#
# 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 __future__ import annotations
from . import Image, ImageFilter, ImageStat
# Modes whose enhance() can be a lookup table on each band.
_LUT_MODES = ("L", "LA", "RGB", "RGBA")
[docs]
class _Enhance:
image: Image.Image
degenerate: Image.Image
[docs]
def enhance(self, factor: float) -> Image.Image:
"""
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.
"""
levels = self._levels()
if levels is not None and self.image.mode in _LUT_MODES:
return self.image.point(self._lut(levels, factor))
return Image.blend(self.degenerate, self.image, factor)
def _levels(self) -> tuple[int, ...] | None:
"""The degenerate image's value in each band if it is constant there,
alpha excepted, which is the image's own; otherwise None."""
return None
def _lut(self, levels: tuple[int, ...], factor: float) -> list[int]:
# Image.blend of a 0..255 gradient against the levels: each pixel of
# the image gets the bytes that blending it would give.
bands = self.image.getbands()
gradient = Image.frombytes("L", (256, 1), bytes(range(256)))
ramp = Image.merge(self.image.mode, [gradient] * len(bands))
flat = [
gradient if b == "A" else Image.new("L", (256, 1), level)
for b, level in zip(bands, levels)
]
out = Image.blend(Image.merge(self.image.mode, flat), ramp, factor)
return [v for b in range(len(bands)) for v in out.getchannel(b).tobytes()]
[docs]
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: Image.Image) -> None:
self.image = image
self.intermediate_mode = "L"
if "A" in image.getbands():
self.intermediate_mode = "LA"
if self.intermediate_mode != image.mode:
image = image.convert(self.intermediate_mode).convert(image.mode)
self.degenerate = image
[docs]
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 gray image. A factor of 1.0 gives the original image.
"""
def __init__(self, image: Image.Image) -> None:
self.image = image
if image.mode != "L":
image = image.convert("L")
self._mean = int(ImageStat.Stat(image).mean[0] + 0.5)
self._degenerate: Image.Image | None = None
self._custom = False
@property
def degenerate(self) -> Image.Image:
# Made when first needed: enhance() mostly uses a lookup table.
if self._degenerate is None:
self._degenerate = Image.new("L", self.image.size, self._mean)
if self._degenerate.mode != self.image.mode:
self._degenerate = self._degenerate.convert(self.image.mode)
if "A" in self.image.getbands():
self._degenerate.putalpha(self.image.getchannel("A"))
return self._degenerate
@degenerate.setter
def degenerate(self, value: Image.Image) -> None:
self._degenerate, self._custom = value, True
def _levels(self) -> tuple[int, ...] | None:
if self._custom:
return None
# The mean converted to the image's mode, as the degenerate image is.
level = Image.new("L", (1, 1), self._mean).convert(self.image.mode)
value = level.getpixel((0, 0))
return value if isinstance(value, tuple) else (int(value or 0),)
[docs]
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: Image.Image) -> None:
self.image = image
self._degenerate: Image.Image | None = None
self._custom = False
@property
def degenerate(self) -> Image.Image:
# Made when first needed: enhance() mostly uses a lookup table.
if self._degenerate is None:
self._degenerate = Image.new(self.image.mode, self.image.size, 0)
if "A" in self.image.getbands():
self._degenerate.putalpha(self.image.getchannel("A"))
return self._degenerate
@degenerate.setter
def degenerate(self, value: Image.Image) -> None:
self._degenerate, self._custom = value, True
def _levels(self) -> tuple[int, ...] | None:
return None if self._custom else (0,) * len(self.image.getbands())
[docs]
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: Image.Image) -> None:
self.image = image
self.degenerate = image.filter(ImageFilter.SMOOTH)
if "A" in image.getbands():
self.degenerate.putalpha(image.getchannel("A"))