From 460b05963de555fd22de3b33020b8a4ee58ca567 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kornel=20Lesi=C5=84ski?= <kornel@geekhood.net>
Date: Fri, 1 Jun 2018 16:45:40 +0100
Subject: [PATCH] Parallel alphas

---
 src/png/mod.rs | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/png/mod.rs b/src/png/mod.rs
index 12fdb3e2..a213969c 100644
--- a/src/png/mod.rs
+++ b/src/png/mod.rs
@@ -15,6 +15,7 @@ use std::fs::File;
 use std::io::{Read, Seek, SeekFrom};
 use std::iter::Iterator;
 use std::path::Path;
+use rayon::prelude::*;
 
 const STD_COMPRESSION: u8 = 8;
 const STD_STRATEGY: u8 = 2; // Huffman only
@@ -601,13 +602,16 @@ impl PngData {
 
     pub fn try_alpha_reduction(&mut self, alphas: &HashSet<AlphaOptim>) {
         assert!(!alphas.is_empty());
+        let alphas = alphas.iter().collect::<Vec<_>>();
         let best = alphas
-            .iter()
-            .filter_map(|alpha| {
+            .par_iter()
+            .with_max_len(1)
+            .filter_map(|&alpha| {
                 let mut image = self.clone();
                 image.reduce_alpha_channel(*alpha);
                 STD_FILTERS
-                    .iter()
+                    .par_iter()
+                    .with_max_len(1)
                     .filter_map(|f| {
                         deflate::deflate(
                             &image.filter_image(*f),