Implement heuristic filter mode and optimize modes 1-4
This commit is contained in:
Joshua Holmer
parent
4765c2133a
commit
11e475ba15
1 changed files with 113 additions and 35 deletions
148
src/png.rs
148
src/png.rs
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@ -280,13 +280,13 @@ impl PngData {
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// This avoids casting to and from floats, which is expensive
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let tmp = self.ihdr_data.bit_depth.as_u8() * self.bits_per_pixel_raw();
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let bpp = (tmp + tmp % 8) >> 3;
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let mut last_line: Option<Vec<u8>> = None;
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let mut last_line: Vec<u8> = vec![];
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for line in self.scan_lines() {
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unfiltered.push(line.filter);
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match line.filter {
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0 => {
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let mut data = line.data.clone();
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last_line = Some(data.clone());
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last_line = data.clone();
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unfiltered.append(&mut data);
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}
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1 => {
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@ -297,28 +297,28 @@ impl PngData {
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None => data.push(*byte),
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}
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}
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last_line = Some(data.clone());
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last_line = data.clone();
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unfiltered.append(&mut data);
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}
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2 => {
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let mut data = Vec::with_capacity(line.data.len());
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for (i, byte) in line.data.iter().enumerate() {
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if let Some(last) = last_line.clone() {
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data.push(byte.wrapping_add(last[i]));
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if last_line.len() > 0 {
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data.push(byte.wrapping_add(last_line[i]));
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} else {
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data.push(*byte);
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};
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}
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last_line = Some(data.clone());
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last_line = data.clone();
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unfiltered.append(&mut data);
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}
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3 => {
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let mut data = Vec::with_capacity(line.data.len());
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for (i, byte) in line.data.iter().enumerate() {
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if let Some(last) = last_line.clone() {
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if last_line.len() > 0 {
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data.push(match i.checked_sub(bpp as usize) {
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Some(x) => byte.wrapping_add((line.data[x] + last[i]) >> 1),
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None => byte.wrapping_add(last[i] >> 1),
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Some(x) => byte.wrapping_add(((line.data[x] as u16 + last_line[i] as u16) >> 1) as u8),
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None => byte.wrapping_add(last_line[i] >> 1),
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});
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} else {
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data.push(match i.checked_sub(bpp as usize) {
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@ -327,20 +327,20 @@ impl PngData {
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});
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};
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}
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last_line = Some(data.clone());
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last_line = data.clone();
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unfiltered.append(&mut data);
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}
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4 => {
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let mut data = Vec::with_capacity(line.data.len());
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for (i, byte) in line.data.iter().enumerate() {
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if let Some(last) = last_line.clone() {
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if last_line.len() > 0 {
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data.push(match i.checked_sub(bpp as usize) {
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Some(x) => {
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byte.wrapping_add(paeth_predictor(line.data[x],
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last[i],
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last[x]))
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last_line[i],
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last_line[x]))
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}
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None => byte.wrapping_add(last[i]),
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None => byte.wrapping_add(last_line[i]),
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});
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} else {
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data.push(match i.checked_sub(bpp as usize) {
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@ -349,7 +349,7 @@ impl PngData {
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});
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};
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}
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last_line = Some(data.clone());
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last_line = data.clone();
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unfiltered.append(&mut data);
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}
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_ => panic!("Unreachable"),
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@ -362,20 +362,15 @@ impl PngData {
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// This avoids casting to and from floats, which is expensive
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let tmp = self.ihdr_data.bit_depth.as_u8() * self.bits_per_pixel_raw();
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let bpp = (tmp + tmp % 8) >> 3;
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let mut last_line: Option<Vec<u8>> = None;
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let mut last_line: Vec<u8> = vec![];
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// We could try a different filter method for each line
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// But that would be prohibitively slow and probably not provide much benefit
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// So we just use one filter method for the whole image
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for line in self.scan_lines() {
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let internal_filter = match filter {
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5 => {
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// TODO: Heuristically guess best filter per line
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0
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}
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x => x,
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};
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filtered.push(internal_filter);
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match internal_filter {
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if filter != 5 {
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filtered.push(filter);
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}
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match filter {
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0 => {
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let mut data = line.data.clone();
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filtered.append(&mut data);
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@ -390,8 +385,8 @@ impl PngData {
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}
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2 => {
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for (i, byte) in line.data.iter().enumerate() {
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if let Some(last) = last_line.clone() {
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filtered.push(byte.wrapping_sub(last[i]));
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if last_line.len() > 0 {
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filtered.push(byte.wrapping_sub(last_line[i]));
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} else {
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filtered.push(*byte);
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};
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@ -399,10 +394,10 @@ impl PngData {
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}
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3 => {
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for (i, byte) in line.data.iter().enumerate() {
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if let Some(last) = last_line.clone() {
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if last_line.len() > 0 {
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filtered.push(match i.checked_sub(bpp as usize) {
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Some(x) => byte.wrapping_sub((line.data[x] + last[i]) >> 1),
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None => byte.wrapping_sub(last[i] >> 1),
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Some(x) => byte.wrapping_sub(((line.data[x] as u16 + last_line[i] as u16) >> 1) as u8),
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None => byte.wrapping_sub(last_line[i] >> 1),
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});
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} else {
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filtered.push(match i.checked_sub(bpp as usize) {
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@ -414,14 +409,14 @@ impl PngData {
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}
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4 => {
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for (i, byte) in line.data.iter().enumerate() {
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if let Some(last) = last_line.clone() {
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if last_line.len() > 0 {
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filtered.push(match i.checked_sub(bpp as usize) {
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Some(x) => {
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byte.wrapping_sub(paeth_predictor(line.data[x],
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last[i],
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last[x]))
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last_line[i],
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last_line[x]))
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}
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None => byte.wrapping_sub(last[i]),
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None => byte.wrapping_sub(last_line[i]),
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});
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} else {
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filtered.push(match i.checked_sub(bpp as usize) {
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@ -431,9 +426,92 @@ impl PngData {
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};
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}
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}
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5 => {
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// Heuristically guess best filter per line
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// Really simple algorithm, maybe we could replace this with something better
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// libpng's heuristic no longer exists so I can't reference it
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// Yes I know this code is ugly, but I didn't want to mess with mutable
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// references from a HashMap that return options
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// FIXME: Regardless of that, this is not very memory efficient
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// Someone who's better at Rust can clean this up if they want
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let line_0 = line.data.clone();
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let mut line_1 = Vec::with_capacity(line.data.len());
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let mut line_2 = Vec::with_capacity(line.data.len());
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let mut line_3 = Vec::with_capacity(line.data.len());
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let mut line_4 = Vec::with_capacity(line.data.len());
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for (i, byte) in line.data.iter().enumerate() {
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if last_line.len() > 0 {
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match i.checked_sub(bpp as usize) {
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Some(x) => {
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line_1.push(byte.wrapping_sub(line.data[x]));
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line_2.push(byte.wrapping_sub(last_line[i]));
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line_3.push(byte.wrapping_sub(((line.data[x] as u16 + last_line[i] as u16) >> 1) as u8));
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line_4.push(byte.wrapping_sub(paeth_predictor(line.data[x],
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last_line[i],
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last_line[x])));
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},
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None => {
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line_1.push(*byte);
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line_2.push(byte.wrapping_sub(last_line[i]));
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line_3.push(byte.wrapping_sub(last_line[i] >> 1));
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line_4.push(byte.wrapping_sub(last_line[i]));
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},
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}
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} else {
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match i.checked_sub(bpp as usize) {
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Some(x) => {
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line_1.push(byte.wrapping_sub(line.data[x]));
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line_2.push(*byte);
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line_3.push(byte.wrapping_sub(line.data[x] >> 1));
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line_4.push(byte.wrapping_sub(line.data[x]));
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},
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None => {
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line_1.push(*byte);
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line_2.push(*byte);
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line_3.push(*byte);
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line_4.push(*byte);
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},
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}
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};
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}
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// Count the number of unique bytes and take the lowest
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let mut uniq_0 = line_0.clone();
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uniq_0.sort();
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uniq_0.dedup();
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let mut uniq_1 = line_1.clone();
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uniq_1.sort();
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uniq_1.dedup();
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let mut uniq_2 = line_2.clone();
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uniq_2.sort();
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uniq_2.dedup();
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let mut uniq_3 = line_3.clone();
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uniq_3.sort();
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uniq_3.dedup();
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let mut uniq_4 = line_4.clone();
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uniq_4.sort();
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uniq_4.dedup();
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let mut best: (u8, &[u8], usize) = (0, &line_0, uniq_0.len());
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if uniq_1.len() < best.2 {
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best = (1, &line_1, uniq_1.len());
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}
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if uniq_2.len() < best.2 {
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best = (2, &line_2, uniq_2.len());
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}
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if uniq_3.len() < best.2 {
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best = (3, &line_3, uniq_3.len());
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}
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if uniq_4.len() < best.2 {
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best = (4, &line_4, uniq_4.len());
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}
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filtered.push(best.0);
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let mut data = best.1.to_owned();
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filtered.append(&mut data);
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}
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_ => panic!("Unreachable"),
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}
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last_line = Some(line.data.clone());
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last_line = line.data.clone();
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}
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filtered
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}
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