remove pypng dependency

Author: emmanuelle

.circleci/create_conda_optional_env.sh

@@ -16,7 +16,7 @@ if [ ! -d $HOME/miniconda/envs/circle_optional ]; then
     # Create environment
     # PYTHON_VERSION=2.7 or 3.5
     $HOME/miniconda/bin/conda create -n circle_optional --yes python=$PYTHON_VERSION \
-requests nbformat six retrying psutil pandas decorator pytest mock nose poppler xarray scikit-image ipython jupyter ipykernel ipywidgets statsmodels pypng
+requests nbformat six retrying psutil pandas decorator pytest mock nose poppler xarray scikit-image ipython jupyter ipykernel ipywidgets statsmodels
 
     # Install orca into environment
     $HOME/miniconda/bin/conda install --yes -n circle_optional -c plotly plotly-orca==1.3.1

packages/python/plotly/plotly/express/_imshow.py

@@ -5,7 +5,7 @@
 import base64
 from .imshow_utils import rescale_intensity, _integer_ranges, _integer_types
 import pandas as pd
-import png
+from .png import Writer, from_array
 import numpy as np
 
 try:
@@ -57,10 +57,10 @@ def _array_to_b64str(img, backend="pil", compression=4):
         sh = img.shape
         if ndim == 3:
             img = img.reshape((sh[0], sh[1] * sh[2]))
-        w = png.Writer(
+        w = Writer(
             sh[1], sh[0], greyscale=(ndim == 2), alpha=alpha, compression=compression
         )
-        img_png = png.from_array(img, mode=mode)
+        img_png = from_array(img, mode=mode)
         prefix = "data:image/png;base64,"
         with BytesIO() as stream:
             w.write(stream, img_png.rows)