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74 lines
2.3 KiB
ReStructuredText
74 lines
2.3 KiB
ReStructuredText
.. py:module:: PIL.ImageStat
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.. py:currentmodule:: PIL.ImageStat
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:py:mod:`~PIL.ImageStat` Module
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===============================
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The :py:mod:`~PIL.ImageStat` module calculates global statistics for an image, or
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for a region of an image.
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.. py:class:: Stat(image_or_list, mask=None)
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Calculate statistics for the given image. If a mask is included,
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only the regions covered by that mask are included in the
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statistics. You can also pass in a previously calculated histogram.
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:param image: A PIL image, or a precalculated histogram.
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.. note::
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For a PIL image, calculations rely on the
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:py:meth:`~PIL.Image.Image.histogram` method. The pixel counts are
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grouped into 256 bins, even if the image has more than 8 bits per
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channel. So ``I`` and ``F`` mode images have a maximum ``mean``,
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``median`` and ``rms`` of 255, and cannot have an ``extrema`` maximum
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of more than 255.
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:param mask: An optional mask.
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.. py:attribute:: extrema
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Min/max values for each band in the image.
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.. note::
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This relies on the :py:meth:`~PIL.Image.Image.histogram` method, and
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simply returns the low and high bins used. This is correct for
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images with 8 bits per channel, but fails for other modes such as
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``I`` or ``F``. Instead, use :py:meth:`~PIL.Image.Image.getextrema` to
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return per-band extrema for the image. This is more correct and
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efficient because, for non-8-bit modes, the histogram method uses
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:py:meth:`~PIL.Image.Image.getextrema` to determine the bins used.
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.. py:attribute:: count
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Total number of pixels for each band in the image.
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.. py:attribute:: sum
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Sum of all pixels for each band in the image.
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.. py:attribute:: sum2
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Squared sum of all pixels for each band in the image.
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.. py:attribute:: mean
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Average (arithmetic mean) pixel level for each band in the image.
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.. py:attribute:: median
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Median pixel level for each band in the image.
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.. py:attribute:: rms
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RMS (root-mean-square) for each band in the image.
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.. py:attribute:: var
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Variance for each band in the image.
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.. py:attribute:: stddev
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Standard deviation for each band in the image.
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