private void writeHeader(
final DataOutputStream stream,
final int xsize,
final int ysize,
final int zsize,
final boolean rle)
throws IOException {
// effects: outputs the 512-byte IRIS RGB header to STREAM, using xsize,
// ysize, and depth as the dimensions of the image. NOTE that
// the following defaults are used:
// STORAGE = 1 (storage format = RLE)
// BPC = 1 (# bytes/channel)
// DIMENSION = 3
// PIXMIN = 0
// PIXMAX = 255
// IMAGENAME = <80 nulls>
// COLORMAP = 0
// See ftp://ftp.sgi.com/pub/sgi/SGIIMAGESPEC for more details.
// write out MAGIC, STORAGE, BPC
stream.writeShort(474);
stream.write((rle ? 1 : 0));
stream.write(1);
// write out DIMENSION
stream.writeShort(3);
// write XSIZE, YSIZE, ZSIZE
stream.writeShort(xsize);
stream.writeShort(ysize);
stream.writeShort(zsize);
// write PIXMIN, PIXMAX
stream.writeInt(0);
stream.writeInt(255);
// write DUMMY
stream.writeInt(0);
// write IMAGENAME
for (int i = 0; i < 80; i++) stream.write(0);
// write COLORMAP
stream.writeInt(0);
// write DUMMY (404 bytes)
for (int i = 0; i < 404; i++) stream.write(0);
}
private void writeImage(
final File file,
byte[] data,
final int xsize,
final int ysize,
final int zsize,
final boolean yflip)
throws IOException {
// Input data is in RGBRGBRGB or RGBARGBARGBA format; first unswizzle it
final byte[] tmpData = new byte[xsize * ysize * zsize];
int dest = 0;
for (int i = 0; i < zsize; i++) {
for (int j = i; j < (xsize * ysize * zsize); j += zsize) {
tmpData[dest++] = data[j];
}
}
data = tmpData;
// requires: DATA must be an array of size XSIZE * YSIZE * ZSIZE,
// indexed in the following manner:
// data[0] ...data[xsize-1] == first row of first channel
// data[xsize]...data[2*xsize-1] == second row of first channel
// ... data[(ysize - 1) * xsize]...data[(ysize * xsize) - 1] ==
// last row of first channel
// Later channels follow the same format.
// *** NOTE that "first row" is defined by the BOTTOM ROW of
// the image. That is, the origin is in the lower left corner.
// effects: writes out an SGI image to FILE, RLE-compressed, INCLUDING
// header, of dimensions (xsize, ysize, zsize), and containing
// the data in DATA. If YFLIP is set, outputs the data in DATA
// in reverse order vertically (equivalent to a flip about the
// x axis).
// Build the offset tables
final int[] starttab = new int[ysize * zsize];
final int[] lengthtab = new int[ysize * zsize];
// Temporary buffer for holding RLE data.
// Note that this makes the assumption that RLE-compressed data will
// never exceed twice the size of the input data.
// There are surely formal proofs about how big the RLE buffer should
// be, as well as what the optimal look-ahead size is (i.e. don't switch
// copy/repeat modes for less than N repeats). However, I'm going from
// empirical evidence here; the break-even point seems to be a look-
// ahead of 3. (That is, if the three values following this one are all
// the same as the current value, switch to repeat mode.)
final int lookahead = 3;
final byte[] rlebuf = new byte[2 * xsize * ysize * zsize];
int cur_loc = 0; // current offset location.
int ptr = 0;
int total_size = 0;
int ystart = 0;
int yincr = 1;
int yend = ysize;
if (yflip) {
ystart = ysize - 1;
yend = -1;
yincr = -1;
}
final boolean DEBUG = false;
for (int z = 0; z < zsize; z++) {
for (int y = ystart; y != yend; y += yincr) {
// RLE-compress each row.
int x = 0;
byte count = 0;
boolean repeat_mode = false;
boolean should_switch = false;
final int start_ptr = ptr;
int num_ptr = ptr++;
byte repeat_val = 0;
while (x < xsize) {
// see if we should switch modes
should_switch = false;
if (repeat_mode) {
if (imgref(data, x, y, z, xsize, ysize, zsize) != repeat_val) {
should_switch = true;
}
} else {
// look ahead to see if we should switch to repeat mode.
// stay within the scanline for the lookahead
if ((x + lookahead) < xsize) {
should_switch = true;
for (int i = 1; i <= lookahead; i++) {
if (DEBUG)
System.err.println(
"left side was "
+ ((int) imgref(data, x, y, z, xsize, ysize, zsize))
+ ", right side was "
+ (int) imgref(data, x + i, y, z, xsize, ysize, zsize));
if (imgref(data, x, y, z, xsize, ysize, zsize)
!= imgref(data, x + i, y, z, xsize, ysize, zsize)) should_switch = false;
}
}
}
if (should_switch || (count == 127)) {
// update the number of elements we repeated/copied
if (x > 0) {
if (repeat_mode) rlebuf[num_ptr] = count;
else rlebuf[num_ptr] = (byte) (count | 0x80);
}
// perform mode switch if necessary; output repeat_val if
// switching FROM repeat mode, and set it if switching
// TO repeat mode.
if (repeat_mode) {
if (should_switch) repeat_mode = false;
rlebuf[ptr++] = repeat_val;
} else {
if (should_switch) repeat_mode = true;
repeat_val = imgref(data, x, y, z, xsize, ysize, zsize);
}
if (x > 0) {
// reset the number pointer
num_ptr = ptr++;
// reset number of bytes copied
count = 0;
}
}
// if not in repeat mode, copy element to ptr
if (!repeat_mode) {
rlebuf[ptr++] = imgref(data, x, y, z, xsize, ysize, zsize);
}
count++;
if (x == xsize - 1) {
// Need to store the number of pixels we copied/repeated.
if (repeat_mode) {
rlebuf[num_ptr] = count;
// If we ended the row in repeat mode, store the
// repeated value
rlebuf[ptr++] = repeat_val;
} else rlebuf[num_ptr] = (byte) (count | 0x80);
// output zero counter for the last value in the row
rlebuf[ptr++] = 0;
}
x++;
}
// output this row's length into the length table
final int rowlen = ptr - start_ptr;
if (yflip) lengthtab[ysize * z + (ysize - y - 1)] = rowlen;
else lengthtab[ysize * z + y] = rowlen;
// add to the start table, and update the current offset
if (yflip) starttab[ysize * z + (ysize - y - 1)] = cur_loc;
else starttab[ysize * z + y] = cur_loc;
cur_loc += rowlen;
}
}
// Now we have the offset tables computed, as well as the RLE data.
// Output this information to the file.
total_size = ptr;
if (DEBUG) System.err.println("total_size was " + total_size);
final DataOutputStream stream =
new DataOutputStream(new BufferedOutputStream(IOUtil.getFileOutputStream(file, true)));
writeHeader(stream, xsize, ysize, zsize, true);
final int SIZEOF_INT = 4;
for (int i = 0; i < (ysize * zsize); i++)
stream.writeInt(starttab[i] + 512 + (2 * ysize * zsize * SIZEOF_INT));
for (int i = 0; i < (ysize * zsize); i++) stream.writeInt(lengthtab[i]);
for (int i = 0; i < total_size; i++) stream.write(rlebuf[i]);
stream.close();
}