Read EXR files exported with BAT

The OpenEXR library should be installed on the system before using this code. The installation can be done by:

sudo apt-get install libopenexr-dev zlib1g-dev
pip install --no-binary openexr openexr

Usage

Use the OpenEXRReader in a with statement:

with OpenEXRReader(PATH, CHSTR) as exr:
    ...

The data in the EXR file can be accessed through the attributes of the exr variable. The existence of these attributes depends on the channel string (CHSTR).

For example, when loading the R,G and B channels:

with OpenEXRReader(PATH, 'rgb') as exr:
    r_channel = exr.r
    g_channel = exr.g
    b_channel = exr.b

will work fine, but

with OpenEXRReader(PATH, 'rgb') as exr:
    r_channel = exr.r
    g_channel = exr.g
    b_channel = exr.b
    a_channel = exr.a

will result in an AttributeError because the alpha channel is not loaded (for that, the channel string should be 'rgba'). See the OpenEXRReader class description for the list of all channel keys that can be used in the channel string.

Additionally, a loader can be specified. When using the default loader (None), the channels will be loaded as 1D Python lists (using the built-in array.array). NumPy and PyTorch can also be used as loaders, in which case, the loaded channels will be 1D NumPy arrays or PyTorch tensors, respectively:

with OpenEXRReader(PATH, 'a') as exr:
    type(exr.a)  # list

import numpy as np
with OpenEXRReader(PATH, 'a', np) as exr:
    type(exr.a)  # np.array

import torch
with OpenEXRReader(PATH, 'a', torch) as exr:
    type(exr.a)  # torch.Tensor

See test/test.py for further examples.