matplotlib · AryanSheka · Feb 25, 2019 · story645 · Jul 31, 2023
diff --git a/doc/api/next_api_changes/behavior/26050-AS.rst b/doc/api/next_api_changes/behavior/26050-AS.rst
@@ -0,0 +1,13 @@
+Seed for ``path.sketch`` will have a rolling (auto incrementing) behaviour
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The seed for the internal Pseudo number generator will now have an auto changing behavior.
+This means that the C code of every artist will get a different seed every time it is called
+and this will be done in a deterministic manner.
+
+Two figures sketched with the same parameters and different seed will look different from one another.
+
+``Artist.get_sketch_params()`` will now return a 4-tuple instead of a 3-tuple consisting of
+(scale, length, randomness, seed) of the form (float, float, float, int).
+
+See 'What's new' on how to set a value to the seed and its behaviour.
diff --git a/doc/users/next_whats_new/sketch_seed.rst b/doc/users/next_whats_new/sketch_seed.rst
@@ -0,0 +1,67 @@
+``sketch_seed`` parameter for rcParams
+--------------------------------------
+
+`~matplotlib.rcParams` now has a new parameter ``path.sketch_seed``.
+Its default value is 0 and accepted values are any non negative integer.
+This allows the user to set the seed for the internal pseudo random number generator in one of three ways.
+
+1) Directly changing the rcParam:
+
+    rcParams['path.sketch_seed'] = 20
+
+2) Passing a value to the new *seed* parameter of `~matplotlib.pyplot.xkcd` function:
+
+    plt.xkcd(seed=20)
+
+3) Passing a value to the new *seed* parameter of matplotlib.artist.set_sketch_params function:
+
+    ln = plt.plot(x, y)
+    ln[0].set_sketch_params(seed = 20)
+
+The seed will also have a changing characteristic for every artist which will be done in a deterministic manner.
+
+
+.. plot::
+    :include-source: true
+
+    import matplotlib.pyplot as plt
+    from matplotlib import rcParams
+
+    with plt.xkcd():
+        rcParams['path.sketch_seed']=0
+        rcParams['path.sketch']=(2,120,40)
+        pat,txt=plt.pie([10,20,30,40],wedgeprops={'edgecolor':'black'})
+        plt.legend(pat,['first','second','third','fourth'],loc='best')
+        plt.title("seed = 0")
+    plt.show()
+
+.. plot::
+    :include-source: true
+
+    import matplotlib.pyplot as plt
+    from matplotlib import rcParams
+
+    fig, ax = plt.subplots()
+    x = np.linspace(0.7, 1.42, 100)
+    y = x ** 2
+    ln = ax.plot(x, y, color='black')
+    ln[0].set_sketch_params(100, 100, 20, 40)
+    plt.title("seed = 40")
+    plt.show()
+
+.. plot::
+    :include-source: true
+
+    import matplotlib.pyplot as plt
+    from matplotlib import rcParams
+
+    with plt.xkcd(seed=19680801):
+        import matplotlib
+        from matplotlib import gridspec
+
+        rcParams['path.sketch']=(2,120,40)
+
+        pat,txt=plt.pie([10,20,30,40],wedgeprops={'edgecolor':'black'})
+        plt.legend(pat,['first','second','third','fourth'],loc='best')
+        plt.title("seed = 19680801")
+    plt.show()
diff --git a/lib/matplotlib/artist.py b/lib/matplotlib/artist.py
@@ -209,6 +209,7 @@ def __init__(self):
         self._gid = None
         self._snap = None
         self._sketch = mpl.rcParams['path.sketch']
+        self._sketch_seed = mpl.rcParams['path.sketch_seed']
         self._path_effects = mpl.rcParams['path.effects']
         self._sticky_edges = _XYPair([], [])
         self._in_layout = True
@@ -681,7 +682,8 @@ def get_sketch_params(self):
         """
         return self._sketch
 
-    def set_sketch_params(self, scale=None, length=None, randomness=None):
+    def set_sketch_params(self, scale=None, length=None, randomness=None,
+                          seed=None):
         """
         Set the sketch parameters.
 
@@ -701,12 +703,21 @@ def set_sketch_params(self, scale=None, length=None, randomness=None):
             The PGF backend uses this argument as an RNG seed and not as
             described above. Using the same seed yields the same random shape.
 
-            .. ACCEPTS: (scale: float, length: float, randomness: float)
+        seed : int, optional
+            Seed for the internal pseudo-random number generator.
+
+            .. versionadded:: 3.8
+
+            .. ACCEPTS: (scale: float, length: float, randomness: float, seed: int)
         """
+        if seed is not None:
+            self._sketch_seed = seed
+
         if scale is None:
             self._sketch = None
         else:
-            self._sketch = (scale, length or 128.0, randomness or 16.0)
+            self._sketch = (scale, length or 128.0, randomness or 16.0,
+                            self._sketch_seed)
         self.stale = True
 
     def set_path_effects(self, path_effects):

diff --git a/lib/matplotlib/artist.pyi b/lib/matplotlib/artist.pyi
@@ -76,12 +76,13 @@ class Artist:
     def set_gid(self, gid: str | None) -> None: ...
     def get_snap(self) -> bool | None: ...
     def set_snap(self, snap: bool | None) -> None: ...
-    def get_sketch_params(self) -> tuple[float, float, float] | None: ...
+    def get_sketch_params(self) -> tuple[float, float, float, int] | None: ...
     def set_sketch_params(
         self,
         scale: float | None = ...,
         length: float | None = ...,
         randomness: float | None = ...,
+        seed: int | None = ...,
     ) -> None: ...
     def set_path_effects(self, path_effects: list[AbstractPathEffect]) -> None: ...
     def get_path_effects(self) -> list[AbstractPathEffect]: ...

diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -754,6 +754,19 @@ def _draw_disabled(self):
 
         return _setattr_cm(self, **no_ops)
 
+    @property
+    def _seed_increment(self):
+        """
+        seed increment for renderer.
+        It is used to implement the rolling characteristic for seed
+        """
+        self.__seed_increment += 1
+        return self.__seed_increment
+
+    @_seed_increment.setter
+    def _seed_increment(self, value):
+        self.__seed_increment = value
+
 
 class GraphicsContextBase:
     """An abstract base class that provides color, line styles, etc."""
@@ -1062,7 +1075,8 @@ def get_sketch_params(self):
         """
         return self._sketch
 
-    def set_sketch_params(self, scale=None, length=None, randomness=None):
+    def set_sketch_params(self, scale=None, length=None, randomness=None,
+                          seed=None):
         """
         Set the sketch parameters.
 
@@ -1076,10 +1090,19 @@ def set_sketch_params(self, scale=None, length=None, randomness=None):
             The length of the wiggle along the line, in pixels.
         randomness : float, default: 16
             The scale factor by which the length is shrunken or expanded.
+        seed : int, optional
+            Seed for the internal pseudo-random number generator.
+
+            .. versionadded:: 3.8
         """
+
         self._sketch = (
             None if scale is None
-            else (scale, length or 128., randomness or 16.))
+            else (scale,
+                  length or rcParams['path.sketch'][1],
+                  randomness or rcParams['path.sketch'][2],
+                  seed or rcParams['path.sketch_seed'])
+        )
 
 
 class TimerBase:

diff --git a/lib/matplotlib/backend_bases.pyi b/lib/matplotlib/backend_bases.pyi
@@ -136,6 +136,10 @@ class RendererBase:
     def stop_rasterizing(self) -> None: ...
     def start_filter(self) -> None: ...
     def stop_filter(self, filter_func) -> None: ...
+    @property
+    def _seed_increment(self) -> int: ...
+    @_seed_increment.setter
+    def _seed_increment(self, value: int) -> None: ...
 
 class GraphicsContextBase:
     def __init__(self) -> None: ...
@@ -180,6 +184,7 @@ class GraphicsContextBase:
         scale: float | None = ...,
         length: float | None = ...,
         randomness: float | None = ...,
+        seed:int | None = ...,
     ) -> None: ...
 
 class TimerBase:

diff --git a/lib/matplotlib/backends/backend_pgf.py b/lib/matplotlib/backends/backend_pgf.py
@@ -575,7 +575,7 @@ def _print_pgf_path(self, gc, path, transform, rgbFace=None):
             # and has a separate "scale" argument for the amplitude.
             # -> Use "randomness" as PRNG seed to allow the user to force the
             # same shape on multiple sketched lines
-            scale, length, randomness = sketch_params
+            scale, length, randomness, seed = sketch_params
             if scale is not None:
                 # make matplotlib and PGF rendering visually similar
                 length *= 0.5

diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -45,6 +45,7 @@
     Artist, allow_rasterization, _finalize_rasterization)
 from matplotlib.backend_bases import (
     DrawEvent, FigureCanvasBase, NonGuiException, MouseButton, _get_renderer)
+
 import matplotlib._api as _api
 import matplotlib.cbook as cbook
 import matplotlib.colorbar as cbar
@@ -3141,6 +3142,7 @@ def draw(self, renderer):
 
             artists = self._get_draw_artists(renderer)
             try:
+                renderer._seed_increment = 0
                 renderer.open_group('figure', gid=self.get_gid())
                 if self.axes and self.get_layout_engine() is not None:
                     try:

diff --git a/lib/matplotlib/lines.py b/lib/matplotlib/lines.py
@@ -823,7 +823,8 @@ def draw(self, renderer):
             gc.set_foreground(ec_rgba, isRGBA=True)
             if self.get_sketch_params() is not None:
                 scale, length, randomness = self.get_sketch_params()
-                gc.set_sketch_params(scale/2, length/2, 2*randomness)
+                seed = self._sketch_seed
+                gc.set_sketch_params(scale/2, length/2, 2*randomness, seed)
 
             marker = self._marker
 

diff --git a/lib/matplotlib/mpl-data/matplotlibrc b/lib/matplotlib/mpl-data/matplotlibrc
@@ -677,6 +677,7 @@
                     #     - *randomness* is the factor by which the length is
                     #         randomly scaled.
 #path.effects:
+#path.sketch_seed: 0 # seed for the internal pseudo number generator.
 
 
 ## ***************************************************************************

diff --git a/lib/matplotlib/patches.py b/lib/matplotlib/patches.py
@@ -563,7 +563,9 @@ def _draw_paths_with_artist_properties(
             gc.set_hatch_color(self._hatch_color)
 
         if self.get_sketch_params() is not None:
-            gc.set_sketch_params(*self.get_sketch_params())
+            scale, length, randomness = self.get_sketch_params()
+            gc.set_sketch_params(scale, length, randomness,
+                                 self._sketch_seed+renderer._seed_increment)
 
         if self.get_path_effects():
             from matplotlib.patheffects import PathEffectRenderer

diff --git a/lib/matplotlib/path.py b/lib/matplotlib/path.py
@@ -382,8 +382,8 @@ def iter_segments(self, transform=None, remove_nans=True, clip=None,
             If True, curve segments will be returned as curve segments.
             If False, all curves will be converted to line segments.
         sketch : None or sequence, optional
-            If not None, must be a 3-tuple of the form
-            (scale, length, randomness), representing the sketch parameters.
+            If not None, must be a 4-tuple of the form
+            (scale, length, randomness, seed), representing the sketch parameters.
         """
         if not len(self):
             return

diff --git a/lib/matplotlib/path.pyi b/lib/matplotlib/path.pyi
@@ -61,7 +61,7 @@ class Path:
         stroke_width: float = ...,
         simplify: bool | None = ...,
         curves: bool = ...,
-        sketch: tuple[float, float, float] | None = ...,
+        sketch: tuple[float, float, float, int] | None = ...,
     ) -> Generator[tuple[np.ndarray, np.uint8], None, None]: ...
     def iter_bezier(self, **kwargs) -> Generator[BezierSegment, None, None]: ...
     def cleaned(
@@ -74,7 +74,7 @@ class Path:
         curves: bool = ...,
         stroke_width: float = ...,
         snap: bool | None = ...,
-        sketch: tuple[float, float, float] | None = ...
+        sketch: tuple[float, float, float, int] | None = ...
     ) -> Path: ...
     def transformed(self, transform: Transform) -> Path: ...
     def contains_point(

diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
@@ -701,8 +701,8 @@ def setp(obj, *args, **kwargs):
 
 
 def xkcd(
-    scale: float = 1, length: float = 100, randomness: float = 2
-) -> ExitStack:
+    scale: float = 1, length: float = 100, randomness: float = 2,
+     seed: int | None = None) -> ExitStack:
     """
     Turn on `xkcd <https://xkcd.com/>`_ sketch-style drawing mode.  This will
     only have effect on things drawn after this function is called.
@@ -718,6 +718,8 @@ def xkcd(
         The length of the wiggle along the line.
     randomness : float, optional
         The scale factor by which the length is shrunken or expanded.
+    seed: int, optional
+        Seed for the internal pseudo-random number generator.
 
     Notes
     -----
@@ -738,6 +740,9 @@ def xkcd(
     # This cannot be implemented in terms of contextmanager() or rc_context()
     # because this needs to work as a non-contextmanager too.
 
+    if seed is not None:
+        rcParams['path.sketch_seed'] = seed
+
     if rcParams['text.usetex']:
         raise RuntimeError(
             "xkcd mode is not compatible with text.usetex = True")

diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -565,6 +565,15 @@ def validate_sketch(s):
         raise ValueError("Expected a (scale, length, randomness) triplet")
 
 
+def validate_sketch_seed(s):
+    s = validate_int(s)
+
+    if s >= 0:
+        return s
+    else:
+        raise ValueError("seed must be a non negative integer")
+
+
 def _validate_greaterthan_minushalf(s):
     s = validate_float(s)
     if s > -0.5:
@@ -1288,6 +1297,7 @@ def _convert_validator_spec(key, conv):
     "path.simplify_threshold": _validate_greaterequal0_lessequal1,
     "path.snap":               validate_bool,
     "path.sketch":             validate_sketch,
+    "path.sketch_seed":        validate_sketch_seed,
     "path.effects":            validate_anylist,
     "agg.path.chunksize":      validate_int,  # 0 to disable chunking
 

diff --git a/lib/matplotlib/rcsetup.pyi b/lib/matplotlib/rcsetup.pyi
@@ -140,6 +140,7 @@ def _validate_linestyle(s: Any) -> LineStyleType: ...
 def validate_markeverylist(s: Any) -> list[MarkEveryType]: ...
 def validate_bbox(s: Any) -> Literal["tight", "standard"] | None: ...
 def validate_sketch(s: Any) -> None | tuple[float, float, float]: ...
+def validate_sketch_seed(s: Any) -> int: ...
 def validate_hatch(s: Any) -> str: ...
 def validate_hatchlist(s: Any) -> list[str]: ...
 def validate_dashlist(s: Any) -> list[list[float]]: ...

diff --git a/lib/matplotlib/tests/baseline_images/test_path/xkcd.png b/lib/matplotlib/tests/baseline_images/test_path/xkcd.png
diff --git a/lib/matplotlib/tests/baseline_images/test_path/xkcd_marker.png b/lib/matplotlib/tests/baseline_images/test_path/xkcd_marker.png
diff --git a/lib/matplotlib/tests/test_backend_pgf.py b/lib/matplotlib/tests/test_backend_pgf.py
@@ -384,7 +384,7 @@ def test_sketch_params():
     ax.set_yticks([])
     ax.set_frame_on(False)
     handle, = ax.plot([0, 1])
-    handle.set_sketch_params(scale=5, length=30, randomness=42)
+    handle.set_sketch_params(scale=5, length=30, randomness=42, seed=0)
 
     with BytesIO() as fd:
         fig.savefig(fd, format='pgf')