Allow get_child_images to access JPEG thumbnails

Tests/test_file_jpeg.py

@@ -415,6 +415,13 @@ class TestFileJpeg:
             info = im._getexif()
             assert info[305] == "Adobe Photoshop CS Macintosh"
 
+    def test_get_child_images(self):
+        with Image.open("Tests/images/flower.jpg") as im:
+            ims = im.get_child_images()
+
+        assert len(ims) == 1
+        assert_image_equal_tofile(ims[0], "Tests/images/flower_thumbnail.png")
+
     def test_mp(self):
         with Image.open("Tests/images/pil_sample_rgb.jpg") as im:
             assert im._getmp() is None

src/PIL/Image.py

@@ -1454,6 +1454,49 @@ class Image:
         self._exif._loaded = False
         self.getexif()
 
+    def get_child_images(self):
+        child_images = []
+        exif = self.getexif()
+        ifds = []
+        if ExifTags.Base.SubIFDs in exif:
+            subifd_offsets = exif[ExifTags.Base.SubIFDs]
+            if subifd_offsets:
+                if not isinstance(subifd_offsets, tuple):
+                    subifd_offsets = (subifd_offsets,)
+                for subifd_offset in subifd_offsets:
+                    ifds.append((exif._get_ifd_dict(subifd_offset), subifd_offset))
+        ifd1 = exif.get_ifd(ExifTags.IFD.IFD1)
+        if ifd1 and ifd1.get(513):
+            ifds.append((ifd1, exif._info.next))
+
+        offset = None
+        for ifd, ifd_offset in ifds:
+            current_offset = self.fp.tell()
+            if offset is None:
+                offset = current_offset
+
+            fp = self.fp
+            thumbnailOffset = ifd.get(513)
+            if thumbnailOffset is not None:
+                try:
+                    thumbnailOffset += self._exif_offset
+                except AttributeError:
+                    pass
+                self.fp.seek(thumbnailOffset)
+                data = self.fp.read(ifd.get(514))
+                fp = io.BytesIO(data)
+
+            with open(fp) as im:
+                if thumbnailOffset is None:
+                    im._frame_pos = [ifd_offset]
+                    im._seek(0)
+                im.load()
+                child_images.append(im)
+
+        if offset is not None:
+            self.fp.seek(offset)
+        return child_images
+
     def getim(self):
         """
         Returns a capsule that points to the internal image memory.

src/PIL/JpegImagePlugin.py

@@ -89,6 +89,7 @@ def APP(self, marker):
         if "exif" not in self.info:
             # extract EXIF information (incomplete)
             self.info["exif"] = s  # FIXME: value will change
+            self._exif_offset = self.fp.tell() - n + 6
     elif marker == 0xFFE2 and s[:5] == b"FPXR\0":
         # extract FlashPix information (incomplete)
         self.info["flashpix"] = s  # FIXME: value will change

src/PIL/TiffImagePlugin.py

@@ -1153,39 +1153,6 @@ class TiffImageFile(ImageFile.ImageFile):
         """Return the current frame number"""
         return self.__frame
 
-    def get_child_images(self):
-        if SUBIFD not in self.tag_v2:
-            return []
-        child_images = []
-        exif = self.getexif()
-        offset = None
-        for im_offset in self.tag_v2[SUBIFD]:
-            # reset buffered io handle in case fp
-            # was passed to libtiff, invalidating the buffer
-            current_offset = self._fp.tell()
-            if offset is None:
-                offset = current_offset
-
-            fp = self._fp
-            ifd = exif._get_ifd_dict(im_offset)
-            jpegInterchangeFormat = ifd.get(513)
-            if jpegInterchangeFormat is not None:
-                fp.seek(jpegInterchangeFormat)
-                jpeg_data = fp.read(ifd.get(514))
-
-                fp = io.BytesIO(jpeg_data)
-
-            with Image.open(fp) as im:
-                if jpegInterchangeFormat is None:
-                    im._frame_pos = [im_offset]
-                    im._seek(0)
-                im.load()
-                child_images.append(im)
-
-        if offset is not None:
-            self._fp.seek(offset)
-        return child_images
-
     def getxmp(self):
         """
         Returns a dictionary containing the XMP tags.