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In Pl_TIFFPredictor::processRow optimize 8 bits_per_sample case

This commit is contained in:
m-holger 2024-01-26 20:17:56 +00:00
parent b7abb12f55
commit 20ca1e8644
1 changed files with 36 additions and 14 deletions
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50
libqpdf/Pl_TIFFPredictor.cc
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@ -58,24 +58,46 @@ void
Pl_TIFFPredictor::processRow()
{
QTC::TC("libtests", "Pl_TIFFPredictor processRow", (action == a_decode ? 0 : 1));
BitWriter bw(p_next);
BitStream in(cur_row.data(), cur_row.size());
previous.assign(samples_per_pixel, 0);
for (unsigned int col = 0; col < this->columns; ++col) {
for (auto& prev: previous) {
long long sample = in.getBitsSigned(this->bits_per_sample);
long long new_sample = sample;
if (action == a_encode) {
new_sample -= prev;
prev = sample;
} else {
new_sample += prev;
prev = new_sample;
if (bits_per_sample != 8) {
BitWriter bw(p_next);
BitStream in(cur_row.data(), cur_row.size());
for (unsigned int col = 0; col < this->columns; ++col) {
for (auto& prev: previous) {
long long sample = in.getBitsSigned(this->bits_per_sample);
long long new_sample = sample;
if (action == a_encode) {
new_sample -= prev;
prev = sample;
} else {
new_sample += prev;
prev = new_sample;
}
bw.writeBitsSigned(new_sample, this->bits_per_sample);
}
}
bw.flush();
} else {
auto next = cur_row.begin();
auto cr_end = cur_row.end();
auto pr_end = previous.end();
while (next != cr_end) {
for (auto prev = previous.begin(); prev != pr_end && next != cr_end; ++prev, ++next) {
long long sample = *next;
long long new_sample = sample;
if (action == a_encode) {
new_sample -= *prev;
*prev = sample;
} else {
new_sample += *prev;
*prev = new_sample;
}
auto out = static_cast<unsigned char>(255U & new_sample);
p_next->write(&out, 1);
}
bw.writeBitsSigned(new_sample, this->bits_per_sample);
}
}
bw.flush();
}
void