diff --git a/packages/python/plotly/_plotly_utils/data_utils.py b/packages/python/plotly/_plotly_utils/data_utils.py
new file mode 100644
index 00000000000..5fb05b03114
--- /dev/null
+++ b/packages/python/plotly/_plotly_utils/data_utils.py
@@ -0,0 +1,75 @@
+from io import BytesIO
+import base64
+from .png import Writer, from_array
+
+try:
+ from PIL import Image
+
+ pil_imported = True
+except ImportError:
+ pil_imported = False
+
+
+def image_array_to_data_uri(img, backend="pil", compression=4, ext="png"):
+ """Converts a numpy array of uint8 into a base64 png or jpg string.
+
+ Parameters
+ ----------
+ img: ndarray of uint8
+ array image
+ backend: str
+ 'auto', 'pil' or 'pypng'. If 'auto', Pillow is used if installed,
+ otherwise pypng.
+ compression: int, between 0 and 9
+ compression level to be passed to the backend
+ ext: str, 'png' or 'jpg'
+ compression format used to generate b64 string
+ """
+ # PIL and pypng error messages are quite obscure so we catch invalid compression values
+ if compression < 0 or compression > 9:
+ raise ValueError("compression level must be between 0 and 9.")
+ alpha = False
+ if img.ndim == 2:
+ mode = "L"
+ elif img.ndim == 3 and img.shape[-1] == 3:
+ mode = "RGB"
+ elif img.ndim == 3 and img.shape[-1] == 4:
+ mode = "RGBA"
+ alpha = True
+ else:
+ raise ValueError("Invalid image shape")
+ if backend == "auto":
+ backend = "pil" if pil_imported else "pypng"
+ if ext != "png" and backend != "pil":
+ raise ValueError("jpg binary strings are only available with PIL backend")
+
+ if backend == "pypng":
+ ndim = img.ndim
+ sh = img.shape
+ if ndim == 3:
+ img = img.reshape((sh[0], sh[1] * sh[2]))
+ w = Writer(
+ sh[1], sh[0], greyscale=(ndim == 2), alpha=alpha, compression=compression
+ )
+ img_png = from_array(img, mode=mode)
+ prefix = "data:image/png;base64,"
+ with BytesIO() as stream:
+ w.write(stream, img_png.rows)
+ base64_string = prefix + base64.b64encode(stream.getvalue()).decode("utf-8")
+ else: # pil
+ if not pil_imported:
+ raise ImportError(
+ "pillow needs to be installed to use `backend='pil'. Please"
+ "install pillow or use `backend='pypng'."
+ )
+ pil_img = Image.fromarray(img)
+ if ext == "jpg" or ext == "jpeg":
+ prefix = "data:image/jpeg;base64,"
+ ext = "jpeg"
+ else:
+ prefix = "data:image/png;base64,"
+ ext = "png"
+ with BytesIO() as stream:
+ pil_img.save(stream, format=ext, compress_level=compression)
+ base64_string = prefix + base64.b64encode(stream.getvalue()).decode("utf-8")
+ return base64_string
diff --git a/packages/python/plotly/plotly/express/png.py b/packages/python/plotly/_plotly_utils/png.py
similarity index 100%
rename from packages/python/plotly/plotly/express/png.py
rename to packages/python/plotly/_plotly_utils/png.py
diff --git a/packages/python/plotly/plotly/express/_imshow.py b/packages/python/plotly/plotly/express/_imshow.py
index 218a824e154..9c12ae575c6 100644
--- a/packages/python/plotly/plotly/express/_imshow.py
+++ b/packages/python/plotly/plotly/express/_imshow.py
@@ -1,12 +1,10 @@
import plotly.graph_objs as go
from _plotly_utils.basevalidators import ColorscaleValidator
from ._core import apply_default_cascade
-from io import BytesIO
-import base64
from .imshow_utils import rescale_intensity, _integer_ranges, _integer_types
import pandas as pd
-from .png import Writer, from_array
import numpy as np
+from plotly.utils import image_array_to_data_uri
try:
import xarray
@@ -14,81 +12,10 @@
xarray_imported = True
except ImportError:
xarray_imported = False
-try:
- from PIL import Image
-
- pil_imported = True
-except ImportError:
- pil_imported = False
_float_types = []
-def _array_to_b64str(img, backend="pil", compression=4, ext="png"):
- """Converts a numpy array of uint8 into a base64 png string.
-
- Parameters
- ----------
- img: ndarray of uint8
- array image
- backend: str
- 'auto', 'pil' or 'pypng'. If 'auto', Pillow is used if installed,
- otherwise pypng.
- compression: int, between 0 and 9
- compression level to be passed to the backend
- ext: str, 'png' or 'jpg'
- compression format used to generate b64 string
- """
- # PIL and pypng error messages are quite obscure so we catch invalid compression values
- if compression < 0 or compression > 9:
- raise ValueError("compression level must be between 0 and 9.")
- alpha = False
- if img.ndim == 2:
- mode = "L"
- elif img.ndim == 3 and img.shape[-1] == 3:
- mode = "RGB"
- elif img.ndim == 3 and img.shape[-1] == 4:
- mode = "RGBA"
- alpha = True
- else:
- raise ValueError("Invalid image shape")
- if backend == "auto":
- backend = "pil" if pil_imported else "pypng"
- if ext != "png" and backend != "pil":
- raise ValueError("jpg binary strings are only available with PIL backend")
-
- if backend == "pypng":
- ndim = img.ndim
- sh = img.shape
- if ndim == 3:
- img = img.reshape((sh[0], sh[1] * sh[2]))
- w = Writer(
- sh[1], sh[0], greyscale=(ndim == 2), alpha=alpha, compression=compression
- )
- img_png = from_array(img, mode=mode)
- prefix = "data:image/png;base64,"
- with BytesIO() as stream:
- w.write(stream, img_png.rows)
- base64_string = prefix + base64.b64encode(stream.getvalue()).decode("utf-8")
- else: # pil
- if not pil_imported:
- raise ImportError(
- "pillow needs to be installed to use `backend='pil'. Please"
- "install pillow or use `backend='pypng'."
- )
- pil_img = Image.fromarray(img)
- if ext == "jpg" or ext == "jpeg":
- prefix = "data:image/jpeg;base64,"
- ext = "jpeg"
- else:
- prefix = "data:image/png;base64,"
- ext = "png"
- with BytesIO() as stream:
- pil_img.save(stream, format=ext, compress_level=compression)
- base64_string = prefix + base64.b64encode(stream.getvalue()).decode("utf-8")
- return base64_string
-
-
def _vectorize_zvalue(z, mode="max"):
alpha = 255 if mode == "max" else 0
if z is None:
@@ -422,7 +349,7 @@ def imshow(
for ch in range(img.shape[-1])
]
)
- img_str = _array_to_b64str(
+ img_str = image_array_to_data_uri(
img_rescaled,
backend=binary_backend,
compression=binary_compression_level,
diff --git a/packages/python/plotly/plotly/utils.py b/packages/python/plotly/plotly/utils.py
index 0af0a49f710..23c8a4441f4 100644
--- a/packages/python/plotly/plotly/utils.py
+++ b/packages/python/plotly/plotly/utils.py
@@ -4,7 +4,7 @@
from pprint import PrettyPrinter
from _plotly_utils.utils import *
-
+from _plotly_utils.data_utils import *
# Pretty printing
def _list_repr_elided(v, threshold=200, edgeitems=3, indent=0, width=80):