Adding method to detect if image formats should be supported by servo

components/net_traits/image/base.rs

@@ -3,7 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use ipc_channel::ipc::IpcSharedMemory;
-use piston_image::{self, DynamicImage, GenericImage};
+use piston_image::{self, DynamicImage, GenericImage, ImageFormat};
 use stb_image::image as stb_image2;
 use util::vec::byte_swap;
 
@@ -31,7 +31,13 @@ pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
         return None;
     }
 
-    if is_jpeg(buffer) {
+    let image_fmt_result = detect_image_format(buffer);
+    match image_fmt_result {
+        Err(msg) => {
+            debug!("{}", msg);
+            None
+        }
+        Ok(ImageFormat::JPEG) => {
             // For JPEG images, we use stb_image because piston_image does not yet support progressive
             // JPEG.
 
@@ -63,7 +69,8 @@ pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
                     None
                 }
             }
-    } else {
+        }
+        _ => {
             match piston_image::load_from_memory(buffer) {
                 Ok(image) => {
                     let mut rgba = match image {
@@ -85,6 +92,18 @@ pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
             }
         }
     }
+}
+
+
+// https://developer.mozilla.org/en-US/docs/Web/HTML/Element/img
+pub fn detect_image_format(buffer: &[u8]) -> Result<ImageFormat, &str> {
+    if is_gif(buffer)       { Ok(ImageFormat::GIF) }
+    else if is_jpeg(buffer) { Ok(ImageFormat::JPEG) }
+    else if is_png(buffer)  { Ok(ImageFormat::PNG) }
+    else if is_bmp(buffer)  { Ok(ImageFormat::BMP) }
+    else if is_ico(buffer)  { Ok(ImageFormat::ICO) }
+    else { Err("Image Format Not Supported") }
+}
 
 fn is_gif(buffer: &[u8]) -> bool {
     match buffer {
@@ -96,3 +115,15 @@ fn is_gif(buffer: &[u8]) -> bool {
 fn is_jpeg(buffer: &[u8]) -> bool {
     buffer.starts_with(&[0xff, 0xd8, 0xff])
 }
+
+fn is_png(buffer: &[u8]) -> bool {
+    buffer.starts_with(&[0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A])
+}
+
+fn is_bmp(buffer: &[u8]) -> bool {
+    buffer.starts_with(&[0x42, 0x4D])
+}
+
+fn is_ico(buffer: &[u8]) -> bool {
+    buffer.starts_with(&[0x00, 0x00, 0x01, 0x00])
+}

components/servo/Cargo.toml

@@ -26,6 +26,9 @@ path = "../../tests/unit/gfx"
 [dev-dependencies.net_tests]
 path = "../../tests/unit/net"
 
+[dev-dependencies.net_traits_tests]
+path = "../../tests/unit/net_traits"
+
 [dev-dependencies.script_tests]
 path = "../../tests/unit/script"
 

tests/unit/net_traits/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "net_traits_tests"
+version = "0.0.1"
+authors = ["The Servo Project Developers"]
+
+[lib]
+name = "net_traits_tests"
+path = "lib.rs"
+doctest = false
+
+[dependencies.net_traits]
+path = "../../../components/net_traits"

tests/unit/net_traits/image.rs

@@ -0,0 +1,24 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use net_traits::image::base::detect_image_format;
+
+#[test]
+fn test_supported_images() {
+    let gif1 = [b'G', b'I', b'F', b'8', b'7', b'a'];
+    let gif2 = [b'G', b'I', b'F', b'8', b'9', b'a'];
+    let jpeg = [0xff, 0xd8, 0xff];
+    let png = [0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A];
+    let bmp = [0x42, 0x4D];
+    let ico = [0x00, 0x00, 0x01, 0x00];
+    let junk_format = [0x01, 0x02, 0x03, 0x04, 0x05];
+
+    assert!(detect_image_format(&gif1).is_ok());
+    assert!(detect_image_format(&gif2).is_ok());
+    assert!(detect_image_format(&jpeg).is_ok());
+    assert!(detect_image_format(&png).is_ok());
+    assert!(detect_image_format(&bmp).is_ok());
+    assert!(detect_image_format(&ico).is_ok());
+    assert!(detect_image_format(&junk_format).is_err());
+}

tests/unit/net_traits/lib.rs

@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+extern crate net_traits;
+
+#[cfg(test)] mod image;