[Matplotlib-users] PowerNorm runtime warning

[Андрей Парамонов]

Hello!

When running

import matplotlib.colors as colors
cmap = colors.PowerNorm(vmin = -1, vmax = 1, gamma = 3)
print(cmap(-1))
print(cmap(+0))
print(cmap(+1))

I expectedly get

0.0
0.125
1.0

However PowerNorm.autoscale* have

if self.vmin < 0:
    self.vmin = 0
    warnings.warn("Power-law scaling on negative values is ill-defined,
clamping to 0.")

Why is it so? PowerNorm does work correctly for negative vmin!

Best wishes,
Andrey Paramonov
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