Pillow/PIL/ImageEnhance.py

#
# The Python Imaging Library.
# $Id$
#
# image enhancement classes
#
# For a background, see "Image Processing By Interpolation and
# Extrapolation", Paul Haeberli and Douglas Voorhies.  Available
# at http://www.graficaobscura.com/interp/index.html
#
# History:
# 1996-03-23 fl  Created
# 2009-06-16 fl  Fixed mean calculation
#
# Copyright (c) Secret Labs AB 1997.
# Copyright (c) Fredrik Lundh 1996.
#
# See the README file for information on usage and redistribution.
#

from . import Image, ImageFilter, ImageStat


class _Enhance(object):

    def enhance(self, factor):
        """
        Returns an enhanced image.

        :param factor: A floating point value controlling the enhancement.
                       Factor 1.0 always returns a copy of the original image,
                       lower factors mean less color (brightness, contrast,
                       etc), and higher values more. There are no restrictions
                       on this value.
        :rtype: :py:class:`~PIL.Image.Image`
        """
        return Image.blend(self.degenerate, self.image, factor)


class Color(_Enhance):
    """Adjust image color balance.

    This class can be used to adjust the colour balance of an image, in
    a manner similar to the controls on a colour TV set. An enhancement
    factor of 0.0 gives a black and white image. A factor of 1.0 gives
    the original image.
    """
    def __init__(self, image):
        self.image = image
        self.intermediate_mode = 'L'
        if 'A' in image.getbands():
            self.intermediate_mode = 'LA'

        self.degenerate = image.convert(self.intermediate_mode).convert(image.mode)


class Contrast(_Enhance):
    """Adjust image contrast.

    This class can be used to control the contrast of an image, similar
    to the contrast control on a TV set. An enhancement factor of 0.0
    gives a solid grey image. A factor of 1.0 gives the original image.
    """
    def __init__(self, image):
        self.image = image
        mean = int(ImageStat.Stat(image.convert("L")).mean[0] + 0.5)
        self.degenerate = Image.new("L", image.size, mean).convert(image.mode)

        if 'A' in image.getbands():
            self.degenerate.putalpha(image.split()[-1])


class Brightness(_Enhance):
    """Adjust image brightness.

    This class can be used to control the brightness of an image.  An
    enhancement factor of 0.0 gives a black image. A factor of 1.0 gives the
    original image.
    """
    def __init__(self, image):
        self.image = image
        self.degenerate = Image.new(image.mode, image.size, 0)

        if 'A' in image.getbands():
            self.degenerate.putalpha(image.split()[-1])


class Sharpness(_Enhance):
    """Adjust image sharpness.

    This class can be used to adjust the sharpness of an image. An
    enhancement factor of 0.0 gives a blurred image, a factor of 1.0 gives the
    original image, and a factor of 2.0 gives a sharpened image.
    """
    def __init__(self, image):
        self.image = image
        self.degenerate = image.filter(ImageFilter.SMOOTH)

        if 'A' in image.getbands():
            self.degenerate.putalpha(image.split()[-1])