matplotlib · Sreekanth-M8 · Jan 4, 2026
diff --git a/lib/matplotlib/colors.py b/lib/matplotlib/colors.py
@@ -2805,7 +2805,8 @@ def halfrange(self, halfrange):
             self.vmax = self.vcenter + abs(halfrange)
 
 
-def make_norm_from_scale(scale_cls, base_norm_cls=None, *, init=None):
+def make_norm_from_scale(scale_cls, base_norm_cls=None, *, init=None,
+                         norm_before_trf=False):
     """
     Decorator for building a `.Normalize` subclass from a `~.scale.ScaleBase`
     subclass.
@@ -2837,7 +2838,8 @@ class norm_cls(Normalize):
     """
 
     if base_norm_cls is None:
-        return functools.partial(make_norm_from_scale, scale_cls, init=init)
+        return functools.partial(make_norm_from_scale, scale_cls, init=init,
+                                 norm_before_trf=norm_before_trf)
 
     if isinstance(scale_cls, functools.partial):
         scale_args = scale_cls.args
@@ -2851,13 +2853,13 @@ def init(vmin=None, vmax=None, clip=False): pass
 
     return _make_norm_from_scale(
         scale_cls, scale_args, scale_kwargs_items,
-        base_norm_cls, inspect.signature(init))
+        base_norm_cls, inspect.signature(init), norm_before_trf)
 
 
 @functools.cache
 def _make_norm_from_scale(
     scale_cls, scale_args, scale_kwargs_items,
-    base_norm_cls, bound_init_signature,
+    base_norm_cls, bound_init_signature, norm_before_trf
 ):
     """
     Helper for `make_norm_from_scale`.
@@ -2889,7 +2891,7 @@ def __reduce__(self):
                 pass
             return (_picklable_norm_constructor,
                     (scale_cls, scale_args, scale_kwargs_items,
-                     base_norm_cls, bound_init_signature),
+                     base_norm_cls, bound_init_signature, norm_before_trf),
                     vars(self))
 
         def __init__(self, *args, **kwargs):
@@ -2918,6 +2920,14 @@ def __call__(self, value, clip=None):
                 clip = self.clip
             if clip:
                 value = np.clip(value, self.vmin, self.vmax)
+
+            if norm_before_trf:
+                value -= self.vmin
+                value /= (self.vmax - self.vmin)
+                t_value = self._trf.transform(value).reshape(np.shape(value))
+                t_value = np.ma.masked_invalid(t_value, copy=False)
+                return t_value[0] if is_scalar else t_value
+
             t_value = self._trf.transform(value).reshape(np.shape(value))
             t_vmin, t_vmax = self._trf.transform([self.vmin, self.vmax])
             if not np.isfinite([t_vmin, t_vmax]).all():
@@ -2932,10 +2942,17 @@ def inverse(self, value):
                 raise ValueError("Not invertible until scaled")
             if self.vmin > self.vmax:
                 raise ValueError("vmin must be less or equal to vmax")
+            value, is_scalar = self.process_value(value)
+
+            if norm_before_trf:
+                value = self._trf.inverted().transform(value).reshape(np.shape(value))
+                rescaled = value * (self.vmax - self.vmin)
+                rescaled += self.vmin
+                return rescaled[0] if is_scalar else rescaled
+
             t_vmin, t_vmax = self._trf.transform([self.vmin, self.vmax])
             if not np.isfinite([t_vmin, t_vmax]).all():
                 raise ValueError("Invalid vmin or vmax")
-            value, is_scalar = self.process_value(value)
             rescaled = value * (t_vmax - t_vmin)
             rescaled += t_vmin
             value = (self._trf
@@ -3084,6 +3101,10 @@ def linear_width(self, value):
         self._scale.linear_width = value
 
 
+@make_norm_from_scale(
+    scale.PowerScale,
+    init=lambda gamma, vmin=None, vmax=None, clip=False: None,
+    norm_before_trf=True)
 class PowerNorm(Normalize):
     r"""
     Linearly map a given value to the 0-1 range and then apply
@@ -3120,56 +3141,13 @@ class PowerNorm(Normalize):
 
     For input values below *vmin*, gamma is set to one.
     """
-    def __init__(self, gamma, vmin=None, vmax=None, clip=False):
-        super().__init__(vmin, vmax, clip)
-        self.gamma = gamma
-
-    def __call__(self, value, clip=None):
-        if clip is None:
-            clip = self.clip
-
-        result, is_scalar = self.process_value(value)
-
-        self.autoscale_None(result)
-        gamma = self.gamma
-        vmin, vmax = self.vmin, self.vmax
-        if vmin > vmax:
-            raise ValueError("minvalue must be less than or equal to maxvalue")
-        elif vmin == vmax:
-            result.fill(0)
-        else:
-            if clip:
-                mask = np.ma.getmask(result)
-                result = np.ma.array(np.clip(result.filled(vmax), vmin, vmax),
-                                     mask=mask)
-            resdat = result.data
-            resdat -= vmin
-            resdat /= (vmax - vmin)
-            resdat[resdat > 0] = np.power(resdat[resdat > 0], gamma)
-
-            result = np.ma.array(resdat, mask=result.mask, copy=False)
-        if is_scalar:
-            result = result[0]
-        return result
-
-    def inverse(self, value):
-        if not self.scaled():
-            raise ValueError("Not invertible until scaled")
-
-        result, is_scalar = self.process_value(value)
-
-        gamma = self.gamma
-        vmin, vmax = self.vmin, self.vmax
-
-        resdat = result.data
-        resdat[resdat > 0] = np.power(resdat[resdat > 0], 1 / gamma)
-        resdat *= (vmax - vmin)
-        resdat += vmin
+    @property
+    def gamma(self):
+        return self._scale.gamma
 
-        result = np.ma.array(resdat, mask=result.mask, copy=False)
-        if is_scalar:
-            result = result[0]
-        return result
+    @gamma.setter
+    def gamma(self, value):
+        self._scale.gamma = value
 
 
 class BoundaryNorm(Normalize):

diff --git a/lib/matplotlib/colors.pyi b/lib/matplotlib/colors.pyi
@@ -339,14 +339,16 @@ def make_norm_from_scale(
     scale_cls: type[scale.ScaleBase],
     base_norm_cls: type[Normalize],
     *,
-    init: Callable | None = ...
+    init: Callable | None = ...,
+    norm_before_trf: bool = ...,
 ) -> type[Normalize]: ...
 @overload
 def make_norm_from_scale(
     scale_cls: type[scale.ScaleBase],
     base_norm_cls: None = ...,
     *,
-    init: Callable | None = ...
+    init: Callable | None = ...,
+    norm_before_trf: bool = ...,
 ) -> Callable[[type[Normalize]], type[Normalize]]: ...
 
 class FuncNorm(Normalize):
@@ -389,14 +391,17 @@ class AsinhNorm(Normalize):
     def linear_width(self, value: float) -> None: ...
 
 class PowerNorm(Normalize):
-    gamma: float
     def __init__(
         self,
         gamma: float,
         vmin: float | None = ...,
         vmax: float | None = ...,
         clip: bool = ...,
     ) -> None: ...
+    @property
+    def gamma(self) -> float: ...
+    @gamma.setter
+    def gamma(self, value: float) -> None: ...
 
 class BoundaryNorm(Normalize):
     boundaries: np.ndarray

diff --git a/lib/matplotlib/scale.py b/lib/matplotlib/scale.py
@@ -17,6 +17,7 @@
 "log"         `LogScale`            `LogTransform`                   `InvertedLogTransform`
 "logit"       `LogitScale`          `LogitTransform`                 `LogisticTransform`
 "symlog"      `SymmetricalLogScale` `SymmetricalLogTransform`        `InvertedSymmetricalLogTransform`
+"power"       `PowerScale`          `PowerTransform`                 `InvertedPowerTransform`
 ============= ===================== ================================ =================================
 
 A user will often only use the scale name, e.g. when setting the scale through
@@ -282,6 +283,109 @@ def set_default_locators_and_formatters(self, axis):
             axis.set_minor_locator(NullLocator())
 
 
+class PowerTransform(Transform):
+    """
+    A simple power transformation used by `.PowerScale`.
+
+    This transformation applies a power-law scaling to positive values, while
+    nonpositive values remain unchanged.
+    """
+    input_dims = output_dims = 1
+
+    def __init__(self, gamma):
+        """
+        Parameters
+        ----------
+        gamma : float
+            Power law exponent.
+        """
+        super().__init__()
+        self.gamma = gamma
+
+    def __str__(self):
+        return "{}(gamma={})".format(
+            type(self).__name__, self.gamma)
+
+    def transform_non_affine(self, values):
+        with np.errstate(divide="ignore", invalid="ignore"):
+            nonpos = ~(values > 0)
+            out = np.power(values, self.gamma)
+            out[nonpos] = values[nonpos]
+            return out
+
+    def inverted(self):
+        return InvertedPowerTransform(self.gamma)
+
+
+class InvertedPowerTransform(Transform):
+    """
+    The inverse of the `.PowerTransform`.
+
+    This transformation applies an inverse power-law scaling to positive values,
+    while nonpositive values remain unchanged.
+    """
+    input_dims = output_dims = 1
+
+    def __init__(self, gamma):
+        """
+        Parameters
+        ----------
+        gamma : float
+            Power law exponent.
+        """
+        super().__init__()
+        if gamma == 0:
+            raise ValueError('gamma cannot be 0')
+        self.gamma = gamma
+
+    def transform_non_affine(self, values):
+        with np.errstate(divide="ignore", invalid="ignore"):
+            nonpos = ~(values > 0)
+            out = np.power(values, 1.0 / self.gamma)
+            out[nonpos] = values[nonpos]
+            return out
+
+    def inverted(self):
+        return PowerTransform(self.gamma)
+
+
+class PowerScale(ScaleBase):
+    """
+    A standard power scale
+    """
+    name = 'power'
+
+    @_make_axis_parameter_optional
+    def __init__(self, axis=None, *, gamma=0.5):
+        """
+        Parameters
+        ----------
+        axis : `~matplotlib.axis.Axis`
+            The axis for the scale.
+        gamma : float, default: 0.5
+            Power law exponent.
+        """
+        self._transform = PowerTransform(gamma)
+
+    gamma = property(lambda self: self._transform.gamma)
+
+    def get_transform(self):
+        """Return the `.PowerTransform` associated with this scale."""
+        return self._transform
+
+    def set_default_locators_and_formatters(self, axis):
+        # docstring inherited
+        axis.set_major_locator(AutoLocator())
+        axis.set_major_formatter(ScalarFormatter())
+        axis.set_minor_formatter(NullFormatter())
+        # update the minor locator for x and y axis based on rcParams
+        if (axis.axis_name == 'x' and mpl.rcParams['xtick.minor.visible'] or
+                axis.axis_name == 'y' and mpl.rcParams['ytick.minor.visible']):
+            axis.set_minor_locator(AutoMinorLocator())
+        else:
+            axis.set_minor_locator(NullLocator())
+
+
 class LogTransform(Transform):
     input_dims = output_dims = 1
 
@@ -807,6 +911,7 @@ def limit_range_for_scale(self, vmin, vmax, minpos):
     'logit':  LogitScale,
     'function': FuncScale,
     'functionlog': FuncScaleLog,
+    'power': PowerScale,
     }
 
 # caching of signature info
@@ -821,6 +926,7 @@ def limit_range_for_scale(self, vmin, vmax, minpos):
     'logit': True,
     'function': True,
     'functionlog': True,
+    'power': True,
 }
 
 

diff --git a/lib/matplotlib/scale.pyi b/lib/matplotlib/scale.pyi
@@ -40,6 +40,29 @@ class FuncScale(ScaleBase):
         ],
     ) -> None: ...
 
+class PowerTransform(Transform):
+    def __init__(self, gamma: float) -> None: ...
+    def __str__(self) -> str: ...
+    def transform_non_affine(self, values: ArrayLike) -> ArrayLike: ...
+    def inverted(self) -> InvertedPowerTransform: ...
+
+class InvertedPowerTransform(Transform):
+    def __init__(self, gamma: float) -> None: ...
+    def transform_non_affine(self, values: ArrayLike) -> ArrayLike: ...
+    def inverted(self) -> PowerTransform: ...
+
+class PowerScale(ScaleBase):
+    name: str
+    def __init__(
+        self,
+        axis: Axis | None = ...,
+        *,
+        gamma: float = ...,
+    ) -> None: ...
+    @property
+    def gamma(self) -> float: ...
+    def get_transform(self) -> PowerTransform: ...
+
 class LogTransform(Transform):
     input_dims: int
     output_dims: int

diff --git a/lib/matplotlib/tests/baseline_images/test_scale/power_scale.png b/lib/matplotlib/tests/baseline_images/test_scale/power_scale.png