private Point hilbertOrderData(ImageData id, byte pixData[]) {
int order = 0;
for (int n = 1; n < id.width; n *= 2) {
order++;
}
/* Skanky; use an otherwise-unused ImageData field
* to keep track of maxX.
*/
Point p = new Point(0, 0);
int oldIdX = id.x;
int oldIdY = id.y;
id.x = id.y = 0;
try {
hilbertWalk(id, new ByteArrayInputStream(pixData), order, 0, 0, HILBERT_DIR_E);
p.x = id.x;
p.y = id.y;
} catch (IOException ex) {
System.err.println("Exception during hilbertWalk()");
p.x = id.height;
p.y = id.width;
}
id.x = oldIdX;
id.y = oldIdY;
return p;
}
private void hilbertWalk(ImageData id, InputStream pixData, int order, int x, int y, int dir)
throws IOException {
if (x >= id.width || y >= id.height) {
return;
} else if (order == 0) {
try {
int p = pixData.read();
if (p >= 0) {
// flip along x=y axis; assume width == height
id.setPixel(y, x, p);
/* Skanky; use an otherwise-unused ImageData field
* to keep track of the max x,y used. Note that x and y are inverted.
*/
if (y > id.x) {
id.x = y;
}
if (x > id.y) {
id.y = x;
}
}
// xxx just give up; don't bother walking the rest of the image
} catch (IllegalArgumentException ex) {
System.out.println(
"bad pixels: order "
+ order
+ ", dir "
+ dir
+ ", w "
+ id.width
+ ", h "
+ id.height
+ ", x "
+ x
+ ", y "
+ y);
throw ex;
}
} else {
order--;
int delta = 1 << order;
int nextX = x + delta;
int nextY = y + delta;
switch (dir) {
case HILBERT_DIR_E:
hilbertWalk(id, pixData, order, x, y, HILBERT_DIR_N);
hilbertWalk(id, pixData, order, x, nextY, HILBERT_DIR_E);
hilbertWalk(id, pixData, order, nextX, nextY, HILBERT_DIR_E);
hilbertWalk(id, pixData, order, nextX, y, HILBERT_DIR_S);
break;
case HILBERT_DIR_N:
hilbertWalk(id, pixData, order, x, y, HILBERT_DIR_E);
hilbertWalk(id, pixData, order, nextX, y, HILBERT_DIR_N);
hilbertWalk(id, pixData, order, nextX, nextY, HILBERT_DIR_N);
hilbertWalk(id, pixData, order, x, nextY, HILBERT_DIR_W);
break;
case HILBERT_DIR_S:
hilbertWalk(id, pixData, order, nextX, nextY, HILBERT_DIR_W);
hilbertWalk(id, pixData, order, x, nextY, HILBERT_DIR_S);
hilbertWalk(id, pixData, order, x, y, HILBERT_DIR_S);
hilbertWalk(id, pixData, order, nextX, y, HILBERT_DIR_E);
break;
case HILBERT_DIR_W:
hilbertWalk(id, pixData, order, nextX, nextY, HILBERT_DIR_S);
hilbertWalk(id, pixData, order, nextX, y, HILBERT_DIR_W);
hilbertWalk(id, pixData, order, x, y, HILBERT_DIR_W);
hilbertWalk(id, pixData, order, x, nextY, HILBERT_DIR_N);
break;
default:
throw new RuntimeException("Unexpected Hilbert direction " + dir);
}
}
}