Faster palette reduction
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Kornel Lesiński
Kornel Lesiński
parent
686adcdebd
commit
e05c2f6268
1 changed files with 79 additions and 149 deletions
228
src/png/mod.rs
228
src/png/mod.rs
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@ -1,7 +1,7 @@
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use std::collections::hash_map::Entry::*;
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use rgb::RGBA8;
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use rgb::RGBA8;
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use rgb::ComponentSlice;
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use rgb::ComponentSlice;
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use atomicmin::AtomicMin;
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use atomicmin::AtomicMin;
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use bit_vec::BitVec;
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use byteorder::{BigEndian, WriteBytesExt};
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use byteorder::{BigEndian, WriteBytesExt};
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use colors::{AlphaOptim, BitDepth, ColorType};
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use colors::{AlphaOptim, BitDepth, ColorType};
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use crc::crc32;
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use crc::crc32;
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@ -10,7 +10,7 @@ use error::PngError;
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use filters::*;
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use filters::*;
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use headers::*;
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use headers::*;
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use interlace::{deinterlace_image, interlace_image};
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use interlace::{deinterlace_image, interlace_image};
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use itertools::{flatten, Itertools};
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use itertools::flatten;
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#[cfg(feature = "parallel")]
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#[cfg(feature = "parallel")]
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use rayon::prelude::*;
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use rayon::prelude::*;
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use reduction::bit_depth::*;
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use reduction::bit_depth::*;
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@ -358,171 +358,101 @@ impl PngData {
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return false;
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return false;
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}
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}
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// A map of old indexes to new ones, for any moved
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let mut palette_map = [0u8; 256];
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let mut index_map: HashMap<u8, u8> = HashMap::new();
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let mut used = [false; 256];
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let mut palette = match self.palette {
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Some(ref p) => p.clone(),
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None => return false,
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};
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// A list of (original) indices that are duplicates and no longer needed
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let mut duplicates: Vec<u8> = Vec::new();
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{
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{
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// Find duplicate entries in the palette
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let palette = match self.palette {
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let mut seen: HashMap<RGBA8, u8> = HashMap::with_capacity(palette.len());
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Some(ref p) => p,
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for (i, color) in palette.iter().cloned().enumerate() {
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None => return false,
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if seen.contains_key(&color) {
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};
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let index = seen[&color];
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duplicates.push(i as u8);
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// Find palette entries that are never used
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index_map.insert(i as u8, index);
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for line in self.scan_lines() {
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} else {
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match self.ihdr_data.bit_depth {
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seen.insert(color, i as u8);
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BitDepth::Eight => for &byte in line.data {
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used[byte as usize] = true;
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},
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BitDepth::Four => for &byte in line.data {
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used[(byte & 0x0F) as usize] = true;
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used[(byte >> 4) as usize] = true;
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},
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BitDepth::Two => for &byte in line.data {
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used[(byte & 0x03) as usize] = true;
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used[((byte >> 2) & 0x03) as usize] = true;
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used[((byte >> 4) & 0x03) as usize] = true;
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used[(byte >> 6) as usize] = true;
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},
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_ => unreachable!(),
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}
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}
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}
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}
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let mut next_index = 0;
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let mut seen = HashMap::with_capacity(palette.len());
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for (i, (used, palette_map)) in used.iter().cloned().zip(palette_map.iter_mut()).enumerate() {
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if !used {
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continue;
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}
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// There are invalid files that use pixel indices beyond palette size
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let color = palette.get(i).cloned().unwrap_or(RGBA8::new(0,0,0,255));
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match seen.entry(color) {
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Vacant(new) => {
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*palette_map = next_index;
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new.insert(next_index);
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next_index += 1;
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},
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Occupied(remap_to) => {
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*palette_map = *remap_to.get();
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},
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}
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}
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if (0..palette.len()).all(|i| palette_map[i] == i as u8) {
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return false;
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}
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}
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}
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// Remove duplicates from the data
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self.do_palette_reduction(&palette_map, &used);
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if !duplicates.is_empty() {
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self.do_palette_reduction(&duplicates, &mut index_map, &mut palette);
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}
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// Find palette entries that are never used
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let mut seen = HashSet::with_capacity(palette.len());
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for line in self.scan_lines() {
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match self.ihdr_data.bit_depth {
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BitDepth::Eight => for &byte in line.data {
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seen.insert(byte);
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},
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BitDepth::Four => {
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let bitvec = BitVec::from_bytes(&line.data);
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let mut current = 0u8;
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for (i, bit) in bitvec.iter().enumerate() {
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let mod_i = i % 4;
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if bit {
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current += 1u8 << (3 - mod_i);
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}
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if mod_i == 3 {
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seen.insert(current);
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current = 0;
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}
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}
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}
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BitDepth::Two => {
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let bitvec = BitVec::from_bytes(&line.data);
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let mut current = 0u8;
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for (i, bit) in bitvec.iter().enumerate() {
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let mod_i = i % 2;
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if bit {
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current += 1u8 << (1 - mod_i);
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}
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if mod_i == 1 {
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seen.insert(current);
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current = 0;
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}
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}
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}
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_ => unreachable!(),
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}
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if seen.len() == palette.len() {
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// Exit early if no further possible optimizations
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// Check at the end of each line
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// Checking after every pixel would be overly expensive
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return !duplicates.is_empty();
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}
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}
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let unused: Vec<u8> = (0..palette.len() as u8)
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.filter(|i| !seen.contains(i))
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.collect();
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// Remove unused palette indices
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self.do_palette_reduction(&unused, &mut index_map, &mut palette);
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true
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true
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}
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}
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fn do_palette_reduction(
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fn do_palette_reduction(&mut self, palette_map: &[u8; 256], used: &[bool; 256]) {
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&mut self,
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indices_to_remove: &[u8],
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index_map: &mut HashMap<u8, u8>,
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palette: &mut Vec<RGBA8>,
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) {
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let mut new_data = Vec::with_capacity(self.raw_data.len());
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let mut new_data = Vec::with_capacity(self.raw_data.len());
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let original_len = palette.len();
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let mut byte_map = *palette_map;
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for idx in indices_to_remove.iter().cloned().sorted_by(|a, b| b.cmp(a)) {
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for i in (idx as usize + 1)..original_len {
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// low bit-depths can be pre-computed for every byte value
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let existing = index_map.entry(i as u8).or_insert(i as u8);
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match self.ihdr_data.bit_depth {
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if *existing >= idx {
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BitDepth::Four => for byte in 0..=255 {
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*existing -= 1;
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byte_map[byte as usize] = palette_map[(byte & 0x0F) as usize] |
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}
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(palette_map[(byte >> 4) as usize] << 4);
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}
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},
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palette.remove(idx as usize);
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BitDepth::Two => for byte in 0..=255 {
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byte_map[byte as usize] = palette_map[(byte & 0x03) as usize] |
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(palette_map[((byte >> 2) & 0x03) as usize] << 2) |
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(palette_map[((byte >> 4) & 0x03) as usize] << 4) |
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(palette_map[((byte >> 6)) as usize] << 6);
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},
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_ => {}
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}
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}
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// Reassign data bytes to new indices
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// Reassign data bytes to new indices
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for line in self.scan_lines() {
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for line in self.scan_lines() {
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new_data.push(line.filter);
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new_data.push(line.filter);
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match self.ihdr_data.bit_depth {
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for &byte in line.data {
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BitDepth::Eight => for &byte in line.data {
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new_data.push(byte_map[byte as usize])
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if let Some(&new_idx) = index_map.get(&byte) {
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new_data.push(new_idx);
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} else {
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new_data.push(byte);
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}
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},
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BitDepth::Four => for &byte in line.data {
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let upper = byte & 0b1111_0000;
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let lower = byte & 0b0000_1111;
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let mut new_byte = 0u8;
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new_byte |= if let Some(&new_idx) = index_map.get(&(upper >> 4)) {
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new_idx << 4
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} else {
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upper
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};
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new_byte |= if let Some(&new_idx) = index_map.get(&lower) {
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new_idx
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} else {
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lower
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};
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new_data.push(new_byte);
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},
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BitDepth::Two => for &byte in line.data {
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let one = byte & 0b1100_0000;
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let two = byte & 0b0011_0000;
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let three = byte & 0b0000_1100;
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let four = byte & 0b0000_0011;
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let mut new_byte = 0u8;
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new_byte |= if let Some(&new_idx) = index_map.get(&(one >> 6)) {
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new_idx << 6
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} else {
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one
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};
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new_byte |= if let Some(&new_idx) = index_map.get(&(two >> 4)) {
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new_idx << 4
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} else {
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two
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};
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new_byte |= if let Some(&new_idx) = index_map.get(&(three >> 2)) {
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new_idx << 2
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} else {
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three
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};
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new_byte |= if let Some(&new_idx) = index_map.get(&four) {
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new_idx
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} else {
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four
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};
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new_data.push(new_byte);
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},
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_ => unreachable!(),
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}
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}
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}
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}
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index_map.clear();
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self.raw_data = new_data;
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self.raw_data = new_data;
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self.transparency_pixel = None;
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self.transparency_pixel = None;
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self.palette = Some(palette.clone());
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if let Some(palette) = self.palette.take() {
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let max_index = palette_map.iter().max().cloned().unwrap_or(0) as usize;
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let mut new_palette = vec![RGBA8::new(0,0,0,255); max_index+1];
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for (color, (map_to, used)) in palette.into_iter().zip(palette_map.iter().cloned().zip(used.iter().cloned())) {
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if used {
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new_palette[map_to as usize] = color;
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}
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}
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self.palette = Some(new_palette);
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}
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}
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}
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/// Attempt to reduce the color type of the image
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/// Attempt to reduce the color type of the image
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