Support 16 bit per channel image buffers

Add 16 bit buffers for all 16 bit types in ColorType. Include these as
supported types in DynamicImage. These 16 bit images are currently only
supported with u16 representation; changing this would require
specialization and macroing of color conversions.

Load 16 bit PNGs at full bit depth rather than squashing to 8 bit.

Note that tests will not pass until upgrading to a release of image-png
including image-rs/image-png#174.

Closes image-rs#560.
Closes image-rs#665.
Closes image-rs#940.

Cargo.toml

@@ -29,10 +29,11 @@ name = "image"
 path = "./src/lib.rs"
 
 [dependencies]
-byteorder = "1.2.1"
+byteorder = "1.3.2"
 num-iter = "0.1.32"
 num-rational = { version = "0.2.1", default-features = false }
 num-traits = "0.2.0"
+zerocopy = "0.2.8"
 
 [dependencies.gif]
 version = "0.10.0"

src/buffer.rs

@@ -4,12 +4,14 @@ use std::ops::{Deref, DerefMut, Index, IndexMut, Range};
 use std::path::Path;
 use std::slice::{Chunks, ChunksMut};
 
-use color::{ColorType, FromColor, Luma, LumaA, Rgb, Rgba, Bgr, Bgra};
+use color::{ChannelsType, ColorType, FromColor, Luma, LumaA, Rgb, Rgba, Bgr, Bgra};
 use flat::{FlatSamples, SampleLayout};
 use dynimage::{save_buffer, save_buffer_with_format};
 use image::{GenericImage, GenericImageView, ImageFormat, ImageResult};
 use traits::Primitive;
 use utils::expand_packed;
+use zerocopy::AsBytes;
+
 
 /// A generalized pixel.
 ///
@@ -42,13 +44,10 @@ pub trait Pixel: Copy + Clone {
         Self::COLOR_MODEL
     }
 
-    /// ColorType for this pixel format
-    const COLOR_TYPE: ColorType;
+    /// Channels for this pixel format
+    const CHANNELS_TYPE: ChannelsType;
     /// Returns the ColorType for this pixel format
-    #[deprecated(note="please use COLOR_TYPE associated constant")]
-    fn color_type() -> ColorType {
-        Self::COLOR_TYPE
-    }
+    fn color_type() -> ColorType;
 
     /// Returns the channels of this pixel as a 4 tuple. If the pixel
     /// has less than 4 channels the remainder is filled with the maximum value
@@ -655,7 +654,7 @@ where
         FlatSamples {
             samples: self.data,
             layout,
-            color_hint: Some(P::COLOR_TYPE),
+            color_hint: Some(P::color_type()),
         }
     }
 
@@ -669,7 +668,7 @@ where
         FlatSamples {
             samples: self.data.as_ref(),
             layout,
-            color_hint: Some(P::COLOR_TYPE),
+            color_hint: Some(P::color_type()),
         }
     }
 }
@@ -745,8 +744,9 @@ where
 
 impl<P, Container> ImageBuffer<P, Container>
 where
-    P: Pixel<Subpixel = u8> + 'static,
-    Container: Deref<Target = [u8]>,
+    P: Pixel + 'static,
+    P::Subpixel: AsBytes,
+    Container: Deref<Target = [P::Subpixel]>,
 {
     /// Saves the buffer to a file at the path specified.
     ///
@@ -759,18 +759,19 @@ where
         // This is valid as the subpixel is u8.
         save_buffer(
             path,
-            self,
+            self.as_bytes(),
             self.width(),
             self.height(),
-            <P as Pixel>::COLOR_TYPE,
+            <P as Pixel>::color_type(),
         )
     }
 }
 
 impl<P, Container> ImageBuffer<P, Container>
 where
-    P: Pixel<Subpixel = u8> + 'static,
-    Container: Deref<Target = [u8]>,
+    P: Pixel + 'static,
+    P::Subpixel: AsBytes,
+    Container: Deref<Target = [P::Subpixel]>,
 {
     /// Saves the buffer to a file at the specified path in
     /// the specified format.
@@ -784,10 +785,10 @@ where
         // This is valid as the subpixel is u8.
         save_buffer_with_format(
             path,
-            self,
+            self.as_bytes(),
             self.width(),
             self.height(),
-            <P as Pixel>::COLOR_TYPE,
+            <P as Pixel>::color_type(),
             format,
         )
     }
@@ -1076,6 +1077,14 @@ pub type GrayAlphaImage = ImageBuffer<LumaA<u8>, Vec<u8>>;
 pub(crate) type BgrImage = ImageBuffer<Bgr<u8>, Vec<u8>>;
 /// Sendable Bgr + alpha channel image buffer
 pub(crate) type BgraImage = ImageBuffer<Bgra<u8>, Vec<u8>>;
+/// Sendable 16-bit Rgb image buffer
+pub type Rgb16Image = ImageBuffer<Rgb<u16>, Vec<u16>>;
+/// Sendable 16-bit Rgb + alpha channel image buffer
+pub type Rgba16Image = ImageBuffer<Rgba<u16>, Vec<u16>>;
+/// Sendable 16-bit grayscale image buffer
+pub type Gray16Image = ImageBuffer<Luma<u16>, Vec<u16>>;
+/// Sendable 16-bit grayscale + alpha channel image buffer
+pub type GrayAlpha16Image = ImageBuffer<LumaA<u16>, Vec<u16>>;
 
 #[cfg(test)]
 mod test {