ImageStat Module

The ImageStat module calculates global statistics for an image, or for a region of an image.

class PIL.ImageStat.Stat(image_or_list: Image | list[int], mask: Image | None = None)[source]
__init__(image_or_list: Image | list[int], mask: Image | None = None) → None[source]

Calculate statistics for the given image. If a mask is included, only the regions covered by that mask are included in the statistics. You can also pass in a previously calculated histogram.

Parameters:

  • image –

    A PIL image, or a precalculated histogram.

    Note

    For a PIL image, calculations rely on the histogram() method. The pixel counts are grouped into 256 bins, even if the image has more than 8 bits per channel. So I and F mode images have a maximum mean, median and rms of 255, and cannot have an extrema maximum of more than 255.

  • mask – An optional mask.

property count: list[int]

Total number of pixels for each band in the image.

property extrema: list[tuple[int, int]]

Min/max values for each band in the image.

Note

This relies on the histogram() method, and simply returns the low and high bins used. This is correct for images with 8 bits per channel, but fails for other modes such as I or F. Instead, use getextrema() to return per-band extrema for the image. This is more correct and efficient because, for non-8-bit modes, the histogram method uses getextrema() to determine the bins used.

property mean: list[float]

Average (arithmetic mean) pixel level for each band in the image.

property median: list[int]

Median pixel level for each band in the image.

property rms: list[float]

RMS (root-mean-square) for each band in the image.

property stddev: list[float]

Standard deviation for each band in the image.

property sum: list[float]

Sum of all pixels for each band in the image.

property sum2: list[float]

Squared sum of all pixels for each band in the image.

property var: list[float]

Variance for each band in the image.