Support 32-bit encoding

src/encoder/colortype.rs

@@ -24,6 +24,13 @@ impl ColorType for Gray16 {
     const BITS_PER_SAMPLE: &'static [u16] = &[16];
 }
 
+pub struct Gray32;
+impl ColorType for Gray32 {
+    type Inner = u32;
+    const TIFF_VALUE: PhotometricInterpretation = PhotometricInterpretation::BlackIsZero;
+    const BITS_PER_SAMPLE: &'static [u16] = &[32];
+}
+
 pub struct RGB8;
 impl ColorType for RGB8 {
     type Inner = u8;
@@ -38,6 +45,13 @@ impl ColorType for RGB16 {
     const BITS_PER_SAMPLE: &'static [u16] = &[16, 16, 16];
 }
 
+pub struct RGB32;
+impl ColorType for RGB32 {
+    type Inner = u32;
+    const TIFF_VALUE: PhotometricInterpretation = PhotometricInterpretation::RGB;
+    const BITS_PER_SAMPLE: &'static [u16] = &[32, 32, 32];
+}
+
 pub struct RGBA8;
 impl ColorType for RGBA8 {
     type Inner = u8;
@@ -52,6 +66,13 @@ impl ColorType for RGBA16 {
     const BITS_PER_SAMPLE: &'static [u16] = &[16, 16, 16, 16];
 }
 
+pub struct RGBA32;
+impl ColorType for RGBA32 {
+    type Inner = u16;
+    const TIFF_VALUE: PhotometricInterpretation = PhotometricInterpretation::RGB;
+    const BITS_PER_SAMPLE: &'static [u16] = &[32, 32, 32, 32];
+}
+
 pub struct CMYK8;
 impl ColorType for CMYK8 {
     type Inner = u8;