Every time I have to work with rows and columns I always mix this up - it must be because of the “across the hall and up the stairs” phrase I remember from school geography lessons.

When dealing with arrays and looking at their shape, python will always report the rows first and then the columns. You can think of this however you like (i,j) or (x,y) or (rows,cols). Whatever your preference, j, y or rows come first followed by i or x or cols.

In [113]: image_array.shape
Out[113]: (11000, 6000)

# Image is 11000 rows by 6000 columns

Python goes down the stairs and across the hall - perhaps this is the result of the serpentine link to snakes and ladders - the snake wants you to slip back down to the beginning as opposed to going across and up a ladder… alas, I digress.