# Copyright 2014, Sandia Corporation. Under the terms of Contract
# DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains certain
# rights in this software.
"""Bitmap management and manipulation.
"""
import base64
import io
import logging
import numpy
import png
import toyplot.color
log = logging.getLogger(__name__)
[docs]def to_png(data, stream, bitdepth=None):
"""Convert an in-memory bitmap to PNG format.
Parameters
----------
data: :class:`numpy.ndarray`, required
Source array containing bitmap data to be converted. Valid array shapes
are :math:`M \\times N \\times 1` (greyscale data), :math:`M \\times N \\times 2`
(greyscale plus alpha channel), :math:`M \\times N \\times 3`
(RGB data), or :math:`M \\times N \\times 4` (RGB + alpha). Floating
point values are scaled and converted to unsigned 8 bit integers.
stream: file-like object, required
Target file to receive PNG data.
bitdepth: integer, optional
Override the default output bit depth. Allowed color / bitdepth combinations
are: greyscale (1/2/4/8/16), greyscale + alpha (8/16), RGB (8/16), and RGB + alpha (8/16).
"""
if data.dtype == toyplot.color.dtype:
data = numpy.dstack((data["r"], data["g"], data["b"], data["a"]))
if issubclass(data.dtype.type, numpy.bool_):
if bitdepth is None:
bitdepth = 1
else:
if bitdepth is None:
bitdepth = 8
if issubclass(data.dtype.type, numpy.floating):
if bitdepth == 8:
data = (data * 255.0).astype("uint8")
elif bitdepth == 16:
data = (data * 65535.0).astype("uint16")
width = data.shape[1]
height = data.shape[0]
greyscale = data.shape[2] < 3
alpha = data.shape[2] == 2 or data.shape[2] == 4
writer = png.Writer(width=width, height=height, greyscale=greyscale, alpha=alpha, bitdepth=bitdepth)
writer.write(stream, numpy.reshape(data, (-1, data.shape[1] * data.shape[2])))
[docs]def to_png_data_uri(data):
"""Convert an in-memory bitmap to PNG format, encoded as a data: URI.
Parameters
----------
data: :class:`numpy.ndarray`, required
Source array containing bitmap data to be converted. Valid array shapes
are :math:`M \\times N \\times 1` (greyscale data), :math:`M \\times N \\times 2`
(greyscale plus alpha channel), :math:`M \\times N \\times 3`
(RGB data), or :math:`M \\times N \\times 4` (RGB + alpha). Floating
point values are scaled and converted to unsigned 8 bit integers.
Returns
-------
uri: str
A data: URI containing the base64 encoded bitmap.
"""
stream = io.BytesIO()
to_png(data, stream)
return "data:image/png;base64," + base64.standard_b64encode(stream.getvalue()).decode("ascii")