Repository: python-pillow/Pillow

Issue:
AttributeError: module 'PIL._imaging' has no attribute 'group4_decoder'
### What did you do?

Executed this a script (code below) to get the dimensions of a tiff group4 image.

### What did you expect to happen?

I expected that the dimensions of the images would be printed

### What actually happened?

crash with the error

```
AttributeError: module 'PIL._imaging' has no attribute 'group4_decoder'
```

full output:

```
['DEFAULT_STRATEGY', 'FILTERED', 'FIXED', 'HAVE_LIBJPEGTURBO', 'HUFFMAN_ONLY', 'PILLOW_VERSION', 'RLE', '__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', 'alpha_composite', 'bcn_decoder', 'bit_decoder', 'blend', 'clear_cache', 'convert', 'draw', 'effect_mandelbrot', 'effect_noise', 'eps_encoder', 'fill', 'fli_decoder', 'font', 'get_alignment', 'get_block_size', 'get_blocks_max', 'get_stats', 'getcodecstatus', 'gif_decoder', 'gif_encoder', 'hex_decoder', 'hex_encoder', 'jp2klib_version', 'jpeg2k_decoder', 'jpeg2k_encoder', 'jpeg_decoder', 'jpeg_encoder', 'jpeglib_version', 'libtiff_decoder', 'libtiff_encoder', 'libtiff_version', 'linear_gradient', 'map_buffer', 'merge', 'new', 'outline', 'packbits_decoder', 'path', 'pcd_decoder', 'pcx_decoder', 'pcx_encoder', 'radial_gradient', 'raw_decoder', 'raw_encoder', 'reset_stats', 'set_alignment', 'set_block_size', 'set_blocks_max', 'sgi_rle_decoder', 'sun_rle_decoder', 'tga_rle_decoder', 'tga_rle_encoder', 'wedge', 'xbm_decoder', 'xbm_encoder', 'zip_decoder', 'zip_encoder', 'zlib_version']
5.4.1
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/dist-packages/PIL/Image.py", line 455, in _getdecoder
    decoder = getattr(core, decoder_name + "_decoder")
AttributeError: module 'PIL._imaging' has no attribute 'group4_decoder'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "bug.py", line 36, in <module>
    print(dimensionsFromBlobImage(blob))
  File "bug.py", line 24, in dimensionsFromBlobImage
    ImPar.feed(chunk)
  File "/usr/local/lib/python3.7/dist-packages/PIL/ImageFile.py", line 416, in feed
    im.mode, d, a, im.decoderconfig
  File "/usr/local/lib/python3.7/dist-packages/PIL/Image.py", line 458, in _getdecoder
    raise IOError("decoder %s not available" % decoder_name)
OSError: decoder group4 not available
```

### What are your OS, Python and Pillow versions?

* OS: Linux Debian (reproduced it on stable and sid)
* Python: 3.7.2+
* Pillow: 5.4.1

Note that I do have `libtiff5` and `libtiff5-dev` installed.

Here's the script:

```python
import PIL
from PIL import Image, TiffImagePlugin
from PIL import ImageFile

TiffImagePlugin.READ_LIBTIFF=True
print(dir(PIL._imaging))
print(PIL.PILLOW_VERSION)

def dimensionsFromBlobImage(blob):
    ImPar = ImageFile.Parser()
    chunk = blob.read(2048)
    while chunk != "":
        ImPar.feed(chunk)
        if ImPar.image:
            break
        chunk = blob.read(2048)
    return ImPar.image.size


with (open("I1GS1051890001.tif", mode='rb')) as blob:
    print(dimensionsFromBlobImage(blob))
```

and the image:

[I1GS1051890001.tif.zip](https://github.com/python-pillow/Pillow/files/3017275/I1GS1051890001.tif.zip)

Note that the script works fine when replacing the function with:

```python
def dimensionsFromBlobImage(blob):
    im = Image.open(blob)
    return im.size
```


Discussion:

Resolving patch:
diff --git a/src/PIL/TiffImagePlugin.py b/src/PIL/TiffImagePlugin.py
--- a/src/PIL/TiffImagePlugin.py
+++ b/src/PIL/TiffImagePlugin.py
@@ -1121,7 +1121,7 @@ def _load_libtiff(self):
         # (self._compression, (extents tuple),
         #   0, (rawmode, self._compression, fp))
         extents = self.tile[0][1]
-        args = list(self.tile[0][3]) + [self.tag_v2.offset]
+        args = list(self.tile[0][3])
 
         # To be nice on memory footprint, if there's a
         # file descriptor, use that instead of reading
@@ -1328,8 +1328,8 @@ def _setup(self):
 
             # Offset in the tile tuple is 0, we go from 0,0 to
             # w,h, and we only do this once -- eds
-            a = (rawmode, self._compression, False)
-            self.tile.append((self._compression, (0, 0, xsize, ysize), 0, a))
+            a = (rawmode, self._compression, False, self.tag_v2.offset)
+            self.tile.append(("libtiff", (0, 0, xsize, ysize), 0, a))
 
         elif STRIPOFFSETS in self.tag_v2 or TILEOFFSETS in self.tag_v2:
             # striped image


Test patch:
diff --git a/Tests/test_file_libtiff.py b/Tests/test_file_libtiff.py
--- a/Tests/test_file_libtiff.py
+++ b/Tests/test_file_libtiff.py
@@ -121,7 +121,7 @@ def test_adobe_deflate_tiff(self):
 
         self.assertEqual(im.mode, "RGB")
         self.assertEqual(im.size, (278, 374))
-        self.assertEqual(im.tile[0][:3], ("tiff_adobe_deflate", (0, 0, 278, 374), 0))
+        self.assertEqual(im.tile[0][:3], ("libtiff", (0, 0, 278, 374), 0))
         im.load()
 
         self.assert_image_equal_tofile(im, "Tests/images/tiff_adobe_deflate.png")
@@ -644,10 +644,10 @@ def test_16bit_RGB_tiff(self):
             im.tile,
             [
                 (
-                    "tiff_adobe_deflate",
+                    "libtiff",
                     (0, 0, 100, 40),
                     0,
-                    ("RGB;16N", "tiff_adobe_deflate", False),
+                    ("RGB;16N", "tiff_adobe_deflate", False, 8),
                 )
             ],
         )
@@ -661,7 +661,8 @@ def test_16bit_RGBa_tiff(self):
         self.assertEqual(im.mode, "RGBA")
         self.assertEqual(im.size, (100, 40))
         self.assertEqual(
-            im.tile, [("tiff_lzw", (0, 0, 100, 40), 0, ("RGBa;16N", "tiff_lzw", False))]
+            im.tile,
+            [("libtiff", (0, 0, 100, 40), 0, ("RGBa;16N", "tiff_lzw", False, 38236))],
         )
         im.load()
 
@@ -680,7 +681,7 @@ def test_gimp_tiff(self):
         self.assertEqual(im.mode, "RGB")
         self.assertEqual(im.size, (256, 256))
         self.assertEqual(
-            im.tile, [("jpeg", (0, 0, 256, 256), 0, ("RGB", "jpeg", False))]
+            im.tile, [("libtiff", (0, 0, 256, 256), 0, ("RGB", "jpeg", False, 5122))]
         )
         im.load()