Reduce allocations in filtering by reusing buffers

Cargo.lock

@@ -80,6 +80,14 @@ dependencies = [
  "vec_map 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "cloudabi"
+version = "0.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "bitflags 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "cloudflare-zlib"
 version = "0.2.2"
@@ -157,6 +165,11 @@ name = "either"
 version = "1.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "fuchsia-cprng"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "glob"
 version = "0.2.11"
@@ -201,6 +214,15 @@ name = "libc"
 version = "0.2.58"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "lock_api"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "owning_ref 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "scopeguard 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "lzw"
 version = "0.10.0"
@@ -274,6 +296,21 @@ name = "numtoa"
 version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "object-pool"
+version = "0.3.1"
+dependencies = [
+ "parking_lot 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "owning_ref"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "stable_deref_trait 1.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "oxipng"
 version = "2.2.2"
@@ -287,12 +324,34 @@ dependencies = [
  "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "miniz_oxide 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "num_cpus 1.10.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "object-pool 0.3.1",
  "rayon 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rgb 0.8.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "wild 2.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "zopfli 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "parking_lot"
+version = "0.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "lock_api 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "parking_lot_core"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "libc 0.2.58 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.6.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "png"
 version = "0.14.1"
@@ -304,6 +363,102 @@ dependencies = [
  "num-iter 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "rand"
+version = "0.6.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "autocfg 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.58 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_chacha 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_hc 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_isaac 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_jitter 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_os 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_pcg 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_xorshift 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "autocfg 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
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+]
+
+[[package]]
+name = "rand_core"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "rand_hc"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "rand_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
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+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "rand_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
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+
+[[package]]
+name = "rand_jitter"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "libc 0.2.58 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rand_os"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "fuchsia-cprng 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.58 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rdrand 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rand_pcg"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "autocfg 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rand_xorshift"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "rand_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "rayon"
 version = "1.1.0"
@@ -326,6 +481,14 @@ dependencies = [
  "num_cpus 1.10.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "rdrand"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "rand_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "redox_syscall"
 version = "0.1.54"
@@ -344,11 +507,42 @@ name = "rgb"
 version = "0.8.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "rustc_version"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "semver 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "scopeguard"
 version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "semver"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "semver-parser 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "semver-parser"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "smallvec"
+version = "0.6.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "stable_deref_trait"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "strsim"
 version = "0.8.0"
@@ -439,6 +633,7 @@ dependencies = [
 "checksum cc 1.0.37 (registry+https://github.com/rust-lang/crates.io-index)" = "39f75544d7bbaf57560d2168f28fd649ff9c76153874db88bdbdfd839b1a7e7d"
 "checksum cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)" = "b486ce3ccf7ffd79fdeb678eac06a9e6c09fc88d33836340becb8fffe87c5e33"
 "checksum clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)" = "5067f5bb2d80ef5d68b4c87db81601f0b75bca627bc2ef76b141d7b846a3c6d9"
+"checksum cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "ddfc5b9aa5d4507acaf872de71051dfd0e309860e88966e1051e462a077aac4f"
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 "checksum crc 1.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "d663548de7f5cca343f1e0a48d14dcfb0e9eb4e079ec58883b7251539fa10aeb"
@@ -448,12 +643,14 @@ dependencies = [
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 "checksum libc 0.2.58 (registry+https://github.com/rust-lang/crates.io-index)" = "6281b86796ba5e4366000be6e9e18bf35580adf9e63fbe2294aadb587613a319"
+"checksum lock_api 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "62ebf1391f6acad60e5c8b43706dde4582df75c06698ab44511d15016bc2442c"
 "checksum lzw 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7d947cbb889ed21c2a84be6ffbaebf5b4e0f4340638cba0444907e38b56be084"
 "checksum memoffset 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "0f9dc261e2b62d7a622bf416ea3c5245cdd5d9a7fcc428c0d06804dfce1775b3"
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@@ -464,13 +661,32 @@ dependencies = [
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src/filters.rs

@@ -1,12 +1,12 @@
-pub fn filter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8]) -> Vec<u8> {
+pub fn filter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8], buf: &mut Vec<u8>) {
-    let mut filtered = Vec::with_capacity(data.len());
+    buf.reserve(data.len());
     match filter {
         0 => {
-            filtered.extend_from_slice(data);
+            buf.extend_from_slice(data);
         }
         1 => {
-            filtered.extend_from_slice(&data[0..bpp]);
+            buf.extend_from_slice(&data[0..bpp]);
-            filtered.extend(
+            buf.extend(
                 data.iter()
                     .skip(bpp)
                     .zip(data.iter())
@@ -15,9 +15,9 @@ pub fn filter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8]) -> Vec
         }
         2 => {
             if last_line.is_empty() {
-                filtered.extend_from_slice(data);
+                buf.extend_from_slice(data);
             } else {
-                filtered.extend(
+                buf.extend(
                     data.iter()
                         .zip(last_line.iter())
                         .map(|(cur, last)| cur.wrapping_sub(*last)),
@@ -27,12 +27,12 @@ pub fn filter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8]) -> Vec
         3 => {
             for (i, byte) in data.iter().enumerate() {
                 if last_line.is_empty() {
-                    filtered.push(match i.checked_sub(bpp) {
+                    buf.push(match i.checked_sub(bpp) {
                         Some(x) => byte.wrapping_sub(data[x] >> 1),
                         None => *byte,
                     });
                 } else {
-                    filtered.push(match i.checked_sub(bpp) {
+                    buf.push(match i.checked_sub(bpp) {
                         Some(x) => byte.wrapping_sub(
                             ((u16::from(data[x]) + u16::from(last_line[i])) >> 1) as u8,
                         ),
@@ -44,12 +44,12 @@ pub fn filter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8]) -> Vec
         4 => {
             for (i, byte) in data.iter().enumerate() {
                 if last_line.is_empty() {
-                    filtered.push(match i.checked_sub(bpp) {
+                    buf.push(match i.checked_sub(bpp) {
                         Some(x) => byte.wrapping_sub(data[x]),
                         None => *byte,
                     });
                 } else {
-                    filtered.push(match i.checked_sub(bpp) {
+                    buf.push(match i.checked_sub(bpp) {
                         Some(x) => {
                             byte.wrapping_sub(paeth_predictor(data[x], last_line[i], last_line[x]))
                         }
@@ -60,7 +60,6 @@ pub fn filter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8]) -> Vec
         }
         _ => unreachable!(),
     }
-    filtered
 }
 
 pub fn unfilter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8]) -> Vec<u8> {

src/png/mod.rs

@@ -305,11 +305,14 @@ impl PngImage {
     /// 4: Paeth
     /// 5: All (heuristically pick the best filter for each line)
     pub fn filter_image(&self, filter: u8) -> Vec<u8> {
+        //dbg!(self.data.len());
         let mut filtered = Vec::with_capacity(self.data.len());
         let bpp = ((self.ihdr.bit_depth.as_u8() * self.channels_per_pixel() + 7) / 8) as usize;
         let mut last_line: &[u8] = &[];
         let mut last_pass: Option<u8> = None;
+        let mut f_buf = Vec::new();
         for line in self.scan_lines() {
+            f_buf.clear();
             match filter {
                 0 | 1 | 2 | 3 | 4 => {
                     let filter = if last_pass == line.pass || filter <= 1 {
@@ -318,28 +321,34 @@ impl PngImage {
                         0
                     };
                     filtered.push(filter);
-                    filtered.extend_from_slice(&filter_line(filter, bpp, &line.data, last_line));
+                    filter_line(filter, bpp, &line.data, last_line, &mut f_buf);
+                    filtered.extend_from_slice(&f_buf);
                 }
                 5 => {
                     // Heuristically guess best filter per line
                     // Uses MSAD algorithm mentioned in libpng reference docs
                     // http://www.libpng.org/pub/png/book/chapter09.html
-                    let mut trials: Vec<(u8, Vec<u8>)> = Vec::with_capacity(5);
+                    let mut best_filter = 0;
+                    let mut best_line = Vec::new();
+                    let mut best_size = std::u64::MAX;
+                    
                     // Avoid vertical filtering on first line of each interlacing pass
                     for filter in if last_pass == line.pass { 0..5 } else { 0..2 } {
-                        trials.push((filter, filter_line(filter, bpp, &line.data, last_line)));
+                        filter_line(filter, bpp, &line.data, last_line, &mut f_buf);
+                        let size = f_buf.iter().fold(0u64, |acc, &x| {
+                            let signed = x as i8;
+                            acc + i16::from(signed).abs() as u64
+                        });
+                        if size < best_size {
+                            best_size = size;
+                            best_filter = filter;
+                            std::mem::swap(&mut best_line, &mut f_buf);
+                        }
+                        f_buf.clear() //discard buffer, and start again
+
                     }
-                    let (best_filter, best_line) = trials
+                    filtered.push(best_filter);
-                        .iter()
+                    filtered.extend_from_slice(&best_line);
-                        .min_by_key(|(_, line)| {
-                            line.iter().fold(0u64, |acc, &x| {
-                                let signed = x as i8;
-                                acc + i16::from(signed).abs() as u64
-                            })
-                        })
-                        .unwrap();
-                    filtered.push(*best_filter);
-                    filtered.extend_from_slice(best_line);
                 }
                 _ => unreachable!(),
             }