Add a test for bigtiff encoding

tests/encode_images.rs

@@ -48,6 +48,45 @@ fn encode_decode() {
     }
 }
 
+#[test]
+fn encode_decode_big() {
+    let mut image_data = Vec::new();
+    for x in 0..100 {
+        for y in 0..100u8 {
+            let val = x + y;
+            image_data.push(val);
+            image_data.push(val);
+            image_data.push(val);
+        }
+    }
+    let mut file = Cursor::new(Vec::new());
+    {
+        let mut tiff = TiffEncoder::new_big(&mut file).unwrap();
+
+        let mut image = tiff.new_image::<colortype::RGB8>(100, 100).unwrap();
+        image
+            .encoder()
+            .write_tag(Tag::Artist, "Image-tiff")
+            .unwrap();
+        image.write_data(&image_data).unwrap();
+    }
+    {
+        file.seek(SeekFrom::Start(0)).unwrap();
+        let mut decoder = Decoder::new(&mut file).unwrap();
+        assert_eq!(decoder.colortype().unwrap(), ColorType::RGB(8));
+        assert_eq!(decoder.dimensions().unwrap(), (100, 100));
+        assert_eq!(
+            decoder.get_tag(Tag::Artist).unwrap(),
+            ifd::Value::Ascii("Image-tiff".into())
+        );
+        if let DecodingResult::U8(img_res) = decoder.read_image().unwrap() {
+            assert_eq!(image_data, img_res);
+        } else {
+            panic!("Wrong data type");
+        }
+    }
+}
+
 #[test]
 /// Test that attempting to encode when the input buffer is undersized returns
 /// an error rather than panicking.