auto merge of #1288 : ryanhc/servo/transparent_png, r=larsbergstrom

Modified to use libpng to read .png files. We use stb_image to read all other image files.
This requires updated submodule: https://github.com/mozilla-servo/rust-png/pull/13

This patch is for:
https://github.com/mozilla/servo/issues/1279

src/components/gfx/gfx.rc

@@ -15,6 +15,7 @@ extern mod extra;
 extern mod geom = "rust-geom";
 extern mod layers = "rust-layers";
 extern mod stb_image;
+extern mod png;
 extern mod servo_net (name = "net");
 extern mod servo_util (name = "util");
 extern mod style;

src/components/gfx/render_context.rs

@@ -17,6 +17,7 @@ use geom::rect::Rect;
 use geom::size::Size2D;
 use geom::side_offsets::SideOffsets2D;
 use servo_net::image::base::Image;
+use png::{RGBA8, K8, KA8};
 use servo_util::geometry::Au;
 use std::vec;
 use std::libc::types::common::c99::uint16_t;
@@ -103,11 +104,17 @@ impl<'self> RenderContext<'self>  {
     pub fn draw_image(&self, bounds: Rect<Au>, image: Arc<~Image>) {
         let image = image.get();
         let size = Size2D(image.width as i32, image.height as i32);
-        let stride = image.width * 4;
+        let pixel_width = match image.color_type {
+            RGBA8 => 4,
+            K8    => 1,
+            KA8   => 2,
+            _     => fail!(~"color type not supported"),
+        };
+        let stride = image.width * pixel_width;
 
         self.draw_target.make_current();
         let draw_target_ref = &self.draw_target;
-        let azure_surface = draw_target_ref.create_source_surface_from_data(image.data, size,
+        let azure_surface = draw_target_ref.create_source_surface_from_data(image.pixels, size,
                                                                             stride as i32, B8G8R8A8);
         let source_rect = Rect(Point2D(0 as AzFloat, 0 as AzFloat),
                                Size2D(image.width as AzFloat, image.height as AzFloat));

src/components/main/compositing/run.rs

@@ -359,7 +359,7 @@ pub fn run_compositor(compositor: &CompositorTask) {
             let img = png::Image {
                 width: width as u32,
                 height: height as u32,
-                color_type: png::RGB8,
+                color_type: png::RGBA8,
                 pixels: pixels,
             };
             let res = png::store_png(&img, &path);

src/components/net/image/base.rs

@@ -4,14 +4,19 @@
 
 use std::vec;
 use stb_image = stb_image::image;
+use png;
 
 // FIXME: Images must not be copied every frame. Instead we should atomically
 // reference count them.
+pub type Image = png::Image;
 
-pub type Image = stb_image::Image<u8>;
-
-pub fn Image(width: uint, height: uint, depth: uint, data: ~[u8]) -> Image {
-    stb_image::new_image(width, height, depth, data)
+pub fn Image(width: u32, height: u32, color_type: png::ColorType, data: ~[u8]) -> Image {
+    png::Image {
+        width: width,
+        height: height,
+        color_type: color_type,
+        pixels: data,
+    }
 }
 
 static TEST_IMAGE: &'static [u8] = include_bin!("test.jpeg");
@@ -21,6 +26,13 @@ pub fn test_image_bin() -> ~[u8] {
 }
 
 pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
+    if png::is_png(buffer) {
+        match png::load_png_from_memory(buffer) {
+            Ok(png_image) => Some(png_image),
+            Err(_err) => None,
+        }
+    } else {
+        // For non-png images, we use stb_image
         // Can't remember why we do this. Maybe it's what cairo wants
         static FORCE_DEPTH: uint = 4;
 
@@ -42,9 +54,10 @@ pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
 
                 assert!(image.data.len() == data.len());
 
-            Some(Image(image.width, image.height, image.depth, data))
+                Some(Image(image.width as u32, image.height as u32, png::RGBA8, data))
             }
             stb_image::ImageF32(_image) => fail!(~"HDR images not implemented"),
             stb_image::Error => None
         }
     }
+}

src/components/net/net.rc

@@ -15,6 +15,7 @@ extern mod http;
 extern mod servo_util (name = "util");
 extern mod stb_image;
 extern mod extra;
+extern mod png;
 
 /// Image handling.
 ///

src/support/png/rust-png

@@ -1 +1 @@
-Subproject commit bd3b394e35dee36989e3c80abd9bcc1f99affa27
+Subproject commit 519c291139813bf6cda192a45745013d543c99fe