in_code, old_code,
bits, code, count, i, datum, data_size, first, top, bi;
boolean skipZero = false;
if (prefix == null)
prefix = new short[MaxStackSize];
if (suffix == null)
suffix = new byte[MaxStackSize];
if (pixelStack == null)
pixelStack = new byte[MaxStackSize+1];
m_line_stride = (iw * m_bpc + 7) / 8;
m_out = new byte[m_line_stride * ih];
int pass = 1;
int inc = interlace ? 8 : 1;
int line = 0;
int xpos = 0;
// Initialize GIF data stream decoder.
data_size = in.read();
clear = 1 < < data_size;
end_of_information = clear + 1;
available = clear + 2;
old_code = NullCode;
code_size = data_size + 1;
code_mask = (1 < < code_size) - 1;
for (code = 0; code < clear; code++) {
prefix[code] = 0;
suffix[code] = (byte) code;
}
// Decode GIF pixel stream.
datum = bits = count = first = top = bi = 0;
for (i = 0; i < npix; ) {
if (top == 0) {
if (bits < code_size) {
// Load bytes until there are enough bits for a code.
if (count == 0) {
// Read a new data block.
count = readBlock();
if (count < = 0) {
skipZero = true;
break;
}
bi = 0;
}
datum += (block[bi] & 0xff) < < bits;
bits += 8;
bi++;
count--;
continue;
}
// Get the next code.
code = datum & code_mask;
datum > >= code_size;
bits -= code_size;
// Interpret the code
if ((code > available) || (code == end_of_information))
break;
if (code == clear) {
// Reset decoder.
code_size = data_size + 1;
code_mask = (1 < < code_size) - 1;
available = clear + 2;
old_code = NullCode;
continue;
}
if (old_code == NullCode) {
pixelStack[top++] = suffix[code];
old_code = code;
first = code;
continue;
}
in_code = code;
if (code == available) {
pixelStack[top++] = (byte) first;
code = old_code;
}
while (code > clear) {
pixelStack[top++] = suffix[code];
code = prefix[code];
}
first = suffix[code] & 0xff;
// Add a new string to the string table,
if (available >= MaxStackSize)
break;
pixelStack[top++] = (byte) first;
prefix[available] = (short) old_code;
suffix[available] = (byte) first;
available++;
if (((available & code_mask) == 0) && (available < MaxStackSize)) {
code_size++;
code_mask += available;
}
old_code = in_code;
}
// Pop a pixel off the pixel stack.
top--;
i++;
setPixel(xpos, line, pixelStack[top]);
++xpos;
if (xpos >= iw) {
xpos = 0;
line += inc;
if (line >= ih) {
if (interlace) {
do {
pass++;
switch (pass) {
case 2:
line = 4;
break;
case 3:
line = 2;
inc = 4;
break;
case 4:
line = 1;
inc = 2;
break;
default: // this shouldn't happen
line = ih - 1;
inc = 0;
}
} while (line >= ih);
}
else {
line = ih - 1; // this shouldn't happen
inc = 0;
}
}
}
}
return skipZero;
}
|
public int getFrameCount() {
return frames.size();
} Gets the number of frames the gif has. |
public int[] getFramePosition(int frame) {
GifFrame gf = (GifFrame)frames.get(frame - 1);
return new int[]{gf.ix, gf.iy};
} Gets the [x,y] position of the frame in reference to the
logical screen. |
public Image getImage(int frame) {
GifFrame gf = (GifFrame)frames.get(frame - 1);
return gf.image;
} Gets the image from a frame. The first frame is 1. |
public int[] getLogicalScreen() {
return new int[]{width, height};
} Gets the logical screen. The images may be smaller and placed
in some position in this screen to playback some animation.
No image will be be bigger that this. |
protected static int newBpc(int bpc) {
switch (bpc) {
case 1:
case 2:
case 4:
break;
case 3:
return 4;
default:
return 8;
}
return bpc;
} |
void process(InputStream is) throws IOException {
in = new DataInputStream(new BufferedInputStream(is));
readHeader();
readContents();
if (frames.isEmpty())
throw new IOException("The file does not contain any valid image.");
} |
protected int readBlock() throws IOException {
blockSize = in.read();
if (blockSize < = 0)
return blockSize = 0;
for (int k = 0; k < blockSize; ++k) {
int v = in.read();
if (v < 0) {
return blockSize = k;
}
block[k] = (byte)v;
}
return blockSize;
} Reads next variable length block from input. |
protected byte[] readColorTable(int bpc) throws IOException {
int ncolors = 1 < < bpc;
int nbytes = 3*ncolors;
bpc = newBpc(bpc);
byte table[] = new byte[(1 < < bpc) * 3];
in.readFully(table, 0, nbytes);
return table;
} |
protected void readContents() throws IOException {
// read GIF file content blocks
boolean done = false;
while (!done) {
int code = in.read();
switch (code) {
case 0x2C: // image separator
readImage();
break;
case 0x21: // extension
code = in.read();
switch (code) {
case 0xf9: // graphics control extension
readGraphicControlExt();
break;
case 0xff: // application extension
readBlock();
skip(); // don't care
break;
default: // uninteresting extension
skip();
}
break;
default:
done = true;
break;
}
}
} |
protected void readGraphicControlExt() throws IOException {
in.read(); // block size
int packed = in.read(); // packed fields
dispose = (packed & 0x1c) > > 2; // disposal method
if (dispose == 0)
dispose = 1; // elect to keep old image if discretionary
transparency = (packed & 1) != 0;
delay = readShort() * 10; // delay in milliseconds
transIndex = in.read(); // transparent color index
in.read(); // block terminator
} Reads Graphics Control Extension values |
protected void readHeader() throws IOException {
String id = "";
for (int i = 0; i < 6; i++)
id += (char)in.read();
if (!id.startsWith("GIF8")) {
throw new IOException("Gif signature nor found.");
}
readLSD();
if (gctFlag) {
m_global_table = readColorTable(m_gbpc);
}
} Reads GIF file header information. |
protected void readImage() throws IOException {
ix = readShort(); // (sub)image position & size
iy = readShort();
iw = readShort();
ih = readShort();
int packed = in.read();
lctFlag = (packed & 0x80) != 0; // 1 - local color table flag
interlace = (packed & 0x40) != 0; // 2 - interlace flag
// 3 - sort flag
// 4-5 - reserved
lctSize = 2 < < (packed & 7); // 6-8 - local color table size
m_bpc = newBpc(m_gbpc);
if (lctFlag) {
m_curr_table = readColorTable((packed & 7) + 1); // read table
m_bpc = newBpc((packed & 7) + 1);
}
else {
m_curr_table = m_global_table;
}
if (transparency && transIndex >= m_curr_table.length / 3)
transparency = false;
if (transparency && m_bpc == 1) { // Acrobat 5.05 doesn't like this combination
byte tp[] = new byte[12];
System.arraycopy(m_curr_table, 0, tp, 0, 6);
m_curr_table = tp;
m_bpc = 2;
}
boolean skipZero = decodeImageData(); // decode pixel data
if (!skipZero)
skip();
Image img = null;
try {
img = new ImgRaw(iw, ih, 1, m_bpc, m_out);
PdfArray colorspace = new PdfArray();
colorspace.add(PdfName.INDEXED);
colorspace.add(PdfName.DEVICERGB);
int len = m_curr_table.length;
colorspace.add(new PdfNumber(len / 3 - 1));
colorspace.add(new PdfString(m_curr_table));
PdfDictionary ad = new PdfDictionary();
ad.put(PdfName.COLORSPACE, colorspace);
img.setAdditional(ad);
if (transparency) {
img.setTransparency(new int[]{transIndex, transIndex});
}
}
catch (Exception e) {
throw new ExceptionConverter(e);
}
img.setOriginalType(Image.ORIGINAL_GIF);
img.setOriginalData(fromData);
img.setUrl(fromUrl);
GifFrame gf = new GifFrame();
gf.image = img;
gf.ix = ix;
gf.iy = iy;
frames.add(gf); // add image to frame list
//resetFrame();
} |
protected void readLSD() throws IOException {
// logical screen size
width = readShort();
height = readShort();
// packed fields
int packed = in.read();
gctFlag = (packed & 0x80) != 0; // 1 : global color table flag
m_gbpc = (packed & 7) + 1;
bgIndex = in.read(); // background color index
pixelAspect = in.read(); // pixel aspect ratio
} Reads Logical Screen Descriptor |
protected int readShort() throws IOException {
// read 16-bit value, LSB first
return in.read() | (in.read() < < 8);
} Reads next 16-bit value, LSB first |
protected void resetFrame() {
// it does nothing in the pdf context
//boolean transparency = false;
//int delay = 0;
} Resets frame state for reading next image. |
protected void setPixel(int x,
int y,
int v) {
if (m_bpc == 8) {
int pos = x + iw * y;
m_out[pos] = (byte)v;
}
else {
int pos = m_line_stride * y + x / (8 / m_bpc);
int vout = v < < (8 - m_bpc * (x % (8 / m_bpc))- m_bpc);
m_out[pos] |= vout;
}
} |
protected void skip() throws IOException {
do {
readBlock();
} while (blockSize > 0);
} Skips variable length blocks up to and including
next zero length block. |
com.lowagie.text.pdf.codec.GifImage
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