Restore previous position after failed seek

Author: radarhere

Tests/test_file_jxl.py

@@ -37,7 +37,7 @@ def test_version(self) -> None:
 
     def test_read_rgb(self) -> None:
         """
-        Can we read a RGB mode Jpeg XL file without error?
+        Can we read an RGB mode JPEG XL file without error?
         Does it have the bits we expect?
         """
 
@@ -52,9 +52,22 @@ def test_read_rgb(self) -> None:
             # djxl hopper.jxl hopper_jxl_bits.ppm
             assert_image_similar_tofile(im, "Tests/images/hopper_jxl_bits.ppm", 1)
 
+    def test_read_rgba(self) -> None:
+        # Generated with `cjxl transparent.png transparent.jxl -q 100 -e 8`
+        with Image.open("Tests/images/transparent.jxl") as im:
+            assert im.mode == "RGBA"
+            assert im.size == (200, 150)
+            assert im.format == "JPEG XL"
+            im.load()
+            im.getdata()
+
+            im.tobytes()
+
+            assert_image_similar_tofile(im, "Tests/images/transparent.png", 1)
+
     def test_read_i16(self) -> None:
         """
-        Can we read 16-bit Grayscale Jpeg XL image?
+        Can we read 16-bit Grayscale JPEG XL image?
         """
 
         with Image.open("Tests/images/jxl/16bit_subcutaneous.cropped.jxl") as im:

Tests/test_file_jxl_alpha.py

@@ -21,7 +21,7 @@ def test_n_frames() -> None:
         assert im.is_animated
 
 
-def test_float_duration() -> None:
+def test_duration() -> None:
     with Image.open("Tests/images/iss634.jxl") as im:
         assert im.info["duration"] == 70
         assert im.info["timestamp"] == 0
@@ -66,8 +66,11 @@ def test_seek() -> None:
 
 def test_seek_errors() -> None:
     with Image.open("Tests/images/iss634.jxl") as im:
-        with pytest.raises(EOFError):
+        with pytest.raises(EOFError, match="attempt to seek outside sequence"):
             im.seek(-1)
 
-        with pytest.raises(EOFError):
+        im.seek(1)
+        with pytest.raises(EOFError, match="no more images in JPEG XL file"):
             im.seek(47)
+
+        assert im.tell() == 1

Tests/test_file_jxl_animated.py

@@ -39,7 +39,7 @@ def test_read_exif_metadata() -> None:
     with Image.open("Tests/images/flower.jpg") as im_jpeg:
         expected_exif = im_jpeg.info["exif"]
 
-    # jpeg xl always returns exif without 'Exif\0\0' prefix
+    # JPEG XL always returns exif without 'Exif\0\0' prefix
     assert exif_data == expected_exif[6:]
 
 

Tests/test_file_jxl_metadata.py

@@ -50,7 +50,7 @@ def _open(self) -> None:
         if icc := self._decoder.get_icc():
             self.info["icc_profile"] = icc
         if exif := self._decoder.get_exif():
-            # jpeg xl does some weird shenanigans when storing exif
+            # JPEG XL does some weird shenanigans when storing exif
             # it omits first 6 bytes of tiff header but adds 4 byte offset instead
             if len(exif) > 4:
                 exif_start_offset = struct.unpack(">I", exif[:4])[0]
@@ -89,10 +89,12 @@ def seek(self, frame: int) -> None:
             self._decoder.rewind()
             self.info["timestamp"] = 0
 
+        last_frame = self.__frame
         while self.__frame < frame:
             self._get_next()
             self.__frame += 1
             if self._n_frames is not None and self._n_frames < frame:
+                self.seek(last_frame)
                 msg = "no more images in JPEG XL file"
                 raise EOFError(msg)