Auto merge of #21877 - servo:webgl, r=jdm

Improve some byte-swap and premultiply operations

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components/net_traits/Cargo.toml

@@ -24,6 +24,7 @@ malloc_size_of = { path = "../malloc_size_of" }
 malloc_size_of_derive = { path = "../malloc_size_of_derive" }
 msg = {path = "../msg"}
 num-traits = "0.2"
+pixels = {path = "../pixels"}
 serde = "1.0"
 servo_arc = {path = "../servo_arc"}
 servo_config = {path = "../config"}

components/net_traits/image/base.rs

@@ -4,6 +4,7 @@
 
 use ipc_channel::ipc::IpcSharedMemory;
 use piston_image::{self, DynamicImage, ImageFormat};
+use pixels;
 use std::fmt;
 use webrender_api;
 
@@ -46,24 +47,6 @@ pub struct ImageMetadata {
 // FIXME: Images must not be copied every frame. Instead we should atomically
 // reference count them.
 
-// TODO(pcwalton): Speed up with SIMD, or better yet, find some way to not do this.
-fn byte_swap_and_premultiply(data: &mut [u8]) {
-    let length = data.len();
-
-    let mut i = 0;
-    while i < length {
-        let r = data[i + 2];
-        let g = data[i + 1];
-        let b = data[i + 0];
-
-        data[i + 0] = r;
-        data[i + 1] = g;
-        data[i + 2] = b;
-
-        i += 4;
-    }
-}
-
 pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
     if buffer.is_empty() {
         return None;
@@ -82,7 +65,7 @@ pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
                         DynamicImage::ImageRgba8(rgba) => rgba,
                         image => image.to_rgba(),
                     };
-                    byte_swap_and_premultiply(&mut *rgba);
+                    pixels::byte_swap_colors_inplace(&mut *rgba);
                     Some(Image {
                         width: rgba.width(),
                         height: rgba.height(),

components/net_traits/lib.rs

@@ -17,6 +17,7 @@ extern crate ipc_channel;
 #[macro_use] extern crate malloc_size_of_derive;
 extern crate msg;
 extern crate num_traits;
+extern crate pixels;
 #[macro_use] extern crate serde;
 extern crate servo_arc;
 extern crate servo_url;