Backwards Incompatible Changes

Python 3.3 Dropped

Python 3.3 is EOL and no longer supported due to moving testing from nose, which is deprecated, to pytest, which doesn’t support Python 3.3. We will not be creating binaries, testing, or retaining compatibility with this version. The final version of Pillow for Python 3.3 is 4.3.0.

Decompression Bombs now raise Exceptions

Pillow has previously emitted warnings for images that are unexpectedly large and may be a denial of service. These warnings are now upgraded to DecompressionBombErrors for images that are twice the size of images that trigger the DecompressionBombWarning. The default threshold is 128Mpx, or 0.5GB for an RGB or RGBA image. This can be disabled or changed by setting Image.MAX_IMAGE_PIXELS = None.


The scripts formerly installed by Pillow have been split into a separate package, pillow-scripts, living at https://github.com/python-pillow/pillow-scripts .

API Changes


The olefile module is no longer a required dependency when installing Pillow. Support for plugins requiring olefile will not be loaded if it is not installed. This allows library consumers to avoid installing this dependency if they choose. Some library consumers have little interest in the format support and would like to keep dependencies to a minimum.

Further, the vendored version was removed in Pillow 4.0.0 and replaced with a deprecation warning that PIL.OleFileIO would be removed in a future version. This warning has been upgraded to an import error pending future removal.

Check parameter on _save

Several image plugins supported a named check parameter on their nominally private _save method to preflight if the image could be saved in that format. That parameter has been removed.

API Additions


A new named parameter, fillcolor, has been added to Image.transform. This color specifies the background color to use in the area outside the transformed area in the output image. This parameter takes the same color specifications as used in Image.new.

GIF Disposal

Multiframe GIF images now take an optional disposal parameter to specify the disposal option for changed pixels.

Other Changes

Compressed TIFF Images

Previously, there were some compression modes (JPEG, Packbits, and LZW) that were supported with Pillow’s internal TIFF decoder. All compressed TIFFs are now read using the libtiff decoder, as it implements the compression schemes more correctly.

Libraqm is now Dynamically Linked

The libraqm dependency for complex text scripts is now linked dynamically at runtime rather than at packaging time. This allows us to release binaries with support for libraqm if it is installed on the user’s machine.

Source Layout Changes

The Pillow source is now stored within the src directory of the distribution. This prevents accidental imports of the PIL directory when running Python from the project directory.

Setup.py Changes

Multiarch support on Linux should be more robust, especially on Debian derivatives on ARM platforms. Debian’s multiarch platform configuration is run in preference to the sniffing of machine platform and architecture.