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.. _PNG-PIL:

PNG-PIL Portable network graphics
=================================

Extensions: ``.png``

A PNG format based on Pillow.

This format supports grayscale, RGB and RGBA images.

Parameters for reading
----------------------
ignoregamma : bool
    Avoid gamma correction. Default True.
pilmode : str
    From the Pillow documentation:

    * 'L' (8-bit pixels, grayscale)
    * 'P' (8-bit pixels, mapped to any other mode using a color palette)
    * 'RGB' (3x8-bit pixels, true color)
    * 'RGBA' (4x8-bit pixels, true color with transparency mask)
    * 'CMYK' (4x8-bit pixels, color separation)
    * 'YCbCr' (3x8-bit pixels, color video format)
    * 'I' (32-bit signed integer pixels)
    * 'F' (32-bit floating point pixels)

    PIL also provides limited support for a few special modes, including
    'LA' ('L' with alpha), 'RGBX' (true color with padding) and 'RGBa'
    (true color with premultiplied alpha).

    When translating a color image to grayscale (mode 'L', 'I' or 'F'),
    the library uses the ITU-R 601-2 luma transform::

        L = R * 299/1000 + G * 587/1000 + B * 114/1000
as_gray : bool
    If True, the image is converted using mode 'F'. When `mode` is
    not None and `as_gray` is True, the image is first converted
    according to `mode`, and the result is then "flattened" using
    mode 'F'.

Parameters for saving
---------------------
optimize : bool
    If present and true, instructs the PNG writer to make the output file
    as small as possible. This includes extra processing in order to find
    optimal encoder settings.
transparency:
    This option controls what color image to mark as transparent.
dpi: tuple of two scalars
    The desired dpi in each direction.
pnginfo: PIL.PngImagePlugin.PngInfo
    Object containing text tags.
compress_level: int
    ZLIB compression level, a number between 0 and 9: 1 gives best speed,
    9 gives best compression, 0 gives no compression at all. Default is 9.
    When ``optimize`` option is True ``compress_level`` has no effect
    (it is set to 9 regardless of a value passed).
compression: int
    Compatibility with the freeimage PNG format. If given, it overrides
    compress_level.
icc_profile:
    The ICC Profile to include in the saved file.
bits (experimental): int
    This option controls how many bits to store. If omitted,
    the PNG writer uses 8 bits (256 colors).
quantize:
    Compatibility with the freeimage PNG format. If given, it overrides
    bits. In this case, given as a number between 1-256.
dictionary (experimental): dict
    Set the ZLIB encoder dictionary.


