坐标默认是从上到下，从左到右，例如 ：
matplotlib
.pyplot
.imshow(X, cmap
=None, norm
=None, aspect
=None, interpolation
=None, alpha
=None,
vmin
=None, vmax
=None, origin
=None, extent
=None, shape
=None,
filternorm
=1, filterrad
=4.0, imlim
=None, resample
=None,
url
=None, hold
=None,
data=None,
**kwargs
他的参数很多，找了很久，才发现，应该是设置origin参数。
origin : [‘
upper’ | ‘
lower’], optional, default: None
Place
the [
0,
0] index
of the array
in the upper left
or lower left corner
of the axes.
If None, default
to rc image.origin.
设origin=‘lower’，就得到如下图：
