----------- Core API v2 ----------- .. py:currentmodule:: imageio.v2 .. warning:: This API exists for backwards compatibility. It is a wrapper around calls to the v3 API and new code should use the v3 API directly. Check the migration instructions below for detailed information on how to migrate. These functions represent imageio's main interface for the user. They provide a common API to read and write image data for a large variety of formats. All read and write functions accept keyword arguments, which are passed on to the backend that does the actual work. To see what keyword arguments are supported by a specific format, use the :func:`.help` function. .. note:: All read-functions return images as numpy arrays, and have a ``meta`` attribute; the meta-data dictionary can be accessed with ``im.meta``. To make this work, imageio actually makes use of a subclass of ``np.ndarray``. If needed, the image can be converted to a plain numpy array using ``np.asarray(im)``. .. autofunction:: imageio.help .. autofunction :: imageio.show_formats Functions for reading ^^^^^^^^^^^^^^^^^^^^^ .. autosummary:: :toctree: ../_autosummary/ imageio.v2.imread imageio.v2.mimread imageio.v2.volread imageio.v2.mvolread Functions for writing ^^^^^^^^^^^^^^^^^^^^^ .. autosummary:: :toctree: ../_autosummary/ imageio.v2.imwrite imageio.v2.mimwrite imageio.v2.volwrite imageio.v2.mvolwrite More control ^^^^^^^^^^^^ For a larger degree of control, imageio provides functions :func:`.get_reader` and :func:`.get_writer`. They respectively return an :class:`.Reader` and an :class:`.Writer` object, which can be used to read/write data and meta data in a more controlled manner. This also allows specific scientific formats to be exposed in a way that best suits that file-format. .. autofunction:: imageio.v2.get_reader .. autofunction:: imageio.v2.get_writer ---- .. autoclass:: imageio.core::Format.Reader :inherited-members: :members: .. autoclass:: imageio.core::Format.Writer :inherited-members: :members: .. _migration_from_v2: Migrating to the v3 API ^^^^^^^^^^^^^^^^^^^^^^^ .. note:: Make sure to have a look at the :doc:`narrative docs for the v3 API ` to build some intuition on how to use the new API. The primary novelty of the v3 API compared to the v2 API is that images are now treated as ndimages, a generalization of (flat) 2D images to N dimensions. This change allows us to design a much simpler API; however, comes with a few backwards incompatible changes. .. rubric:: Avoiding Migration for Legacy Scripts If you have an old script that you do not wish to migrate, you can avoid most of the migration by explicitly importing the v2 API:: import imageio.v2 as imageio This will give you access to most of the old API. However, calls will still rely on the new (v3) plugins and backends, which may cause behavioral changes. As such, you should prefer a full migration to v3 and should avoid using the v2 API in new code. This is meant as a quick way for you to postpone a full migration until it is convenient for you to do so. Reading Images -------------- `iio.imread` can now return a ndimage instead of being limited to flat images. As such, `iio.volread` has merged into `iio.imread` and is now gone. Similarly, `iio.mimread` and `iio.mvolread` have merged into a new function called `iio.imiter`, which returns a generator that yields ndimages from a file in the order in which they appear. Further, the default behavior of `iio.imread` has changed and it has become more context aware. Now it will either return the first stored ndimage (like before) or, depending on the format, all images if this is the more common use-case. To reproduce similar behavior to the v2 API in cases where the incompatibility matters use one of the following snippets:: # img = iio.v2.imread(image_resource) img = iio.v3.imread(image_resource, index=...)[0] # img = iio.v2.volread(image_resource) img = iio.v3.imread(image_resource) # img = iio.v2.mimread(image_resource) # img = iio.v2.mvolread(image_resource) img = [im for im in iio.v3.imiter(image_resource)] Writing Images -------------- Similar to reading images, the new `iio.imwrite` can handle ndimages and lists of images, like ``iio.mimwrite`` and consorts. ``iio.mimwrite``, ``iio.volwrite``, and ``iio.mvolwrite`` have all disappeared. The same goes for their aliases ``iio.mimsave``, ``iio.volsave``, ``iio.mvolsave``, and ``iio.imsave``. They are now all covered by ``iio.imwrite``. To reproduce similar behavior to the v2 API behavior use one of the following snippets:: # img = iio.v2.imwrite(image_resource, ndimage) # img = iio.v2.volwrite(image_resource, ndimage) img = iio.v3.imwrite(image_resource, ndimage) # img = iio.v2.mimwrite(image_resource, list_of_ndimages) # img = iio.v2.mvolwrite(image_resource, list_of_ndimages) img = iio.v3.imwrite(image_resource, list_of_ndimages) Reader and Writer ----------------- Previously, the `reader` and `writer` objects provided an advanced way to read/write data with more control. These are no longer needed. Likewise, the functions ``iio.get_reader``, ``iio.get_writer``, ``iio.read``, and ``iio.save`` have become obsolete. Instead, the plugin object is used directly, which is instantiated in mode ``r`` (reading) or ``w`` (writing). To create such a plugin object, call ``iio.imopen`` and use it as a context manager:: # reader = iio.get_reader(image_resource) # reader = iio.read(image_resource) with iio.imopen(image_resource, "r") as reader: # file is only open/accessible here # img = reader.read(index=0) # meta = reader.metadata(index=0) # ... pass # writer = iio.get_writer(image_resource) # writer = iio.save(image_resource) with iio.imopen(image_resource, "w") as writer: # file is only open/accessible here # writer.write(ndimage) # ... pass Metadata -------- The v3 API makes handling of metadata much more consistent and explicit. Previously in v2, metadata was provided as a ``dict`` that was attached to the image by returning a custom subclass of ``np.ndarray``. Now metadata is served independently from pixel data:: # metadata = iio.imread(image_resource).meta metadata = iio.immeta(image_resource) Further, ImageIO now provides a curated set of standardized metadata, which is called :class:`ImageProperties `, in addition to above metadata. The difference between the two is as follows: The metadata dict contains metadata using format-specific keys to the extent the reading plugin supports them. The ImageProperties dataclass contains generally available metadata using standardized attribute names. Each plugin provides the same set of properties, and if the plugin or format doesn't provide a field it is set to a default value; usually ``None``. To access ImageProperties use:: props = iio.improps(image_resource) Caveats and Notes ----------------- This section is a collection of notes and feedback that we got from other developers that were migrating to ImageIO V3, which might be useful to know while you are migrating your own code. - The old ``format`` kwarg has been deprecated in favor of ``plugin`` and ``extension`` respectively. Use ``plugin`` to select the plugin/backend to use and ``extension`` to select the file extension (aka. format). - The old pillow plugin used to ``np.squeeze`` the image before writing it. This has been removed in V3 to match pillows native behavior. A trailing axis with dimension 1, e.g., ``(256, 256, 1)`` will now raise an exception. (see `#842 `_) - The old pillow plugin featured a kwarg called ``as_gray`` which would convert images to grayscale before returning them. This is redundant and has been deprecated in favor of using ``mode="F"``(backwards compatible) or ``mode="L"`` (integer result), which is pillow's native kwarg for controlling the returned color space. - When reading 16-bit grayscale PNGs using pillow, the v2 pillow plugin used a hardcoded copy to convert pillow's 32-bit result to 16-bit. We removed this copy in v3, which means that you get a 32-bit result when using an older version of pillow (pre v10). Starting with pillow v10, pillow can directly decode into a 16-bit array resulting in a 16-bit result from ImageIO.