Function from_array

_plotly_utils/png.py:1077–1249

Create a PNG :class:`Image` object from a 2-dimensional array. One application of this function is easy PIL-style saving: ``png.from_array(pixels, 'L').save('foo.png')``. Unless they are specified using the *info* parameter, the PNG's height and width are taken from the array s

(a, mode=None, info={})

def from_array(a, mode=None, info={}):
    """
    Create a PNG :class:`Image` object from a 2-dimensional array.
    One application of this function is easy PIL-style saving:
    ``png.from_array(pixels, 'L').save('foo.png')``.

    Unless they are specified using the *info* parameter,
    the PNG's height and width are taken from the array size.
    The first axis is the height; the second axis is the
    ravelled width and channel index.
    The array is treated is a sequence of rows,
    each row being a sequence of values (``width*channels`` in number).
    So an RGB image that is 16 pixels high and 8 wide will
    occupy a 2-dimensional array that is 16x24
    (each row will be 8*3 = 24 sample values).

    *mode* is a string that specifies the image colour format in a
    PIL-style mode.  It can be:

    ``'L'``
      greyscale (1 channel)
    ``'LA'``
      greyscale with alpha (2 channel)
    ``'RGB'``
      colour image (3 channel)
    ``'RGBA'``
      colour image with alpha (4 channel)

    The mode string can also specify the bit depth
    (overriding how this function normally derives the bit depth,
    see below).
    Appending ``';16'`` to the mode will cause the PNG to be
    16 bits per channel;
    any decimal from 1 to 16 can be used to specify the bit depth.

    When a 2-dimensional array is used *mode* determines how many
    channels the image has, and so allows the width to be derived from
    the second array dimension.

    The array is expected to be a ``numpy`` array,
    but it can be any suitable Python sequence.
    For example, a list of lists can be used:
    ``png.from_array([[0, 255, 0], [255, 0, 255]], 'L')``.
    The exact rules are: ``len(a)`` gives the first dimension, height;
    ``len(a[0])`` gives the second dimension.
    It's slightly more complicated than that because
    an iterator of rows can be used, and it all still works.
    Using an iterator allows data to be streamed efficiently.

    The bit depth of the PNG is normally taken from
    the array element's datatype
    (but if *mode* specifies a bitdepth then that is used instead).
    The array element's datatype is determined in a way which
    is supposed to work both for ``numpy`` arrays and for Python
    ``array.array`` objects.
    A 1 byte datatype will give a bit depth of 8,
    a 2 byte datatype will give a bit depth of 16.
    If the datatype does not have an implicit size,