Source code for napari.utils.notebook_display
import base64
import html
from io import BytesIO
from warnings import warn
try:
from lxml.etree import ParserError
from lxml.html import document_fromstring
from lxml.html.clean import Cleaner
lxml_unavailable = False
except ImportError:
lxml_unavailable = True
from napari.utils.io import imsave_png
__all__ = ['NotebookScreenshot', 'nbscreenshot']
[docs]
class NotebookScreenshot:
"""Display napari screenshot in the jupyter notebook.
Functions returning an object with a _repr_png_() method
will displayed as a rich image in the jupyter notebook.
https://ipython.readthedocs.io/en/stable/api/generated/IPython.display.html
Parameters
----------
viewer : napari.Viewer
The napari viewer.
canvas_only : bool, optional
If True includes the napari viewer frame in the screenshot,
otherwise just includes the canvas. By default, True.
Examples
--------
>>> import napari
>>> from napari.utils import nbscreenshot
>>> from skimage.data import chelsea
>>> viewer = napari.view_image(chelsea(), name='chelsea-the-cat')
>>> nbscreenshot(viewer)
# screenshot just the canvas with the napari viewer framing it
>>> nbscreenshot(viewer, canvas_only=False)
"""
def __init__(
self,
viewer,
*,
canvas_only=False,
alt_text=None,
) -> None:
"""Initialize screenshot object.
Parameters
----------
viewer : napari.Viewer
The napari viewer
canvas_only : bool, optional
If False include the napari viewer frame in the screenshot,
and if True then take screenshot of just the image display canvas.
By default, False.
alt_text : str, optional
Image description alternative text, for screenreader accessibility.
Good alt-text describes the image and any text within the image
in no more than three short, complete sentences.
"""
self.viewer = viewer
self.canvas_only = canvas_only
self.image = None
self.alt_text = self._clean_alt_text(alt_text)
def _clean_alt_text(self, alt_text):
"""Clean user input to prevent script injection."""
if alt_text is not None:
if lxml_unavailable:
warn(
'The lxml_html_clean library is not installed, and is '
'required to sanitize alt text for napari screenshots. '
'Alt Text will be stripped altogether.'
)
return None
# cleaner won't recognize escaped script tags, so always unescape
# to be safe
alt_text = html.unescape(str(alt_text))
cleaner = Cleaner()
try:
doc = document_fromstring(alt_text)
alt_text = cleaner.clean_html(doc).text_content()
except ParserError:
warn(
'The provided alt text does not constitute valid html, so it was discarded.',
stacklevel=3,
)
alt_text = ''
if alt_text == '':
alt_text = None
return alt_text
def _repr_png_(self):
"""PNG representation of the viewer object for IPython.
Returns
-------
In memory binary stream containing PNG screenshot image.
"""
from napari._qt.qt_event_loop import get_qapp
get_qapp().processEvents()
self.image = self.viewer.screenshot(
canvas_only=self.canvas_only, flash=False
)
with BytesIO() as file_obj:
imsave_png(file_obj, self.image)
file_obj.seek(0)
png = file_obj.read()
return png
def _repr_html_(self):
png = self._repr_png_()
url = 'data:image/png;base64,' + base64.b64encode(png).decode('utf-8')
_alt = html.escape(self.alt_text) if self.alt_text is not None else ''
return f'<img src="{url}" alt="{_alt}"></img>'
nbscreenshot = NotebookScreenshot
