Added IMT tests

Tests/test_file_imt.py

@@ -0,0 +1,19 @@
+import io
+
+import pytest
+
+from PIL import Image, ImtImagePlugin
+
+from .helper import assert_image_equal_tofile
+
+
+def test_sanity():
+    with Image.open("Tests/images/bw_gradient.imt") as im:
+        assert_image_equal_tofile(im, "Tests/images/bw_gradient.png")
+
+
+@pytest.mark.parametrize("data", (b"\n", b"\n-", b"width 1\n"))
+def test_invalid_file(data):
+    with io.BytesIO(data) as fp:
+        with pytest.raises(SyntaxError):
+            ImtImagePlugin.ImtImageFile(fp)

src/PIL/ImtImagePlugin.py

@@ -74,13 +74,13 @@ class ImtImageFile(ImageFile.ImageFile):
                 if not m:
                     break
                 k, v = m.group(1, 2)
-                if k == "width":
+                if k == b"width":
                     xsize = int(v)
                     self._size = xsize, ysize
-                elif k == "height":
+                elif k == b"height":
                     ysize = int(v)
                     self._size = xsize, ysize
-                elif k == "pixel" and v == "n8":
+                elif k == b"pixel" and v == b"n8":
                     self.mode = "L"