incremental tile decoding, refactoring

tests/decode_images.rs

@@ -245,3 +245,47 @@ fn test_tiled_whiteiszero_gray_i8() {
 fn test_tiled_cmyk_i8() {
     test_image_sum_i8("tiled-cmyk-i8.tif", ColorType::CMYK(8), 1759101);
 }
+
+#[test]
+fn test_tiled_incremental() {
+    let file = "tiled-rgb-u8.tif";
+    let expected_type = ColorType::RGB(8);
+    let sums = [
+        188760, 195639, 108148, 81986, 665088, 366140, 705317, 423366, 172033, 324455, 244102,
+        81853, 181258, 247971, 129486, 55600, 565625, 422102, 730888, 379271, 232142, 292549,
+        244045, 86866, 188141, 115036, 150785, 84389, 353170, 459325, 719619, 329594, 278663,
+        220474, 243048, 113563, 189152, 109684, 179391, 122188, 279651, 622093, 724682, 302459,
+        268428, 204499, 224255, 124674, 170668, 121868, 192768, 183367, 378029, 585651, 657712,
+        296790, 241444, 197083, 198429, 134869, 182318, 86034, 203655, 182338, 297255, 601284,
+        633813, 242531, 228578, 206441, 193552, 125412, 181527, 165439, 202531, 159538, 268388,
+        565790, 611382, 272967, 236497, 215154, 158881, 90806, 106114, 182342, 191824, 186138,
+        215174, 393193, 701228, 198866, 227944, 193830, 166330, 49008, 55719, 122820, 197316,
+        161969, 203152, 170986, 624427, 188605, 186187, 111064, 115192, 39538, 48626, 163929,
+        144682, 135796, 194141, 154198, 584125, 180255, 153524, 121433, 132641, 35743, 47798,
+        152343, 162874, 167664, 160175, 133038, 659882, 138339, 166470, 124173, 118929, 51317,
+        45267, 155776, 161331, 161006, 130052, 137618, 337291, 106481, 161999, 127343, 87724,
+        59540, 63907, 155677, 140668, 141523, 108061, 168657, 186482, 98599, 147614, 139963, 90444,
+        56602, 92547, 125644, 134212, 126569, 144153, 179800, 174516, 133969, 129399, 117681,
+        83305, 55075, 110737, 115108, 128572, 128911, 130922, 179986, 143288, 145884, 155856,
+        96683, 94057, 56238, 79649, 71651, 70182, 75010, 77009, 98855, 78979, 74341, 83482, 53403,
+        59842, 30305,
+    ];
+
+    let path = PathBuf::from(TEST_IMAGE_DIR).join(file);
+    let img_file = File::open(path).expect("Cannot find test image!");
+    let mut decoder = Decoder::new(img_file).expect("Cannot create decoder");
+    assert_eq!(decoder.colortype().unwrap(), expected_type);
+
+    let tiles = decoder.tile_count().unwrap();
+    assert_eq!(tiles as usize, sums.len());
+
+    for tile in 0..tiles {
+        match decoder.read_tile().unwrap() {
+            DecodingResult::U8(res) => {
+                let sum: u64 = res.into_iter().map(<u64>::from).sum();
+                assert_eq!(sum, sums[tile as usize]);
+            }
+            _ => panic!("Wrong bit depth"),
+        }
+    }
+}