pyplot 在哪里定义级别数

Question

我试图了解如何在轮廓工具链中创建级别、值、边界。

import matplotlib.pyplot as plt
import matplotlib as mpl

t=np.array([[-5,0,5,0,0,0],[0,0,5,0,0,0],[0,0,5,0,0,0],[5,5.2,10,5,5,0],
            [0,0,5,0,0,0]], dtype=np.double)
print ("print as is")
print (t)
print ("appearing in a contourf as:")
print (np.flipud((t)))
# assuming indices: array[x,y]
# value 10 supposed to be at 0,0
# contourf's pos. x-axis is pointing up!! 
xmin, xmax=-2, 3
ymin, ymax=-3, 1

fig, axs = plt.subplots(nrows=1, ncols=2)
ax0 = axs[0]
ax1 = axs[1]

# plot and add colorbar
set0 = ax0.contourf(t, extent=(xmin,xmax,ymin,ymax), cmap="brg")

#colorbar with coarse steps
cba = plt.colorbar(set0,ax=ax0)
# # This makes the colorbar "appear continuos"
# cba.boundaries=None
# cba.values = None
set0.changed()

# define colorbar and then plot
cNorm = mpl.colors.Normalize(vmin=np.min(t), vmax=np.max(t))
sm = mpl.cm.ScalarMappable(cNorm, cmap="brg")
cbb = plt.colorbar(sm,ax=ax1)

set1 = ax1.contourf(t, extent=(ymin,ymax,xmin,xmax), cmap="brg")

plt.show()
print("left .boundaries: {:s}".format(str(cba.boundaries)))
print("left ._boundaries: {:s}".format(str(cba._boundaries)))
print("right .boundaries: {:s}".format(str(cbb.boundaries)))
print("right len(._boundaries): {:s}".format(str(len(cbb._boundaries))))

对于左图，颜色条有 9 个边界和 8 个离散颜色值，右图有 257 个边界。 我对各种对象做了一些 vars(...) 和 dir(...) 。边界和价值的数量是在哪里做出的决定？ 右图颜色条创建与默认行为的偏差是什么？