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.