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, mask=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.

extrema

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.

count

Total number of pixels for each band in the image.

sum

Sum of all pixels for each band in the image.

sum2

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

mean

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

median

Median pixel level for each band in the image.

rms

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

var

Variance for each band in the image.

stddev

Standard deviation for each band in the image.