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Inline and optimize ContourLabeler.get_label_coords. #19018

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Nov 27, 2020
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Inline and optimize ContourLabeler.get_label_coords. #19018

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3 changes: 3 additions & 0 deletions doc/api/next_api_changes/deprecations/19018-AL.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
``ContourLabeler.get_label_coords`` is deprecated
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It is considered an internal helper.
57 changes: 28 additions & 29 deletions lib/matplotlib/contour.py
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Expand Up @@ -217,6 +217,7 @@ def too_close(self, x, y, lw):
return any((x - loc[0]) ** 2 + (y - loc[1]) ** 2 < thresh
for loc in self.labelXYs)

@_api.deprecated("3.4")
def get_label_coords(self, distances, XX, YY, ysize, lw):
"""
Return x, y, and the index of a label location.
Expand Down Expand Up @@ -278,37 +279,35 @@ def locate_label(self, linecontour, labelwidth):
"""
Find good place to draw a label (relatively flat part of the contour).
"""

# Number of contour points
nsize = len(linecontour)
if labelwidth > 1:
xsize = int(np.ceil(nsize / labelwidth))
else:
xsize = 1
if xsize == 1:
ysize = nsize
else:
ysize = int(labelwidth)

XX = np.resize(linecontour[:, 0], (xsize, ysize))
YY = np.resize(linecontour[:, 1], (xsize, ysize))
# I might have fouled up the following:
yfirst = YY[:, :1]
ylast = YY[:, -1:]
xfirst = XX[:, :1]
xlast = XX[:, -1:]
s = (yfirst - YY) * (xlast - xfirst) - (xfirst - XX) * (ylast - yfirst)
L = np.hypot(xlast - xfirst, ylast - yfirst)
ctr_size = len(linecontour)
n_blocks = int(np.ceil(ctr_size / labelwidth)) if labelwidth > 1 else 1
block_size = ctr_size if n_blocks == 1 else int(labelwidth)
# Split contour into blocks of length ``block_size``, filling the last
# block by cycling the contour start (per `np.resize` semantics). (Due
# to cycling, the index returned is taken modulo ctr_size.)
xx = np.resize(linecontour[:, 0], (n_blocks, block_size))
yy = np.resize(linecontour[:, 1], (n_blocks, block_size))
yfirst = yy[:, :1]
ylast = yy[:, -1:]
xfirst = xx[:, :1]
xlast = xx[:, -1:]
s = (yfirst - yy) * (xlast - xfirst) - (xfirst - xx) * (ylast - yfirst)
l = np.hypot(xlast - xfirst, ylast - yfirst)
# Ignore warning that divide by zero throws, as this is a valid option
with np.errstate(divide='ignore', invalid='ignore'):
dist = np.sum(np.abs(s) / L, axis=-1)
x, y, ind = self.get_label_coords(dist, XX, YY, ysize, labelwidth)

# There must be a more efficient way...
lc = [tuple(l) for l in linecontour]
dind = lc.index((x, y))

return x, y, dind
distances = (abs(s) / l).sum(axis=-1)
# Labels are drawn in the middle of the block (``hbsize``) where the
# contour is the closest (per ``distances``) to a straight line, but
# not `too_close()` to a preexisting label.
hbsize = block_size // 2
adist = np.argsort(distances)
# If all candidates are `too_close()`, go back to the straightest part
# (``adist[0]``).
for idx in np.append(adist, adist[0]):
x, y = xx[idx, hbsize], yy[idx, hbsize]
if not self.too_close(x, y, labelwidth):
break
return x, y, (idx * block_size + hbsize) % ctr_size

def calc_label_rot_and_inline(self, slc, ind, lw, lc=None, spacing=5):
"""
Expand Down