Add comment to prix
+# prix.py
+
+"""
+prix (Python Raster Image eXtensions)
+
+A collection of routines useful for raster image processing,
+mostly not associate with the PNG format, but
+using datatypes from PyPNG.
+"""
def window(rows, info, tl, br):
"""*rows* and *info* are the rows and info object for
