463 lines
14 KiB
Python
463 lines
14 KiB
Python
#
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# The Python Imaging Library.
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# $Id$
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#
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# standard image operations
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#
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# History:
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# 2001-10-20 fl Created
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# 2001-10-23 fl Added autocontrast operator
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# 2001-12-18 fl Added Kevin's fit operator
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# 2004-03-14 fl Fixed potential division by zero in equalize
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# 2005-05-05 fl Fixed equalize for low number of values
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#
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# Copyright (c) 2001-2004 by Secret Labs AB
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# Copyright (c) 2001-2004 by Fredrik Lundh
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#
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# See the README file for information on usage and redistribution.
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#
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from PIL import Image
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from PIL._util import isStringType
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import operator
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from functools import reduce
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#
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# helpers
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def _border(border):
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if isinstance(border, tuple):
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if len(border) == 2:
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left, top = right, bottom = border
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elif len(border) == 4:
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left, top, right, bottom = border
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else:
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left = top = right = bottom = border
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return left, top, right, bottom
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def _color(color, mode):
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if isStringType(color):
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from PIL import ImageColor
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color = ImageColor.getcolor(color, mode)
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return color
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def _lut(image, lut):
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if image.mode == "P":
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# FIXME: apply to lookup table, not image data
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raise NotImplementedError("mode P support coming soon")
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elif image.mode in ("L", "RGB"):
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if image.mode == "RGB" and len(lut) == 256:
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lut = lut + lut + lut
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return image.point(lut)
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else:
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raise IOError("not supported for this image mode")
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#
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# actions
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def autocontrast(image, cutoff=0, ignore=None):
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"""
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Maximize (normalize) image contrast. This function calculates a
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histogram of the input image, removes **cutoff** percent of the
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lightest and darkest pixels from the histogram, and remaps the image
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so that the darkest pixel becomes black (0), and the lightest
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becomes white (255).
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:param image: The image to process.
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:param cutoff: How many percent to cut off from the histogram.
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:param ignore: The background pixel value (use None for no background).
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:return: An image.
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"""
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histogram = image.histogram()
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lut = []
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for layer in range(0, len(histogram), 256):
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h = histogram[layer:layer+256]
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if ignore is not None:
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# get rid of outliers
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try:
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h[ignore] = 0
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except TypeError:
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# assume sequence
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for ix in ignore:
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h[ix] = 0
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if cutoff:
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# cut off pixels from both ends of the histogram
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# get number of pixels
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n = 0
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for ix in range(256):
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n = n + h[ix]
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# remove cutoff% pixels from the low end
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cut = n * cutoff // 100
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for lo in range(256):
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if cut > h[lo]:
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cut = cut - h[lo]
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h[lo] = 0
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else:
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h[lo] -= cut
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cut = 0
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if cut <= 0:
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break
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# remove cutoff% samples from the hi end
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cut = n * cutoff // 100
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for hi in range(255, -1, -1):
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if cut > h[hi]:
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cut = cut - h[hi]
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h[hi] = 0
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else:
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h[hi] -= cut
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cut = 0
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if cut <= 0:
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break
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# find lowest/highest samples after preprocessing
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for lo in range(256):
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if h[lo]:
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break
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for hi in range(255, -1, -1):
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if h[hi]:
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break
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if hi <= lo:
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# don't bother
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lut.extend(list(range(256)))
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else:
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scale = 255.0 / (hi - lo)
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offset = -lo * scale
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for ix in range(256):
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ix = int(ix * scale + offset)
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if ix < 0:
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ix = 0
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elif ix > 255:
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ix = 255
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lut.append(ix)
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return _lut(image, lut)
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def colorize(image, black, white):
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"""
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Colorize grayscale image. The **black** and **white**
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arguments should be RGB tuples; this function calculates a color
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wedge mapping all black pixels in the source image to the first
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color, and all white pixels to the second color.
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:param image: The image to colorize.
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:param black: The color to use for black input pixels.
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:param white: The color to use for white input pixels.
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:return: An image.
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"""
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assert image.mode == "L"
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black = _color(black, "RGB")
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white = _color(white, "RGB")
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red = []
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green = []
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blue = []
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for i in range(256):
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red.append(black[0]+i*(white[0]-black[0])//255)
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green.append(black[1]+i*(white[1]-black[1])//255)
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blue.append(black[2]+i*(white[2]-black[2])//255)
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image = image.convert("RGB")
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return _lut(image, red + green + blue)
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def crop(image, border=0):
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"""
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Remove border from image. The same amount of pixels are removed
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from all four sides. This function works on all image modes.
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.. seealso:: :py:meth:`~PIL.Image.Image.crop`
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:param image: The image to crop.
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:param border: The number of pixels to remove.
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:return: An image.
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"""
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left, top, right, bottom = _border(border)
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return image.crop(
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(left, top, image.size[0]-right, image.size[1]-bottom)
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)
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def deform(image, deformer, resample=Image.BILINEAR):
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"""
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Deform the image.
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:param image: The image to deform.
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:param deformer: A deformer object. Any object that implements a
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**getmesh** method can be used.
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:param resample: What resampling filter to use.
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:return: An image.
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"""
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return image.transform(
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image.size, Image.MESH, deformer.getmesh(image), resample
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)
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def equalize(image, mask=None):
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"""
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Equalize the image histogram. This function applies a non-linear
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mapping to the input image, in order to create a uniform
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distribution of grayscale values in the output image.
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:param image: The image to equalize.
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:param mask: An optional mask. If given, only the pixels selected by
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the mask are included in the analysis.
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:return: An image.
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"""
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if image.mode == "P":
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image = image.convert("RGB")
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h = image.histogram(mask)
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lut = []
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for b in range(0, len(h), 256):
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histo = [_f for _f in h[b:b+256] if _f]
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if len(histo) <= 1:
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lut.extend(list(range(256)))
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else:
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step = (reduce(operator.add, histo) - histo[-1]) // 255
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if not step:
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lut.extend(list(range(256)))
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else:
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n = step // 2
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for i in range(256):
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lut.append(n // step)
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n = n + h[i+b]
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return _lut(image, lut)
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def expand(image, border=0, fill=0):
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"""
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Add border to the image
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:param image: The image to expand.
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:param border: Border width, in pixels.
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:param fill: Pixel fill value (a color value). Default is 0 (black).
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:return: An image.
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"""
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"Add border to image"
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left, top, right, bottom = _border(border)
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width = left + image.size[0] + right
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height = top + image.size[1] + bottom
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out = Image.new(image.mode, (width, height), _color(fill, image.mode))
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out.paste(image, (left, top))
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return out
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def fit(image, size, method=Image.NEAREST, bleed=0.0, centering=(0.5, 0.5)):
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"""
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Returns a sized and cropped version of the image, cropped to the
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requested aspect ratio and size.
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This function was contributed by Kevin Cazabon.
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:param size: The requested output size in pixels, given as a
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(width, height) tuple.
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:param method: What resampling method to use. Default is
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:py:attr:`PIL.Image.NEAREST`.
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:param bleed: Remove a border around the outside of the image (from all
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four edges. The value is a decimal percentage (use 0.01 for
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one percent). The default value is 0 (no border).
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:param centering: Control the cropping position. Use (0.5, 0.5) for
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center cropping (e.g. if cropping the width, take 50% off
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of the left side, and therefore 50% off the right side).
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(0.0, 0.0) will crop from the top left corner (i.e. if
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cropping the width, take all of the crop off of the right
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side, and if cropping the height, take all of it off the
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bottom). (1.0, 0.0) will crop from the bottom left
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corner, etc. (i.e. if cropping the width, take all of the
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crop off the left side, and if cropping the height take
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none from the top, and therefore all off the bottom).
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:return: An image.
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"""
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# by Kevin Cazabon, Feb 17/2000
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# kevin@cazabon.com
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# http://www.cazabon.com
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# ensure inputs are valid
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if not isinstance(centering, list):
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centering = [centering[0], centering[1]]
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if centering[0] > 1.0 or centering[0] < 0.0:
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centering[0] = 0.50
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if centering[1] > 1.0 or centering[1] < 0.0:
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centering[1] = 0.50
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if bleed > 0.49999 or bleed < 0.0:
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bleed = 0.0
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# calculate the area to use for resizing and cropping, subtracting
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# the 'bleed' around the edges
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# number of pixels to trim off on Top and Bottom, Left and Right
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bleedPixels = (
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int((float(bleed) * float(image.size[0])) + 0.5),
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int((float(bleed) * float(image.size[1])) + 0.5)
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)
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liveArea = (0, 0, image.size[0], image.size[1])
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if bleed > 0.0:
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liveArea = (
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bleedPixels[0], bleedPixels[1], image.size[0] - bleedPixels[0] - 1,
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image.size[1] - bleedPixels[1] - 1
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)
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liveSize = (liveArea[2] - liveArea[0], liveArea[3] - liveArea[1])
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# calculate the aspect ratio of the liveArea
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liveAreaAspectRatio = float(liveSize[0])/float(liveSize[1])
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# calculate the aspect ratio of the output image
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aspectRatio = float(size[0]) / float(size[1])
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# figure out if the sides or top/bottom will be cropped off
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if liveAreaAspectRatio >= aspectRatio:
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# liveArea is wider than what's needed, crop the sides
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cropWidth = int((aspectRatio * float(liveSize[1])) + 0.5)
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cropHeight = liveSize[1]
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else:
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# liveArea is taller than what's needed, crop the top and bottom
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cropWidth = liveSize[0]
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cropHeight = int((float(liveSize[0])/aspectRatio) + 0.5)
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# make the crop
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leftSide = int(liveArea[0] + (float(liveSize[0]-cropWidth) * centering[0]))
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if leftSide < 0:
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leftSide = 0
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topSide = int(liveArea[1] + (float(liveSize[1]-cropHeight) * centering[1]))
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if topSide < 0:
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topSide = 0
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out = image.crop(
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(leftSide, topSide, leftSide + cropWidth, topSide + cropHeight)
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)
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# resize the image and return it
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return out.resize(size, method)
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def flip(image):
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"""
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Flip the image vertically (top to bottom).
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:param image: The image to flip.
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:return: An image.
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"""
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return image.transpose(Image.FLIP_TOP_BOTTOM)
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def grayscale(image):
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"""
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Convert the image to grayscale.
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:param image: The image to convert.
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:return: An image.
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"""
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return image.convert("L")
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def invert(image):
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"""
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Invert (negate) the image.
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:param image: The image to invert.
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:return: An image.
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"""
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lut = []
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for i in range(256):
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lut.append(255-i)
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return _lut(image, lut)
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def mirror(image):
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"""
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Flip image horizontally (left to right).
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:param image: The image to mirror.
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:return: An image.
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"""
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return image.transpose(Image.FLIP_LEFT_RIGHT)
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def posterize(image, bits):
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"""
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Reduce the number of bits for each color channel.
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:param image: The image to posterize.
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:param bits: The number of bits to keep for each channel (1-8).
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:return: An image.
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"""
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lut = []
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mask = ~(2**(8-bits)-1)
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for i in range(256):
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lut.append(i & mask)
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return _lut(image, lut)
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def solarize(image, threshold=128):
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"""
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Invert all pixel values above a threshold.
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:param image: The image to solarize.
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:param threshold: All pixels above this greyscale level are inverted.
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:return: An image.
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"""
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lut = []
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for i in range(256):
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if i < threshold:
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lut.append(i)
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else:
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lut.append(255-i)
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return _lut(image, lut)
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# --------------------------------------------------------------------
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# PIL USM components, from Kevin Cazabon.
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def gaussian_blur(im, radius=None):
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""" PIL_usm.gblur(im, [radius])"""
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if radius is None:
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radius = 5.0
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im.load()
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return im.im.gaussian_blur(radius)
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gblur = gaussian_blur
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def unsharp_mask(im, radius=None, percent=None, threshold=None):
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""" PIL_usm.usm(im, [radius, percent, threshold])"""
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if radius is None:
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radius = 5.0
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if percent is None:
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percent = 150
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if threshold is None:
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threshold = 3
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im.load()
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return im.im.unsharp_mask(radius, percent, threshold)
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usm = unsharp_mask
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def box_blur(image, radius):
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"""
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Blur the image by setting each pixel to the average value of the pixels
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in a square box extending radius pixels in each direction.
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Supports float radius of arbitrary size. Uses an optimized implementation
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which runs in linear time relative to the size of the image
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for any radius value.
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:param image: The image to blur.
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:param radius: Size of the box in one direction. Radius 0 does not blur,
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returns an identical image. Radius 1 takes 1 pixel
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in each direction, i.e. 9 pixels in total.
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:return: An image.
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"""
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image.load()
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return image._new(image.im.box_blur(radius))
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