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Similarly optimize unfilter mode 2

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Unfilter mode 1 can't benefit from this optimization
because it modifies and reads from the same line of data
This commit is contained in:
Joshua Holmer 2016-05-02 15:58:45 -04:00
parent 3652a69255
commit aaf443fca7
1 changed files with 8 additions and 7 deletions
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15
src/png.rs
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@ -1149,13 +1149,14 @@ fn unfilter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8]) -> Vec<u
}
}
2 => {
for (i, byte) in data.iter().enumerate() {
if last_line.is_empty() {
unfiltered.push(*byte);
} else {
unfiltered.push(byte.wrapping_add(last_line[i]));
};
}
if last_line.is_empty() {
unfiltered.extend_from_slice(data);
} else {
unfiltered.extend_from_slice(&data.iter()
.zip(last_line.iter())
.map(|(cur, last)| cur.wrapping_add(*last))
.collect::<Vec<u8>>());
};
}
3 => {
for (i, byte) in data.iter().enumerate() {