Added tests and finalized i8 support

src/decoder/mod.rs

@@ -923,6 +923,12 @@ impl<R: Read + Seek> Decoder<R> {
                 reader.read_u64_into(&mut buffer[..bytes / 8])?;
                 bytes / 8
             }
+            (ColorType::RGBA(8), DecodingBuffer::I8(ref mut buffer))
+            | (ColorType::RGB(8), DecodingBuffer::I8(ref mut buffer))
+            | (ColorType::CMYK(8), DecodingBuffer::I8(ref mut buffer)) => {
+                reader.read_i8_into(&mut buffer[..bytes])?;
+                bytes
+            }
             (ColorType::RGBA(16), DecodingBuffer::I16(ref mut buffer))
             | (ColorType::RGB(16), DecodingBuffer::I16(ref mut buffer))
             | (ColorType::CMYK(16), DecodingBuffer::I16(ref mut buffer)) => {
@@ -957,6 +963,15 @@ impl<R: Read + Seek> Decoder<R> {
                 }
                 bytes / 2
             }
+            (ColorType::Gray(8), DecodingBuffer::I8(ref mut buffer)) => {
+                reader.read_i8_into(&mut buffer[..bytes])?;
+                if self.photometric_interpretation == PhotometricInterpretation::WhiteIsZero {
+                    for datum in buffer[..bytes].iter_mut() {
+                        *datum = !*datum;
+                    }
+                }
+                bytes
+            }
             // The following conversions interpret the image as in libtiff.
             // In particular, MIN is white and MAX is black and not Zero as the name would imply.
             (ColorType::Gray(16), DecodingBuffer::I16(ref mut buffer)) => {

tests/decode_images.rs

@@ -29,6 +29,7 @@ macro_rules! test_image_sum {
 }
 
 test_image_sum!(test_image_sum_u8, U8, u64);
+test_image_sum!(test_image_sum_i8, I8, i64);
 test_image_sum!(test_image_sum_u16, U16, u64);
 test_image_sum!(test_image_sum_i16, I16, i64);
 test_image_sum!(test_image_sum_u32, U32, u64);
@@ -136,6 +137,16 @@ fn test_rgb_f32() {
     test_image_sum_f32("gradient-3c-32b-float.tiff", ColorType::RGB(32), 472.8405);
 }
 
+#[test]
+fn test_int8() {
+    test_image_sum_i8("int8.tif", ColorType::Gray(8), 3111)
+}
+
+#[test]
+fn test_int8_rgb() {
+    test_image_sum_i8("int8_rgb.tif", ColorType::RGB(8), -10344)
+}
+
 #[test]
 fn test_int16() {
     test_image_sum_i16("int16.tif", ColorType::Gray(16), 354396);