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Preserve explicitly set figure DPI when pickling #32233

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Preserve explicitly set figure DPI when pickling #32233

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5 changes: 3 additions & 2 deletions lib/matplotlib/figure.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2412,7 +2412,7 @@ def set_dpi(self, val):
----------
val : float
"""
self._parent.dpi = val
self._parent.set_dpi(val)
self.stale = True

def _get_renderer(self):
Expand Down Expand Up @@ -3293,7 +3293,8 @@ def set_dpi(self, val):
----------
val : float
"""
self.dpi = val
self._original_dpi = val
self._set_dpi(val * self.canvas.device_pixel_ratio)
self.stale = True

def set_figwidth(self, val, forward=True):
Expand Down
35 changes: 35 additions & 0 deletions lib/matplotlib/tests/test_figure.py
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Original file line number Diff line number Diff line change
Expand Up @@ -655,6 +655,20 @@ def test_savefig_pixel_ratio(backend):
assert ratio1 == ratio2


@pytest.mark.parametrize("target", ["figure", "subfigure"])
def test_set_dpi_savefig(target):
fig = Figure(figsize=(2, 1), dpi=40)
fig.canvas._set_device_pixel_ratio(2)
(fig if target == "figure" else fig.subfigures()).set_dpi(60)

with io.BytesIO() as buf:
fig.savefig(buf, format="png", dpi="figure")
assert Image.open(buf).size == (120, 60)

assert fig.dpi == 120
assert fig.canvas.device_pixel_ratio == 2


def test_savefig_preserve_layout_engine():
fig = plt.figure(layout='compressed')
fig.savefig(io.BytesIO(), bbox_inches='tight')
Expand Down Expand Up @@ -1726,6 +1740,27 @@ def test_unpickle_with_device_pixel_ratio():
)


@pytest.mark.parametrize("target", ["figure", "subfigure"])
@pytest.mark.parametrize("set_dpi_first", [False, True])
@pytest.mark.parametrize("device_pixel_ratio", [1, 7])
def test_unpickle_with_set_dpi(target, set_dpi_first, device_pixel_ratio):
fig = Figure(dpi=42)
target = fig if target == "figure" else fig.subfigures()

if set_dpi_first:
target.set_dpi(84)
fig.canvas._set_device_pixel_ratio(device_pixel_ratio)
else:
fig.canvas._set_device_pixel_ratio(device_pixel_ratio)
target.set_dpi(84)

assert fig.dpi == 84 * device_pixel_ratio
restored = pickle.loads(pickle.dumps(fig))
assert restored.dpi == 84
np.testing.assert_allclose(
fig.bbox.max / device_pixel_ratio, restored.bbox.max)


def test_gridspec_no_mutate_input():
gs = {'left': .1}
gs_orig = dict(gs)
Expand Down
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