// Applies simple sharpening to the row data to improve performance of the 1D Readers.
@Override
public BitArray getBlackRow(int y, BitArray row) throws NotFoundException {
LuminanceSource source = getLuminanceSource();
int width = source.getWidth();
if (row == null || row.getSize() < width) {
row = new BitArray(width);
} else {
row.clear();
}
initArrays(width);
byte[] localLuminances = source.getRow(y, luminances);
int[] localBuckets = buckets;
for (int x = 0; x < width; x++) {
int pixel = localLuminances[x] & 0xff;
localBuckets[pixel >> LUMINANCE_SHIFT]++;
}
int blackPoint = estimateBlackPoint(localBuckets);
int left = localLuminances[0] & 0xff;
int center = localLuminances[1] & 0xff;
for (int x = 1; x < width - 1; x++) {
int right = localLuminances[x + 1] & 0xff;
// A simple -1 4 -1 box filter with a weight of 2.
int luminance = ((center * 4) - left - right) / 2;
if (luminance < blackPoint) {
row.set(x);
}
left = center;
center = right;
}
return row;
}
@Override
public void delete(final int pre, final int nr) {
if (nr == 0) return;
dirty();
// get first block
cursor(pre);
// some useful variables to make code more readable
int from = pre - fpre;
final int last = pre + nr;
// check if all entries are in current block: handle and return
if (last - 1 < npre) {
final Buffer bf = bm.current();
copy(bf.data, from + nr, bf.data, from, npre - last);
updatePre(nr);
// if whole block was deleted, remove it from the index
if (npre == fpre) {
// mark the block as empty
usedPages.clear(pages[page]);
Array.move(fpres, page + 1, -1, used - page - 1);
Array.move(pages, page + 1, -1, used - page - 1);
--used;
readPage(page);
}
return;
}
// handle blocks whose entries are to be deleted entirely
// first count them
int unused = 0;
while (npre < last) {
if (from == 0) {
++unused;
// mark the blocks as empty; range clear cannot be used because the
// blocks may not be consecutive
usedPages.clear(pages[page]);
}
setPage(page + 1);
from = 0;
}
// if the last block is empty, clear the corresponding bit
readBlock(pages[page]);
final Buffer bf = bm.current();
if (npre == last) {
usedPages.clear((int) bf.pos);
++unused;
if (page < used - 1) readPage(page + 1);
else ++page;
} else {
// delete entries at beginning of current (last) block
copy(bf.data, last - fpre, bf.data, 0, npre - last);
}
// now remove them from the index
if (unused > 0) {
Array.move(fpres, page, -unused, used - page);
Array.move(pages, page, -unused, used - page);
used -= unused;
page -= unused;
}
// update index entry for this block
fpres[page] = pre;
fpre = pre;
updatePre(nr);
}
