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AGG 滤镜#
Matplotlib 中大多数基于像素的后端使用 Anti-Grain Geometry (AGG) 进行渲染。可以通过 Artist.set_agg_filter 应用滤镜来修改 Artists 的渲染效果。
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.artist import Artist
import matplotlib.cm as cm
from matplotlib.colors import LightSource
import matplotlib.transforms as mtransforms
def smooth1d(x, window_len):
# copied from https://cookbook.scipy.org.cn/items/SignalSmooth.html
s = np.r_[2*x[0] - x[window_len:1:-1], x, 2*x[-1] - x[-1:-window_len:-1]]
w = np.hanning(window_len)
y = np.convolve(w/w.sum(), s, mode='same')
return y[window_len-1:-window_len+1]
def smooth2d(A, sigma=3):
window_len = max(int(sigma), 3) * 2 + 1
A = np.apply_along_axis(smooth1d, 0, A, window_len)
A = np.apply_along_axis(smooth1d, 1, A, window_len)
return A
class BaseFilter:
def get_pad(self, dpi):
return 0
def process_image(self, padded_src, dpi):
raise NotImplementedError("Should be overridden by subclasses")
def __call__(self, im, dpi):
pad = self.get_pad(dpi)
padded_src = np.pad(im, [(pad, pad), (pad, pad), (0, 0)], "constant")
tgt_image = self.process_image(padded_src, dpi)
return tgt_image, -pad, -pad
class OffsetFilter(BaseFilter):
def __init__(self, offsets=(0, 0)):
self.offsets = offsets
def get_pad(self, dpi):
return int(max(self.offsets) / 72 * dpi)
def process_image(self, padded_src, dpi):
ox, oy = self.offsets
a1 = np.roll(padded_src, int(ox / 72 * dpi), axis=1)
a2 = np.roll(a1, -int(oy / 72 * dpi), axis=0)
return a2
class GaussianFilter(BaseFilter):
"""Simple Gaussian filter."""
def __init__(self, sigma, alpha=0.5, color=(0, 0, 0)):
self.sigma = sigma
self.alpha = alpha
self.color = color
def get_pad(self, dpi):
return int(self.sigma*3 / 72 * dpi)
def process_image(self, padded_src, dpi):
tgt_image = np.empty_like(padded_src)
tgt_image[:, :, :3] = self.color
tgt_image[:, :, 3] = smooth2d(padded_src[:, :, 3] * self.alpha,
self.sigma / 72 * dpi)
return tgt_image
class DropShadowFilter(BaseFilter):
def __init__(self, sigma, alpha=0.3, color=(0, 0, 0), offsets=(0, 0)):
self.gauss_filter = GaussianFilter(sigma, alpha, color)
self.offset_filter = OffsetFilter(offsets)
def get_pad(self, dpi):
return max(self.gauss_filter.get_pad(dpi),
self.offset_filter.get_pad(dpi))
def process_image(self, padded_src, dpi):
t1 = self.gauss_filter.process_image(padded_src, dpi)
t2 = self.offset_filter.process_image(t1, dpi)
return t2
class LightFilter(BaseFilter):
"""Apply LightSource filter"""
def __init__(self, sigma, fraction=1):
"""
Parameters
----------
sigma : float
sigma for gaussian filter
fraction: number, default: 1
Increases or decreases the contrast of the hillshade.
See `matplotlib.colors.LightSource`
"""
self.gauss_filter = GaussianFilter(sigma, alpha=1)
self.light_source = LightSource()
self.fraction = fraction
def get_pad(self, dpi):
return self.gauss_filter.get_pad(dpi)
def process_image(self, padded_src, dpi):
t1 = self.gauss_filter.process_image(padded_src, dpi)
elevation = t1[:, :, 3]
rgb = padded_src[:, :, :3]
alpha = padded_src[:, :, 3:]
rgb2 = self.light_source.shade_rgb(rgb, elevation,
fraction=self.fraction,
blend_mode="overlay")
return np.concatenate([rgb2, alpha], -1)
class GrowFilter(BaseFilter):
"""Enlarge the area."""
def __init__(self, pixels, color=(1, 1, 1)):
self.pixels = pixels
self.color = color
def __call__(self, im, dpi):
alpha = np.pad(im[..., 3], self.pixels, "constant")
alpha2 = np.clip(smooth2d(alpha, self.pixels / 72 * dpi) * 5, 0, 1)
new_im = np.empty((*alpha2.shape, 4))
new_im[:, :, :3] = self.color
new_im[:, :, 3] = alpha2
offsetx, offsety = -self.pixels, -self.pixels
return new_im, offsetx, offsety
class FilteredArtistList(Artist):
"""A simple container to filter multiple artists at once."""
def __init__(self, artist_list, filter):
super().__init__()
self._artist_list = artist_list
self._filter = filter
def draw(self, renderer):
renderer.start_rasterizing()
renderer.start_filter()
for a in self._artist_list:
a.draw(renderer)
renderer.stop_filter(self._filter)
renderer.stop_rasterizing()
def filtered_text(ax):
# mostly copied from contour_demo.py
# prepare image
delta = 0.025
x = np.arange(-3.0, 3.0, delta)
y = np.arange(-2.0, 2.0, delta)
X, Y = np.meshgrid(x, y)
Z1 = np.exp(-X**2 - Y**2)
Z2 = np.exp(-(X - 1)**2 - (Y - 1)**2)
Z = (Z1 - Z2) * 2
# draw
ax.imshow(Z, interpolation='bilinear', origin='lower',
cmap=cm.gray, extent=(-3, 3, -2, 2), aspect='auto')
levels = np.arange(-1.2, 1.6, 0.2)
CS = ax.contour(Z, levels,
origin='lower',
linewidths=2,
extent=(-3, 3, -2, 2))
# contour label
cl = ax.clabel(CS, levels[1::2], # label every second level
inline=True,
fmt='%1.1f',
fontsize=11)
# change clabel color to black
from matplotlib.patheffects import Normal
for t in cl:
t.set_color("k")
# to force TextPath (i.e., same font in all backends)
t.set_path_effects([Normal()])
# Add white glows to improve visibility of labels.
white_glows = FilteredArtistList(cl, GrowFilter(3))
ax.add_artist(white_glows)
white_glows.set_zorder(cl[0].get_zorder() - 0.1)
ax.xaxis.set_visible(False)
ax.yaxis.set_visible(False)
def drop_shadow_line(ax):
# copied from examples/misc/svg_filter_line.py
# draw lines
l1, = ax.plot([0.1, 0.5, 0.9], [0.1, 0.9, 0.5], "bo-")
l2, = ax.plot([0.1, 0.5, 0.9], [0.5, 0.2, 0.7], "ro-")
gauss = DropShadowFilter(4)
for l in [l1, l2]:
# draw shadows with same lines with slight offset.
xx = l.get_xdata()
yy = l.get_ydata()
shadow, = ax.plot(xx, yy)
shadow.update_from(l)
# offset transform
transform = mtransforms.offset_copy(l.get_transform(), ax.figure,
x=4.0, y=-6.0, units='points')
shadow.set_transform(transform)
# adjust zorder of the shadow lines so that it is drawn below the
# original lines
shadow.set_zorder(l.get_zorder() - 0.5)
shadow.set_agg_filter(gauss)
shadow.set_rasterized(True) # to support mixed-mode renderers
ax.set_xlim(0., 1.)
ax.set_ylim(0., 1.)
ax.xaxis.set_visible(False)
ax.yaxis.set_visible(False)
def drop_shadow_patches(ax):
# Copied from barchart_demo.py
N = 5
group1_means = [20, 35, 30, 35, 27]
ind = np.arange(N) # the x locations for the groups
width = 0.35 # the width of the bars
rects1 = ax.bar(ind, group1_means, width, color='r', ec="w", lw=2)
group2_means = [25, 32, 34, 20, 25]
rects2 = ax.bar(ind + width + 0.1, group2_means, width,
color='y', ec="w", lw=2)
drop = DropShadowFilter(5, offsets=(1, 1))
shadow = FilteredArtistList(rects1 + rects2, drop)
ax.add_artist(shadow)
shadow.set_zorder(rects1[0].get_zorder() - 0.1)
ax.set_ylim(0, 40)
ax.xaxis.set_visible(False)
ax.yaxis.set_visible(False)
def light_filter_pie(ax):
fracs = [15, 30, 45, 10]
explode = (0.1, 0.2, 0.1, 0.1)
pies = ax.pie(fracs, explode=explode)
light_filter = LightFilter(9)
for p in pies[0]:
p.set_agg_filter(light_filter)
p.set_rasterized(True) # to support mixed-mode renderers
p.set(ec="none",
lw=2)
gauss = DropShadowFilter(9, offsets=(3, -4), alpha=0.7)
shadow = FilteredArtistList(pies[0], gauss)
ax.add_artist(shadow)
shadow.set_zorder(pies[0][0].get_zorder() - 0.1)
if __name__ == "__main__":
fix, axs = plt.subplots(2, 2)
filtered_text(axs[0, 0])
drop_shadow_line(axs[0, 1])
drop_shadow_patches(axs[1, 0])
light_filter_pie(axs[1, 1])
axs[1, 1].set_frame_on(True)
plt.show()
脚本总运行时间：（0 分钟 1.344 秒）